Abstract
Spatiotemporally-localised prediction of virus emergence from wildlife requires focused studies on the ecology and immunology of reservoir hosts in their native habitat. Reliable predictions from mathematical models remain difficult in most systems due to a dearth of appropriate empirical data. Our goal was to study the circulation and immune dynamics of zoonotic viruses in bat populations and investigate the effects of maternally-derived and acquired immunity on viral persistence. Using rare age-specific serological data from wild-caught Eidolon helvum fruit bats as a case study, we estimated viral transmission parameters for a stochastic infection model. We estimated mean durations of around 6 months for maternally-derived immunity to Lagos bat virus and African henipavirus, whereas acquired immunity was long-lasting (Lagos bat virus: mean 12 years, henipavirus: mean 4 years). In the presence of a seasonal birth pulse, the effect of maternally-derived immunity on virus persistence within modelled bat populations was highly dependent on transmission characteristics. To explain previous reports of viral persistence within small natural and captive E. helvum populations, we hypothesise that some bats must experience prolonged infectious periods or within-host latency. By further elucidating plausible mechanisms of virus persistence in bat populations, we contribute to guidance of future field studies.
Highlights
Mathematical modelling approaches can circumvent some of these challenges and allow exploration of underlying processes, which can be tested across a broad range of systems
We have previously shown that persistence of the henipavirus Hendra virus was unlikely within single populations with the short infectious period demonstrated in experimentally infected animals[16]
We focus on two viruses for which E. helvum is a reservoir (LBV and African henipavirus), we look for evidence for the presence of maternally-derived antibodies (MatAb) in wild E. helvum and, uniquely, we use unique age-specific data to model waning rates of maternally- and infection- derived antibodies
Summary
Mathematical modelling approaches can circumvent some of these challenges and allow exploration of underlying processes, which can be tested across a broad range of systems. Logistical challenges aside, island populations provide ideal natural experiments for studying host and disease ecology at a population level[12] This is the case for bats, where species traits such as nomadicism and fission-fusion population structures[13,14], make it otherwise challenging to separate the dynamical effect of pathogen reintroduction into a study population from the transmission dynamics expected within a closed population. The population of African straw-coloured fruit bats (Eidolon helvum) on the remote Annobón island, Equatorial Guinea presents a rare opportunity to study viral dynamics in bat populations. This species is common and widely-distributed across continental sub-Saharan Africa and offshore islands, and recognised as a reservoir host for several potentially-zoonotic viruses across its range, including African bat henipavirus and Lagos bat virus (LBV, genus Lyssavirus)[15]. Applied to E. helvum bats in the isolated population on Annobón island, our results suggest that viral persistence would require long infectious periods or within-host viral latency, allowing us to narrow in on plausible mechanisms of virus persistence in bat populations and better understand infectious disease emergence
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