Researchers surveying stray cats and dogs across Peninsular Malaysia have documented a strikingly structured community of flea-borne bacteria, including several previously uncharacterised lineages of Bartonella. The study, published in Parasites & Vectors, examined 296 stray animals in urban, peri-urban and rural landscapes and screened every recovered flea individually for three bacterial groups of public health concern.
Overall, 95 of the 296 animals carried fleas, an infestation prevalence of 32.09 percent. Cats were significantly more likely to be infested than dogs, at 39.44 percent versus 13.25 percent. In total, 636 fleas were collected and identified morphologically. The team found complete host-associated segregation: Ctenocephalides felis, with 485 individuals, occurred exclusively on cats, while C. orientis, with 151 individuals, occurred exclusively on dogs.
Molecular screening using polymerase chain reaction assays followed by Sanger sequencing and phylogenetic analysis detected flea-borne pathogens in 457 of the 636 fleas, or 71.86 percent. The pathogens identified included Bartonella henselae, B. clarridgeiae, B. koehlerae, several uncharacterised Bartonella lineages, Rickettsia felis and R. asembonensis. No Orientia tsutsugamushi, the agent of scrub typhus, was detected in any flea sample.
Landscape type shaped the pathogen communities in a species-specific way. Urban environments were associated with significantly higher Bartonella prevalence in C. felis, reaching 70.05 percent. In contrast, C. orientis on dogs was overwhelmingly dominated by R. asembonensis, which accounted for 94.04 percent of detections in that flea species.
The ecological analyses went beyond simple prevalence counts. Using alpha diversity indices, non-metric multidimensional scaling, permutational multivariate analysis of variance and tripartite ecological network analysis, the researchers showed significant landscape-associated variation in pathogen community composition among C. felis populations, but not among C. orientis populations. Peri-urban environments supported greater pathogen diversity, while urban landscapes showed higher Bartonella detection in cat fleas.
One of the most notable findings came from the phylogenetic work: a distinct, well-supported clade of previously uncharacterised Bartonella lineages, recovered with 100 percent bootstrap support. This expands the known diversity of flea-associated Bartonella in Malaysia, though the authors note these lineages remain uncharacterised and their clinical significance is not yet established.
Risk factors for flea infestation, Bartonella occurrence and Rickettsia occurrence were evaluated with generalized linear models, generalized linear mixed-effects models and Firth’s penalized logistic regression, respectively.
The authors conclude that flea-borne pathogen communities in Peninsular Malaysia are structured by strong host-vector associations and by ecological landscape. They argue that integrating molecular epidemiology with community ecology improves surveillance of emerging flea-borne zoonoses, particularly as urbanisation continues to reshape contact zones between stray animals, fleas and people in Southeast Asia.
As an observational survey of fleas from stray animals, the study documents associations rather than direct transmission risk to humans. Nevertheless, the high overall pathogen detection rate, the strict host-flea segregation and the discovery of novel Bartonella lineages mark the region’s stray carnivore populations as a meaningful reservoir landscape for flea-borne bacteria.
Subject of Research: Flea-borne bacterial pathogens and their ecological structure in stray carnivores across urban, peri-urban and rural Peninsular Malaysia
Article Title: Ecological niche partitioning and urbanization-driven restructuring of flea-borne pathogen communities in stray carnivores of Peninsular Malaysia: discovery of uncharacterised Bartonella lineages
Article References: Alison, J. T., Taufik, A. S., Jahfar, A.-I., AbdulHalim, A. A., Husin, N. A., Izwan-Anas, N., Mansor, M. S., & Ya’cob, Z. (2026). Ecological niche partitioning and urbanization-driven restructuring of flea-borne pathogen communities in stray carnivores of Peninsular Malaysia: discovery of uncharacterised Bartonella lineages. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07693-7
Image Credits: AI Generated
DOI: 10.1186/s13071-026-07693-7
Keywords: Bartonella, Rickettsia felis, Ctenocephalides felis, Ctenocephalides orientis, stray cats, stray dogs, Peninsular Malaysia, urbanization, flea-borne pathogens, phylogenetics, zoonoses, ecological networks
News Source: Drew Townsend. (October 29, 2026). Stray cats and dogs in Malaysia carry uncharacterised Bartonella lineages in fleas. Scienmag.
