Survey occurrence of serum antibodies against Leishmania spp., Toxoplasma gondii and Trypanosoma cruzi, agents with zoonotic potential, in horses from the state of São Paulo, Brazil.

Overview

• This study investigated the presence of antibodies against three zoonotic protozoan parasites—Leishmania spp., Toxoplasma gondii, and Trypanosoma cruzi—in horses from São Paulo, Brazil, to assess their exposure to these pathogens.
• The research revealed varying levels of exposure to these parasites among horses, notably a higher prevalence of antibodies to Leishmania spp., with additional analyses exploring associations between seropositivity, demographic factors, and geography.

Study Background and Purpose

• Leishmania spp., Toxoplasma gondii, and Trypanosoma cruzi are protozoan parasites with zoonotic potential, meaning they can be transmitted from animals to humans.
• Horses may act as sentinels or reservoirs for these parasites, so understanding their exposure is important for veterinary and public health surveillance.
• The study aimed to perform a seroepidemiological survey to estimate the frequency of antibodies against these pathogens in horses from the northwestern region of São Paulo state, Brazil.

Study Design and Methods

• Researchers collected serum samples from 202 horses across 21 different properties/farms.
• Serological tests used included:
  • Enzyme-linked immunosorbent assay (ELISA) for detecting antibodies against Leishmania spp.
  • Direct agglutination test (DAT) for detecting antibodies against Toxoplasma gondii.
  • Tests to detect antibodies against Trypanosoma cruzi (exact serological method not specified in abstract).
• The tests aimed to identify prior exposure by detecting antibodies rather than current infection.
• Statistical analyses such as Chi-square tests were used to compare antibody prevalence among the parasites and to examine associations with demographic factors (age, sex, breed, function).
• Geographic analysis involved assessing correlations between seropositivity patterns and distance between farms to infer spatial transmission factors.

Key Findings

• Out of 202 horses:
  • 48 horses (23.76%) had antibodies against Leishmania spp.
  • 29 horses (14.36%) had antibodies against Toxoplasma gondii
  • 2 horses (0.99%) had antibodies against Trypanosoma cruzi
• A significantly higher occurrence of antibodies to Leishmania spp. was found compared to T. gondii and T. cruzi (Chi-Square = 46.7, p < 0.001).
• There were no significant associations between seropositivity and horse attributes such as age group, sex, breed, or function (e.g., riding, work, breeding).
• The ELISA test was more effective at detecting Leishmania antibodies, while the direct agglutination test detected T. gondii antibodies more frequently.
• A weak but statistically significant correlation existed between seropositivity patterns and geographic distance among farms, suggesting that environmental or management factors might influence parasite transmission, potentially due to differences in parasite lifecycle and transmission vectors.

Significance and Novelty

• This research provides important epidemiological data on exposure to zoonotic protozoa in horses in São Paulo, Brazil, contributing to veterinary and public health knowledge.
• The finding that Leishmania antibodies are more prevalent may reflect local environmental conditions favoring vector presence or transmission dynamics.
• The detection of antibodies against Trypanosoma cruzi, though rare, is notable as this is the first reported seroepidemiological survey of T. cruzi exposure in horses in southeastern Brazil.
• The lack of association between demographic factors and seropositivity suggests that exposure risk may be broadly distributed or influenced more by environmental and management factors rather than intrinsic horse characteristics.
• The weak spatial correlation implies that targeted interventions or further ecological studies could focus on environmental conditions at the farm level to control these parasites.

Limitations and Future Directions

• The study is limited to a specific region within São Paulo state; results may not generalize to other regions or countries.
• The serological methods detect exposure but not active infection, so clinical significance and transmission potential remain to be explored.
• Further research could:
  • Include vector studies to better understand transmission cycles.
  • Investigate the role of horses in the epidemiology of these zoonotic protozoa.
  • Utilize molecular diagnostics to confirm active infections.
  • Explore potential environmental or management variables that contribute to differing transmission patterns.