Flying Fox Scientists Profile Equine Hendra Virus Cases

Queensland scientists are reviewing hendra virus cases from previous years to better understand why some horses become infected and others don't.

Biosecurity Queensland researcher Hume Field, BVSc, MSc, PhD, MACVS, said the common factor in most cases was horses resting under trees where flying foxes (a type of fruit bat) were active.

"On more than 80% of properties where there were hendra virus cases, horses ´camped´ under trees that flying foxes were feeding in," Field said. "This reinforces the importance of Biosecurity Queensland advice about stopping horse access to fruiting and flowering trees that may attract flying foxes."

Field said the Queensland Centre for Emerging Infectious Diseases (QCEID) was in the process of analyzing the data from properties in Queensland and northern New South Wales where the cluster of hendra virus cases occurred in 2011 and 2012 to look for patterns.

"QCEID scientists are using profiling to identify characteristics common to affected properties," he said. Profiling is a technique used to identify characteristics associated with particular behaviors, actions or outcomes.

"We gather information on local flying fox activity on and around the property, on horse characteristics and behavior, and on horse husbandry practices," he explained. "By talking with the property owner, and walking around the property we can often identify the potential ´ground zero´ for flying foxes and horses coming into contact."

Field said early findings from the 2011 cases showed quite a clear picture of potential interaction: "Almost 90% of properties showed evidence of recent flying fox activity including food debris and urine or feces under trees, and on more than 80% of properties, horses ´camped´ under trees that flying foxes were feeding in.

"We are also looking at pasture abundance and quality, but we´re not seeing a direct relationship with hendra virus risk," he added. "Even when pasture was poor, horses were generally in good condition because of supplementary feeding, so poor nutrition or hunger don´t appear to be risk factors However, we are continuing to explore whether a horse´s natural inquisitiveness or desire for green ´pick´ in short pasture may increase the risk of eating contaminated material."

Hendra virus has been known to yield numerous clinical signs in horses including respiratory distress, frothy nasal discharge, elevated body temperature (above 40°C, or 104°F), and elevated heart rate; however, authorities caution that hendra infection does not have specific signs. The disease is zoonotic, meaning it can be transmitted from horses to humans, and as proved deadly for several humans exposed to sick horses in the past.

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