Hendra Virus Infection Dynamics in Australian Fruit Bats

Abstract

Hendra virus is a recently emerged zoonotic agent in Australia. Since first described in 1994, the virus has spilled from its wildlife reservoir (pteropid fruit bats, or ‘flying foxes’) on multiple occasions causing equine and human fatalities. We undertook a three-year longitudinal study to detect virus in the urine of free-living flying foxes (a putative route of excretion) to investigate Hendra virus infection dynamics. Pooled urine samples collected off plastic sheets placed beneath roosting flying foxes were screened for Hendra virus genome by quantitative RT-PCR, using a set of primers and probe derived from the matrix protein gene. A total of 1672 pooled urine samples from 67 sampling events was collected and tested between 1 July 2008 and 30 June 2011, with 25% of sampling events and 2.5% of urine samples yielding detections. The proportion of positive samples was statistically associated with year and location. The findings indicate that Hendra virus excretion occurs periodically rather than continuously, and in geographically disparate flying fox populations in the state of Queensland. The lack of any detection in the Northern Territory suggests prevalence may vary across the range of flying foxes in Australia. Finally, our findings suggest that flying foxes can excrete virus at any time of year, and that the apparent seasonal clustering of Hendra virus incidents in horses and associated humans (70% have occurred June to October) reflects factors other than the presence of virus. Identification of these factors will strengthen risk minimization strategies for horses and ultimately humans.

Isolation of multiple novel paramyxoviruses from pteropid bat urine

“…The urine samples were screened for HeV by reverse transcription-PCR, and positive samples were targeted for virus isolation. The Cedar Grove 25 September 2009 collection had an unusually high rate of HeV PCR positives (12 % compared with ,5 % seen previously) and was of great interest, as this was the first time that such a high proportion of HeV positives was observed in bat pooled urine samples (Field et al, 2011). In addition, 2011 was an unprecedented year with regard to the number of HeV cases.…”

“…In recent years, our group has focused on developing optimized procedures for isolation of live viruses; from urine collection protocols, sample transportation medium and storage conditions to the development of specialized bat primary cell lines (Crameri et al, 2009). In previous reports, we have described the isolation of Hendra virus (HeV) (Smith et al, 2011), Menangle virus (MenPV) and the novel henipavirus, Cedar virus (CedPV) , from beneath colonies of pteropid bats (commonly known as flying foxes) in Queensland (QLD), Australia, utilizing these optimized procedures.…”

“…The bat colonies sampled were targeted based on their close proximity to a known HeV spillover event into a horse(s). The Cedar Grove and Tolga Scrub colonies were the exception; these colonies were routinely sampled by members of our team as part of a longitudinal study (Field et al, 2011). No HeV spillover events occurred in these parts of QLD in 2009.…”

“…No HeV spillover events occurred in these parts of QLD in 2009. Generally, once a horse had been confirmed to be infected with HeV, the team would identify the closest readily accessible bat colony to the location of the spillover event and sample urine from beneath the colony as described previously (Field et al, 2011). Briefly, urine was pooled off plastic sheets from underneath bat colonies and collected in a tube containing transport medium (either 500 ml sucrose-phosphate-glutamate-albumin plus antibiotic/antimycotic buffer, or 100 ml 10 % BSA in PBS plus double-strength antibiotic/ antimycotic).…”

“…Previously, our group has reported viruses isolated from this collection of flying-fox urine: four bat isolates of HeV (Smith et al, 2011), a bat isolate of MenPV and the novel henipavirus, CedPV . In addition to these viruses, we have now isolated four additional novel paramyxoviruses, all in the genus Rubulavirus.…”