Sunday, March 28, 2021

New strain of deadly Hendra virus discovered

The Australian veterinarian-led research project, ‘Horses as Sentinels,’ has identified a new strain of the deadly Hendra virus (HeV) as the cause of a previously unexplained horse death.

Hendra virus is highly lethal in both horses and humans, with mortality rates approximately 79% and 60% respectively. The originally recognised strain of Hendra virus has resulted in the deaths of four humans and over 100 horses in Australia, since 1994. 


Hendra virus was first identified in 1994 when racehorse trainer Vic Rail died after suffering a mysterious pneumonia like illness when 20 racehorses in Hendra, Queensland, also died. Subsequently, a previously-unknown virus was identified as the cause of both the trainer’s and the horses’ deaths. 


The attending veterinarian was Dr Peter Reid. Nineteen years later, Dr Reid teamed up with Dr Annand – a veterinarian involved in the discovery of Australian bat lyssavirus in horses in 2013, and Dr Ina Smith of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Risk Evaluation and Preparedness Program to launch the ‘Horses as Sentinels’ project. The research team now also includes collaborators from around Australia and the United States.


Flying foxes (fruit bats) are known to spread the virus. The original strain of Hendra virus has been found within the range of black flying foxes and spectacled flying foxes. However, the new HeV variant has also been isolated from Grey-headed flying foxes. This species migrates, and their range includes parts of southern Australia that have so far been considered to be at low risk of Hendra virus in horses and people.


The finding indicates that HeV should be considered as a possible diagnosis in unvaccinated horses anywhere in Australia that flying foxes are present, and that unwell, suspect horses which return an initial negative Hendra virus test should continue to be treated with the same caution as a Hendra virus positive case, until testing for the new variant is performed. 


The ‘Horses as Sentinels’ research team has developed updated diagnostic laboratory techniques capable of identifying the new strain, and will be sharing them with relevant laboratories. They have also established that the current Hendra virus horse vaccine is expected to be equally effective against the new strain.


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