There are several different forms of tularemia all of them caused by a
bacterium called Francisella tularensis (F. tularensis). The bacterium is found all over
the world. F. tularensis is a hardy bacterium that is capable of
surviving for weeks at low temperatures in water, moist soil, hay, straw and
decaying animal carcasses. In addition to humans it infects voles,
mice, water rats, squirrels, rabbits, and hares. An average of 124 cases
of tularemia were reported annually in the United States from 1990 to 2000 (9,
47, 59, 62, 63,
64). Cases of tularemia have been reported from every state in
the United States except Hawaii.
There are two subspecies of F. tularensis that commonly cause disease
in humans are; F. tularensis subsp. tularensis and F.
tularensis subsp. holarctica. The subspecies (F. tularensis subsp.
the United States is more likely to cause severe disease and is called the
Jellison A type. The Jellison B subspecies found in Europe (F. tularensis subsp.
holarctica) results in a
People get tularemia many different ways:
Tularemia does not spread from person-to-person. People who have tularemia do not need to be isolated. People who have been exposed to the tularemia bacteria should be treated as soon as possible.
The form of tularemia a person gets depends on how they were infected by
the bacterium. There are 5 different forms of this disease: ulceroglandular (skin
ulcer at site of infection with swollen lymph nodes), pneumonic
(infection of lungs), typhoidal (ingestion of bacteria), oropharyngeal
(ingestion with infection of throat, tonsils, and lymph nodes) and oculoglandular
(infection of eye and lymph nodes).
This form of the disease is the most serious form of tularemia and can occur as a complication in the other forms of tularemia. There have been two recent outbreaks of this form of tularemia in Martha’s Vineyard, Massachusetts. One outbreak occurred in 1978 the other in 2000 (63, 64). During the 2000 outbreak 15 people got tularemia with 11 acquiring pneumonic tularemia. In studying the 2000 outbreak it was determined that lawn mowing or brush cutting were risk factors for pneumonic tularemia (63). It is likely that dead animal carcasses or fecal matter from these animals are in the lawns. When the brush-cutter or lawn mower runs over the carcass or fecal matter the machine aerosolizes the organism. The person will then inhale the bacteria. Only small numbers of bacteria are needed to cause infection. Symptoms include fever, chills, dry cough, pain just under the middle of the ribcage, apprehension and an extremely ill patient. In severe cases the patient can go into shock. Chest X-rays will usually show inflammation in the lungs. Symptoms usually appear 3 to 5 days after exposure to the bacteria, but can take as long as 14 days. If not treated the death rate can be as high as 30%.
Both of these forms of the disease occur following ingestion of the bacteria.
Over a million organisms are needed to cause these forms of tularemia.
Oropharyngeal tularemia occurs following infection of the throat, tonsils and/or
lymph nodes just below the jaw. The patient will have sore throat, swollen
tonsils that are oftentimes covered with a grayish white membrane. The lymph
nodes under and behind the jaw will also be swollen.
Typhoidal tularemia is more severe resulting in infection of the liver, spleen and blood stream. The patient will have a continuous high fever, muscle pains and swollen liver and spleen. This disease is similar to many other diseases and is difficult for physicians to diagnose.
This form of tularemia is the least common. It involves infection of the eye
and the lymph nodes in the head and neck. Symptoms include eye pain,
photophobia, intense eye redness, itching, tearing of the eyes, swelling of the
membranes that cover the eye (conjunctiva) and a whitish discharge from the eye
(mucopurulent discharge). The lymph nodes in the head and neck will also be
Why is tularemia an attractive BW?
infectious. A small number (10-50 organisms) can cause disease. If F.
tularensis were used as a BW, the bacteria would likely be delivered as an
aerosol. People who inhale an infectious aerosol
would generally experience severe respiratory illness, including
life-threatening pneumonia and systemic infection, if not treated. The bacteria
that cause tularemia occur widely in nature and could be isolated and grown in
quantity in a laboratory. A World Health Organization model for a
tularemia release over a metropolitan area with 5 million inhabitants predicted
250,000 people incapacitated and 19,000 deaths. It is also well known that
several different nations investigated the use of tularemia as a BW (7,
Rapid diagnostic testing for tularemia is not widely available. Physicians
who suspect inhalation tularemia will collect blood and sputum samples. They
also need to alert the laboratory so they can implement special diagnostic and
safety procedures. F.
tularensis may be identified through direct examination of
secretions, exudates, or biopsy specimens using special staining techniques. A
blood sample might also be taken to look for antibodies to the bacterium.
Growth of F. tularensis
in culture is the definitive means of confirming the diagnosis of tularemia. It
can be grown from pharyngeal washings, sputum specimens, and even fasting
gastric aspirates in a high proportion of patients with inhalational tularemia.
It is only occasionally isolated from blood.
Isolation is not necessary for
tularemia patients, since there is no person-to-person transmission. Antibiotics
are essential in treatment of this disease. Either streptomycin or erythromycin
is commonly used in treating this infection. Other antibiotics can also be used
Tularemia occurs naturally in most of the United States. Using insect repellent containing DEET on your skin, or treat clothing with repellent containing permethrin, to prevent insect bites. Wash your hands often, using soap and warm water, especially after handling animal carcasses. Be sure to cook your food thoroughly and that your drinking water is from a safe source.
A new vaccine is currently being developed. It is likely however, that at first the vaccine will only be available for military personnel.
© 2005 Neal Chamberlain. All rights reserved.
Site Last Revised 5/13/05
Neal Chamberlain, Ph.D. A. T. Still University of Health Sciences/Kirksville College of Osteopathic Medicine.
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