Evidence of Endemic Hendra Virus Infection in Flying-Foxes (Pteropus conspicillatus)—Implications for Disease Risk Management

Abstract

This study investigated the seroepidemiology of Hendra virus in a spectacled flying-fox (Pteropus conspicillatus) population in northern Australia, near the location of an equine and associated human Hendra virus infection in late 2004. The pattern of infection in the population was investigated using a serial cross-sectional serological study over a 25-month period, with blood sampled from 521 individuals over six sampling sessions. Antibody titres to the virus were determined by virus neutralisation test. In contrast to the expected episodic infection pattern, we observed that seroprevalence gradually increased over the two years suggesting infection was endemic in the population over the study period. Our results suggested age, pregnancy and lactation were significant risk factors for a detectable neutralizing antibody response. Antibody titres were significantly higher in females than males, with the highest titres occurring in pregnant animals. Temporal variation in antibody titres suggests that herd immunity to the virus may wax and wane on a seasonal basis. These findings support an endemic infection pattern of henipaviruses in bat populations suggesting their infection dynamics may differ significantly from the acute, self limiting episodic pattern observed with related viruses (e.g. measles virus, phocine distemper virus, rinderpest virus) hence requiring a much smaller critical host population size to sustain the virus. These findings help inform predictive modelling of henipavirus infection in bat populations, and indicate that the life cycle of the reservoir species should be taken into account when developing risk management strategies for henipaviruses.

Persistent or long-term coronavirus infection in Australian bats

“…Previous studies suggested that physiological stress associated with pregnancy and lactation was a risk factor for increased seroprevalence of virus infections in bats 26,27 . Similarly, a correlation between the detection of coronaviruses in female bats associated with maternity colonies has also been established 28,29 .…”

Physiological biomarkers of Hendra virus infection in Australian Flying-foxes (Pteropus spp.)

“…Previous studies have suggested that a range of physiological and ecological factors constitute risk factors for Hendra virus infection in flying-foxes (Field 2005, Plowright et al 2008, Breed et al 2011, including physiological stress associated with reproduction and sub-optimal nutrition (Plowright et al 2008), and by extension pose an increased risk of spill over into another species Field et al 2012;Plowright et al 2015). Understanding Hendra virus infection dynamics in flying-foxes and the putative causal risk factors is fundamental to elaborating the disease ecology of the virus and thus effective exposure risk management in horses and humans (Figure 1.8).…”

“…Previous studies suggest that physiological and ecological factors, including physiological stress associated with reproduction and sub-optimal nutrition constitute risk factors for infection in flyingfoxes (Field 2005;Plowright et al 2008;Breed et al 2011), and by extension pose an increased risk of spill-over into another species Field et al 2012;Plowright et al 2015). However, it is essential to know the normal range of physiological biomarkers and their possible seasonal variability before seeking physiological associations with infection and/or disease.…”

“…A number of previous studies have suggested that various physiological factors (including physiological stress associated with reproduction and sub-optimal nutrition) may be positively associated with Hendra virus infection in flying-foxes (Field 2005;Plowright et al 2008;Breed et al 2011), and by extension, with spill over to horses and humans Field et al 2012;Plowright et al 2014 plus animals tested as Hendra virus positive, excluded from the reference range calculation. The study was a discrete component of a larger epidemiological study of Hendra virus disease ecology reported elsewhere (Edson et al 2015 b ).…”

“…Previous studies have suggested that a range of physiological and ecological factors constitute risk factors for Hendra virus infection in flying-foxes (Field 2005, Plowright et al 2008, Breed et al 2011, including physiological stress associated with reproduction and sub-optimal nutritional (Plowright et al 2008). However, to rigorously investigate the putative association between stress and Hendra virus infection dynamics in flying-foxes, a robust method of measuring stress in free-living flying-foxes is needed.…”