Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium Francisella tularensis. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infection may occur.The bacterium is typically spread by ticks, deer flies, or contact with infected animals. It may also be spread by drinking contaminated water or breathing in contaminated dust. It does not spread directly between people. Diagnosis is by blood tests or cultures of the infected site.Prevention is by using insect repellent, wearing long pants, rapidly removing ticks, and not disturbing dead animals. Treatment is typically with the antibiotic streptomycin. Gentamicin, doxycycline, or ciprofloxacin may also be used.Between the 1970s and 2015, around 200 cases were reported in the United States a year. Males are affected more often than females. It occurs most frequently in the young and the middle aged. In the United States, most cases occur in the summer. The disease is named after Tulare County, California, where the disease was discovered in 1911. A number of other animals, such as rabbits, may also be infected. Signs and symptoms
Depending on the site of infection, tularemia has six characteristic clinical variants: ulceroglandular (the most common type representing 75% of all forms), glandular, oropharyngeal, pneumonic, oculoglandular, and typhoidal.The incubation period for tularemia is one to 14 days; most human infections become apparent after three to five days. In most susceptible mammals, the clinical signs include fever, lethargy, loss of appetite, signs of sepsis, and possibly death.
In the United States, practical research into using rabbit fever as a biological warfare agent took place in 1954 at Pine Bluff Arsenal, Arkansas, an extension of the Fort Detrick program. It was viewed as an attractive agent because:

it is easy to aerosolize
it is highly infective; between 10 and 50 bacteria are sufficient to infect victims
it is nonpersistent and easy to decontaminate (unlike anthrax)
it is highly incapacitating to infected persons
it has comparatively low lethality, which is useful where enemy soldiers are in proximity to noncombatants, e.g. civiliansThe Schu S4 strain was standardized as "Agent UL" for use in the United States M143 bursting spherical bomblet. It was a lethal biological warfare agent with an anticipated fatality rate of 40 to 60%. The rate-of-action was around three days, with a duration-of-action of one to three weeks (treated) and two to three months (untreated), with frequent relapses. UL was streptomycin resistant. The aerobiological stability of UL was a major concern, being sensitive to sunlight, and losing virulence over time after release. When the 425 strain was standardized as "agent JT" (an incapacitant rather than lethal agent), the Schu S4 strains symbol was changed again to SR.Both wet and dry types of F. tularensis (identified by the codes TT and ZZ) were examined during the "Red Cloud" tests, which took place from November 1966 to February 1967 in the Tanana Valley, Alaska.