Dirofilaria immitis and Dirofilaria repens: Investigating the Prevalence of Zoonotic Parasites in Dogs and Humans in a Hyperenzootic Area

The mosquito-borne zoonotic nematode parasites <i>Dirofilaria immitis</i> and <i>Dirofilaria repens</i> primarily affect dogs. In recent years, their distribution has expanded due to various factors influencing vector-borne pathogens. This study aimed to investigate the comparative prevalence of infection in dogs and humans within a hyperenzootic region of Europe, and to estimate the proportional relationship between infection prevalence in dogs and humans, within the concept of "One Health". To this end, 604 blood samples from dogs and 625 serum samples from humans living in the Thrace region of northeastern Greece were collected. The dog samples were examined for <i>Dirofilaria</i> spp. microfilariae using Kott's test and for <i>D. immitis</i> antigen using a commercial serological test. The human sera were analyzed for both parasites by Western blot. The overall prevalence of infection in dogs was 177 (29.3%), with 173 (28.6%) testing positive for <i>D. immitis</i> and 7 (1.2%) for <i>D. repens</i>, including 6 (1%) cases of mixed infection. Specific IgG antibodies were detected in 42 (6.7%) human samples, with 24 (3.8%) positive for <i>D. immitis</i> and 18 (2.9%) for <i>D. repens</i>. The infection proportion in humans was 23.4% of the corresponding canine infections, indicating a high risk of human infection in this hyperenzootic region.