Tularemia

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. 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 are 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. 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. Nonhuman mammals rarely develop the skin lesions seen in people. Subclinical infections are common, and animals often develop specific antibodies to the organism. Fever is moderate or very high, and tularemia bacilli can be isolated from blood cultures at this stage. The face and eyes redden and become inflamed. Inflammation spreads to the lymph nodes, which enlarge and may suppurate (mimicking bubonic plague). Lymph node involvement is accompanied by a high fever. Tularemia is caused by the bacteria Francisella tularensis which is typically spread by ticks, deer flies, and contact with infected animals. The bacteria can penetrate into the body through damaged skin, mucous membranes, and inhalation. Humans are most often infected by tick/deer fly bite or through handling an infected animal. Ingesting infected water, soil, or food can also cause infection. Hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process. It has been contracted from inhaling particles from an infected rabbit ground up in a lawnmower (see below). Tularemia is not spread directly from person to person. Humans can also be infected through bioterrorism attempts. Francisella tularensis can live both within and outside the cells of the animal it infects, meaning it is a facultative intracellular bacterium. It primarily infects macrophages, a type of white blood cell, and thus is able to evade the immune system. The course of disease involves the spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system. The course of disease is different depending on the route of exposure. Mortality in untreated (before the antibiotic era) patients has been as high as 50% in the pneumoniac and typhoidal forms of the disease, which however account for less than 10% of cases.