Conditions affecting the timing and magnitude of Hendra virus shedding across pteropodid bat populations in Australia

Abstract

SUMMARY Understanding infection dynamics in animal hosts is fundamental to managing spillover and emergence of zoonotic infections. Hendra virus is endemic in Australian pteropodid bat populations and can be lethal to horses and humans. However, we know little about the factors driving Hendra virus prevalence in resevoir bat populations, making spillover difficult to predict. We use Hendra virus prevalence data collected from 13 000 pooled bat urine samples across space and time to determine if pulses of prevalence are periodic and synchronized across sites. We also test whether site-specific precipitation and temperature affect the amplitude of the largest annual prevalence pulses. We found little evidence for a periodic signal in Hendra virus prevalence. Although the largest amplitude pulses tended to occur over winter, pulses could also occur in other seasons. We found that Hendra virus prevalence was weakly synchronized across sites over short distances, suggesting that prevalence is driven by local-scale effects. Finally, we found that drier conditions in previous seasons and the abundance of Pteropus alecto were positively correlated with the peak annual values of Hendra virus prevalence. Our results suggest that in addition to seasonal effects, bat density and local climatic conditions interact to drive Hendra virus infection dynamics.

Climate Change Could Increase the Geographic Extent of Hendra Virus Spillover Risk

“…Empirical evidence suggests that HeV spillover is related to climate by several different mechanisms acting at different temporal and spatial scales. From broad to fine: the spatial and temporal abundance patterns of HeV reservoir hosts, flying foxes, are related to climatic suitability (Martin et al 2016); the spatial dynamics of bats are largely governed by food resources that are dependent on climate (Hudson et al 2010; Giles et al 2016); the levels of HeV shedding may be linked to low food productivity and availability after severe weather events (Plowright et al 2008; McFarlane et al 2011; Páez et al 2017; Peel et al 2017); and lastly HeV survival in microclimates which might facilitate indirect transmission, is also dependent on climate (Martin et al 2015, 2017). …”

Changing resource landscapes and spillover of henipaviruses

“…Recent work by Paez et al . on HeV suggested that bat abundance may play a role in peak HeV prevalence detected at roost sites, so the association between bat density, roost density, HeV prevalence, and spillover remains unclear.…”

“…Intense episodic shedding of HeV and NiV in bat urine seems to occur in discrete spatiotemporal pulses that are distinct from low levels of background HNV shedding . Recent work suggests that HNV shedding is correlated with environmental conditions that are presumably stressful . In Australia, the roosts closest to HeV spillover clusters in 2011 and 2013 were occupied by actively shedding bats experiencing conditions consistent with food shortage .…”

“…In Australia, the roosts closest to HeV spillover clusters in 2011 and 2013 were occupied by actively shedding bats experiencing conditions consistent with food shortage . In addition, intensity of HeV excretion from P. alecto is associated with low rainfall levels in preceding months, which is known to negatively affect the flowering and nectar intensity of primary eucalypt diet plants . When preferred foods are unavailable, P. alecto and other pteropodids feed on alternative food sources, including native and exotic fruits that may have low nutritional or energetic value, poor digestibility, and harmful secondary metabolites .…”

“…) . Very little is understood about HNV dynamics in bat populations (see below) . Seroprevalence patterns suggest that HNVs are predominately horizontally transmitted among bats, and this could plausibly occur through urination in three‐dimensional roost structures .…”