Dirofilaria immitis antigenemia and microfilaremia in Iberian wolves and red foxes from Portugal

Abstract

Background: Dirofilaria immitis is a parasitic nematode endemic in the Mediterranean countries, which causes cardiopulmonary dirofilariosis in wild and domestic animals. Despite being recognized hosts of D. immitis, wild carnivores such as wolves and foxes are frequently disregarded when considering a potential role in the transmission of these zoonotic nematodes. In Portugal, studies available regarding D. immitis circulation are scarce, likely underestimating its relevance. To add knowledge on this, we sought to assess Iberian wolves (Canis lupus signatus) and red foxes (Vulpes vulpes) from northern Portugal for D. immitis antigenemia and microfilaremia. Methods: Blood samples from 42 Iberian wolves and 19 red foxes were collected, during 2010–2012, in Peneda-Gerês National Park. Antigenemia was searched for by rapid antigen detection test kits (Uranotest Dirofilaria ®). Microfilaremia was assessed by polymerase chain reaction (PCR). Nucleic acids were extracted from blood using QIAamp® DNA Mini Kit (Qiagen), and DNA was screened for the presence of microfilaria using a conventional PCR targeting the 5.8S-internal transcribed spacer 2–28S regions, followed by bidirectional sequencing, Basic Local Alignment Search Tool analysis and phylogenetic analysis. Results: Three red foxes had antigenemia, with an occurrence of 15.8% (95% confidence interval [CI] 3.4–39.6), while showing no evidence for the presence of microfilaremia. No wolf samples presented evidence for D. immitis antigenemia. Nevertheless, two wolves were positive for D. immitis microfilaremia (4.8%; 95% CI 0.6–16.2%) as revealed by PCR and confirmed by bidirectional sequencing. Conclusions: Although Dirofilaria microfilaremia in wolves does not necessarily correlate to an endangerment of the infected animal's health, positive individuals can act as a reservoir for further infection if the intermediate mosquito hosts are present. To the best of our knowledge, one single study had reported that wolves were suitable Dirofilaria hosts, but microfilaremia have never been reported. Graphical Abstract: [Figure not available: see fulltext.]