Flying-Fox Roost Disturbance and Hendra Virus Spillover Risk

Abstract

Bats of the genus Pteropus (flying-foxes) are the natural host of Hendra virus (HeV) which periodically causes fatal disease in horses and humans in Australia. The increased urban presence of flying-foxes often provokes negative community sentiments because of reduced social amenity and concerns of HeV exposure risk, and has resulted in calls for the dispersal of urban flying-fox roosts. However, it has been hypothesised that disturbance of urban roosts may result in a stress-mediated increase in HeV infection in flying-foxes, and an increased spillover risk. We sought to examine the impact of roost modification and dispersal on HeV infection dynamics and cortisol concentration dynamics in flying-foxes. The data were analysed in generalised linear mixed models using restricted maximum likelihood (REML). The difference in mean HeV prevalence in samples collected before (4.9%), during (4.7%) and after (3.4%) roost disturbance was small and non-significant (P = 0.440). Similarly, the difference in mean urine specific gravity-corrected urinary cortisol concentrations was small and non-significant (before = 22.71 ng/mL, during = 27.17, after = 18.39) (P= 0.550). We did find an underlying association between cortisol concentration and season, and cortisol concentration and region, suggesting that other (plausibly biological or environmental) variables play a role in cortisol concentration dynamics. The effect of roost disturbance on cortisol concentration approached statistical significance for region, suggesting that the relationship is not fixed, and plausibly reflecting the nature and timing of disturbance. We also found a small positive statistical association between HeV excretion status and urinary cortisol concentration. Finally, we found that the level of flying-fox distress associated with roost disturbance reflected the nature and timing of the activity, highlighting the need for a ‘best practice’ approach to dispersal or roost modification activities. The findings usefully inform public discussion and policy development in relation to Hendra virus and flying-fox management.

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

“…Previous studies have also shown associations between bat species and Hendra virus prevalence. Most evidence suggests that variation in prevalence is explained by the relative abundances of spectacled (Pteropus conspicillatus) and black (Pteropus alecto) flying foxes [16][17][18][19]. However, P. alecto is of particular concern because this species is widely distributed in coastal North Eastern Australia, and often forages in urban and peri-urban areas [20,21].…”

Changing resource landscapes and spillover of henipaviruses

“…Beyond these nutritional markers, HeV positivity was associated with other health markers such as greater lymphocyte counts, plasma alkaline phosphatase levels, and urinary protein levels, alongside lower neutrophil counts . Two separate studies also report a statistically significant relationship between detection of HeV RNA in pooled under‐roost urine and increased concentration of urinary cortisol, which can be elevated during acute or chronic stress and malnutrition . The current state of knowledge is inconclusive as few studies include extensive spatial and temporal sampling of HNVs with direct consideration of bat ecology.…”

Henipaviruses: bat-borne paramyxoviruses

“…Known for their important role in the pollination of flora, seed dispersal and insect population control, bats also play a key role in the spread and perseverance of many notable zoonotic viruses which cause severe disease and potentially fatal outcomes for humans, livestock and many other species 1,4 . In particular, megabats belonging to the genus Pteropus, are important natural reservoirs for many significant pathogenic viruses such as Hendra virus (HeV), Nipah virus (NiV), SARS Coronavirus, Australian bat Lyssavirus and Menangle virus [4][5][6][7][8][9] .…”

“…In particular, megabats belonging to the genus Pteropus, are important natural reservoirs for many significant pathogenic viruses such as Hendra virus (HeV), Nipah virus (NiV), SARS Coronavirus, Australian bat Lyssavirus and Menangle virus [4][5][6][7][8][9] .…”