Prevalence of exposure to Dirofilaria immitis in cats in multiple areas of the United States
Miller, M.W.; Atkins, C.E.; Stemme, K.; Robertson-Plouch, C.; Guerrero, J.
Veterinary Therapeutics Research in Applied Veterinary Medicine 1(3): 169-175
2000
ISSN/ISBN: 1528-3593 PMID: 19757579 Document Number: 518084
A study was conducted to determine the prevalence of successful transmission of heartworm (exposure) to pet cats, using a commercial feline heartworm antibody (Ab) test. Trial sites were selected in 21 areas (106 contributing clinics) of the USA, most of which had not been previously studied and which were not considered to be highly endemic for heartworm disease. Cats included in the study had lived in the area for at least 12 months and were not receiving heartworm preventative. Patient entry was conducted in January, February and March 1998 over a period of approx. 75 days. 2181 cats, ranging in age from 1 to 16 years, were available for analysis. More than 90% of cats were asymptomatic, being presented for routine vaccinations, elective surgery or signs not suggestive of heartworm disease. Overall, 259 of the 2181 cats demonstrated evidence of exposure by testing Ab positive. The cumulative Ab-positive rate was 11.9% for all areas surveyed (range, 5 to 33%). The highest percentages of Ab-positive cats were found in the Auburn (California) and Miami (Florida) areas, with rates of 33% and 21%, respectively. Overall, 8 (3.1%) of the 259 Ab-positive cats were positive for heartworm antigen (Ag). While the percentage of Ab-positive cats that were also Ag positive was highest for the Kansas City area (20%), followed by Dallas, Texas (14%), the absolute number of Ag-positive animals is so low that the importance of regional differences is uncertain. Although it was apparent that outdoor exposure increases the risk of both exposure (Ab positivity) and infection (Ag positivity), a history of total indoor housing did not provide complete protection to exposure of infection, suggesting that heartworm preventive may be indicated for both indoor and outdoor cats.