Molecular Detection of Trypanosoma evansi and Trypanosoma vivax in Household Dogs from Semnan Province, Iran: Implications for One Health Surveillance at the Wildlife–Livestock–Human Interface

Background: Salivarian trypanosomes, particularly Trypanosoma evansi and Trypanosoma vivax, are important hemoflagellate parasites causing veterinary and public health concerns worldwide. These pathogens infect diverse domestic and wild animals and have recognized zoonotic potential. Semnan Province, central Iran, includes protected ecosystems, including Kavir and Touran National Parks, where interactions among wildlife, domestic animals, vectors, and humans may facilitate pathogen transmission. This study investigated the occurrence and distribution of salivarian trypanosomes in household dogs from Semnan Province using molecular diagnostic techniques.

Methods: Blood samples were collected from 140 healthy household dogs (93 from Semnan and 47 from Shahroud). Thin blood smears were examined microscopically after Giemsa staining. Genomic DNA was extracted and analyzed by polymerase chain reaction targeting the internal transcribed spacer 1 region for detection of Trypanosoma spp. Samples positive for T. vivax were confirmed using species specific TVW primers.

Results: No trypanosomes were detected by microscopy. However, PCR identified 17 infected dogs (12.14%). Trypanosoma evansi was detected in 10 dogs (7.14%), whereas T. vivax was identified in seven dogs (5.00%). Coinfection with both species occurred in two animals. Estimated prevalences of T. evansi and T. vivax were higher in Semnan (11.45% and 8.50%, respectively) than in Shahroud (2.82% and 1.47%, respectively). No significant association was found between infection status and sex or geographic location (P > 0.05). PCR showed markedly greater sensitivity than smear examination.

Conclusions: Molecular detection of T. evansi and T. vivax in apparently healthy dogs highlights the potential role of canines as reservoirs or sentinels of infection in sensitive areas. The presence of zoonotic trypanosomes near protected wildlife habitats raises concerns regarding pathogen circulation at the human animal environment interface. These findings emphasize the need for molecular surveillance, vector monitoring, and One Health based control strategies to reduce transmission risks to domestic animals, wildlife, and human populations.