How People Get Tularemia

The American dog tick (Dermacentor variabilis), one of the ticks that can carry tularemia. CDC image.

Francisella tularensis, the bacterium that causes tularemia, is highly infectious. It can enter the body through the skin, eyes, mouth or lungs, and the illness it causes depends on the route. Tularemia has not been reported to spread from person to person. Most people who get it run a fever, which can reach 104°F; other symptoms vary with how the bacteria got in.

Tick and deer fly bites

In the United States, ticks that pass tularemia to people include the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni) and the lone star tick (Amblyomma americanum). Deer flies (Chrysops species) have been shown to spread it in the western United States. Infections from bites usually take the ulceroglandular or glandular form.

The lone star tick (Amblyomma americanum). CDC image.

Handling infected animals

The bacteria can pass through the skin when people handle infected animal tissue — especially when hunting or skinning infected rabbits, muskrats, prairie dogs and other rodents. Many other animals can also get tularemia. Domestic cats are very susceptible and have passed it to people. Outbreaks have occurred among hamsters sold in pet stores, and at least one U.S. child caught tularemia from a pet hamster's bite. Take care when handling any sick or dead animal. Infections from handling animals can be glandular, ulceroglandular or oculoglandular, and eating undercooked meat from an infected animal can cause oropharyngeal tularemia.

Dust, aerosols and water

People can breathe in dust or aerosols contaminated with the bacteria, for example during farming or landscaping when a tractor or mower runs over infected animals or carcasses. Though rare, this can cause pneumonic tularemia, one of the most severe forms. Water can be contaminated by infected animals, and drinking untreated contaminated water can cause oropharyngeal tularemia — a route that seems much more common in Europe than in the United States.

Sources

• Centers for Disease Control and Prevention: "How Tularemia Spreads."