Prevalence and risk factors for Acanthocheilonema reconditum infection in dogs in the municipality of Lages, Santa Catarina, Brazil.

Acanthocheilonema reconditum (syn. Dipetalonema reconditum) is a filarial nematode transmitted by arthropods (fleas, lice, and ticks), primarily parasitizing the subcutaneous tissue of canids, but also found in perirenal fat. The clinical relevance of A. reconditum is often overshadowed by Dirofilaria immitis, a more pathogenic nematode with which it can be easily confused during diagnosis There are no reports of D. immitis in Lages, Santa Catarina (SC), neither in the Santa Catarina Plateau, Brazil. However, local laboratories observed microfilariae in canine blood samples and requested identification by the Veterinary Parasitology Laboratory of the State University of Santa Catarina. Morphological evaluation confirmed A. reconditum larvae. This study aimed to determine the prevalence of A. reconditum infection and assess risk factors in dogs from Lages. A total of 444 blood samples were collected from dogs in different neighborhoods, with simultaneous coat inspection for ectoparasites. Information on age, sex, origin, breed, ectoparasite control, and presence or absence of clinical signs was obtained through an epidemiological questionnaire to assess risk factors for A. reconditum infection. Blood samples were analyzed by blood smear, modified Knott's test, and immunochromatographic test. The prevalence of A. reconditum was 22.07 % (98/444) by the modified Knott's test, whereas the blood smear detected only 4.27 % (19/444). None of the evaluated samples showed characteristics compatible with D. immitis in the Knott's test, and all tested negative in the immunochromatographic test, indicating the absence of circulating antigen of this species. Ectoparasites were found in 35.58 % (158/444) of the animals, with no general association as a risk factor for A. reconditum infection. Among ectoparasites, Siphonaptera predominated, present in 93.02 % of parasitized animals, with a significant association between Pulex irritans presence (p = 0.003) and A. reconditum infection. This study confirmed the absence of D. immitis in Lages and highlighted a high prevalence of A. reconditum, underscoring the zoonotic potential and the need for further investigations.