Tularemia is a bacterial disease that affects people and many species of wild and domestic animals. It is caused by toxins in the blood produced by the bacterium Francisella tularensis. The bacteria can survive for weeks or months in a moist environment. There are 3 types of organisms that differ based on the severity of the disease they produce. Type A is most likely to cause severe disease and is found most commonly in North America. Disease resulting from Type B infection is less severe and occurs most commonly as a result of contact with aquatic animals or ingestion of contaminated water in North America and Eurasia. Type C is also less severe than Type A and is the least common form.
In domestic animals, sheep are most often infected, but clinical infection has been reported in dogs, pigs, horses, and cats. Wild rabbits (cottontail and jackrabbits) are an important source of the infection. Cats are at higher risk than many other domestic animals due to their predatory behavior. Cats also appear to have a greater susceptibility than other domesticated animals.
The disease can be transmitted by several routes. These include spread of the organism through the air; direct contact with bacteria in the tissue of infected animals; eating infected undercooked meat or an infected carcass; being bitten by ticks, fleas, or deer flies; and contact with contaminated water. The most common source of infection for people is through the bite of an infected tick or eating undercooked wild game. Rarely, the bite of a cat that has recently fed on an infected animal has been found to be a source of human infection.
The signs of infection depend on the bacterial species and route of infection. Some cats will show no signs of disease, whereas others will become very ill. In most mammals, signs of illness may include heavy tick infestation, the sudden onset of high fever, swollen glands, lethargy, and poor appetite. Other signs such as stiffness, reduced mobility, increased pulse and respiratory rates, coughing, diarrhea, and frequent urination are occasionally seen. Cats may develop open sores in the mouth and throat. Blood infections can spread the disease to multiple organs, including the lungs, liver, spleen, and lymph nodes. Collapse and death may occur in a few hours or days.
Tularemia is diagnosed with laboratory tests. Because the disease can spread to humans, animal infections need to be reported to public officials in some areas. Affected animals are treated with an antibiotic. Early treatment should prevent death; however, prolonged treatment may be necessary. Control is difficult and is limited to reducing tick infestation, keeping pets confined to reduce predatory behavior, and rapid diagnosis and treatment. Animals that recover develop a long-lasting immunity.
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