Abstract
BackgroundWild carnivores such as the grey wolf (Canis lupus), red fox (Vulpes vulpes) and golden jackal (Canis aureus) are recognized hosts of Dirofilaria immitis. However, few studies have focused on their actual role in the epidemiology of heartworm infection. This study describes the prevalence and distribution of D. immitis in wolves in a heartworm-endemic area in northern Italy where wolves have recently returned after long-time eradication, and investigates the fertility status of the collected adult nematodes.MethodsIn the frame of a long-term wolf monitoring programme in northwestern Italy, 210 wolf carcasses from four provinces were inspected for the presence of filarioid nematodes in the right heart and pulmonary arteries. Female heartworms were measured, and their uterine content analyzed according to a previously described “embryogram” technique.ResultsThree wolves, all originating from a single province (Alessandria), were positive for D. immitis (1.42%, 95% CI: 0.48–4.11%, in the whole study area; 13.6%, 95% CI: 4.7–33.3%, limited to the single province from which infected wolves originated). Mean intensity was 5 worms (range: 3–7) and the female worms measured 21–28 cm in length. Six out of 9 female worms harbored uterine microfilariae: 5 were classified as gravid; 1 showed a “discontinuous gradient”; and 3 were non-gravid.ConclusionsThe present data show that heartworm infection is already prevalent in wolves that have recolonized the known heartworm-endemic area. Based on “embryogram” results, wolves were shown suitable heartworm hosts. Interestingly, investigated wolves appeared similarly exposed to heartworm infection as sympatric unprotected dogs (owned dogs that have never received any heartworm prevention treatment) sampled at the beginning of the wolf return process.
Highlights
Wild carnivores such as the grey wolf (Canis lupus), red fox (Vulpes vulpes) and golden jackal (Canis aureus) are recognized hosts of Dirofilaria immitis
A total of 15 specimens of D. immitis (9 females and 6 males) were collected from 3 female wolves in January 2016, April 2017 and March 2019
Our study shows that, in wolves with heartworm infections comprising both sexes, a high number of female nematodes reach sexual maturity and harbor uterine microfilariae (Table 2)
Summary
Wild carnivores such as the grey wolf (Canis lupus), red fox (Vulpes vulpes) and golden jackal (Canis aureus) are recognized hosts of Dirofilaria immitis. Heartworm disease is a cardio-pulmonary pathology affecting dogs and other mammalian carnivores worldwide. It is caused by Dirofilaria immitis, a large-sized nematode transmitted by several mosquito vectors. Several carnivores have been described as heartworm definitive hosts in wildlife: coyote (Canis latrans); red fox (V. vulpes); grey fox (Urocyon cinereoargenteus) [5, 11, 12]; golden jackal (Canis aureus) [7, 9, 13]; red wolf (Canis rufus) [14]; European wildcat (Felis silvestris) [13]; and Eurasian otter (Lutra lutra) [13, 15]. Data on heartworm infection in the grey wolf (Canis lupus), the closest wild relative of the domestic dog, are still scarce, having been reported only sporadically in Europe since 2001 [7, 16,17,18,19,20,21,22,23]
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