Bacterial Pathogens of Non-native Rodents and Shrews of Busol Watershed and Forest Reservation, Baguio City: A Preliminary Study of Diversity and Potential Infection and Transmission Dynamics

Paglingayen, Kimberly P.

In the Philippines, small mammal infections are poorly studied and are limited to zoonotic pathogens. To assess potential infectious threats to native non-volant mammal species within the Busol Watershed and Forest Reservations (BWFR), the pathogenic bacteria in synanthropic rodents and shrews were investigated using 16S rRNA gene sequencing. Potential transmission pathways of these pathogens were also studied through phylogenic analyses and literature review. Twenty-seven non-native rodents and shrews were captured (12 Suncus murinus, 11 Rattus exulans, and four (4) R. tanezumi) and screened for putative bacterial pathogens. Out of the 34-identified bacterial phylotypes, eight (8) are pathogenic to mammals. These are Morganella morganii, Ehrlichia japonica, Exiguobacterium aurantiacum, Clostridium neonatale, Corynebacterium phocines, Campylobacter curves, Spodiobacter cordis, and sp. The S. cordis was detected in the pooled blood samples while Ralstonia sp. was from the fecal samples. The presence of Ralstonia in feces suggests transmission through environmental exposure. Statistical test also showed that the pathogen prevalence and dissimilarity had no association with all the investigated host attributes (i-e., species, sex, and maturity), indicating that these are not limited to higher infection risk of individuals. This was also supported by the phylogenetic analyses wherein obtained sequences did not form distinct clades with genotypes associated with single host species. This study posits that synanthropic rodents and shrews in BWFR harbor pathogenic bacteria capable of cross-species transmission. Investigating these transmissions is important in predicting infection dynamics among small, non-volant mammal and human populations and the pathogen exposure risk of native mammal species within the BWFR.