BENCHMARK I

PART 3

1) Biological Agents.

Bacteria: . Anthrax . Bubonic Plague

. Cholera . Tularemia

. Pneumonic Plague . Q Fever

Virus: . Smallpox

. Venezuelan Equine Encephalitis

. Viral Hemorrhagic Fevers

Toxin: . Botulinum

. Staphylococcal Enterotoxin B

. Saxitoxin

. Ricin

. Mycotoxins

Biological Warfare Agents

And Their Effects

Anthrax

Anthrax is a zoonotic disease caused by Bacillus anthracis. There are two types of this disease: cutaneous anthrax and inhalation anthrax. Cutaneous anthrax develops when a bacterial organism from infected animal tissues becomes deposited under the skin.

The disease begins after an incubation period varying from 1-6 days.

Inhalation anthrax develops when the bacterial organism is inhaled into the lungs. A progressive infection follows.

A lethal dose of anthrax is considered to be 10,000 spores; 80 percent of a population that inhaled such a dose would die. Less than one millionth of a gram is invariably fatal within five days to a week after exposure.

The initial symptoms are followed in 2-3 days by the abrupt development of severe respiratory distress with dyspnea, diaphoresis, strider, and cyanosis. Physical findings may include evidence of pleural effusions, edema of the chest wall, and meningitis. Chest x-ray reveals a dramatically widened mediastinum, often with pleural effusions, but typically without infiltrates. Shock and death usually follow within 24-36 hours of respiratory distress onset.

A biological warfare attack with anthrax spores delivered by aerosol would cause inhalation anthrax, an extraordinarily rare form of the naturally occurring disease.

Botulinum Toxins

Botulism is caused by intoxication with the any of the seven distinct neurotoxins produced by the bacillus, Clostridium botulinum. The toxins are proteins with molecular weights of approximately 150,000, which bind to the presynaptic membrane of neurons at peripheral cholinergic synapses to prevent release of acetylcholine and block neurotransmission.

Symptoms of inhalation botulism may begin as early as 24-36 hours following exposure or as late as several days. Initial signs and symptoms include ptosis, generalized weakness, lassitude, and dizziness. Diminished salivation with extreme dryness of the mouth and throat may cause complaints of a sore throat. Urinary retention or ileus may also occur. Motor symptoms usually are present early in the disease; cranial nerves are affected first with blurred vision, diplopia, ptosis, and photophobia. Development of respiratory failure may be abrupt. Mucous membranes of the mouth may be dry and crusted. Neurological examination shows flaccid muscle weakness of the palate, tongue, larynx, respiratory muscles, and extremities. Deep tendon reflexes vary from intact to absent.

Respiratory failure secondary to paralysis of respiratory muscles is the most serious complication and, generally, the cause of death.

A biological warfare attack with botulinum toxin delivered by aerosol would be expected to cause symptoms similar in most respects to those observed with food-borne botulism.

Brucellosis.

Brucellosis is a systemic zoonotic disease caused by one of four species of bacteria: Brucella melitensis, B. abortus, B. suis, and B. canis; virulence for humans decreases somewhat in the order given. These bacteria are small gram-negative, aerobic, non-motile coccobacilli that grow within monocytes and macrophages. Their natural reservoir is domestic animals, such as goats, sheep, and camels (B. melitensis); cattle (B. abortus); and pigs (B. suis). Brucella canis is primarily a pathogen of dogs, and only occasionally causes disease in humans. Humans are infected when they inhale contaminated aerosols, ingest raw (unpasteurized) infected milk or meat, or have abraded skin or conjunctival surfaces that come in contact with the bacteria.

Brucellosis presents after an incubation period normally ranging from 3-4 weeks, but may be as short as 1 week or as long as several months. Clinical disease presents typically as an acute, non-specific febrile illness with chills, sweats, headache, fatigue, myalgias, arthralgias, and anorexia. Cough occurs in 15-25%, but the chest x-ray usually is normal. (Complications include sacroiliitis, arthritis, vertebral osteomyelitis, epididymo-orchitis, and rarely endocarditis. Physical findings include Iymphadenopathy in 10-20% and splenomegaly in 20-30% of cases). Brucellosis may be indistinguishable clinically from the typhoidal form of tularemia or from typhoid fever itself. The disease in humans is characterized by a multitud e of somatic complaints, including fever, sweats, anorexia, fatigue, malaise, weight loss, and depression.

When used as a biological warfare agent, Brucellae would most likely be delivered by the aerosol route; the resulting infection would be expected to mimic natural disease.

Cholera.

Cholera is a diarrheal disease caused by Vibrio cholera, a short, curved, gram-negative bacillus. Humans acquire the disease by consuming water or food contaminated with the organism. The organism multiplies in the small intestine and secretes an enterotoxin that causes a secretory diarrhea. Without treatment, death may result from severe dehydration, hypovole mia and shock. Vomiting is often present early in the illness and may complicate oral replacement of fluid losses. There is little or no fever or abdominal pain.

Watery diarrhea can also be caused by enterotoxigenic E. coli, rotavirus or other viruses, noncholera vibrios, or food poisoning due to ingestion of preformed toxins such as those of Clostridium perfringens, Bacillus cereus, or Staphylococcus aureus.

When employed as a BW agent, cholera will most likely be used to contaminate water supplies. It is unlikely to be used in aerosol form.

Clostridium Perfringens Toxins.

Clostridium perfringens is a common anaerobic bacterium associated with three distinct disease syndromes; gas gangrene or clostridial myonecrosis; enteritis necroticans (pig-bel); and clostridium food poisoning.

It is difficult to imagine a general scenario in which the spores or vegetative organisms could be used as a biological warfare agent. There are, however, at least 12 protein toxins elaborated, and one or more of these could be produced, concentrated, and used as a weapon. Waterborne disease is conceivable, but unlikely. The alpha toxin would be lethal by aerosol. This is a well characterized, highly toxic phospholipase C. Other toxins from the organism might be co-weaponized and enhance effectiveness.

Gas gangrene is a well-recognized, life-threatening emergency. Symptoms of the disease may be subtle before fulminant toxemia develops, and the diagnosis is often made at postmortem examination. The bacteria produce toxins that create the high mortality from clostridial myonecrosis, and which produce the characteristic intense pain out of proportion to the wound. Within hours signs of systemic toxicity appear, including confusion, tachycardia, and sweating.

Congo-Crimean Hemorrhagic Fever.

Congo-Crimean hemorrhagic fever (CCHF) is a viral disease caused by CCHF virus. The virus, first isolated in Congo, next found in the Crimea, occurs also in the Middle East, the Balkans, the former USSR, and eastern China.

Little is known about variations in the virus properties over the huge geographic area involved. Humans become infected through tick bites, crushing an infected tick, or at the slaughter of viremic livestock. Even in epidemics, cases do not show narrow clustering and person-to-person spread is rare.

Following infection via tick bite, the incubation period is usually one to three days, with a maximum of nine days. The incubation period following contact with infected blood or tissues is usually five to six days, with a documented maximum of 13 days. There is severe headache, lumbar pain, nausea and vomiting, delirium, and prostration. Fatal cases are associated with extensive hemorrhage, coma, and shock.

Convalescence in survivors is prolonged with asthenia, dizziness, and often hair loss.

Patients with suspected or confirmed CCHF should be isolated and cared for using barrier nursing techniques.

The virus is aerosol-infectious and additional precautions (for example, respirators) might be considered in a biological warfare setting.

CCHF would probably be delivered by aerosol if used as a BW agent.

Ebola Haemorrhagic Fever

Ebola Haemorrhagic Fever is one of the most virulent viral diseases known to humankind, causing death in 50-90% of all clinical cases.

The disease has its origins in the jungles of Africa and Asia and several different forms of Ebola virus have been identified and may be associated with other clinical expressions, on which further research is required.

The Ebola virus is transmitted by direct contact with the blood, secretions, organs or semen of infected persons. Transmission through semen may occur up to 7 weeks after clinical recovery, as with Marburg Haemorrhagic fever.

After an incubation period of 2 to 21 days, Ebola is often characterised by the sudden onset of fever, weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, limited kidney and liver functions, and both internal and external bleeding

Suspected cases should be isolated from other patients and strict barrier nursing techniques practised. All hospital personnel should be briefed on the nature of the disease and its routes of transmission.

Hospital staff should have individual gowns, gloves and masks. Gloves and masks must not be reused unless disinfected. Patients who die from the disease should be promptly buried or cremated.

Consequently, it has figured prominently in popular discussions of biological warfare.

As a biological warfare agent remain speculative.

Melioidosis.

Melioidosis is an infectious disease of humans and animals caused by Pseudomonas pseudomallei, a gram-negative bacillus. It is especially prevalent in Southeast Asia but has been described from many countries around the world.

Infection by inoculation results in a subcutaneous nodule with acute lymphangitis and regional lymphadenitis, generally with fever. Pneumonia may occur after inhalation or hematogenous dissemination of infection. It may vary in intensity from mild to fulminant, usually involves the upper lobes, and often results in cavitation. Pleural effusions are uncommon. An acute fulminant septicemia may occur characterized by rapid appearance of hypotension and shock. A chronic suppurative form may involve virtually any organ in the body.

A biological warfare attack with this organism would most likely be by the aerosol route.

Plague.

Plague is a zoonotic disease caused by Yersinia pestis. Under natural conditions, humans become infected as a result of contact with rodents, and their fleas. The transmission of the gram-negative coccobacillus is by the bite of the infected flea, Xenopsylla cheopis, the oriental rat flea, or Pulex irritans, the human flea. Under natural conditions, three syndromes are recognized: bubonic, primary septicemia, or pneumonic. In bubonic plague, the incubation period ranges from 2 to 10 days. The onset is acute and often fulminant with malaise, high fever, and one or more tender lymph nodes. Inguinal lymphadenitis (bubo) predominates, but cervical and axillary lymph nodes c an also be involved. The involved nodes are tender, fluctuant, and necrotic. Bubonic plague may progress spontaneously to the septicemia form with organisms spread to the central nervous system, lungs (producing pneumonic disease), and elsewhere. The mortality is 50 percent in untreated patients with the terminal event being circulatory collapse, hemorrhage, and peripheral thrombosis.

o In primary pneumonic plague, the incubation period is 2 to 3 days. The onset is acute and fulminant with malaise, high fever, chills, headache, myalgia, cough with production of a bloody sputum, and toxemia. The pneumonia progresses rapidly, resulting in dyspnea, strider, and cyanosis. In untreated patients, the mortality is 100 percent with the terminal event being respiratory failure, circulatory collapse, and a bleeding diathesis.

Plague may be spread from person to person by droplets. Strict isolation procedures for all cases are indicated

In a biological warfare scenario, the plague bacillus could be delivered via contaminated vectors (fleas) causing the bubonic type or, more likely, via aerosol causing the pneumonic type.

Q Fever.

Q fever is a zoonotic disease caused by a rickettsia, Coxiella burnetii. The most common animal reservoirs are sheep, cattle and goats. Humans acquire the disease by inhalation of particles contaminated with the organisms. A biological warfare attack would cause disease similar to that occurring naturally.

Following an incubation period of 10-20 days, Q fever generally occurs as a self-limiting febrile illness lasting 2 days to 2 weeks. Pneumonia occurs frequently, usually manifested only by an abnormal chest x-ray. A nonproductive cough and pleuritic chest pain occur in about one-fourth of patients with Q fever pneumonia. Patients usually recover uneventfully.

Q fever usually presents as an undifferentiated febrile illness, or a primary atypical pneumonia, which must be differentiated from pneumonia caused by mycoplasma, legionnaire's disease, psittacosis or Chlamydia pneumonia. More rapidly progressive forms of pneumonia may look like bacterial pneumonias including tularemia or plague.

A biological warfare attack would cause disease similar to that occurring naturally.

Ricin.

Ricin is a glycoprotein toxin (66,000 daltons) from the seed of the castor plant. It blocks protein synthesis by altering the rRNA, thus killing the cell.

All reported serious or fatal cases of castor bean ingestion have taken approximately the same course: rapid onset of nausea, vomiting, abdominal cramps and severe diarrhea with vascular collapse; death has occurred on the third day or later. Following inhalation, one might expect nonspecific symptoms of weakness, fever, cough, and hypothermia followed by hypotension and cardiovascular collapse. The exact cause of death is unknown and probably varies with route of intoxication. High doses by inhalation appear to produce severe enough pulmonary damage to cause death.

Ricin's significance as a potential biological warfare agent relates to its availability world wide, its ease of production, and extreme pulmonary toxicity when inhaled.

Rift Valley Fever.

Rift Valley Fever (RVF) is a viral disease caused by RVF virus. The virus circulates in sub-Saharan Africa as a mosquito-borne agent. Epizootics occur when susceptible domestic animals are infected, and because of the large amount of virus in their serum, amplify infection to biting arthropods. Deaths and abortions among susceptible species such as cattle and sheep constitute a major economic consequence of these epizootics, as well as providing a diagnostic clue and a method of surveillance. Humans become infected by the bite of mosquitoes or by exposure to virus-laden aerosols or droplets. The human disease appears to be similar whether acquired by aerosol or by mosquito bite.

The incubation is two to five days and is usually followed by an incapacitating febrile illness of similar duration. The typical physical findings are fever, conjunctival injection, and sometimes-abdominal tenderness. A small proportion of cases (approximately one percent) will progress to a viral hemorrhagic fever syndrome; mortality in this group is roughly 50 percent. A small number of infections will lead to a late encephalitis. After apparent recovery from a typical febrile illness, the patient develops fever, meningeal signs, obtundation, and focal defects. These patients may die or often have serious sequelae.

The occurrence of an epidemic with febrile disease, hemorrhagic fever, eye lesions, and encephalitis in different patients would be characteristic of RVF. Demonstration of viral antigen in blood by ELISA is rapid and successful in a high proportion of acute cases of uncomplicated disease or hemorrhagic fever.

A biological warfare attack, most likely delivered by aerosol, would be expected to elicit the rather specific spectrum of human clinical manifestations and to cause disease in sheep and cattle in the exposed area.

Saxitoxin.

Saxitoxin is the parent compound of a family of chemically related neurotoxins. In nature they are predominantly produced by marine dinoflagellates, although they have also been identified in association with such diverse organisms as blue-green algae, crabs, and the blue-ringed octopus. Human intoxications are principally due to ingestion of bivalve molluscs, which have accumulated dinoflagellates during filter feeding. The resulting intoxication, known as paralytic shellfish poisoning (PSP), is known throughout the world as a severe, life-threatening illness requiring immediate medical intervention.

Onset of symptoms typically begins 10-60 minutes after exposure, but may be delayed several hours depending upon the dose and individual idiosyncrasy. Initial symptoms are numbness or tingling of the lips, tongue and fingertips, followed by numbness of the neck and extremities and general muscular incoordination. Respiratory distress and flaccid muscular paralysis are the terminal stages and can occur 2-12 hours after intoxication. Death results from respiratory paralysis.

In a BW scenario, the most likely route of delivery is by inhalation or toxic projectile. In addition, saxitoxin could be used in a confined area to contaminate water supplies.

Smallpox.

Smallpox virus, an orthopoxvirus with a narrow host range confined to humans, was an important cause of morbidity and mortality in the developing world until recent times. Eradication of the natural disease was completed in 1977 and the last human case s (laboratory infections) occurred in 1978. Under natural conditions, t he virus is transmitted by direct (face-to face) contact with an infected case, by fomites, and occasionally by aerosols. Smallpox virus is highly stable and retains infectivity for long periods outside of the host. A related virus, monkeypox, clinically resembles smallpox and causes sporadic human disease in West and Central Africa.

The incubation period is typically 12 days (range, 10-17 days). The illness begins with a prodrome lasting 2-3 days, with generalized malaise, fever, rigors, headache, and backache. This is followed by defervescence and the appearance of a typical skin eruption characterized by progression over 7-10 days of lesions through successive stages, from macules to papules to vesicles to pustules. The latter finally form crusts and, upon healing, leave depressed depigmented scars. The case fatality rate is app roximately 35% in unvaccinated individuals

The virus exists today only in 2 laboratory repositories in the U.S. and Russia. Appearance of human cases outside the laboratory would signal use of the virus as a biological weapon.

Staphylococcal Enterotoxin B. [SEB]

Staphylococcal Enterotoxin B (SEB) is one of several exotoxins produced by Staphylococcus aureus, causing food poisoning when ingested.

The disease begins 1-6 hours after exposure with the sudden onset of fever, chills, headache, myalgia, and nonproductive cough. In more severe cases, dyspnea and retrosternal chest pain may also be present. Fever, which may reach 103-106° F, has lasted 2-5 days, but cough may persist 1-4 weeks. In many patients nausea, vomiting, and diarrhea will also occur.

In foodborne SEB intoxication, fever and respiratory involvement are not seen, and gastrointestinal symptoms are prominent. The nonspecific findings of fever, nonproductive cough, myalgia, and headache occurring in large numbers of patients in an epide mic setting would suggest any of several infectious respiratory pathogens, particularly influenza, adenovirus, or mycoplasma.

A BW attack with aerosol delivery of SEB to the respiratory tract produces a distinct syndrome causing significant morbidity and potential mortality.

In a BW attack with SEB, cases would likely have their onset within a single day, while naturally occurring outbreaks would prese nt over a more prolonged interval.

Trichothecene Mycotoxins

The trichothecene mycotoxins are a diverse group of more than 40 compounds produced by fungi. They are potent inhibitors of protein synthesis, impair DNA synthesis, alter cell membrane structure and function, and inhibit mitochondrial respiration. Naturally occurring trichothecenes have been identified in agricultu ral products and have been implicated in a disease of animals known as moldy corn toxicosis or poisoning.

Consumption of these mycotoxins results in weight loss, vomiting, skin inflammation, bloody diarrhea, diffuse hemorrhage, and possibly death. The onset of illness following acute exposure to T-2 (IV or inhalation) occurs in hours, resulting in the rapi d onset of circulatory shock characterized by reduced cardiac output, arterial hypotension, lactic acidosis and death within 12 hours.

Clinical signs and symptoms of ATA were hemorrhage, leukopenia, ulcerative pharyngitis, and depletion of bone marrow. The purported use of T-2 as a BW agent resulted in an acute exposure via inhalation and/or dermal routes, as well as oral exposure upo n consumption of contaminated food products and water. Alleged victims reported painful skin lesions, lightheadedness, dyspnea, and a rapid onset of hemomhage, incapacitation and death. Survivors developed a radiation-like sickness including fever, nausea , vomiting, diarrhea, leukopenia, bleeding, and sepsis.

There are no well-documented cases of clinical exposure of humans to trichothecenes. However, strong circumstantial evidence has associated these toxins with alimentary toxic aleukia (ATA), the fatal epidemic seen in Russia during World War II, and with alleged BW incidents ("yellow rain") in Cambodia, Laos and Afghanistan.

Tularemia

Tularemia is a zoonotic disease caused by Francisella tularensis, a gram-negative bacillus. Humans acquire the disease under natural conditions through inoculation of skin or mucous membranes with blood or tissue fluids of infected animals, or bites of infected deerflies, mosquitoes, or ticks.

A variety of clinical forms of tularemia are seen, depending upon the route of inoculation and virulence of the strain. In humans, as few as 10-50 organisms will cause disease if inhaled or injected intradermally, whereas 10⁸ organisms are required with oral challenge. Under natural conditions, ulceroglandular tularemia generally occurs about 3 days after intradermal inoculation (range 2-10 days), and manifests as regional lymphadenopathy, fever, chills, headache, and malaise, with or without a cutaneous ulcer.

Pneumonic tularemia is a severe atypical pneumonia that may be fulmi nant, and can be primary or secondary. Primary pneumonia may follow direct inhalation of infectious aerosols, or may result from aspiration of organisms in cases of pharyngeal tularemia.

Pneumonic tularemia causes fever, headache, malaise, substernal disc omfort, and a non-productive cough; radiologic evidence of pneumonia or mediastinal lymphadenopathy may or may not be present.

A biological warfare attack with F. tularensis would most likely be delivered by aerosol, causing primarily typhoidal tularemia.

A BW attack with F. tularensis delivered by aerosol would primarily cause typhoidal tularemia, a syndrome expected to have a case fatality rate which may be higher than the 5-10% seen when dise ase is acquired naturally.

A clue to the diagnosis of tularem ia delivered as a BW agent might be a large number of temporally clustered patients presenting with similar systemic illnesses, a proportion of whom will have a nonproductive pneumonia

Venezuelan Equine Encephalitis

Eight serologically distinct viruses belonging to the Venezuelan equine encephalitis (VEE) complex have been associated with human disease; the most important of these pathogens are designated subtype 1, variants A, B and C. These agents also cause severe disease in horses, mules, and donkeys (Equidae). Natural infections are acquired by the bites of a wide variety of mosquitoes.

Nearly 100% of those infected suffer an overt illness. After an incubation period of 1-5 days, onset of illness is extremely sudden, with generalized malaise, spiking fever, rigors, severe headache, photophobia, myalgia in the legs and lumbosacral area. Nausea, vomiting, cough, sore throat, and diarrhea may follow. This acute phase lasts 24-72 hours. A prolonged period of aesthenia and lethargy may follow, with full health and activity regained only after 1-2 weeks. Approximately 4% of patients during natural epidemics develop signs of central nervous system infection, with meningismus, convulsions, coma, and paralysis. These necrologic cases are seen almost exclusively in children. The overall case-fatality rate is <1%, but in children with encephalitis, it may reach 20%.

A BW attack with virus disseminated as an aerosol would cause human disease as a primary event. If Equidae were present, disease in these animals would occur simultaneously with human disease. Secondary spread by person-to-person\contact occurs at a negligible rate. However, a BW attack in a region populated by Equidae and appropriate mosquito vectors could initiate an epizootic/epidemic.

A Historical Example of the Use of Biological Weapons

An early instance of the use of biological agents in warfare occurred during a battle at the seaport of Caffa on the Black Sea in 1346 to 1347 in which the Tatars catapulted corpses infected with plague into the city in order to infect the Genoese sailors inside.

The story of the British giving blankets contaminated with smallpox in order to infect Native Americans during the French and Indian Wars (1 754-1767) is another early case of the use of biological agents in warfare.

In World War I, German secret agents even tried to infect Allied horses and cattle destined for the front with the bacterial diseases anthrax and glanders and in the period before and during the Second World War, Japanese scientists experimented with biological warfare at their infamous Unit 731 in China.

The Ebola virus was first identified in a western equatorial province of Sudan and in a nearby region of Zaire in 1976 after significant epidemics in Yamkubu, northern Zaire, and Nzara, southern Sudan. Between June and November 1976 the Ebola virus infected 284 people in Sudan, with 117 deaths. In Zaire there were 318 cases and 280 deaths in September and October. An isolated case occurred in Zaire in 1977, a second outbreak in Sudan in 1979. In 1989 and 1990, a filovirus, named Ebola-Reston, was isola ted in monkeys being held in quarantine in a laboratory in Reston (Virginia), Alice (Texas) and Pennsylvania. In the Philippines, Ebola-Reston infections occurred in the quarantine area for monkeys intended for exportation, near Manila. A large epidemic o ccurred in Kikwit, Zaire in 1995 with 315 cases, 244 with fatal outcomes. One human case of Ebola haemorrhagic fever and several cases in chimpanzees were confirmed in Cфte d'Ivoire in 1994-95. In Gabon, Ebola haemorrhagic fever was first documented in 19 94 and recent outbreaks occurred in February 1996 and July 1996. In all, nearly 1,100 cases with 793 deaths have been documented since the virus was discovered. The natural reservoir of the Ebola virus seems to reside in the rain forests of Africa and Asia but has not yet been identified.