ANTIBODIES TO EHRLICHIA-EQUI IN DOGS FROM THE NORTHEASTERN UNITED-STATES

Objective-To determine whether dogs living in tick-infested areas of t he northeastern United States had been exposed to Ehrlichia equi, an e tiologic agent of granulocytic ehrlichiosis. Design-Analyses of dog se ra. Animals-106 ill dogs and 12 clinically normal dogs. Procedure-Anti bodies to E equi were detected by indirect fluorescent antibody staini ng methods and western blot analyses. Results-10 of 106 (9.4%) sera te sted from ill, privately owned dogs living in tick-infested areas of C onnecticut and New York state had antibodies to E equi, a member of th e E phagocytophila genogroup. Titration end points ranged from 1.80 to 1:1,280. Immunoblots revealed antibodies to proteins of E equi having molecular masses of predominantly 29, 40. 44, 105, 120, and 160 kd. T here was good agreement between results of serologic testing methods, but use of the human isolate (NCH-1 strain) in western blot analyses d etected 2 additional seropositive dogs found to be negative by indirec t fluorescent antibody staining methods with the MRK strain. Clinical Implications-Dogs living in areas where Ixodes scapularis is abundant may be exposed to multiple pathogens, such as E equi or Borrelia burgd orferi. Although mild or subclinical infections with E equi may develo p, dogs with marked leukopenia, thrombocytopenia, or anemia should be viewed as possibly having ehrlichiosis. Laboratory diagnosis should in clude examinations for morulae in granulocytes or monocytes in additio n to serologic analyses.