By Jennifer Coates, DVM
Powassan virus has garnered the attention of people living in the northeastern and Great Lakes regions of the United States, not because it is all that common but because it can cause a potentially devastating illness.
The U.S. Centers for Disease Control and Prevention (CDC) says that only around 50 cases have been reported in the last 10 years. The virus is spread through the bite of an infected tick. Most exposures to the virus do not result in illness, but when symptoms do arise they can be quite severe and include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and seizures. Approximately 50% of people who become sick after Powassan virus infection are permanently affected (chronic headaches, muscle wasting, and poor memory) and 10% die. Treatment is purely symptomatic and supportive.
A number of diseases are spread by ticks to pets, and Powassan virus has been identified in other mammals like woodchucks, squirrels, and chipmunks. This raises the question: Is Powassan virus a threat to pets?
A review of the scientific literature and peer-to-peer communication between veterinarians reveals that Powassan virus appears to pose little threat to pets. Under experimental conditions (e.g., the virus being injected intravenously or directly into the brain), illness or evidence of infection could be induced, but no naturally occurring, symptomatic infections of Powassan virus have been identified in dogs, cats, or horses.
Of course it is possible that Powassan virus infections are being missed due to a lack of testing. The best way to protect pets from all the diseases that ticks can transmit is to avoid areas where ticks are most likely to be found (woodlands and areas with dense brush or tall grass) and to use an effective tick preventative whenever exposure is possible.
California serogroup and Powassan virus infection of cats. Keane DP, Parent J, Little PB. Can J Microbiol. 1987 Aug;33(8):693-7.
Powassan viral encephalitis: a review and experimental studies in the horse and rabbit. Little PB, Thorsen J, Moore W, Weninger N. Vet Pathol. 1985 Sep;22(5):500-7.
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