Bat species assemblage predicts coronavirus prevalence

The research question centers on understanding the relationship between bat species diversity and the prevalence of coronaviruses (CoVs). The study's context is the growing concern over zoonotic diseases, particularly those originating from wildlife reservoirs. Anthropogenic disturbances, such as habitat loss and fragmentation, are increasingly altering species assemblages and potentially increasing the risk of pathogen spillover. Bats, due to their high mobility, diverse roosting behaviors, and known role as CoV reservoirs, are ideal subjects for examining this relationship. The study's purpose is to investigate how changes in bat species richness and community composition influence the prevalence and infection dynamics of CoVs. The importance of the study lies in its potential to inform biodiversity conservation strategies aimed at mitigating zoonotic disease risk. Understanding the interplay between biodiversity and disease prevalence can contribute to the One Health framework, promoting integrated approaches to human, animal, and environmental health.

The introduction cites numerous studies highlighting the impact of anthropogenic activities on biodiversity loss and its correlation with infectious disease emergence. The literature reviewed indicates that bats are significant reservoirs of viruses with zoonotic potential, and their unique immune system and high mobility contribute to pathogen transmission. Existing research suggests a complex relationship between biodiversity and disease, with the dilution effect hypothesis suggesting that higher biodiversity can reduce disease risk, but this is not a universally observed pattern. The authors acknowledge the existing debate about whether a consistent universal relationship exists between biodiversity and disease, emphasizing the importance of examining this connection within specific ecological contexts. Studies on bat CoV infections are also referenced, noting the diversity of CoV strains found in bats and their potential zoonotic risk.

The study involved a two-year longitudinal sampling of approximately 2300 bats across five caves in Ghana. Bat species were identified using morphological criteria and, in some cases, additional genetic sequencing (for Hipposideros caffer complex). Fecal samples were collected and tested for four CoV clades using real-time reverse transcriptase-PCR. CoV prevalence was calculated as the proportion of bats with detectable viral RNA. Statistical analysis involved generalized linear mixed models (GLMMs) to assess the relationship between CoV prevalence and various biodiversity indices (species richness, Shannon, and Simpson indices), along with the relative abundance of specific bat species and subadult bats. Spearman correlation was used to examine the correlation between CoV prevalence and species diversity. Generalized linear models (GLMs) were also employed to compare viral loads across species and age groups. The data was checked for multicollinearity and FDR correction was applied for multiple testing.

The study revealed uneven CoV infection patterns between closely related bat species. Alpha-CoV 229E-like and beta-CoV 2b emerged as multifocal host-pathogens. CoV prevalence showed a weak to moderate negative correlation with bat species diversity (Shannon index: alpha-CoV r=-0.33, p=0.015; beta-CoV r=-0.51, p<0.001). GLMMs indicated that the infection probability for both alpha-CoV 229E-like and beta-CoV 2b was significantly influenced by the relative abundance of certain bat species (e.g., Hipposideros caffer C and D) and the abundance of subadult bats. Viral load differed significantly between bat species and age categories, with subadults exhibiting lower viral loads than adults. Less diverse bat assemblages coincided with a higher abundance of competent hosts, suggesting a dilution effect mechanism. In essence, the presence of many different bat species tended to dilute the prevalence of the studied coronaviruses. The authors highlight the importance of abundance and evenness of species within communities for understanding disease dynamics.

The findings support the dilution effect hypothesis, suggesting that higher bat species diversity can reduce CoV prevalence. However, the observed negative correlation between diversity and prevalence could also be attributed to changes in host abundance and community composition, where competent hosts become dominant in less diverse communities. The authors discuss various aspects of the dilution effect hypothesis including how it can be affected by the abundance of both susceptible and resistant hosts. The study highlights the importance of considering not just species richness but also species abundance and evenness in assessing disease risk. The results underscore the potential of biodiversity loss to increase the risk of zoonotic disease outbreaks, emphasizing the need for conservation efforts to maintain healthy bat communities.

This study demonstrates a significant link between bat species assemblage and coronavirus prevalence. Reduced biodiversity, particularly the dominance of certain competent host species, is associated with higher CoV prevalence. The findings strongly support the importance of biodiversity conservation in preventing the emergence and spread of zoonotic pathogens. Future research could focus on exploring the underlying mechanisms driving the observed relationships, particularly the role of host immune response, gut microbiome, and behavioral factors in mediating CoV infection dynamics. Further investigation into the interplay between diversity metrics and pathogen prevalence is also suggested.

The study was conducted in a specific region of Ghana, limiting the generalizability of findings to other geographical locations. The focus on fecal samples might have underestimated the true CoV prevalence, as not all infected bats shed viruses in their feces. Further, the study focuses on only several abundant species, potentially failing to identify all reservoir species involved.