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Seroprevalence and Factors Associated with Toxoplasma gondii Seropositivity in Small Ruminants in Northeastern Portugal
by
, , , , , and
Tifany Pereira
1,2
,
Carina Rodrigues
3,
Maria João Caldeira
1,4,
Filipa Teixeira Rodrigues
1,
João Jacob-Ferreira
1,5
,
Ana Patrícia Lopes
2,5 and
Hélder Quintas
1,*
1
Associate Laboratory for Sustainability and Technology in Mountains (SusTEC), Mountain Research Centre (CIMO), Polytechnic Institute of Bragança (IPB), Campus de Santa Apolónia, 5300-253 Bragança, Portugal
2
Department of Veterinary Sciences, School of Agrarian and Veterinary Sciences (ECAV), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal
3
LiveWell, Research Centre for Active Living and Wellbeing, School of Health, Polytechnic Institute of Bragança (IPB), Campus de Santa Apolónia, 5300-253 Bragança, Portugal
4
Abel Salazar Biomedical Sciences Institute (ICBAS), University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
5
Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Animal and Veterinary Research Centre (CECAV), Department of Veterinary Sciences, School of Agrarian and Veterinary Sciences (ECAV), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal
*
Author to whom correspondence should be addressed.
Animals 2026, 16(17), 2691; https://doi.org/10.3390/ani16172691
Submission received: 27 July 2026
/
Revised: 25 August 2026
/
Accepted: 26 August 2026
/
Published: 28 August 2026
(This article belongs to the Special Issue Veterinary Epidemiology and Livestock Impact on Public Health)
Simple Summary
Toxoplasma gondii is a parasite that can infect sheep and goats and is relevant to animal production and food safety. Information on its occurrence in sheep and goat farms in northeastern Portugal is limited. This study examined blood samples from 2678 animals belonging to 149 flocks and collected information on animal characteristics and farm practices. Antibodies indicating prior exposure to the parasite were detected in 21.6% of the animals, and flocks containing at least one antibody-positive animal were identified in every municipality studied. Sheep, adult animals, non-native breeds, animals not kept permanently indoors, and animals from farms where cats were present had significantly higher odds of seropositivity. Other management- and farmer-related characteristics were not significantly associated with seropositivity after adjustment for the remaining variables. These findings indicate that T. gondii exposure is widespread throughout the study area and that seropositivity is associated with both animal- and farm-level characteristics. The findings provide evidence to support preventive measures, including protecting feed and water from contamination, limiting cat access to livestock and feed-storage areas, and improving farm hygiene and awareness, thereby benefiting animal health, environmental protection, and food safety.
Abstract
Toxoplasma gondii infection is relevant to animal production, food safety, and public health, but current epidemiological data for small ruminants in northeastern Portugal are limited. This cross-sectional study estimated seroprevalence and investigated factors associated with seropositivity in 2678 animals from 149 flocks sampled between May 2022 and December 2024. Serum samples were tested using an indirect enzyme-linked immunosorbent assay, and associated factors were evaluated using mixed-effects logistic regression with flock as a random effect. The overall true seroprevalence was estimated at 21.5% (apparent seroprevalence: 21.6%). At the flock level, 83.9% (125/149) of the sampled flocks were seropositive. True seroprevalence was higher in sheep than in goats (23.4% versus 14.4%), and seropositivity was detected in all surveyed municipalities. In the multivariable model, higher odds of seropositivity were observed in sheep (adjusted odds ratio 1.74), adult animals (2.78), non-native breeds (1.84), animals not kept in permanent housing (3.16), and animals from farms with cats (1.69). These findings indicate exposure throughout the surveyed area and associations with both host-related and farm-level characteristics. Strengthening farm biosecurity, limiting contamination of feed and water, and integrating animal health, environmental, and food safety measures may contribute to prevention within a One Health framework.
Keywords:
Toxoplasma gondii; seroprevalence; sheep; goats; associated factors; ELISA; northeastern Portugal
