SUMMARY: Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitisandD. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, bothD. immitisandD. repensare themselves hosts to symbiotic bacteria of the genusWolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge ofD. immitisandD. repensand the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism ofDirofilariaspecies; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Cardiopulmonary dirofilariasis is a cosmopolitan disease caused by Dirofilaria immitis, which affects mainly canids and felids. Moreover, it causes zoonotic infections, producing pulmonary dirofilariasis in humans. Heartworm disease is a vector-borne transmitted disease, thus transmission depends on the presence of competent mosquito species, which is directly related to favorable climate conditions for its development and survival. Cardiopulmonary dirofilariasis is mainly located in countries with temperate and tropical climates. Europe is one of the continents where animal dirofilariasis has been studied more extensively. In this article we review the current prevalence of canine and feline cardiopulmonary dirofilariasis in the European continent, the transmission vectors, the current changes in the distribution and the possible causes, though the analysis of the epidemiological studies carried out until 2001 and between 2002 and 2011. The highest prevalences have been observed in the southern European countries, which are considered historically endemic/hyperendemic countries. Studies carried out in the last 10 years suggest an expansion of cardiopulmonary dirofilariasis in dogs toward central and northern Europe. Several factors can exert an influence on the spreading of the disease, such as movement of infected animals, the introduction of new species of mosquitoes able to act as vectors, the climate change caused by the global warming, and development of human activity in new areas. Veterinary controls to prevent the spreading of this disease, programs of control of vectors, and adequate protocols of prevention of dirofilariasis in the susceptible species should be carried out.

Heartworm disease caused by Dirofilaria immitis is a vector-borne disease that affects canids and felids, both domestic and wild, throughout the world. It is a chronic disease which causes vascular damage in pulmonary arteries, and in advanced stages, the presence of pulmonary hypertension and right-sided congestive heart failure can be evidenced. Moreover, pulmonary thromboembolism is caused by the death of the worms, which can be lethal for the infected animal. Furthermore, it is the causative agent of human pulmonary dirofilariosis, being a zoonotic disease. The aim of this review was to update the current epidemiological situation of heartworm in Europe in dogs, cats, wild animals, and vectors insects, and to analyse the factors that may have contributed to the continuous spread of the disease in the last decade (2012–2021). In Europe, the disease has extended to eastern countries, being currently endemic in countries where previously only isolated or imported cases were reported. Furthermore, its prevalence has continued to increase in southern countries, traditionally endemic. This distribution trends and changes are influenced by several factors which are discussed in this review, such as the climate changes, presence of vectors in new areas, the appearance of new competent vector species in the continent, increased movement of pets that travelled to or originated from endemic countries, the urbanisation of rural areas leading to the formation of so-called “heat islands”, or the creation of extensive areas of irrigated crops. The continuous expansion of D. immitis must be monitored, and measures adapted to the situation of each country must be carried out for adequate control.

Currently, climate change, modifications of landscapes and habitats due to human activities, as well as an increase in the movement of reservoirs and new species of competent vectors, have contributed to the spread of canine vector-borne diseases. These are mostly emerging and neglected diseases, some of them with zoonotic potential. Therefore, the objective of this study was to assess the prevalence and distribution of four major canine vector-borne diseases (Dirofilaria immitis, Leishmania infantum, Anaplasma spp., and Ehrlichia canis) in Spain. Between September 2018 and February 2020, blood was sampled from 4643 client-owned dogs from 111 veterinary clinics from the 17 autonomous communities of Spain. All samples were tested for the detection of D. immitis antigens, and for antibodies against L. infantum, Anaplasma spp. and E. canis. Of the studied dogs, 22.14% were positive for one or several diseases while the prevalence was 6.25% (CI: 5.59–6.98) for D. immitis, and the seroprevalences were 10.36% (CI: 9.52–11.27) for L. infantum, 5.06% (CI: 4.47–5.73) for Anaplasma spp., and 4.26% (CI: 3.72–4.88) for E. canis. Co-infections by two and three vector-borne diseases were reported in 13% and 2% of the infected dogs, respectively. The studied vector-borne diseases are widely distributed throughout the Spanish geography, being observed and expanding northward in the case of D. immitis and L. infantum. The results point to an insufficiency of preventive measures to avoid the infection, and the need of the implementation of awareness campaigns among veterinarians and owners. Furthermore, a close collaboration between veterinarians, physicians and health authorities would be necessary for such zoonotic vector-borne diseases.