Powassan Virus
Powassan virus is a flavivirus that causes encephalitis. It is transmitted by Ixodes cookei (Powassan virus, lineage I) in the Great Lakes region and by I scapularis (Powassan virus, lineage II, or deer tick virus) in the northeastern United States. Transmission can occur within 15 minutes of tick attachment.6,20,21
Patients typically present with fever, headache, altered mental status, seizures, and focal neurologic deficits. Gastrointestinal symptoms and rash also have been reported.21 The diagnosis is made based on clinical presentation and laboratory testing with PCR or enzyme-linked immunosorbent assay (ELISA). Cross-reactivity on ELISA exists, necessitating confirmation with a neutralizing antibody or PCR. Treatment is supportive. Corticosteroids and intravenous immunoglobulin have been proposed as treatment modalities, but evidence of their efficacy is limited.22
Tick-borne Encephalitis
Tick-borne encephalitis is caused by the flavivirus tick-borne encephalitis virus in Europe and Asia. The tick-borne encephalitis virus is transmitted by Ixodes ricinus in Europe and by Ixodes persulcatus in eastern Russia, China, and Japan. It also has been associated with consumption of unpasteurized milk.23,24
Tick-borne encephalitis presents in a biphasic pattern. The initial viremic phase can persist for as long as 8 days with headache, nausea, myalgia, and fever. One-third of patients then enter an asymptomatic phase, followed by virus penetration into the central nervous system. The neurologic phase produces continued headache and fever with photophobia, focal neurologic deficits, seizures, respiratory depression, or coma. Neurologic sequelae persist in 10% to 20% of patients.25,26
In the viremic stage, diagnosis is made with PCR or culture. During the latent phase or neurologic phase, serologic testing for tick-borne encephalitis virus antibodies is indicated. Neutralizing antibody evaluation may be necessary due to cross-reactivity among flaviviruses.27 Treatment is supportive. An inactivated vaccine is available for high-risk populations.28
Borrelia miyamotoi Disease
Borrelia miyamotoi is a symbiont of the Ixodes tick formerly believed to have no pathogenic significance; however, B miyamotoi was isolated in febrile patients in Russia in 20117 and was identified as a pathogen in both North America29 and Europe in 2013.30 Disease presentation includes nonspecific symptoms of fever, fatigue, headache, arthralgia, myalgia, and nausea. Rash is uncommon. Laboratory abnormalities include leukopenia, thrombocytopenia, and transaminitis.31,32 Meningoencephalitis may occur in immunocompromised patients.29,30
The diagnosis of B miyamotoi disease is confirmed by PCR or serology. An ELISA that is positive for B burgdorferi IgM but negative with confirmatory immunoblot suggests B miyamotoi disease. Seroconversion using a glpQ protein ELISA also can be assessed.31 If ELISA is positive, Lyme disease can be excluded because B burgdorferi does not possess g1pQ. Treatment is with doxycycline.32
Tick Paralysis
Tick paralysis is an intoxication with holocyclotoxin from the saliva of gravid hard ticks. In the United States, intoxication is associated with ticks of various species of Amblyomma, Dermacentor, and Ixodes in the Northwest, Southeast, and Northeast. In Australia, intoxication is associated with Ixodes.33 Patients present with weakness and fatigue, progressing to ascending flaccid paralysis with sensory sparing. The treatment is tick removal.8,33
Conclusion
Arthropods carry many regional pathogens. Physicians outside of those regions should seek a travel history and be alert for imported disease.