Cameroonian ticks, uncharted viromes: new insights from Rhipicephalus microplus

Ticks are important vectors for zoonotic viruses and other pathogens, and pose a significant risk to public health due to their global distribution and ability to circulate between vertebrate species. Surveillance of tick viromes can act as a warning system to detect and monitor the circulation of local pathogenic virus variants and the risk of zoonotic outbreaks, but this approach remains underused. We collected 58 Rhipicephalus microplus adults from cattle in Buea, Cameroon, with an additional 9 clusters of eggs produced after capture. RNA was extracted from the eggs and the heads of the adult ticks. After sequence-independent single-primer amplification of the RNA, all samples were sequenced using nanopore sequencing. We observed a large viral diversity in the samples, with the predominant virus families being Phenuiviridae, Chuviridae and Flaviviridae. For each of these families, we also observed the presence of viral RNA in eggs laid by infected parents, highlighting the potential for vertical transmission of these viruses. Finally, we also found two new viruses in the adult ticks: an uukuvirus and a thogotovirus, respectively named Microon virus and Rhimica virus. Rhimica virus was found in multiple ticks and is closely related to the zoonotic Oz virus. This study further highlights the valuable insights that tick virome sequencing can offer into circulating tick-borne viruses, especially in understudied regions.