Authors

ML Chocobar³; LG Zanfagnini²; LC Xavier²; R Panarese¹; W Weir¹; EM Schmidt³; AD Pacheco²;  ¹ University of Glasgow , UK;  ² Federal University of Acre, Brazil;  ³ São Paulo State University, Brazil

Discussion

Canine dirofilariasis, commonly known as heartworm disease, is a zoonotic mosquito-borne affliction found in many parts of the world. It is caused by Dirofilaria immitis and Dirofilaria repens and is transmitted by mosquitoes of the genera Aedes, Culex and Anopheles. Relatively few studies have been conducted to date to evaluate the prevalence and distribution of these parasites in Brazil, particularly in the interior of the country. For this reason, it is currently unknown which filarial species circulate among the canine populations in Acre, a non-coastal state in northern Brazil. To address this knowledge gap, the present study aims to characterize the zoonotic filarial species present in a large cohort of dogs domiciled in Rio Branco, the capital of Acre state. Four hundred and forty-four dogs were enrolled in the study, which was conducted at the Veterinary School Clinics of the Federal University of Acre (CVE-UFAC) and the Department of Zoonosis Control of Rio Branco (DCZ). Each dog underwent a clinical examination at which time blood and serum samples were collected. Whole blood samples were analysed using the modified Knott's test and Woo’s test. Microfilaeremic dogs' sera were screened using the Snap 4Dx Plus® rapid test (IDEXX Laboratories®). Of the 444 dogs, 59 (13.28%) were found to be microfilaraemic. The microfilariae (mfs) showed an average length and width of 247.53 ± 16.32 and 4.80 ± 0.48 µm, respectively, and were morphologically identified as Acanthocheilonema reconditum. Among the positive dogs, only three (5.08%) tested positive for D. immitis using the Snap 4Dx Plus^® test. Further analyses will be undertaken on all blood samples using molecular methods (i.e. qPCR and Sanger sequencing) to detect Dirofilaria spp. and Wolbachia DNA. It is anticipated that these molecular tests will reveal a higher prevalence of infection compared to the gross parasitological methods. Importantly, this study reveals the for the first time, the presence of potentially zoonotic filarial species circulating in the Acre dog population, thus highlighting the need for ongoing epidemiological surveillance across under-studied areas of the country. Only with this information can the disease threat be accurately assessed and interventions designed to mitigated the risk to animal and human health.