Conservation of Hendra Virus Isolates | CDC EID

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Volume 16, Number 11–November 2010
Dispatch
Genome Sequence Conservation of Hendra Virus Isolates during Spillover to Horses, Australia

Glenn A. Marsh, Comments to Author Shawn Todd, Adam Foord, Eric Hansson, Kelly Davies, Lynda Wright, Chris Morrissy, Kim Halpin,1 Deborah Middleton, Hume E. Field, Peter Daniels, and Lin-Fa Wang
Author affiliations: Australian Animal Health Laboratory, Geelong, Victoria, Australia (G.A. Marsh, S. Todd, A. Foord, E. Hansson, K. Davies, L. Wright, C. Morrissy, K. Halpin, D. Middleton, P. Daniels, L.-F. Wang); Australian Biosecurity Cooperative Research Centre for Emerging Infectious Diseases, Brisbane, Queensland, Australia (H.E. Field, L.-F. Wang); and Biosecurity Queensland, Brisbane (H.E. Field)

Suggested citation for this article

Abstract
Bat-to-horse transmission of Hendra virus has occurred at least 14 times. Although clinical signs in horses have differed, genome sequencing has demonstrated little variation among the isolates. Our sequencing of 5 isolates from recent Hendra virus outbreaks in horses found no correlation between sequences and time or geographic location of outbreaks.

Hendra virus (HeV) (family Paramyxoviridae, subfamily Paramyxovirinae, genus Henipavirus) was first isolated in 1994 during an outbreak of respiratory disease in horses at a stable in Hendra, a suburb of Brisbane, Queensland, Australia. During the outbreak, all horses at the affected property were tested. Thirteen horses died; 7 recovered with seroconversion, some without clinical signs; and 9 remained uninfected. A horse trainer and a stable worker also became infected, and the trainer subsequently died. In October 1995, HeV infection was diagnosed for a third person, who lived in Mackay, ≈1,000 km north of Brisbane. Retrospective analysis demonstrated that an outbreak had occurred in Mackay in August 1994, where the infected person had assisted with necropsies on 2 horses. At the time, he recovered from a mild undiagnosed infection. Fourteen months later, fatal encephalitis developed, suggesting either virus persistence or late onset of disease symptoms (1). Since 1994, a total of 12 outbreaks have occurred (Table 1).

Serologic evidence identified flying foxes (genus Pteropus) as the likely reservoir host, and HeV was subsequently isolated from 2 species of pteropid bats (2). Serologic evidence of HeV in bats has been demonstrated along the east coast of Australia to Melbourne and west across northern Australia to Darwin. Seroprevalence can be as high as 25% (3). In recent years, the regularity of spillover events has increased. Increased monitoring of bat population sizes, virus in bat populations, and virus characterization is necessary to better learn about trigger(s) for spillover events.

Nipah virus (NiV) is the only other known species within the genus Henipavirus. NiV was first identified during a major outbreak of diseases in pigs and humans in peninsular Malaysia during 1998–99. NiV reemerged in Bangladesh in 2001, with recurrence resulting in human infection almost annually in Bangladesh and India (4). Serologic evidence of NiV or NiV-related viruses has been demonstrated in bats in Thailand (5), Indonesia (6), People's Republic of China (7), Madagascar (8), and west Africa (9); virus has been isolated from flying foxes in Malaysia (10) and Cambodia (11).

A major characteristic of henipavirus infections is their systemic spread, with evidence of infection in multiple organ systems. HeV infection in horses typically produces an acute, febrile respiratory disease (12) with a high case-fatality rate. The 2008 Redlands outbreak was the largest in horses since the first identified outbreak in 1994. During this outbreak, infected horses showed atypical signs of HeV infections, with clinical features of a more neurologic nature (13). Before the outbreak was attributed to HeV, 2 persons became infected, resulting in 1 death and the potential exposure of >50 persons. The reason for the altered clinical picture during this spillover event is unknown.

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Conservation of Hendra Virus Isolates | CDC EID

Suggested Citation for this Article

Marsh GA, Todd S, Foord A, Hansson E, Davies E, Wright L, et al. Genome sequence conservation of Hendra virus isolates during spillover to horses, Australia. Emerg Infect Dis [serial on the Internet]. 2010 Nov [date cited]. http://www.cdc.gov/EID/content/16/11/1767.htm

DOI: 10.3201/eid1611.100501

1Current affiliation: Life Technologies, Singapore.