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17. Main Biologic Agents

Natural Evolution or Intentional Infliction

In this section we will be introduced to some of the most common biologic agents that can cause disease. The nurse as a first responder can utilize this information. Not all the diseases are communicable; however, they can cause widespread infection and major disruption. It is thought that BioWar agents would come as toxins, bacteria, or viruses.

Toxins could include: Staphylococcal Enterotoxin B. (SEB), Botulinum, or Ricin. Bacteria could involve anthrax, glanders, plague, Q fever, and tuleremia. Among the most dangerous viruses are: smallpox, HVF’s, and VEE’s.

Plague, smallpox, viral hemorrhagic fevers and pandemic influenza’s are spread readily person to person by aerosol and require more than standard infection control precautions (gown, mask with eye shield, gloves). All potential victims of BioWar agents or natural pandemics should be in isolation. Medical personnel caring for these patients should wear a HEPA mask in addition to standard precautions pending the results of a more complete evaluation.

Broad-spectrum intravenous antibiotic coverage may be recommended initially for victims if a BioWar agent is suspected. Vaccinations are most likely available for anthrax, botulinum toxin, tularemia, plague, Q fever, and smallpox. Immune protection against ricin and staphylococcal toxins may be feasible in the near future.


Anthrax is a zoonotic infection with a long association in human history. Anthrax was the first disease for which Louis Pasteur developed a live vaccine (1881). Anthrax occurs in domestic, wild, and exotic animals to include goats, sheep, cattle elephants, lions, zebras, and camels. Human infection usually happens via contact with infected animals or contaminated articles and animal products. The predominant form of Anthrax presents as a cutaneous infection but may occur in inhalational or gastrointestinal form. Anthrax occurs worldwide. The organism exists in the soil as a spore. The form of the organism in infected animals is the bacillus. Sporulation occurs only when the organism in the carcass is exposed to air.

The true incidence of human anthrax is unknown. In 1958, an estimated 20,000-100,000 cases occurred worldwide. In the United States, the annual incidence of naturally occurring human anthrax has declined steadily from approximately 127 cases in the early years of this century to approximately 1 per year for the past 10 years.


Gastrointestinal anthrax morbidity is 50-100% due to blood loss, fluid and electrolyte imbalance and shock. Death results from intestinal perforation. By contrast, cutaneous anthrax mortality with antibiotic treatment is about 1%, septicemia is rare. However, Inhalational Anthrax morbidity is 95-100%. Without treatment death is universal. If therapy is started later than 24-48 hours there is a 5% survival chance.


An attenuated vaccine is available and has been used in thousands of military troops and with at-risk civilians. There is a series of vaccinations, usually with six doses every 2 weeks for the first three, and then one at 12 months, and 18 months. Penicillin has been the historical drug of choice treatment of naturally occurring strains, along with doxycycline or ciprofloxacin as alternatives. Cutaneous anthrax can be treated orally while gastrointestinal or inhalational disease should include large IV doses of antibiotics.


Anthrax is federally reportable in all 50 states. It is so rare that, if found, would be assumed to be an intentional release. Bacillus anthracis is a large, aerobic, gram-positive, spore-forming, non-motile bacillus

Inhalation Anthrax

Lethal dose of inhalational anthrax is 10-50 spores; LD50 is believed to be 10,000-20,000 spores in the human with intact immune systems. The spore-bearing particles go into the alveolar spaces, where the macrophages ingest spores, some of which are destroyed through lysis. The surviving spores are transported by macrophages to the mediastinal lymph nodes, which germinate into vegetative cells intensively multiplying once in the lymph. Disease happens rapidly once the multiplication has begun.

The pathogenic stages are as follows:

  1. Accumulation of vegetative cells in the lymphatic system and tissues. This stage is characterized by low bacteremia and low toxemia.

  2. Increasing bactermia, toxemia and rapidly accumulating organisms of bacilli in the lymphatic system.

  3. Rapidly accumulating organisms of anthrax toxins in blood and lymph

  4. Increasing massive edema, hemorrhagic thoracic lymphadenitis, and sometimes-hemorrhagic meningitis

  5. Increasing respiratory dysfunction induced by anthrax toxins

  6. Sepsis

  7. Sepsis shock and death
Clinical Features

In inhalation anthrax, the spores are ingested by alveolar macrophages, which transport them to the regional tracheobronchial lymph nodes, where germination occurs. Once in the tracheobronchial lymph nodes, the local production of toxins by extracellular bacilli gives rise to the characteristic pathologic picture of massive hemorrhagic, edematous, and necrotizing lymphadenitis and mediastinitis. The bacillus then can spread to the blood, leading to septicemia and frequently causing hemorrhagic meningitis. Death results from respiratory failure, overwhelming bacteremia, septic shock, and meningitis.

Inhalation anthrax is the most likely form of disease to follow military or terrorist attack. Such an attack likely will involve the aerosolized delivery of anthrax spores. Also known as woolsorter’s disease, inhalation anthrax has a typical incubation period of 1-6 days, but a latent period as long as 60 days has been described. Initial manifestations are nonspecific and include headache, malaise, fatigue, myalgia, and fever. Associated nonproductive cough and mild chest discomfort may occur. These symptoms usually persist for 2-3 days, and in some patients a short period of improvement may occur. This is followed by the sudden onset of increasing respiratory distress with dyspnea, cyanosis, increased chest pain, and diaphoresis. Associated edema of the chest and neck may be present.

Chest X-rays usually show the characteristic widening of the mediastinum and, often, pleural effusion. Pneumonia is thought to be an uncommon finding. The 10 patients with inhalation anthrax in the United States in September and October 2001 had abnormal chest radiographs on initial presentation. Non-contrast CT scans of the chest may need to be done, as symptoms may not evident on plain chest radiographs. The onset of respiratory distress is followed by the rapid onset of shock and death within 24-36 hours. The mortality rate is 80-90%, but may approach 100% when septic shock develops, despite appropriate treatment.


The diagnosis of inhalation anthrax is extremely difficult because no rapid-screening tests are available, but one should suspect the disease with a history of exposure to a B anthracis–containing aerosol. Early symptoms are entirely nonspecific. The development of respiratory distress in association with radiographic evidence of a widened mediastinum due to hemorrhagic mediastinitis and the presence of hemorrhagic pleural effusions or hemorrhagic meningitis should suggest the diagnosis. Sputum Gram stain and culture usually is not helpful because pneumonia is an uncommon feature of illness. Gram stain of peripheral blood may be positive for gram-positive bacilli, often seen in short and long chains, and should be performed.

Most naturally occurring strains of anthrax are sensitive to penicillin. Penicillin and doxycycline are FDA-approved antibiotics for anthrax. Doxycycline is the preferred option from the tetracycline class of antibiotics. Experts currently recommend initiation of ciprofloxacin with a presumed inhalation anthrax infection.

In a contained casualty setting (a situation in which a modest number of patients require therapy), initiate intravenous antibiotics for symptomatic patients. In experimental models, antibiotic therapy during anthrax infection has prevented development of an immune response. This suggests that even if the antibiotic-treated patient survives anthrax infection, risk of recurrence remains for at least 60 days. Oral therapy should replace intravenous therapy as soon as a patient’s clinical condition improves.

Cutaneous Anthrax

Cutaneous anthrax spores go into the skin through cuts or abrasions and infection begins. The estimated infectious dose is 8,000-50,000 spores. It is believed that spores are ingested locally by the macrophages. Subsequently, spores germinate within macrophages to the vegetative bacilli, which produce capsules and toxins. More than 95% of cases of anthrax are cutaneous. After inoculation, the incubation period is 1-5 days. Patients generally experience fever, malaise, and headache, which may be severe in those with extensive edema.

Bacteria proliferate at these tissue sites and produce the edema and lethal toxins that impair host leukocyte function and lead to the following symptoms: edema, hemorrhage, tissue necrosis, and a relative lack of leukocytes.

The following stages are seen:

  1. Initial pruritic macule or papule

  2. Spherical ulcer

  3. Black, painless, depressed eschar (a characteristic 1- to 5-cm black eschar. The black appearance of the eschar gives anthrax its name Greek anthrakos = coal.)

  4. Lymphadenitis and painful lymphadenopathy with systemic symptoms

Diagnosis is made by gram stain or culture of the lesion confirming the diagnosis. The differential diagnosis should include tularemia and staphylococcal or streptococcal species. A positive skin test to anthracin also has been used to make a retrospective diagnosis of anthrax.


Historically, the treatment of cutaneous anthrax has been oral penicillin. Recent recommendations suggest that oral fluoroquinolones or tetracycline antibiotics, as well as amoxicillin, are suitable alternatives if antibiotic susceptibility is proven. Although previous guidelines have suggested treating cutaneous anthrax with 7-10 days of therapy, recent recommendations suggest treatment for 60 days in the setting of bioterrorism, given the presumed exposure to the primary aerosol. Treatment of cutaneous anthrax generally prevents progression to systemic disease, although it does not prevent the formation and evolution of the eschar.

In pregnant women, experts recommend that ciprofloxacin be given for therapy and post exposure prophylaxis following anthrax attack. Intravenous penicillin should be substituted for the fluoroquinolones if microbiologic testing confirms penicillin susceptibility of the organism.

Gastrointestinal Anthrax

This results from the ingestion of infected meat that has not been cooked sufficiently. After an incubation period of 2-5 days, GI anthrax begins with nonspecific symptoms of nausea, vomiting, and fever. These are followed in most patients by severe abdominal pain. The presenting sign may be an acute abdomen, which may be associated with hematemesis, massive ascites, and diarrhea. Mortality rate in both forms may be as high as 50%, especially in the GI form.

Meningitis may occur following bacteremia as a complication of any of the other clinical forms. Meningitis also may occur, rarely, without any of the other clinical forms of the disease. It often is hemorrhagic and almost invariably fatal.

Diagnosis and Treatment

GI anthrax is exceedingly difficult to diagnose because of the rarity of the disease and nonspecific symptoms. Diagnosis usually is confirmed only with a history of ingesting contaminated meat in the setting of an outbreak.

Meningitis from anthrax is clinically indistinguishable from meningitis due to other etiologies. A distinguishing feature is that the spinal fluid is hemorrhagic in as many as 50% of patients. The diagnosis can be confirmed by identifying the organism in the spinal fluid by microscopy, culture, or both. Serology can be used to make a retrospective diagnosis


Plague is a zoonotic infection is caused by Yersinia pestis, a gram-negative coccobacillus, which has been the cause of 3 great human pandemics (see history). Throughout history, the oriental rat flea (Xenopsylla cheopis) has been largely responsible for spreading bubonic plague. After the flea ingests a blood meal on a bacteremic animal, bacilli can multiply and essentially block the flea’s foregut with a fibrinoid mass of bacteria.

When an infected flea with a blocked foregut attempts to feed again, it regurgitates clotted blood and bacteria into the victim’s blood stream and so passes the infection onto the next victim, whether rat or human. As many as 24,000 organisms may be introduced into the host.

Although the largest outbreaks of plague have been associated with X cheopis, all fleas should be considered dangerous in plague-endemic areas. The most important vector in the United States is Diamanus montanus, the most common flea of rock squirrels and California ground squirrels. The black rat, Rattus rattus, has been most responsible worldwide for the persistence and spread of plague in urban epidemics.

As few as 1-10 organisms of Y pestis are sufficient to infect rodents and primates via the oral, intradermal, subcutaneous, or intravenous routes. Y pestis grows optimally at 28°C. If Y pestis were used as a BioWar agent, it most likely would be inhaled as an infectious aerosol and result in primary pneumonic plague (epidemic pneumonia). If fleas were used as carriers of disease, bubonic or septicemic plague would result.

In the United States today, most patients (85-90%) with human plague present clinically with the bubonic form, 10-15% with the primary septicemia form, and 1% with the pneumonic form. Secondary septicemic plague occurs in 23% of patients who present with bubonic plague, and secondary pneumonic plague occurs in 9%.

Bubonic Plague. Presenting symptoms include severe malaise (75%), headache (20-85%), vomiting (25-49%), chills (40%), cough (25%), abdominal pain (19%), and chest pain (13%). Buboes (enlarged lymph node tender and painful, in groin and axilla) become visible within 24 hours and are characterized by severe pain. Untreated, septicemia develops in 2-6 days.

Approximately 5-15% of bubonic plague patients develop secondary pneumonic plague and thus the ability to spread illness from person to person by respiratory droplets.

Septicemia Plague. Septicemia plague may occur primarily or secondarily as a result of hematogenous dissemination of bubonic plague. Presenting signs and symptoms of primary septicemic plague are essentially the same as those for any gram-negative septicemia and include fever, chills, nausea, vomiting, and diarrhea; later, purpura, disseminated intravascular coagulation (DIC), and necrosis occur.

Pneumonic Plague. Pneumonic plague may occur primarily from inhalation of aerosols or secondarily from hematogenous dissemination. Patients typically have a productive cough with blood-tinged sputum within 24 hours of symptom onset. The findings on chest x-ray are variable, but bilateral alveolar infiltrates appear to be the most common findings in pneumonic plague.

Plague Meningitis. This is observed in 6-7% of patients. The condition manifests itself most often in children after 9-14 days of ineffective treatment. Symptoms are similar to those of other forms of acute bacterial meningitis.

Plague is a suitable pathogen for use as a biological weapon because:

According to a WHO report almost 40 years ago, it was estimated that an aerosol release of 50 kg of dried powder containing Y pestis spores over a city of 5 million people in an economically developed country would produce 150,000 incapacitating illnesses and up to 36,000 deaths. These estimates did not take into consideration secondary cases that would occur through subsequent person-to-person contact. Imagine today’s numbers.


After being introduced into the mammalian host by a flea, the organism is thought to be susceptible initially to phagocytosis and killing by neutrophils. However, some of the bacteria may grow and proliferate within tissue macrophages. Within the human host, several environmental signals (temperature of 37°C, contact with eukaryotic cells, location within mononuclear cells, pH) are thought to induce the synthesis and activity of a multitude of factors that contribute to virulence. Bacteria become resistant to phagocytosis and proliferate unimpeded extracellularly.

During the incubation phase, the bacilli most commonly spread to regional lymph nodes, where supportive lymphadenitis develops. Primary pneumonic plague is rapidly fatal because the inhaled droplets already contain phagocytosis-resistant bacilli, which have arisen from their growth in the vertebrate host. Infection progresses if untreated causing septicemia. The endotoxin probably contributes to the development of septic shock, which is similar to the shock states observed with other causes of gram-negative sepsis.

Tissues most commonly infected include the spleen, liver, lungs, skin, and mucous membranes. Late infection of the meninges also occurs, especially if suboptimal antibiotic therapy has been administered.


BioWar agents could case plague,smalpos, anthrax, glanders, hemorrhagic fevers, and encephalitis. Dissemination of BioWar agents may occur by aerosol sprays, explosives, food, or water contamination. Variables that can alter the effectiveness of a delivery system include particle size of the agent, stability of the agent under desiccating conditions, UV light, wind speed, wind direction, and atmospheric stability.


Plague is characterized by the abrupt onset of high fevers, painful lymphadenopathy, and bacteremia. Septicemic plague sometimes can ensue from untreated bubonic plague after a fleabite. Pneumonic plague is the most severe form of disease and, untreated, has a mortality rate approaching 100%. Patients with the bubonic form of the disease may develop secondary pneumonic plague. This complication can lead to human-to-human spread by the respiratory route and cause primary pneumonic plague.

Mortality from endemic plague continues throughout the world despite the availability of effective antibiotics. People continue to die of plague, not because the bacilli have become resistant but, most often, because physicians do not include plague in their differential diagnosis, and treatment is delayed.


The diagnosis of bubonic plague should be made readily on clinical grounds if a patient presents with a painful bubo, fever, prostration, and history of exposure to rodents or fleas in an endemic area. However, if the patient presents in a non-endemic area or without a bubo, then the diagnosis can be difficult to make. When a bubo is present, the differential diagnosis should include tularemia, cat scratch disease, lymphogranuloma venereum, chancroid, TB, streptococcal adenitis, and scrub typhus.

The differential diagnosis of septicemic plague also includes meningococcemia, gram-negative sepsis, and rickettsioses. A presentation of systemic toxicity, a productive cough, and bloody sputum suggests a large differential diagnosis. However, demonstration of gram-negative coccobacilli in the sputum readily should suggest the correct diagnosis, because Y pestis is perhaps the only gram-negative bacterium that can cause extensive, fulminant pneumonia with bloody sputum in an otherwise healthy, immunocompetent host. In addition, Y pestis has unique bipolar, safety pin morphology. In patients with lymphadenopathy, perform a bubo aspiration.

Cultures of blood, bubo aspirate, sputum, and cerebrospinal fluid (CSF) should be performed. Tiny 1- to 3-mm beaten copper colonies appear on blood agar in 48 hours. It is important to remember that colonies may be negative at 24 hours. Complete blood counts (CBCs) often reveal leukocytosis with a left shift. Platelet counts may be normal or low, and activated partial thromboplastin times (APTTs) may be increased.


Patients with plague should be isolated for the first 48 hours after treatment initiation. If pneumonic plague is present, continue isolation for 4 days. Since l948, streptomycin has been the treatment of choice for bubonic, septicemic, and pneumonic plague. Gentamicin has had much less clinical usage but can be used as an alternative to streptomycin. Continue treatment for a minimum of 10 days or 3-4 days after clinical recovery. Streptomycin is also the treatment of choice for newborns.

Patients are unlikely to survive primary pneumonic plague if antibiotic therapy is not initiated within 18 hours of symptom onset. Without treatment, the mortality rate is 60% for bubonic plague and 100% for the pneumonic and septicemic forms.


All plague control measures must include insecticide use, public education, and reduction of rodent populations with chemicals. Fleas should be targeted before rodents, because killing rodents may release massive amounts of infected fleas.

Treat contacts of patients with pneumonic plague and individuals who have been exposed to aerosols with tetracycline. If tetracycline is not available, doxycycline 100 mg bid is an effective alternative. Contacts of patients with bubonic plague do not require prophylactic therapy. However, administer prophylaxis to people who were in the same environment and potentially exposed to the same source of infection. In addition, previously vaccinated individuals should receive prophylactic antibiotics if they have been exposed to a plague aerosol.

Vaccinate military troops and personnel working in endemic areas, lab personnel working with Y pestis, and people who reside in enzootic or epidemic areas. While epidemiologic evidence supports the efficacy of the current vaccine against bubonic plague, its efficacy against aerosolized Y pestis is believed to be poor.


This agent has been investigated in the past as a biological weapon. Although cholera does not spread easily from human to human, it appears that major drinking water supplies would have to be contaminated heavily for this agent to be effective as a biological weapon. Transmission is made through direct or indirect fecal contamination of water or foods and by heavily soiled hands or utensils. All populations are susceptible, while natural resistance to infection varies.

We have seen that cholera is an acute and potentially severe GI disease caused by Vibrio cholerae. V cholerae is a short, curved, motile, gram-negative, non-sporulating rod. Two serogroups (01, 0139) have been associated with cholera in humans, classical and El Tor. The organisms are strongly anaerobic, preferring alkaline and high-salt environments. They do not invade the intestinal mucosa but rather adhere to it. cholera is the prototype toxigenic diarrhea, which is secretory in nature.


Cholera toxin causes active secretion of chloride and blocks sodium absorption in the small intestine, with the colon relatively insensitive to the toxin. The large volume of fluid produced in the upper intestine overwhelms the capacity of the lower intestine to absorb. The diarrhea is classically thin, grayish brown.

Drying easily kills the organism. It is killed readily by dry heat, steam and boiling, short-term exposure to ordinary disinfectants, and chlorination of water.

It is not viable in pure water but survives up to 24 hours in sewage and as long as 6 weeks in certain types of relatively impure water containing organic matter. It can withstand freezing for 3-4 days.

Clinical Features

Infection generally occurs within the incubation period of 12-72 hours and depends on the dose of ingested organisms. Fever is rare. Initially, the disease presents with intestinal cramping and painless diarrhea. The syndrome is characterized by sudden onset of nausea and vomiting and profuse diarrhea with a classic rice water appearance. If untreated, the disease generally lasts 1-7 days. The clinical manifestations of cholera are related to the profound fluid and electrolyte depletion that occurs. Acute treatment consists of rapid, aggressive fluid resuscitation with isotonic solutions and potassium.

Children may experience seizures caused by hypoglycemia and hypernatremia and may have potassium depletion severe enough to cause an arrhythmia. The rapid loss of body fluids often leads to toxemia and frequent cardiovascular collapse. The mortality rate can range as high as 50% in untreated patients.


On microscopic examination of the stool, few or no red cells, white cells, and almost no protein are found. The absence of inflammatory cells and erythrocytes reflects the noninvasive character of V cholerae infection of the intestinal lumen. Identifying darting motile Vibrio species can identify the organism in liquid stool or enrichment broths by dark field or phase contrast microscopy and. Bacteriologic diagnosis is not necessary for treatment, as it can be diagnosed clinically.


Treatment focuses on replacement of fluids and electrolyte losses. This is accomplished primarily by using oral rehydration therapy, but intravenous fluid replacement is occasionally necessary for persistent vomiting or high rates of stool loss. Antibiotics shorten the duration of diarrhea and reduce fluid losses.


A licensed, killed vaccine is available for use in those considered to be at risk for exposure. The vaccine is protective for only approximately 50% of those immunized, and protection lasts for no more than 6 months. The vaccination schedule is an initial dose followed by another dose 4 weeks later, with booster doses every 6 months. An inactivated oral vaccine is safe and provides rapid short-term protection.


Tularemia a zoonosis is caused by the gram-negative, facultative intracellular bacterium Francisella tularensis. This has been referred as Deerfly Fever, or Rabbit fever and affects birds, reptiles, fish, people and approximately 250 species of mammals. It was originally isolated in 1911 by McCoy and Chapin from ground squirrels with a plague-like illness. Laboratory-related infections to humans with this organism are common.

The disease is characterized by fever, localized skin or mucous membrane ulceration, regional lymphadenopathy, and occasionally pneumonia. Tularensis has been considered an important BW agent because of its high infectivity after aerosolization.

History of Tularemia as a Bio Weapon

In the 1950s and 1960s, the US military developed weapons that would disseminate F. tularensis. From the 1940s to early 1990s, the Soviet Union was also developing tularemia weapons. Francisella tularensis is suitable for weaponization because it can be grown relatively easily, is relatively stable in liquid formulation, and is highly stable in a dry formulation.

Tularemia is caused by one of the most infectious pathogenic bacteria. Inhaling just 10 Francisella tularensis organisms can cause disease. The U.S. and Soviet bioweapon programs both developed tularemia weapons. Tularemia patients develop an ulcer at the infection site. The less common, inhaled form, causes sudden chills, fever, weight loss, abdominal pains, tiredness, headaches and an unusual pneumonia that can be fatal.

The World Health Organization estimates that releasing 50 kilograms of bacteria over a city of 5 million would cause 250,000 incapacitating causalities, including some 19,000 deaths. After incubating for one to 14 days, the disease causes a range of acute, non-specific feverish illnesses. Without antibiotic treatment, tularemia causes respiratory failure and shock; death rates reach 30 to 60 percent with some strains. A vaccine gives incomplete protection, but the disease moves so quickly that vaccination may fail unless given before exposure. There are no simple, rapid, and reliable tests to identify those potentially infected by a tularemia attack.

Vector Transmission

Humans and other mammals become infected with F. tularensis by a variety of modes. The principal reservoir in North America is the tick. In North America, the rabbit is the most common vertebrate associated with transmission of tularemia. In other areas of the world, tularemia is maintained in water rats and other aquatic animals.

F. Tularensis has been recovered from over 54 arthropod species, half of which are known to have transmitted the disease to humans. Ticks are an efficient reservoir as well as a vector for tularemia. In the United States, Dermacentor andersoni (the wood tick), Amblyomma americanum (the lone-star tick) and Dermacentor variabilis (the dog tick) as well as biting flies (e.g., deer flies, Chrysops discalis) and, less commonly, mosquitoes are all known vectors for F. tularensis. The housefly may also play a factor in disease transmission via mechanical transmission during which the flies transmit contaminated material on their legs (tarsal pads).


F. Tularensis usually is introduced into the host through breaks in the skin or through the mucous membranes of the eye, respiratory tract, or GI tract. After inoculation, F tularensis is ingested by and multiplies within macrophages. The host defense against F tularensis is mediated by a T cell-independent mechanism, which appears early after infection (<3 d), and a T cell-dependent mechanism, which appears later (>3 d) after infection. The role of humoral-medicated immunity and neutrophils in the host defense against F tularensis remains unclear.

Clinical Manifestations

Like anthrax, it presents as a cutaneous infection but may occur in gastrointestinal and inhalational forms. Clinical manifestations of natural infections may include a pneumonic form, a typhoidal form, an ulceroglandular form, a glandular form, an oculoglandular form and a gastrointestinal form.

Pneumonic tularemia: Pneumonic tularemia follows deposition of bacteria-bearing particles into the alveolar spaces by an aerosol infection. Macrophages ingest the bacteria, which reside within the phago-lysome and replicate. Eventually macrophages will lyse. Intracellular bacteria are transported by macrophages to mediastinal lymph nodes. Once multiplication has begun, disease follows rapidly. Patients present with fever, headache, muscle pain, shortness of breath, cough, and pleural pains. Chest X-ray may reveal spotted infiltrates in lungs, lobular pneumonia, and pleural exudation.

Typhoidal tularemia: Typhoidal tularemia is tularemia without an obvious site of inoculation. It is also referred to as systemic or septicemic tularemia. Symptoms of typhoidal tularemia include fever without visible foci on skin or without lymphadenopathy. This form of disease could be very difficult to diagnose without collecting a thorough medical history.

Ulceroglandular tularemia: Ulceroglandular tularemia occurs following the deposition of Francisella bacteria into the skin through cuts or abrasions. After the bacteria inoculate skin tissues, infection results in local ulcer and associated lymph node enlargement. This is the most common form of tularemia.

Glandular tularemia: Glandular tularemia typically presents as lymphadenopathy in the absence of an ulcer, usually as a result of contact with contaminated animal tissue or insect bite.

Oculoglandular tularemia: Oculoglandular tularemia is direct contamination of the eye via contaminated hands or possibly by aerosol exposure. Conjunctivitis and swelling of associated lymph nodes may occur.

Gastrointestinal (GI) tularemia: Gastrointestinal tularemia occurs as a result of ingestion of Francisella bacteria into the upper or lower gastrointestinal tract. Depending on the focus of infection, this can result in either the oropharyngeal (upper GI tract) or ileocecal form (lower GI tract).


Patients usually do not have abnormalities in the hemoglobin, hematocrit, or platelet count. The peripheral white blood cell count usually is elevated only mildly and often shows a lymphocytosis late in the disease. Patients may have microscopic pyuria, which may lead to erroneous diagnosis of urinary tract infection.

Diagnosis of acute tularemia infection should be confirmed by culture and identification of the bacterium, and may also involve direct or indirect fluorescent antibody test, or a positive antibody titer test. It is difficult to culture. Standard protocols for laboratory based tests can be found on the CDC website, Rapid diagnostic tests are not widely available in clinical laboratories, although with recent preparedness activities, they are available in state and regional labs, and clinical laboratory staff have increased awareness of tularemia.


Patients with tularemia who do not receive appropriate antibiotic therapy may have a prolonged illness characterized by malaise, weakness, and weight loss. With appropriate therapy, tularemia has a mortality rate of only 1-2.5%. Tetracycline and chloramphenicol are effective, but have been associated with significant relapse rates.


Tetracycline is effective after exposure to an aerosol of tularemia if administered within 24 hours of the exposure at an oral dose of 2 g/d for 14 days. A live attenuated vaccine has been developed and used in humans since 1940.

In the 1960s, a further purified derivative was introduced and called live vaccine strain (LVS). Extensive studies have demonstrated that the LVS vaccine protected humans against an aerosol challenge with virulent F tularensis.

The live vaccine strain was based on the virulent strain 15 of F. tularensis. This vaccine is not completely effective in preventing disease, but can lessen the severity of the disease, and was administered to large numbers of people in the former Soviet Union in the 1930s and 1940s. Vaccination is recommended for people at significantly increased risk of exposure to the organism; however, this vaccine is not currently available. The FDA is reviewing its safety.


The ease of transmission by aerosol suggests that Brucella species may be useful as a BW agent, which is the reason it is mentioned here. Brucellosis is a zoonotic infection of domesticated and wild animals caused by an organism of the genus Brucella.

The organism infects mainly cattle, sheep, goats, and other ruminants, causing abortion, fetal death, and genital infection. Humans, who usually are infected incidentally by contact with infected animals, may develop numerous symptoms in addition to the usual ones of fever, malaise, and muscle pain. The disease often becomes chronic and may relapse, even with appropriate treatment.


Brucellosis rarely, if ever, is transmitted from human to human. Brucella species are small, non-motile, non-sporulating, aerobic, gram-negative coccobacilli that may represent a single species. However, they are classified into 6 species. Each species has a characteristic predilection to infect certain animal species. Only Brucella melitensis, Brucella suis, Brucella abortus, and Brucella canis cause disease in humans.

Animals may transmit Brucella organisms during septic abortion, at the time of slaughter, and in their milk. Brucella species can enter mammalian hosts through skin abrasions or cuts, the conjunctiva, the respiratory tract, and the GI tract. Organisms are ingested rapidly by polymorphonuclear leukocytes, which generally fail to kill them. Organisms also are phagocytized by macrophages, which traffic to lymphoid tissue and eventually localize in lymph nodes, liver, spleen, joints, kidneys, and bone marrow. Brucellosis also can replicate extracellularly in host tissue. The host cellular response may range from abscess formation to granuloma formation with caseous necrosis.

Clinical Features

Clinical manifestations of brucellosis are diverse, and the course of the disease varies. Patients may present with an acute, systemic, febrile illness; an insidious chronic infection; or a localized inflammatory process. The disease may be abrupt or insidious in onset, with an incubation period of three days to several weeks. Patients usually have nonspecific symptoms such as fever, sweats, fatigue, anorexia, and muscle or joint aches. Neuropsychiatric symptoms such as depression, headache, and irritability occur frequently. In addition, focal infection of bones, joints, or the genitourinary tract may cause local pain. Cough and pleuritic chest pain also may be noted.

Symptoms often last 3-6 months, and occasionally for more than a year. Brucellosis usually does not cause leukocytosis, and patients may be neutropenic. B melitensis tends to cause more severe, systemic illness than the other Brucella species. B suis is more likely to cause localized superlative disease.

Infection with B melitensis leads to bone or joint disease in approximately 30% of patients. Sacroiliitis develops in 6-15%, particularly in young adults. Arthritis of large joints occurs with about the same frequency as sacroiliitis. In contrast to septic arthritis caused by pyogenic organisms, joint inflammation observed with B melitensis is mild, and erythema of overlying skin is uncommon. Synovial fluid is exudative, with cell counts in the low thousands, predominantly mononuclear. In both sacroiliitis and peripheral joint infections, destruction of bone is unusual. Organisms can be cultured from fluid in approximately 20% of patients. Spondylitis tends to affect middle-aged or elderly patients, causing back (usually lumbar) pain, local tenderness, and occasionally radicular symptoms.

Radiographic findings, similar to those of tuberculosis infection, include disk space narrowing. Paravertebral abscesses occur rarely. In contrast to frequent infection of the axial skeleton, osteomyelitis of long bones is rare. Infection of the genitourinary tract, an important target in ruminant animals, also may lead to signs and symptoms of disease in humans. Pyelonephritis, cystitis, and, in males, epididymo-orchitis may occur. Both diseases may mimic their tuberculosis counterparts with sterile pyuria on routine bacteriologic cultures.

Lung infections also have been described. Although as many as 25% of patients may complain of respiratory symptoms (mostly cough, dyspnea, or pleuritic pain), chest radiographic examinations usually are normal. Diffuse or focal infiltrates, pleural effusions, abscesses, and granulomas may be observed. Hepatitis and, rarely, liver abscess also occur. Mild elevations of serum lactase dehydrogenate and alkaline phosphatase levels are common. Biopsy findings may show well-formed granulomas or nonspecific hepatitis with collections of mononuclear cells.

Other sites of infection include the heart, central nervous system (CNS), and skin. Brucella endocarditis, a rare but feared complication, accounts for 80% of deaths from brucellosis. CNS infection usually manifests itself as chronic meningoencephalitis, but subarachnoid hemorrhage and myelitis also occur. Cases of skin abscess also have been reported.


A thorough history eliciting details of appropriate exposures (animals, animal products, environmental exposures) is the most important diagnostic tool. Strongly consider brucellosis in the differential diagnosis when military troops exposed to a biological attack have febrile illnesses. PCR and antibody-based antigen detection systems may demonstrate the presence of organisms in environmental samples collected from attack areas.

When the disease is considered, diagnosis usually is made based on serology. The tube agglutination test remains the criterion standard. This test reflects the presence of anti-O-polysaccharide antibody. Most patients already have high titers at the time of clinical presentation. Serum testing always should include dilution to at least 1:320. The tube agglutination test does not detect antibodies to B canis, because this organism does not have O-polysaccharide on its surface. In addition to serologic testing, pursue diagnosis by microbiologic cultures of blood or body fluid samples. Hold cultures for at least 2 months. The reported frequency of isolation from blood varies widely, from less than 10% to 90%. B melitensis is said to be cultured more readily than B abortus. Culture of bone marrow may increase the yield.


Therapy with a single drug has resulted in a high relapse rate; so combined use of antibiotic regimens is suggested. Several studies have demonstrated that treatment with a combination of streptomycin and doxycycline may result in less frequent relapse than treatment with the combination of rifampin and doxycycline.


Animal handlers should wear appropriate protective clothing when working with infected animals. Meat should be well cooked, and milk should be pasteurized. Laboratory workers should culture the organism only with appropriate Biosafety Level 2 or 3.

In the event of a biological attack, the standard gas mask should protect personnel adequately from airborne Brucella species. No commercially available vaccine exists for humans.

Q fever

Q fever is a zoonotic disease caused by Coxiella burnetii, a rickettsia like organism of low virulence but extremely infectious. Under experimental conditions, a single organism is capable of producing infection and disease in humans. A single organism may initiate infection. In addition, despite C burnetii being unable to grow or replicate outside host cells, a spore-like form of the organism is extremely resistant to heat, pressure, and many antiseptic compounds. This allows C burnetii to persist in the environment for long periods under harsh conditions.

In contrast to this high degree of inherent resilience and transmissibility, the acute clinical disease associated with Q fever is usually a benign, although temporarily incapacitating, illness in humans. Even without treatment, most patients recover.

The primary reservoir for natural human infection is livestock, particularly females, and the distribution is worldwide. Humans, who work in animal husbandry, are at risk of acquiring Q fever. The potential of C burnetii as a Bio War agent is related directly to its infectivity. It has been estimated that 50 kg of dried C burnetii would produce casualties at a rate equal to that of similar amounts of anthrax or tularemia organisms.


A number of different strains of C burnetii have been identified worldwide, and different clinical manifestations and complications may be associated with the various strains. The human is the only host identified that experiences an illness as a result of infection. Humans have been infected most commonly by contact with domestic livestock, particularly goats, cattle, and sheep. Survival of the organism on inanimate surfaces, such as straw, hay, or clothing, allows for transmission to individuals who are not in direct contact with infected animals.

Human infection with C burnetii is usually the result of inhalation of infected aerosols. Following this, host cells phagocytize the organisms. After phagocytosis by host cells, dissemination of the pathogen occurs as a result of circulation of organism free in the plasma, on the surface of the cells, and carried by circulatory macrophages.

Q fever develops without formation of a primary infectious focus in the area of the tick bite, and the organism does not infect the vascular endothelium, as do other rickettsial pathogens. The presence of a lipopolysaccharide on the cell surface of C burnetii protects the pathogen from host microbicidal activity.

Clinical Features

Incubation varies from 10-40 days. No characteristic illness is described for acute Q fever, and manifestations may vary considerably between locations where the disease is acquired. The onset of symptomatic Q fever may be abrupt or insidious.

Fever, chills, and headache are the most common signs and symptoms. Diaphoresis, malaise, myalgias, fatigue, and anorexia are also common. Arthralgias are relatively uncommon. Cough often occurs later in the illness. Chest pain occurs in a minority of patients. Although nonspecific, evanescent skin eruptions have been reported. Most patients appear mildly to moderately ill. The temperature tends to fluctuate, with peaks at 39-40°C, and is biphasic in approximately 25% of patients. The fever generally lasts less than 13 days but has been reported to last longer in older adults.

Patients with acute Q fever may present with a clinical picture of acute hepatitis with elevations of aminotransferases that are 2-to 3-fold higher than the upper limit of normal.

Chronic infection with C burnetii usually is manifested by infective endocarditis, which also is the most severe complication of Q fever. In addition, hepatitis, infected vascular prostheses, aneurysms, osteomyelitis, pulmonary infection, cutaneous infection, and an asymptomatic form have been reported. The diagnosis of infective endocarditis secondary to Q fever is confirmed by serologic testing.


Diagnosis of Q fever usually is accomplished using serologic testing; the most common methods are complement fixation, indirect fluorescent antibody, and ELISA. Significant antibody titers usually are not identifiable until 2-3 weeks into the illness.

Of the methods currently used for the diagnosis of Q fever, ELISA is the most sensitive and easiest to perform. This assay can establish a diagnosis of Q fever from a single serum specimen with a sensitivity of 80-84% in early convalescence and 100% in intermediate and late convalescence.


Tetracycline has been the mainstay of therapy since the 1950s. When initiated within the first few days of the illness, treatment significantly shortens its course. Erythromycin and azithromycin, are also effective.

Prevention /Prophylaxis

Although an effective vaccine (Q-Vax) is licensed in Australia, all Q fever vaccines used in the United States are investigational.


In 1980, the World Health Organization (WHO) declared endemic smallpox eradicated, with the last occurrence in Somalia in 1977. Smallpox was an important cause of morbidity and mortality in the developing world until recent times.

Variola, the causative agent of smallpox, is the most notorious of the poxviruses (family Poxviridae). Variola represents a significant threat as a Bio War agent. Variola is highly infectious and is associated with a high mortality rate and secondary spread. Currently, the majority of the U.S. population has no immunity, little vaccine is readily available, and no effective treatment exists for the disease.

Currently, two WHO-approved and inspected repositories remain: the CDC in the United States and Vector Laboratories in Russia; however, clandestine stockpiles may exist.


Variola virus is highly infectious by aerosol, environmentally stable, and can retain infectivity for long periods. After exposure to aerosolized virus, the virus multiplies locally in the respiratory tract. Incubation is a period of 7-17 days then variola is spread hematogenously (primary viremia) to regional lymph nodes, where additional replication occurs.

Subsequently, variola is spread to small dermal blood vessels, where skin inflammatory changes (pox) occur. Two types of smallpox generally are recognized. Variola major, the most severe form, has a fatality rate of 30% in unvaccinated individuals and 3% in those previously vaccinated. Variola minor, a more mild form of smallpox, produces lethality in only 1% of unvaccinated individuals.

Clinical Signs

Variola Major. After a 7-to 17-day incubation period, symptoms begin acutely with high fever, headache, rigors, malaise, myalgias, vomiting, and abdominal and back pain. During the initial phase, 15% of patients develop delirium. After 2-3 days, an exanthem (rash) develops on the face, hands, and forearms and extends gradually to the trunk and lower extremities. The lesions progress synchronously from macules to papules to vesicles to pustules. Centrifugal distribution of the rash is an important diagnostic feature, with a greater number of lesions on the face and extremities compared to the trunk. Patients are most infectious on days 3-6 after the onset of fever. Virus is shed from oropharyngeal and respiratory secretions.

Variola Minor. In variola minor cutaneous lesions are similar but smaller and fewer in number. Patients are not as ill as those who have variola major. Small numbers (3%) of patients develop hemorrhagic lesions, and these patients typically die of disease before papules develop. Flat smallpox with macular, soft, velvety lesions develops in 4% of patients and forebodes a poor prognosis. Frequently, patients with modified disease form no pustules.


The most difficult aspect of diagnosing smallpox is the current lack of familiarity with the disease for most physicians. Chicken pox, or allergic contact dermatitis, can look similar. Smallpox is distinguished from chicken pox by the centrifugal distribution of its rash and the presence of lesions at the same stage of development everywhere on the body.

The failure to recognize mild cases of smallpox in persons with partial immunity permits rapid person-to-person transmission. Exposed people may shed virus from the oropharynx without ever manifesting disease. The usual method of diagnosis is demonstration of characteristic virions on electron microscopy of vesicular scrapings.


It is critical for medical personnel to recognize a vesicular presentation as possible smallpox. Immediate reporting of all possible cases must be made to public health authorities and to the chain of command. Strict quarantine with respiratory isolation for 17 days is applied to all people in direct contact with the index case or cases.

All personnel exposed to either weaponized variola or clinical cases must be vaccinated immediately. Immediate vaccination is effective at ameliorating or preventing illness if accomplished within a few days of exposure. Administer vaccinia immune globulin (VIG) to patients who cannot receive the vaccine. Treatment of smallpox is mainly supportive. The antiviral agent cidofovir is effective in vitro and may be involved in treatment of symptomatic illness.


Smallpox vaccine is made from live vaccinia virus and does not contain variola virus. It is administered by intradermal inoculation with a bifurcated needle. The permanent scar results from a process known as scarification. A vesicle usually appears 5-7 days after inoculation; scabbing over and healing of the site occur over the next 1-2 weeks. Common adverse effects include low-grade fever and axillary lymphadenopathy. The most frequent complication is inadvertent inoculation to other skin or mucous membrane sites or to other people.

Residual Immunity

Protection against disease following primary vaccination begins to fade after 5 years and is probably negligible after 20 years. In individuals who have been successfully revaccinated one or more times, it has been found that residual immunity may persist for 30 years or longer. Epidemiological evidence indicates that vaccination within 2-3 days after exposure to smallpox can result in protection against the disease and, even as late as 4 to 5 days, may protect against a fatal outcome. Relative contraindications include immunosuppression, HIV, pregnancy, and history or evidence of eczema and other skin diseases.


The first case of human monkeypox was identified in 1970, with subsequently confirmed cases totaling less than 400. The monkeypox virus is a naturally occurring relative of variola that is formed in Africa. Some concern exists that monkey pox may be weaponized; however, human monkeypox is less virulent than smallpox. However, pneumonia due to monkeypox has approximately a 50% mortality rate.

The clinical picture of monkeypox is clinically indistinguishable from smallpox with the exception of enlarged cervical and inguinal lymph nodes. The virus is transmitted by respiratory aerosol or direct contact with an infected individual. Immunization against the virus provides protection to 85% of individuals exposed to monkeypox. The treatment for monkeypox remains supportive.

Viral Encephalitides

In the 1930s these viruses first were recovered from horses. Venezuelan equine encephalitis, (VEE) was isolated in Venezuela, western equine encephalitis (WEE) in the San Joaquin Valley of California in 1930, and eastern equine encephalitis (EEE) in Virginia and New Jersey in 1933. The viral encephalitides, (VEE) virus, (WEE) virus, and (EEE) virus, are members of the Alphavirus genus and regularly are associated with encephalitis.

Alphaviruses replicate readily to very high titers and are relatively stable. Although natural infections with these viruses occur following bites from mosquitoes, the viruses also are highly infectious by aerosol. The intentional release as a small-particle aerosol may be expected to infect a high percentage of individuals within an area of a least 10,000 km.


After exposure to these viruses, the tissues of the CNS lymphoid systems are most commonly affected in both humans and animals. A systemic viral febrile syndrome characterizes most infections.

VEE virus has the capacity to produce large human epidemics. Outcomes are significantly worse for young and elderly patients, with case fatalities ranging from 4-35%. WEE and EEE typically produce less fatality rate of 50-75% in those with severe illness.

Clinical Manifestations

After an incubation period of 2-6 days, patients with VEE develop fevers, chills, headache, malaise, myalgias, sore throat, and photophobia. CNS manifestations range from mild confusion and lethargy to seizures, paralysis, and coma. For those that survive, CNS recovery usually is complete.

The incubation period for EEE varies from 5-15 days. Adults may exhibit a viral malaise of up to 11 days before the onset of CNS manifestations. Signs and symptoms include fever, chills, vomiting, muscle rigidity, lethargy, excess salivation, and impaired respiratory regulation. Children frequently develop facial and periorbital edema. CNS effects range from mild confusion to seizures and paralysis. WEE has an incubation period of 5-10 days. Most patients are asymptomatic or have a nonspecific febrile illness, aseptic meningitis picture. Manifestations include fever, nausea, vomiting, malaise, headache, nuchal rigidity, and lethargy. The severity of CNS involvement is inversely proportional to age. Typically, adults recover completely.


Virus may be collected from the nasopharynx for 3 days after the onset of symptoms.


No specific treatment is available for the viral encephalitides. Supportive care may include aggressive airway management and antipyretic and anticonvulsant drug administration.


There is a live attenuated vaccine for VEE. It is administered as 0.5-mL subcutaneous injection for those at high risk, such as laboratory field personnel. Approximately 20% of those who receive the vaccine fail to make a minimum neutralizing antibody response. An additional 25% of those vaccinated develop high fever, chills, and malaise and would require bed rest.

There is an inactivated vaccine that produces only mild tenderness at the injection site. The EEE vaccine (inactivated) is administered in a 0.5-mL subcutaneous injection on days 0 and 28. Minimal side effects are noted, and no long-term problems have occurred. Like the EEE vaccine, the VEE vaccine is inactivated, produces no adverse effects, and requires boosters. The vaccine is administered on days 0, 7, and 28.

Viral Hemorrhagic Fevers

The CDC classified the Hemorrhagic fever (HFV’s) as a Category A Bioweapon because of its potential to spread, (Filoviridae viruses responsible for Hemorrhagic fever, have been “weaponized” by the former Soviet Union and the United States. There have also been reports that Yellow Fever may have been weaponized by North Korea.)

Biological weapons programs in the United States and the Soviet Union developed techniques for aerosolizing Y pestis (plague), thus enhancing the effectiveness of the agent as a potential biological weapon. (Inglesby 2000: Plague as a biological weapon).

The best known of the viral hemorrhagic fever agents is Ebola virus. All

VHF’s are highly infectious via the aerosol route, and most are stable as respiratory aerosols. Thus, they possess characteristics ideal for use by terrorists.


Ricin, a plant protein toxin derived from the beans of the castor plant, is one of the most toxic and easily produced of the plant toxins. Although the lethal toxicity of ricin is approximately 1000 times less than botulinum toxin, the worldwide ready availability of castor beans and the ease with which toxin can be produced give it significant potential as a biological weapon.

Since ancient times, more than 750 cases of ricin intoxication have been described. Ricin may have been used in the highly published assassination of Bulgarian exile Georgi Markov in London in 1978. He was attacked with a device that implanted a pellet containing ricin into his thigh.


The toxicity of ricin varies greatly with the route of administration. Ricin is extremely toxic to cells and acts by inhibiting protein synthesis. Inhalation exposure causes primarily pulmonary symptoms, ingestion causes GI symptoms, and intramuscular exposure results in a localized reaction.

Clinical Manifestations

Following inhalation exposure of ricin, toxicity is characterized by the sudden onset of nasal and throat congestion, nausea and vomiting, itching of the eyes, urticaria, and tightness in the chest. If exposure is significant, pulmonary manifestations occur after 12-24 hours and include airway lesions, alveolar flooding, as well as severe respiratory distress. In animal studies, death occurs 36-48 hours after severe exposure.

Ingestion of ricin is generally less toxic because of its poor absorption and enzymatic degradation in the digestive tract. Out of 751 ingestions recorded, only 14 resulted in a fatality. Clinical manifestations occur rapidly and are characterized by nausea, vomiting, abdominal pain and cramping, diarrhea, fever and chills, hematochezia, and eventually, shock and vascular collapse. Autopsy findings have revealed significant hepatic, splenic, and renal necrosis.

At low doses, intramuscular exposures produce flu-like symptoms, myalgias, and nausea, vomiting, and localized pain and swelling at the injection site. Severe intoxication results in local lymphoid necrosis and GI hemorrhage, as well as diffuse hepatic, splenic, and renal necrosis.


The diagnosis of ricin poisoning is made on the basis of clinical and epidemiologic factors. In a terrorist situation, exposure is likely to occur by inhalation of a toxin aerosol. Consider ricin poisoning when patients experience upper airway and pulmonary symptoms in the setting of a known or suspected mass casualty incident.

Patients may have neutrophilic leukocytosis, hypoxemia, and bilateral infiltrates on chest radiograph. Confirmation of ricin exposure can be made by ELISA analysis of a swab sample from nasal mucosa. Ricin can be identified for up to 24 hours after exposure.


Treatment is supportive. Determine specific treatment largely by the route of exposure and clinical manifestations. Following ingestion, patients should rapidly undergo GI decontamination with gastric lavage and the administration of activated charcoal. Intravenous crystalloid infusion support may be necessary for patients with hypotension.


Currently, no vaccine is available for ricin exposure. Investigational vaccines have proven effective in animals. Some chemotherapeutic agents are being studied as well.

Botulinum Toxin

The anaerobic, spore-forming, gram-positive bacillus Clostridium botulinum produces botulinum toxins as we saw earlier in this course. Botulinum toxins are the most lethal toxins known, with an estimated lethal dose to 50% of the exposed population. Since botulinum toxin is extremely lethal and easy to manufacture and weaponize, it represents a credible threat as a BioWar agent. Exposure is likely to occur following inhalation of aerosolized toxin or ingestion of food contaminated with the preformed toxin or microbial spores. In 1995, Iraq admitted to active research on the offensive use of botulinum toxins and to weaponizing and deploying more than 100 munitions with botulinum toxin.


Botulinum toxins bind to the pre-synaptic nerve terminal at the neuromuscular junction and cholinergic autonomic sites. This prevents the pre-synaptic release of acetylcholine and blocks neurotransmission. Interruption of neurotransmission produces muscular weakness and paralysis.

Clinical Manifestations

Initial signs and symptoms include blurred vision, mydriasis, ptosis, dysphagia, dysarthria, dysphonia, and muscle weakness. After 24-48 hours, neuromuscular manifestations progress to symmetric descending paralysis and respiratory failure. Varying degrees of muscular weakness may occur. Patients may become cyanotic or exhibit narcosis from carbon dioxide retention secondary to respiratory failure. Postural hypotension may occur from autonomic insufficiency. Deep tendon reflexes may be depressed or absent on physical examination. Cranial nerve palsies often are present.


The occurrence of multiple related cases of descending and progressive bulbar and skeletal paralysis in afebrille patients should suggest the diagnosis of botulinum toxicity. Laboratory tests, including CSF studies, generally are not helpful. Oral exposure can be detected by analyzing serum or gastric contents with a mouse neutralization assay. Intoxication by inhalation can be diagnosed using ELISA identification from nasal swabs up to 24 hours after exposure.


The most serious complication of toxicity is respiratory failure. With supportive care and ventilator assistance, fatalities should be less than 5%. For confirmed exposures, a trivalent equine antitoxin is available from the CDC. This antitoxin has all of the disadvantages of horse serum products, including the risks of anaphylaxis and serum sickness.


A toxoid for C botulinum was used to immunize US military troops in the Persian Gulf War. Currently, no indication exists for prophylactic use of the antitoxin except under specialized circumstances.


The trichothecene mycotoxins are a diverse group of more than 40 compounds produced by fungi. They are highly toxic compounds produced by certain species of filamentous fungi (Fusarium, Myrotecium, Cephalosporium, Trichoderma, Verticimonosporium, Stachybotrys species). These mycotoxins cause multiple organ effects, which include emesis, diarrhea, weight loss, nervous disorders, cardiovascular alterations, immunosuppression, skin toxicity, and bone marrow damage.

Because of their antipersonnel properties, ease of large-scale production, and amenability to dispersal by various methods (dusts, droplets, aerosols, smoke, rockets, artillery mines, portable sprays), mycotoxins have an excellent potential for weaponization.

Strong evidence suggests that trichothecenes (‘yellow rain’) have been used as a BioWar agent in Southwest Asia and Afghanistan. From 1974-1981, numerous attacks resulted in at least 6310 deaths in Laos, 981 deaths in Cambodia, and 3042 deaths in Afghanistan.


Extraction of the mycotoxin from fungal cultures yields a yellow-brown liquid that evaporates into a yellow crystalline product (thus, the ‘yellow rain’ nomenclature). These toxins are nonvolatile, low molecular weight compounds that are highly soluble in acetone, ethyl acetate, chloroform, ethanol, methanol, and propylene glycol. The trichothecenes vaporize when heated in organic solvents. These toxins require a 3-5% sodium hydroxide solution and heating at 900°F for 10 minutes or 500°F for 30 minutes for complete inactivation.

Rapid absorption from the gut or pulmonary mucosa can produce initial symptoms in 5 minutes and maximal effects by 60 minutes. The trichothecene mycotoxins are cytotoxic to most eukaryotic cells by way of inhibiting protein synthesis and electron transport.

Clinical Manifestations

Cutaneous manifestations include burning, tender erythema, edema, and blistering with progression to dermal necrosis and sloughing of large skin areas in lethal cases. Respiratory exposure results in nasal itching, pain, sneezing, epistaxis, rhinorrhea, dyspnea, wheezing, cough, and blood-tinged saliva and sputum. This starts to happen almost immediately after exposure.

GI toxicity consisting of: anorexia, nausea and vomiting, abdominal cramping, and watery and/or bloody diarrhea. Following entry into the eyes, pain, tearing, redness, and blurred vision occur. Systemic toxicity may occur and includes weakness, prostration, dizziness, ataxia, tachycardia, hyperthermia or hypothermia, diffuse bleeding, and hypotension. Death may occur within minutes to days depending on the dose and route of exposure.


Many patients presenting with the above symptoms and reporting a yellow rain or smoke attack lend support to the diagnosis. Initial laboratory studies are nonspecific. Elevations of serum creatinine, potassium, and phosphorus may occur, as well as abnormalities of coagulation parameters. An initial rise in absolute neutrophils can be observed. Leukopenia, thrombocytopenia, and anemia may occur 2-4 weeks following initial exposure.


The immediate use of protective clothing and masks during a mycotoxin aerosol attack should prevent illness. If a person is unprotected during an attack, the outer clothing should be removed within 4-6 hours and decontaminated with 5% sodium hydroxide for 6-10 hours. The skin should be washed with copious amounts of soap and uncontaminated water. The eyes, if exposed, should be irrigated with copious amounts of normal saline or sterile water.

After appropriate skin decontamination, give victims of inhalation and oral exposures super activated charcoal orally. Activated charcoal binds mycotoxins. Treat severe respiratory distress with endotracheal intubation and mechanical ventilation as needed. Early use of systemic steroids increases survival time by decreasing the primary injury and shock like state that follows significant poisoning.


No vaccine exists for trichothecene mycotoxin exposure.

Staphylococcal Enterotoxin B.

Staphylococcal enterotoxin B (SEB) is part of a family of enterotoxins commonly associated with food-borne illness. It can be purified into a powder or a mist. Staphylococcal enterotoxin B as a weapon and can be released into the air.

It also may be put into food and public water supplies. Staphylococcus aureus produces a number of exotoxins, one of which is Staphylococcal enterotoxin B, or SEB. Such toxins are referred to as exotoxins since they are excreted from the organism; however, they normally exert their effects on the intestines and therefore are called enterotoxins.

SEB is one of the toxins that commonly causes food poisoning in humans after the toxin is produced in improperly handled foodstuffs and subsequently ingested. SEB has a very broad spectrum of biological activity. This toxin causes a markedly different clinical syndrome when inhaled than it characteristically produces when ingested. Significant morbidity is produced in individuals who are exposed to SEB by either portal of entry to the body.


Staphylococcal enterotoxins produce a variety of toxic effects. Inhalation of SEB can induce extensive pathophysiological changes to include widespread systemic damage and even septic shock. Many of the effects of staphylococcal enterotoxins are mediated by interactions with the host’s own immune system.

The mechanisms of toxicity are complex, but are related to toxin binding directly to the major histocompatibility complex that subsequently stimulates the proliferation of large numbers of T cell lymphocytes. Because these exotoxins are extremely potent activators of T cells, they are commonly referred to as bacterial superantigens. These superantigens stimulate the production and secretion of various cytokines, such as tumor necrosis factor, interferon, interleukin-1 and interleukin-2, from immune system cells. Released cytokines are thought to mediate many of the toxic effects of SEB.


As is the case with botulinum toxins, intoxication due to SEB inhalation is a clinical and epidemiologic diagnosis. Because the symptoms of SEB intoxication may be similar to several respiratory pathogens such as influenza, adenovirus, and mycoplasma, the diagnosis may initially be unclear.

All of these might present with fever, nonproductive cough, myalgia, and headache. SEB attack would cause cases to present in large numbers over a very short period of time, probably within a single 24-hour period.

Naturally occurring staphylococcal food poisoning cases would not present with pulmonary symptoms. SEB intoxication tends to progress rapidly to a fairly stable clinical state, whereas pulmonary anthrax, tularemia pneumonia, or pneumonic plague would all progress if left untreated. Tularemia and plague, as well as Q fever, would be associated with infiltrates on chest radiographs. Nerve agent intoxication would cause fasciculation and copious secretions, and mustard would cause skin lesions in addition to pulmonary findings; SEB inhalation would not be characterized by these findings. The dyspnea associated with botulinum intoxication is associated with obvious signs of muscular paralysis, bulbar palsies, lack of fever, and a dry pulmonary tree due to cholinergic blockade; respiratory difficulties occur late rather than early as with SEB inhalation.

Laboratory findings are not very helpful in the diagnosis of SEB intoxication.


Symptoms include: Cough, difficulty breathing, chest pain and fluid in the lungs (three to 15 hours after contact), Rapid heart rate, headache, nausea and vomiting (three to 15 hours after contact), and fever and muscle pain (eight to 20 hours after contact).

Treatment for SEB Poisoning

Prevention of illness after contact: First, leave the area where the SEB was released and move to fresh air. Remove clothing. Quickly take off clothing that may have SEB on it. If possible, any clothing that has to be pulled over the head should be cut off the body instead so the SEB does not get near the eyes, mouth or nose. If helping other people remove their clothing, try to avoid touching any areas that may have SEB on them, and remove the clothing as fast as possible. Wash affected areas. As quickly as possible, wash any SEB from the skin with lots of soap and water. If the eyes are burning or vision is blurred, rinse the eyes with plain water for 10 to 15 minutes. Remove contact lenses. Wash eyeglasses. Contact the local county health department.


It is thought that BioWar agents could come as toxins, bacteria, or viruses, or new genetically manipulated entities. Potential victims of BioWar agents or natural pandemics should be in isolation. Medical personnel caring for these patients would need protection such as a HEPA mask in addition to standard precautions pending the results of a more complete evaluation.

Epidemiologists and public health departments are working towards creating systems of surveillance and communication within the system. Although now no government is fully prepared for quarantines, or massive vaccines, many agencies are focusing their attention on probable scenarios.