Prevalence of Dirofilaria immitis in cats in eastern Tennessee and associated risk factors

The objectives of this research were to estimate the prevalence of Dirofilaria immitis infection in cats in eastern Tennessee, and to identify risk factors associated with this infection. Blood samples were collected from a convenience sample of 125 cats authorized for euthanasia at a local animal shelter and both heartworm antibody and antigen tests were run. The cats were then necropsied and examined for D immitis Heartworms were found in 3.2% (4/125) of cats Of the 125 serum samples, 2.4% (3/125) were antigen positive, and 7.2% (9/125) were antibody positive Heartworm serology was performed on 803 feline serum samples submitted to the University of Tennessee College of Veterinary Medicine Parasitology laboratory between January 1994 and December 1998. A heartworm antigen test was performed on each sample. Of the 803 samples, yearly prevalence of heartworm antigen positive cats ranged from 26% to 103%with an overall prevalence of 5.5% A correlation was found between yearly heartworm prevalence in cats and yearly precipitation in eastern Tennessee. Serum samples were collected from cats seen at veterinary clinics m Knox county whose owners agreed to participate in the study Serum was tested for both D immitis antibody and antigen Of the 560 samples, 20 (3 6%) were antigen positive, 32 (5 7%) were antibody positive, and 48 (8.6%) were positive on at least one of the two tests Owners were asked to fill out questionnaires regarding physical and behavioral characteristics of the cat. Statistical analyses were performed to determine the association between possible risk factors and D immitis infection in cats Characteristics of cats from the animal shelter, banked serum samples, and cats seen at veterinary clinics were analyzed No statistical difference was found between sex, neuter status, time of day spent outdoors, amount of time spent outdoors, or fur length and heartworm infection status. There was also no association found between clinical signs and heartworm infection status in cats.