Molecular prevalence of Dirofilaria immitis and Wolbachia infections in pet and semi-domesticated cats in Bangkok, Thailand

BACKGROUND AND AIM: Although cats are not natural hosts for heartworm infections (Dirofilaria immitis), evidence suggests that feline heartworm disease can be detrimental because of a severe inflammatory response. Recent studies have found that infection with bacteria of the genus Wolbachia is the principal cause of acute inflammatory filaria disease; nonetheless, the prevalence of cats naturally infected with heartworms and Wolbachia remains unclear. This study aimed to estimate the prevalence and current distribution of feline heartworm disease and its association with Wolbachia infection in pet and semi-domesticated cats in Bangkok, Thailand. MATERIALS AND METHODS: A total of 260 cats (130 pet cats and 130 semi-domesticated cats) were enrolled in this study. Blood samples were placed into ethylenediaminetetraacetic acid tubes for hematological analysis and DNA extraction. A polymerase chain reaction (PCR) was performed to analyze samples for the presence of D. immitis and Wolbachia infections. RESULTS: The prevalence (95% confidence interval [CI]) of D. immitis infection in pet, semi-domesticated, and all cats were 3.9% (1.3-8.8%), 27.7% (20.2-36.2%), and 19.6% (15.0-25.0%), respectively. The prevalence (95% CI) of Wolbachia infection in pet, semi-domesticated, and all cats were 18.5% (12.2-26.2%), 31.5% (23.7-40.3%), and 25.0% (19.9-30.7%), respectively. The prevalence of D. immitis and Wolbachia infections in semi-domesticated cats was significantly higher than in pet cats (p=0.002 and p=0.022, respectively). There was a significant association between D. immitis and Wolbachia infections (p<0.001). There was also a significant association between D. immitis infection and the presence of eosinophilia (p<0.045). CONCLUSION: From the PCR analysis, it can be concluded that semi-domesticated cats were at higher risk for D. immitis infection than pet cats. There was a significant association between positive D. immitis infection and positive Wolbachia infection. Combinations of anthelmintic and antimicrobial therapy should be considered in heartworm-positive cats.