Severe reaction in domestic animals following the bite of Ixodes muris (Acari: Ixodidae).

Free tick identification has been offered by our laboratory since 1989, during which time > 8,000 specimens have been submitted. We have noted that the bite of 1 of the less frequently identified ticks, Ixodes muris Bishopp & Smith, may be associated with a severe reaction in domestic animals characterized by extreme pain and swelling at the site and, with more complete engorgement, lethargy, anorexia, and high fever. These symptoms may be confused with other serious illness if the tick is not found. This reaction has not been seen following the bite of other species of ixodid ticks in Maine. Here we report 43 such cases, most involving dogs and cats from which ticks were removed by veterinarians and submitted to our laboratory for identification. Although I. muris was initially widespread in the United States and eastern Canada, its current range is unclear. In view of the potential for severe reaction to the bite of I. muris, the current distribution of the tick needs better definition, as does the mechanism of this response in animals that are unnatural hosts.