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- Patient Comments: Tularemia - Cause
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- Tularemia facts
- What is tularemia?
- What are the different types of tularemia?
- What causes tularemia?
- What are symptoms and signs of tularemia?
- How is tularemia diagnosed?
- What is the treatment for tularemia?
- Tularemia and bioterrorism
- Is there a vaccine for tularemia?
- Where can people find more information about tularemia?
What are the different types of tularemia?
There are four subspecies of F. tularensis, and all are capable of causing disease in humans (F. tularensis, F. holarctica, F. mediasiatica, and F. novicida). The subspecies tularensis and holarctica are the most common causes of tularemia in humans. The type of tularemia depends on which subspecies is involved and how the organism was acquired. Disease caused by the subspecies F. holarctica is often milder than that caused by F. tularensis.
The type of disease is often named for the most prominent symptoms. Thus, ulceroglandular tularemia is usually caused by inoculation of the skin and is associated with open sores and swollen lymph nodes. If there is no sore but swollen lymph nodes are prominent, the disease may be classified as glandular. If the eye or throat is involved, oculoglandular or pharyngeal tularemia is said to be present. Disease involving the lungs is termed pneumonic disease. Tularemia that predominately affects the bloodstream and body organs is referred to as typhoidal tularemia.
What causes tularemia?
Tularemia is caused by the bacterium Francisella tularensis. Tularemia is an uncommon disease in humans, with statistics showing less than one case per million people per year in the United States. This translates into less than 150 cases per year, with a majority in Arkansas, Kansas, Missouri, and Oklahoma. Illness caused by ticks and insects is most common in the summer months and often occurs in children. Disease caused in winter is associated with hunters who handle dead animals. F. tularensis can infect many types of animals but particularly affects rabbits, hares, and rodents. The disease is sometimes called rabbit fever because it occurs when hunters contact the skin of infected rabbits. Farmers, veterinarians, foresters, landscape workers, and hunters are at risk of contracting tularemia because of their likely direct animal contact, but the disease can also affect others who inadvertently come into contact with animals or are bitten by insects.
Tularemia is usually acquired directly by skinning, eating, or otherwise handling infected animals. In rare instances, transmission has occurred when wild rodents (prairie dogs) were sold as pets. Dried animal material may be aerosolized and inhaled, causing disease. Domestic animals such as cats may pick up the organism on their claws after killing a wild rodent or rabbit. Dogs and cats may also eat contaminated meat, causing fever and swollen nodes. Transmission of tularemia from dogs or cats to humans is rare. Finally, the disease has been transmitted by drinking water contaminated with animal products. Contaminated food and water have been responsible for large outbreaks in times of war. Tularemia does not spread from person to person.