Human dirofilariasis – A potentially significant nematode zoonosis in an era of climate change

Abstract

Dirofilariasis is a mosquito-borne zoonosis caused by several species of the genus Dirofilaria. This disease can manifest as nodular lesions in subcutaneous tissues, various structures of the eye, the lungs and/or visceral organs. The Dirofilaria species and the vectors responsible for transmitting infection differ among various geographical regions. The most competent reservoirs of infection are domestic and wild canids (for Dirofilaria repens and Dirofilaria immitis), raccoons (for Dirofilaria tenuis) and bears (for Dirofilaria ursi), and humans represent aberrant or accidental hosts. Recently, there has been an increasing number of reported clinical cases of dirofilariasis in both animals and humans. It is known that changes in climatic conditions, including increased temperature, relative humidity and rainfall, can contribute to favourable conditions for the development of mosquitoes and larval stages of filarial parasites within their vector. Despite advances in our knowledge of nematodes of the genus Dirofilaria and the pathological changes that they can induce in different hosts, many clinicians are unfamiliar with dirofilariasis. Thus, in clinical settings, nodules associated with dirofilariasis are often misdiagnosed as neoplastic lesions. Often, physicians surgically excise such nodules from affected patients, sometimes in very sensitive or difficult-to-reach anatomical locations, which may be accompanied by complications or serious consequences for the patients’ health, including a stressful experience in the period from the discovery of a nodule to a definitive diagnosis.