Biological Warfare (cont.)
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Tularemia is an infection that can strike humans and animals. It is caused by the bacterium Francisella tularensis. The disease causes fever, localized skin or mucous membrane ulcerations, regional swelling of lymph glands, and occasionally pneumonia.
G.W. McCay discovered the disease in Tulare County, Calif., in 1911. The first confirmed case of human disease was reported in 1914. Edward Francis, who described transmission by deer flies via infected blood, coined the term tularemia in 1921. It has been considered an important biological warfare agent because it can infect many people if dispersed by the aerosol route.
Rabbits and ticks most commonly spread tularemia in North America. In other areas of the world, tularemia is transmitted by water rats and other aquatic animals.
The bacteria are usually introduced into the victim through breaks in the skin or through the mucous membranes of the eye, respiratory tract, or GI tract. Ten virulent organisms injected under the skin from a bite or 10-50 organisms breathed into the lungs can cause infection in humans. Hunters may contract this disease by trapping and skinning rabbits in some parts of the country.
Signs and Symptoms
Tularemia has six major forms:
Victims with the most common form, ulceroglandular type, typically have a single papulo-ulcerative lesion with a central scar (often at the site of a tick bite) and associated tender regional lymphadenopathy (swollen lymph nodes). A sore up to 1 inch across may appear on the skin in a majority of people and is the most common sign of tularemia. If the bite associated with infection was from an animal carrying the disease, the sore is usually on the upper part of a person's body, such as on the arm. If the infection came from an insect bite, the sore might appear on the lower part of the body, such as on the leg.
Enlarged lymph nodes are seen in a majority of victims and may be the initial or the only sign of infection. Although enlarged lymph nodes usually occur as single lesions, they may appear in groups. Enlarged lymph nodes may come and go and last for as long as three years. When swollen, they may be confused with buboes of bubonic plague.
The glandular form of the disease has tender regional lymphadenopathy but no identifiable skin lesion.
Oculoglandular tularemia presents as conjunctivitis (white of the eyes are red and inflamed), increased tearing, photophobia, and tender enlarged lymph nodes in the head and neck region. Pharyngeal tularemia presents with a sore throat, fever, and swelling in the neck.
The most serious forms of tularemia are typhoidal and pneumonic disease. Patients with typhoidal disease can have fever, chills, anorexia, abdominal pain, diarrhea, headache, myalgias, sore throat, and cough. Patients with pneumonic tularemia have mostly pulmonary findings. Many patients with pulmonary findings have underlying typhoidal tularemia.
Tularemia can be diagnosed by growing the bacteria in the laboratory from samples taken of blood, ulcers, sputum, and other body fluids. Serological tests (done to detect antibodies against tularemia), direct fluorescent antibody (DFA) staining of clinical specimens, and polymerase chain reaction (PCR) tests on clinical specimens are available from specialized labs.
Victims with tularemia who do not receive appropriate antibiotics may have a prolonged illness with weakness and weight loss. Treated properly, very few people with tularemia die. If a patient has severe disease, it is recommended to give them a 14-day course of streptomycin or gentamicin. For patients with mild to moderate disease, oral ciprofloxacin or doxycycline is recommended. In children with mild to moderate disease, gentamycin is often recommended. However, despite the concerns over side effects in children, some clinicians may recommend oral treatment with ciprofloxacin or doxycycline.
Although laboratory-related infections with this organism are common, human-to-human spread is unusual. Victims do not need to be isolated from others.
There is no recommendation for prophylactic treatment of people going into areas where tularemia is more common. In fact, in the case of low-risk exposure, observation without antibiotics is recommended.
There no longer exists a vaccine against tularemia. New vaccines are under development.
In the event of a biological attack using Francisella tularensis, the recommendation is to treat exposed people who are not yet ill with 14 days of oral doxycycline or ciprofloxacin.
Medically Reviewed by a Doctor on 6/30/2016
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