DIROFILARIOSIS IN ITALIAN WOLF POPULATION (CANIS LUPUS ITALICUS): A PERSISTENT VECTOR-BORNE DISEASE IN NORTHEN ITALY

INTRODUCTION: Heartworm disease, caused by Dirofilaria immitis, affects domestic and wild carnivores and it is transmitted by various species of mosquitoes. Untreated dogs serve as the primary reservoir for this parasite, usually showing high microfilaraemia and high parasitic burden. In north-western Italy, heartworm infection is prevalent, particularly in humid lowlands. The role of wildlife in maintaining and spreading heartworm is debated, and information on heartworm infection in wolves is limited. However recent studies suggest that this species can act as a competent host in the D. immitis lifecycle. In northwestern Italy, infection rates in wolves recolonizing Alpine mountains appear to be similar to those in untreated dog populations endemic to the area (Moroni et al., 2021. Parasit vectors, 13:482). The present study aimed to assess the prevalence of D. immitis in a large sample of Italian wolves from central-northern Italy, an area experiencing a recent increase in wolf population, and to genetically characterize the helminths found. MATERIALS AND METHODS: From January 2021 to February 2024, a total of 452 wolves were examined for the presence of D. immitis in the pulmonary trunk and heart. All individuals were aged using 3 categories as follows: class 1: ≤12 months; class 2: 1-2 years; class 3: > 2 years. when filarial nematodes were visualized, they were collected, fixed in 70% ethanol, and prepared for morphological evaluation. Additionally, at least one worm from each wolf underwent genetic characterization through sequencing of 12S rDNA, 18S rDNA, and COI mtDNA. The Knott technique was applied to the blood (whenever possible based on carcass preservation) in cases of positive wolves to assess microfilaremia. RESULTS AND CONCLUSIONS: The wolves sampled came from 38 provinces across six different regions in central northern Italy (Piedmont, Lombardy, Emilia-Romagna, Tuscany, Marche, Umbria). The presence of D. immitis adults was observed in 14 individuals (3%), comprising 9 males and 5 females from age classes 2 and 3. Positive wolves came from Emilia-Romagna Region (5% of prevalence), Piedmont (3%) and in one case from Lombardy (3%). Adults were collected and processed for the morphological identification in 12 cases showing a mean intensity of 3 worms. Additionally, blood analysis conducted on two individuals, revealed the presence of microfilaremia. Sequencing of the different molecular markers confirmed the morphological identification of D. immitis, with sequence similarities ranging from 99.4% to 100%. Phylogenetic analysis is currently underway to position our sequences relative to those in available databases from other host species. The prevalence observed in the wolves studied aligns with the seroprevalence estimated in dogs in northern Italy (Mendoza Roldan et al., 2020. Parasit vectors, 13:193). Furthermore, the presence of microfilaremia in wolves confirms their hypothesized role as competent hosts and sheds light on their potential role as a source of D. immitis transmission