Toxoplasma gondii exposure in wildlife in Spain: Is there any predictable threat for humans and domestic animals?

Abstract

Toxoplasmosis is a parasitic zoonosis of key importance in veterinary and public health. This article summarizes the available data (from 2000 to 2023) of exposition to Toxoplasma gondii in wildlife species in Spain based on a systematic bibliographic search, as well as further analysis of its potential relationship with environmental variables, biodiversity, anthropogenic impact on the habitat, and the reported human cases of toxoplasmosis. The overall seroprevalence of T. gondii in carnivorous mammals, birds, ungulate and lagomorph species in Spain was estimated at 69.3 %, 36.4 %, 18.4 %, and 16.2 %, respectively. Among the studies considered, great heterogeneity was observed both between and within taxonomic groups [Cohen's d > 0.8; X2 = 1039.10, df = 4 (p < 0.01) I2 = 97 %, r2 = 1.88, (p < 0.001)] and between and within bioregions [Cohen's d > 0.5; X2 = 368.59, df = 4 (p < 0.01)]. The results of a generalized linear model explaining T. gondii seroprevalence in wild animals suggest the influence of abiotic variables [wetland (p < 0.001), unvegetated (p < 0.001), isothermality (p < 0.001), and mean temperature during wettest quarter (p < 0.05)] and number of intermediate host species as positively associated with increased exposure of wildlife to T. gondii (p < 0.01). Toxoplasma gondii DNA was detected in both wild birds and wild mammals (range: 0.0-51.2 %) mainly from north-centre, northeast, and central-west of Spain. Regarding hospitalisation rates due to toxoplasmosis in humans, some abiotic variables [permanent crops (p < 0.05) and mean temperature during wettest quarter (p < 0.05)] showed a positive association. Despite certain limitations, this research evidences a substantial gap of knowledge on the implication of wildlife in the life cycle of T. gondii in Spain. This lack of knowledge is particularly evident in areas where the human-livestock-wildlife interface overlaps, preventing us from accurately determining its true distribution in different habitats, as well as its potential direct or indirect implications on public and veterinary health.