Detection of Dirofilaria immitis in golden jackals (Canis aureus L.) but not in red foxes (Vulpes vulpes L.) and European badgers (Meles meles L.) in Croatia.

Background: Dirofilariosis is a parasitic mosquito-borne disease caused by members of the genus Dirofilaria, which includes Dirofilaria immitis and Dirofilaria repens. Surveillance studies in Europe have revealed that D. immitis can also be detected in a range of wild carnivores, raising questions over the impact of infections on wild carnivore animal health but also whether these populations may act as a reservoir for infection of other species, including domestic dogs and humans.

Methods: In the current study, we conducted surveillance for the presence of D. immitis in several wild carnivore species, including golden jackals (Canis aureus; n = 77), red foxes (Vulpes vulpes; n = 326), and European badgers (Meles meles; n = 28), collected during an annual rabies surveillance and control program from across continental and coastal regions of Croatia.

Results: Macroscopic examination of the right chambers of the heart during a post-mortem examination resulted in the detection of filarial parasites in 6.5% (5/77) golden jackal carcasses. Morphological identification, confirmed by molecular screening, classified all parasites as D. immitis. No D. immitis were detected in the red foxes or European badgers examined. All infected golden jackals were adults aged from 2 to 7 years with a parasite load ranging from 2 to 7 nematodes per carcass. One animal was infected with a sexually mature pair, while a second harbored pre-mature parasites; the remaining positive jackals were infected with female parasites only. Notably, histological examination of cardiac and lung tissue revealed proliferative endarteritis in the jackal with the highest parasite burden.

Conclusions: Further studies are required to establish whether golden jackals, as well as other wild carnivore hosts, may serve as competent definitive hosts of D. immitis and act as reservoirs for infection of other species including domestic dogs and humans. Histological changes in the cardiac tissue of at least one positive jackal were suggestive of infection with pathological consequences for the host.