Toxoplasmosis in the European brown hare : pathology, strain genotyping and population exposure within the Iberian distribution range

The European brown hare (Lepus europaeus), widely distributed across Eurasia, is a key prey species for many vertebrates. Toxoplasma gondii, a globally distributed zoonotic protist, can infect all homoeothermic animals, including lagomorphs. Hares are highly susceptible, with sporadic toxoplasmosis cases reported in central and northern Europe, but its impact on southern populations remains unclear. Lethal toxoplasmosis was confirmed in two European brown hares from Catalonia, northeastern Spain (2018 and 2021). Samples were collected for histopathology and molecular analyses. Necropsy showed good body condition but revealed splenomegaly, liver necrosis, and pulmonary oedema. Microscopically, necrotizing multiorgan lesions with protozoan-like structures were observed. Toxoplasma gondii DNA was detected in spleen, with microsatellites-genotyping identifying a type II specific variant of the ToxoDB#3 genotype. In addition, 231 serum samples from passive and active surveillance (2013-2023) from Catalonia (n = 205) and other northern Spanish regions (n = 28) were tested for anti-T. gondii IgG antibodies using an indirect ELISA kit, showing a seroprevalence of 1.73% (4/231; 95% CI: 0.05-3.41). These are the first clinical toxoplasmosis cases reported in European brown hares from southern Europe, highlighting their unusual susceptibility. The low seroprevalence, consistent with Mediterranean reports, raises questions about exposure frequency. Further studies are needed to assess the impact of T. gondii on European brown hare populations.