Epidemiological analysis of Dirofilaria immitis (Spirurida: Onchocercidae) infecting pet dogs (Canis lupus familiaris, Linnaeus, 1758) in Baixada Fluminense, Rio de Janeiro.

Dirofilaria immitis infection is routinely detected in dogs during veterinary care in tropical and subtropical regions worldwide. Parasitological tests for the detection of this infection are routinely performed only in areas with a high prevalence. Baixada Fluminense, a region in Rio de Janeiro, was considered heartworm-free until local veterinarians began to receive blood exams results indicating the presence of microfilariae (MF). A laboratory database was hence used to collect data from 2017 to 2020 to understand the extent of spread of the parasite in this area. The results of complete blood count analysis and MF or heartworm antigen detection tests conducted on canine samples sent from veterinary clinics in Baixada Fluminense (Magé, Duque de Caxias, Guapimirim, Nova Iguaçu, and São João de Meriti municipalities) were included. In total, the results of 16,314 hematological tests were considered. The overall prevalence of D. immitis was 3.4% (554/16,314), considering that only one test result was obtained per animal on the same day. This study is highly relevant because it indicates the spreading geographic distribution of the worms, heightens awareness among local health professionals and the general population, and encourages compliance with prophylactic measures to prevent further spread of parasite.

Molecular characterization of canine filarioids in a previously non-endemic area of Rio de Janeiro State, Brazil.

Dirofilaria immitis is the causative agent of canine heartworm disease, a severe health problem in dogs, especially in coastal areas of tropical and subtropical regions of the world. We employed molecular methods to investigate the occurrence of canine infection by filarioids in five municipalities of Baixada Fluminense (Magé, Duque de Caxias, Guapimirim, Nova Iguaçu, and São João de Meriti), a non-endemic area of Rio de Janeiro State, Southeast Brazil. A total of 110 canine blood samples collected from 2017 to 2018 and positive for microfilariae at the modified Knott's test were screened by cPCR targeting DNA fragments of the 12S rDNA gene for filarial nematodes. Seventy-seven samples (70%) tested positive at the molecular analysis. Of these, 72 were identified as D. immitis and 5 (4.5%) as Acanthocheilonema reconditum. Dirofilaria repens was not detected in the studied municipalities of Baixada Fluminense. This is the first record of D. immitis and A. reconditum in the Baixada Fluminense region, Rio de Janeiro State, Brazil. The prevalence of D. immitis cases in the five municipalities suggests the establishment and maintenance of its enzootic cycle in the studied region, which indicate vulnerability to the occurrence of epidemic cycles and, possibly, human cases.