Prevalence and risk factors associated with Dirofilaria immitis infection in dogs using practical methods in hospitals in Thailand.

Abstract

To date, routine diagnosis of canine heartworm disease relies on detecting Dirofilaria immitis antigens in blood or the microscopic examination of blood smears. However, each method has limitations, potentially leading to life-threatening situations for infected dogs. This study aimed to determine the prevalence of filarial infection, risk factors, and appropriate detection methods in practical clinics. A total of 113 dog blood samples from two provinces in Thailand (Chonburi = 73 and Nakhon Nayok = 40) were analyzed for D. immitis infection using buffy coat smears, commercial immunochromatographic tests (SNAP 4Dx Plus), and polymerase chain reaction. Overall prevalence was 51.53% (58/113) across all methods. The positivity rates were 15.38% (12/78) for buffy coat smears, 8.00% (4/50) for SNAP 4Dx Plus, and 45.43% (51/113) for polymerase chain reaction. All positives from the test kits correlated with other methods. A significantly high prevalence was observed in dogs under 2 years old. Accessibility to pet care services in urban areas appeared to have a protective effect. Positive commercial test results could confirm D. immitis infection. However, selecting more than one diagnostic technique in clinics, including morphological examination, immunochromatography, or molecular methods, is recommended for early and more accurate detection, along with the promotion of heartworm prevention strategies.