Transstadial and transovarial perpetuations of Borrelia venezuelensis in Ornithodoros rudis, with demonstration of vector competence.

Ticks of the genus Ornithodoros are recognized vectors of relapsing fever group Borrelia, such as Borrelia venezuelensis, whose infection dynamics in its vector, Ornithodoros rudis, remains poorly understood in Brazil. This study aimed to investigate the transstadial perpetuation and transovarial transmission of B. venezuelensis in O. rudis and the vector competence of all parasitic stages of this tick species. Experimental colonies were maintained under controlled laboratory conditions, and ticks were fed on Syrian hamsters (Mesocricetus auratus). Infection in hamsters was monitored using dark field microscopy and real-time PCR. Borrelia venezuelensis was detected across multiple tick life stages, and its presence in larvae derived from infected females confirmed transovarial transmission. Vector competence for B. venezuelensis was demonstrated for larvae, nymphs and adults of O. rudis. Additionally, neurological symptoms and sudden death were observed in some hamsters, possibly associated with toxicosis due to heavy tick infestation. These findings provide the first experimental evidence of transstadial and transovarial maintenance of B. venezuelensis in O. rudis, reinforcing its role as a competent vector and contributing to a better understanding of the eco-epidemiology of relapsing fever in South America.