Host-pathogen-vector continuum in a changing landscape: Drivers ofBartonellaprevalence and evidence of historic spillover in a multi-host community

Abstract

Our understanding of pathogen spillover is largely based on viral systems associated with bats. Bacterial infections of zoonotic origin also pose a significant public health burden, many of which are associated with small mammals like rodents that live abundantly among humans. When ecologically different species of small mammals are brought in contact with each other due to various factors, including habitat modification, there is potential for bacterial spillover within the host community and subsequently to humans. Small mammals and their ectoparasite communities present a unique system to investigate the eco-epidemiology of multi-host pathogens, which can inform specific bacterial spillover determinants and their interplay. In a rainforest-human-use mosaic, we applied ecological and evolutionary analysis to investigateBartonellaspp. across small mammal and ectoparasite communities.We observed substantial overlap among small mammal communities in different habitat types, predominantly driven by habitat generalists. Most ectoparasites were generalists, infecting multiple hosts, and several host species displayed polyparasitism, i.e., they were infected by multiple ectoparasites. We observed highBartonellaprevalence at both study sites – a forest-plantation mosaic (47.4%) and a protected area (28.8%). Seven of the ten ectoparasite morphotypes sampled were also positive forBartonella, following the prevalence trend in their hosts. A Generalised Linear Model (GLM) revealed an independent association between aggregated ectoparasite load in species andBartonellaprevalence, implicating ectoparasites in transmission.Bartonellalineages from small mammals were host-specific, while ectoparasites showed no host-specific associations. They carriedBartonellaassociated with other hosts, indicating the potential for cross-species transmission. Phylogenetic ancestral trait reconstruction ofBartonellahaplotypes suggests historic spillover events in the small mammal community, validating the potential for contemporary spillover. These results highlight infection risk from such underdiagnosed agents in the landscape, and the necessity to disentangle complex multi-host multi-vector systems to understand their epidemiological consequences.

Identification of distinct rodent-associated adenovirus lineages from a mixed-use landscape in the Western Ghats biodiversity hotspot

“…Small mammals were captured from different land-use types; forest fragments, grasslands, and human habitations (Figure 1) between January and March 2018 (NCBS-Institutional Animal Ethics Committee approval-NCBS-IAEC-2016/10-[M]). Samples included 136 small mammal individuals representing seven distinct species, (previously reported in Ansil et al, 2021Ansil et al, , 2023; Rattus satarae, R. rattus, Mus cf. fernandoni, M. cf.…”

Population genetics of animals in the wild to aid conservation: Uma Ramakrishnan—Recipient of the 2023 Molecular Ecology Prize

“…Not only did Uma's team persist through these intense pressures but their disease ecology stream of research also expanded. They recently documented Bartonella in small mammal communities in the Western Ghats (Ansil et al., 2021) and explored the possible impact of landscape change as its driver (Ansil, Viswanathan, et al., 2023). Similar landscape and anthropogenic impacts on disease have also been documented in birds (Gupta et al., 2019).…”