Dirofilaria Infections in Humans and Other Zoonotic Filarioses

Abstract

Dirofilaria repens and Dirofilaria immitis, the main filariae of domestic and wild carnivores, are responsible for most cases of human infections by zoonotic filariae. Other species of animal filariae that have been reported in human patients include species from the genus Dirofilaria and nematodes from genera Onchocerca, Brugia, and Molinema. The higher frequency of human infection by Dirofilaria spp. compared to infections by other zoonotic filariae may be due to various factors. For example, awareness and attention of physicians for zoonotic filarial infection is higher in developed countries, where the dog represents an important reservoir for Dirofilaria worms. Climate change, together with the movement of infected dogs to previously unsuitable areas, is likely responsible for the increase in areas endemic for D. immitis and D. repens, with the consequence of an increase risk of infection for humans in temperate countries. Infection by D. repens is more frequent in Europe, where the documented infections by D. immitis appear rare, but the situation is different in other countries, e.g., in the USA, where human infections by D. immitis are frequently recorded. Infections by Dirofilaria worms are generally paucisymptomatic, but cases are also reported characterized by a severe clinical picture. The control of Dirofilaria infections in humans is essentially based on the control of the infection in dogs, and particular attention should be devoted to the transit of unprotected dogs (i.e., dogs that do not receive prophylactic treatment) in endemic areas, increasing the risk of acquiring filarial infections and of importing the infection in non-endemic areas.