Dirofilaria spp. infection in cats from the Mediterranean basin: diagnosis and epidemiology

Dirofilaria immitis and Dirofilaria repens, causing heartworm disease and subcutaneous dirofilariosis, respectively, are zoonotic mosquito-borne filarioids infecting a plethora of hosts including cats. Only fragmented data are available on the diagnosis and epidemiology of feline dirofilariosis. We assessed the occurrence of both nematode infections, their risk factors and clinicopathological abnormalities in cats, from six countries of the Mediterranean Basin. In addition, Wolbachia spp. endosymbionts were assessed in Dirofilaria spp.-positive animals. Blood and sera samples were obtained from cats with outdoor access from Spain (n = 354), Portugal (n = 287), Italy (n = 125), Greece (n = 116), Israel (n = 101) and France (n = 100). Cat sera were tested by both direct antigenic (SNAP test, commercial ELISA kit) and indirect antibodies (in-house ELISA) serological tools, and blood samples by real time and conventional PCR targeting Dirofilaria spp. DNA, followed by sequencing. A statistical analysis was run to assess the link between Dirofilaria spp. infection and independent variables, as well as among feline immunodeficiency virus (FIV) and/or feline leukaemia virus (FeLV) co-infections, and clinicopathological abnormalities. Overall, 3.8% (i.e., 41/1,083) cats scored positive for Dirofilaria spp. infection with prevalences ranging from 2% in Israel to 7.8% in Greece. Of the 41 positive cats, 16 were infected by D. immitis (by SNAP test and/or PCR) and two by D. repens (by PCR); the remaining animals were antibody-positive for Dirofilaria spp. using the in-house ELISA. Wolbachia DNA was detected in one D. immitis-infected cat. Nematode positivity was significantly associated with age, breed, hyporexia, dandruff, and dyspnoea. This study provides data on the prevalence of Dirofilaria spp. infection in cats from the Mediterranean Basin, as well as new insights on its diagnosis, revealing the importance of performing strategic chemoprophylactic treatments for cats living in areas where the infection is endemic in dogs.