Prevalence of heartworm infection in healthy cats in the lower peninsula of Michigan.

OBJECTIVE To determine prevalence of heartworm infection among healthy, client-owned cats in the lower peninsula of Michigan. DESIGN Cross-sectional prevalence study. ANIMALS 1,348 healthy cats examined at private veterinary practices throughout the lower peninsula of Michigan. PROCEDURE Sera were tested by use of an ELISA-based antigen test kit to determine infection and 2 commercially available antibody detection kits to determine exposure. A questionnaire was used to collect data to assess risk factors associated with infection. RESULTS 25 cats had positive results for heartworm antigen, yielding an observed prevalence of 1.9%. Neither antibody test was reliable or provided reproducible results, and neither yielded positive results for more than 20% of the antigen-positive heartworm-infected cats. Multivariate regression indicated that cats from southeastern Michigan and cats > or = 2 years old had a higher risk of infection. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that most (80%) heartworm-infected cats in the lower peninsula of Michigan were from the southeastern part of the state, a pattern that closely paralleled the prevalence of heartworm infection in dogs. Therefore, knowledge of the regional prevalence of heartworm infection in dogs may be useful in assessing the risk of infection in cats. Results also suggested that currently available in-clinic heartworm antibody detection kits have limited utility in the diagnosis of heartworm infection in cats.