Molecular and antigen detection of Dirofilaria immitis infection in client-owned cats in Bangkok, Thailand

Feline heartworm disease, caused by Dirofilaria immitis infection, can be potentially fatal to cats. Screening for the infection in cats is important in endemic areas. Clinical utility of molecular techniques for diagnosis of feline heartworm disease is not clearly determined. The objective of this study was to evaluate whether a polymerase chain reaction (PCR) assay could be used for detection of D. immitis infection in cats that were concurrently tested for D. immitis antigen. Blood samples were collected from 100 client-owned cats in a veterinary teaching hospital. Whole blood samples were tested for D. immitis antigen and extracted for total DNA. Presence of D. immitis DNA was analyzed using a PCR assay. Overall, there was one cat (1.0%) positive for D. immitis antigen. None of the cats were positive for D. immitis DNA. The results demonstrated very low prevalence of D. immitis infection in client-owned cats from a veterinary teaching hospital in Bangkok. However, the prevalence might be underestimated because of small sample size of the cats. In this study, the PCR assay was not shown to be superior to the antigen test for detection of D. immitis infection in cats. Dirofilaria immitis infection could not be ruled out based on a negative PCR test result. The clinical utility of PCR assay for diagnosis of feline heartworm disease is limited.