Background:

Nematodes of the genus Dirofilaria are widespread vector-borne helminths (VBH) of increasing relevance. Indeed, dirofilariosis is frequently diagnosed in domestic pets, often dogs, associated with a severe clinical condition known as heartworm disease caused by D. immitis . Assessing the distribution pattern of canine dirofilariosis is pivotal to undertake appropriate control measures and define the risk of infection in animals and humans. This study revealed the occurrence of D. immitis in naïve community dogs from Nepal. Methods An epidemiological study was performed in 2019 in Siddharthanagar (Lumbini region, Nepal). A total of 150 blood specimens were examined using direct microscopy, buffy coat centrifugation and modified Knott's method aiming at isolating and identifying Dirofilaria microfilariae. In addition, hematobiochemical parameters, including packed cell volume (PCV), alanine aminotransferase (SGPT), aspartate aminotransferase (SGOT), alkaline phosphate (ALP), creatinine, blood urea nitrogen (BUN), urea and total protein were analyzed, along with a clinical scoring (i.e., body temperature and respiratory rate) of the animals enrolled in this study. Results Out of 150 dogs sampled, 29 (19.3%) had D. immitis microfilariae. The prevalence of the infection varied according to the technique used, ranging from 16.0% to 19.3% based on direct blood smear microscopy and modified Knott method, respectively. The infection rate was significantly ( P <0.05) higher in dogs aged more than 3 years. A positive correlation was observed between SGPT and SGOT and the presence of microfilariae ( P <0.05). Conclusion The current findings revealed the presence of D. immitis in dogs from Nepal, thus providing an explanation for the diagnosis of this VBH is human cases. Further investigations are warranted to accurately define the prevalence of the infection in other pets, instrumentally to reduce the potential burden on the infection in dogs and, accordingly, to control the spread of this parasite to humans.