Tularemia. (Technical Briefs).

Tularemia is a plaguelike disease in humans. It is caused by the Gram-negative bacteria Francisella tularensis, a hardy non-sporulating aerobic bacteria that can survive at low temperatures in water, soil, organic materials, and carcasses. F. tualernsis is a highly infectious pathogenic bacteria and has long been considered a potential biological weapon.

The bacteria received its name in honor of Edward Francis who recognized and described the human disease. The disease was first described in 1911 in rodents and got its name from the county in which it was discovered, Tulare County, California. Tularemia occurs throughout Europe and North America as well as in various other parts of the globe and is generally considered a rural disease.

It is believed that tularemia is spread naturally by biting flies as well as by contaminated water, plant material, infected animals, carcasses, and aerosolized particles. F. tularensis is transmitted by insect bites, handling of infected materials, ingestion, or inhalation of infected aerosols. Transmission from person-to-person, however, has not been documented.

F. tularensis was reportedly researched as far back as World War II for use as a potential biological weapon. The organism has two main strains, F. tularensis biovar palaearctica [Type B] and F. tularensis biovar tularensis [Type A]. Type A generally is considered the more virulent strain. If F. tularensis were to be used as a biological weapon, aerosolization of the organism would most likely be the method with the greatest impact since very few (as few as five to 10) inhaled organisms are required to cause disease. It has been reported that before the United States terminated its biological weapons program in the early 1970s F. tularensis was one of the biological weapons that had been produced and stockpiled. It is also believed that the former Soviet Union also researched and developed this organism as a biological weapon.

Following contact and infection by the organism, the incubation period for tularemia is approximately two to 10 days. The range of symptoms include chills, fever, malaise, enlarged lymph nodes, skin ulcerations, pneumonia, and muscular pains. According to the Material Safety Data Sheet from Health Canada, Type B strains have a five to 15 percent mortality rate, and Type A has a 35 percent mortality rate from pulmonary tularemia, Treatment with various antibiotics after infection has been successful.

The Centers for Disease Control and Prevention (CDC) maintain a Web page that provides information on recognizing F. tularensis-caused illness, identifies laboratory protocols, and has links to a variety of fact sheets. Readers will find the CDC Web page at http://www.bt.gov/Agent/Tularemia/.