Influence of ecological and management factors on Toxoplasma gondii infection in small ruminants in Algeria.

Toxoplasma gondii is a zoonotic protozoan of major concern for small-ruminant production and public health. This study is among the first to simultaneously compare T. gondii seroprevalence across contrasting Algerian bioclimatic zones. In summer 2024, a cross-sectional study was conducted across 82 herds comprising 4,022 small ruminants in three provinces of central Algeria (Blida, Médéa, Djelfa), representing contrasting bioclimatic zones (humid, semi-arid, and arid). Blood samples were collected from 1,052 animals older than six months to assess the apparent seroprevalence of T. gondii and associated factors. The herd-level apparent seroprevalence was 87.8%, with goat herds showing the highest apparent prevalence (94.4%), followed by mixed (87.5%) and sheep herds (85.4%). The individual animal-level apparent seroprevalence was 38.2%, with goats exhibiting significantly higher seropositivity than sheep (49.8% vs. 34.8%; p < 0.001). A climatic gradient was observed at the individual level, with apparent seroprevalence of 50.8% in the humid region (Blida), 43.4% in the sub-humid region (Médéa), and 27.1% in the arid region (Djelfa) (p < 0.001). After adjustment in a mixed-effects logistic regression model accounting for within-herd clustering, species and province remained significantly associated with seropositivity, while age, sex, and reproductive history were not. At the herd level, small herd size (< 50 animals) (adjusted OR = 14.45, p = 0.004), sedentary farming systems (adjusted OR = 9.75, p = 0.006), and cat exposure (adjusted OR = 22.78, p < 0.001) were significantly associated with seropositivity. However, convenience sampling and a final sample size below the calculated minimum should be considered when interpreting representativeness. These findings highlight the importance of regionally adapted surveillance and risk-based biosecurity measures, particularly in sub-humid peri-urban areas with intensive small-herd management.