Lameira, E. R. P. | Search bioRxiv

bioRxiv2026

Microbial communities in Ornithodoros phacochoerus ticks: spatial structure and influence of African swine fever virus infectious status

AO_SCPLOWBSTRACTC_SCPLOWOrnithodoros phacochoerus are nidicolous soft ticks of the Ornithodoros moubata complex of species known to be vectors of the African swine fever (ASF) virus. These Ornithodoros ticks depend on endosymbionts to produce essential nutrients necessary for their development. However, endosymbionts are only a part of the complex microbiota hosted by the tick. This microbiota often includes primary or secondary endosymbionts, commensal species from the environment, and, most of the time, some pathogens. The present study was performed to understand the organization and spatial distribution of the microbiota of O. phacochoerus. One of the objectives was to investigate if the pathogen of interest (ASF virus) is involved in the organization of the microbiota through pathogen-induced dysbiosis or other interactions. For this purpose, 704 O. phacochoerus ticks were collected from two conservation areas in Mozambique. Sequencing was performed targeting the V3-V4 region of the 16S rRNA gene, and the resulting dataset was processed using FROGS to characterize the bacterial microbiota hosted by the ticks. The results indicate that the microbiota of Ornithodoros phacochoerus contains very low bacterial diversity, with one primary endosymbiont (Francisella-like endosymbiont), one potential secondary endosymbiont (Rickettsiella), and very few environmental or pathogenic bacterial species. We found a clear spatial structure of the microbiota, with ticks from the same sampling site showing similar patterns. On the contrary, no association with the infectious status for African swine fever virus was detected, suggesting that this pathogen does not shape Ornithodoros microbial communities. Our results on tick - microbiota - pathogen - environment interactions in nidicolous soft ticks, showed patterns that differ from most hard tick studies.

microbiology↗

bioRxiv2025

Population genetics of the nidicolous soft tick Ornithodoros phacochoerus in the context of African swine fever sylvatic cycle

Ticks of the species Ornithodoros phacochoerus are endophilic soft ticks which infest warthog burrows. Like other Ornithodoros of the O. moubata species complex, O. phacochoerus is a vector of the African swine fever virus and participates in the maintenance of the virus among warthogs in the sylvatic cycle in Southern and Eastern African countries. In this study, the population genetic structure of O. phacochoerus was investigated using sixteen microsatellite markers. After sampling campaigns that took place between 2020 and 2022, we analyzed 684 ticks from 21 warthog burrows and resting sites from Coutada 9 Game Reserve, Macossa District, Mozambique, and 138 ticks from 3 warthog burrows and resting sites from Gorongosa National Park, Gorongosa District, Mozambique. Burrows and resting sites are regularly used by the common warthog Phacochoerus africanus which is thought to be responsible for the movements of O. phacochoerus between sites. After genotyping, the observed genetic variation followed a model of isolation by distance with a structure at the level of the sampling sites (burrows and resting sites). Gorongosa National Park and Coutada 9 Game Reserve appeared to be completely isolated from each other in terms of gene flow, and Coutada 9 Game Reserve showed a clear signature of a bottleneck effect. Effective population sizes within sampling sites were quite low (4.1 individuals), with an estimated migration rate of 35% and a mean dispersal distance of 209 meters per tick generation. These results suggested frequent tick movements between burrows at a small geographic scale, due to warthog movements between the burrows. As both wildlife conservation areas are positive for African swine fever virus, these results reinforce the suspected role of the ticks in the sylvatic cycle of the virus, as infected ticks could be moved from one burrow to another, maintaining the presence of the virus in several sites of the conservation areas. This confirms the importance of maintaining buffer zones around conservation areas, buffer zones that should remain free of any domestic pigs to prevent vector spillover from the sylvatic cycle to the domestic cycle.

ecology↗