Genetic diversity of Toxoplasma gondii isolates from members of the families camelidae and equidae worldwide: a systematic review.

Overview

• This systematic review examines the genetic diversity of Toxoplasma gondii parasites found in animals from the camelidae (camels, alpacas, llamas) and equidae (horses, donkeys, zebras, mules) families worldwide.
• The study highlights geographical differences in parasite genotypes and underscores the importance of these animals as indicators and potential sources of T. gondii infection to humans.

Background and Importance

• Toxoplasma gondii is a globally prevalent parasite affecting both humans and animals.
• It poses significant public health and veterinary challenges due to its zoonotic potential—meaning it can be transmitted from animals to humans.
• Camelidae and Equidae species are important environmentally and economically as livestock and may act as reservoirs or sentinels for environmental contamination by T. gondii.
• Understanding the genotypic diversity of T. gondii isolates in these animals is crucial for monitoring transmission dynamics and managing human and animal health risks.

Research Approach

• The authors performed a systematic review, searching six electronic databases (PubMed, Web of Science, Scopus, ProQuest, Science Direct, Google Scholar) up to July 20, 2025.
• Selection criteria focused on studies that reported genotypic data of T. gondii isolated from camelidae and equidae species.
• A total of 20 relevant studies were identified, encompassing genotypic information from 103 T. gondii isolates worldwide.

Key Findings by Geographic Region

• Americas and Africa:
  • Atypical genotypes were predominant (88.2% in the Americas and 83.3% in Africa).
  • These regions showed high genetic diversity among T. gondii isolates, indicating multiple unique strains circulating in local environments.
• Asia:
  • The greatest complexity in genotypes was observed, with mostly mixed infections found in 61.1% of isolates.
  • The China I genotype (ToxoDB #9) was identified as the dominant individual lineage.
• Europe:
  • A distinct genotype profile was seen, with Type III predominating in 57.1% of isolates.
  • However, atypical genotypes were also present, indicating some diversity.

Implications of Findings

• T. gondii populations infecting camelidae and equidae hosts are diverse and largely reflect the parasite strains circulating within their specific geographic environments.
• The predominance of non-classical (“atypical”) genotypes contrasts with traditional clonal types (I, II, III), suggesting regional evolutionary variation and adaptation.
• Significant co-existence of genotypes associated with high human virulence (such as Type I and China I) in food animals highlights a real risk for zoonotic transmission to humans consuming or handling these animals.
• These animals can therefore serve as key sentinels for environmental contamination and as direct sources of infection, emphasizing their public health importance.

Recommendations and Future Directions

• Researchers and public health authorities should adopt high-resolution genotyping techniques for T. gondii to provide clearer insight into parasite diversity and transmission patterns.
• A One Health approach is advised, integrating human, animal, and environmental health surveillance to effectively monitor and mitigate T. gondii risks.
• Such surveillance strategies can improve understanding of transmission dynamics, guiding interventions to protect human health and support the economic and cultural value of camelidae and equidae livestock.
• Future studies are encouraged to expand the geographical scope and host range to better map global genetic diversity and zoonotic risk factors.