Tick Season Brings Rise in Tularemia Cases on Long Island

A rare but potentially serious zoonotic disease has been confirmed on Long Island, with a fourth human case of tularemia reported this year. The disease, also known as 'rabbit fever', is caused by the bacterium *Francisella tularensis*, which is spread through the bites of infected ticks and deer flies, as well as through contact with infected animals.

The cluster of cases comes as human emergency department visits for tick bites run at their highest level in nearly a decade, with the Northeast and Midwest hit hardest. The disease affects more than 250 species of wild and domestic mammals, birds, reptiles, and fish, with wild rabbits, hares, and rodents being highly susceptible.

## What is Tularemia?

Tularemia is caused by the highly infectious bacterium *F tularensis*, which can survive for weeks to months in a moist environment. The disease can be spread through bites from infected ticks or deer flies, contact with or ingestion of infected animals, inhalation of contaminated aerosols, and drinking contaminated water.

## Clinical Signs in Animals

Clinical signs of tularemia in animals depend on the host species, bacterial subspecies, and route of infection. In cats and dogs, presentation may include fever, lethargy, lymphadenomegaly, loss of appetite, vomiting, diarrhea, coughing, nasal discharge, and oral ulcers. In wild animals, tularemia is usually diagnosed on postmortem examination, while in domestic animals, the diagnosis rests on clinical signs and ruling out other causes.

## Diagnosis and Treatment

Diagnosis in animals is confirmed by bacterial culture, serologic testing, or polymerase chain reaction assay. The bacterium can be cultured on cysteine-supplemented blood, and isolation from necropsy specimens requires a laboratory equipped for biosafety level 3 procedures. Antimicrobial treatment can be effective when started early, but there is no tularemia vaccine generally available in the US.

### Prevention Advice

Veterinary teams can share the CDC's prevention advice with clients, including using an Environmental Protection Agency-registered insect repellent, wearing long sleeves and pants, promptly removing attached ticks, avoiding mowing over dead animals, and wearing gloves when handling sick or wild animals. Keeping cats indoors and maintaining year-round tick control also reduces the chance a companion animal brings the organism home.

| Species | Affected Species | Route of Infection | | --- | --- | --- | | Cats | Cats, dogs, pigs, horses | Bites from infected ticks or deer flies, contact with or ingestion of infected animals | | Dogs | Cats, dogs, pigs, horses | Bites from infected ticks or deer flies, contact with or ingestion of infected animals | | Wild Animals | Wild rabbits, hares, rodents | Bites from infected ticks or deer flies, contact with or ingestion of infected animals |

The cases arrive during an unusually heavy tick season, with the CDC reporting that weekly emergency department visits for tick bites reached their highest level for the time of year since 2017. Veterinary teams should be aware of the risks associated with tularemia and take necessary precautions to prevent the spread of the disease.