First molecular evidence of Rickettsia spp. in Triatoma rubrofasciata: implications for vector ecology and zoonotic transmission

Rickettsia is an emerging global pathogen with incompletely understood transmission cycles. While triatomine bugs are established vectors for Trypanosoma cruzi, their potential role in the ecology of Rickettsia spp. remains unexplored. This study investigated the presence and genetic characteristics of Rickettsia spp. in Triatoma rubrofasciata and sympatric hosts in southern China.

A total of 362 T. rubrofasciata specimens including the fecal samples, head tissues and gut were screened for Rickettsia DNA using nested PCR targeting six genes (groEL, rrs, gltA, 17-kDa, ompA, and ompB). In addition, 64 fleas, 136 ticks, and 69 wild rodents were tested. Positive amplicons were sequenced and subjected to phylogenetic analysis.

Rickettsia DNA was detected in eight (2.2%, 8/362) T. rubrofasciata specimens, with Rickettsia felis specifically identified in four of these positive samples; the species of the remaining four could not be determined. The bacterium was detected across multiple anatomical sites, including the head (which contains the salivary glands), the gut, and fecal samples. Surveillance of sympatric hosts revealed a markedly higher prevalence in fleas (57.8%) and wild rats (4.3%), whereas ticks harbored a distinct agent related to Candidatus Rickettsia jingxinensis (29.4%). Genomic analyses indicated high conservation of key loci among R. felis strains across hosts, with a stable ompA gene variation distinguishing vector- and rodent-derived lineages. Phylogenetically, all R. felis sequences formed a distinct clade separate from tick-associated rickettsiae.

This study confirms for the first time the presence of Rickettsia in T. rubrofasciata, including R. felis and Rickettsia sp. The R. felis was found co-circulating in fleas and rodents, while ticks harbored a distinct Rickettsia, indicating separate transmission cycles in sympatric hosts. Genetic divergence in ompA further suggests host-adaptive evolution between vector- and rodent-associated strains. These findings suggest that T. rubrofasciata may serve as a previously unrecognized interface in the epidemiology of flea-borne spotted fever in southern China. They also highlight the expanded vector range of Rickettsia and underscoring the ecological complexity of its transmission, calling for broader surveillance of nontraditional vectors in endemic regions.