Hendra virus was first isolated in Queensland following an outbreak at a racing stable in Hendra, Brisbane. Prior to 2011 there had been 14 incidents in Queensland and a single case in NSW. During 2011 there were 18 incidents recorded of which 7 were in NSW and 11 in Queensland. Cases in 2011 occurred between June and October. There have been 7 cases on human infection confirmed, of which 4 have been fatal.
The following describes a case of Hendra virus in a horse which died at Macksville, NSW in July 2011 and is the most southern recorded case of Hendra virus.
A 16 year old thoroughbred mare died after a brief illness predominated by neurological signs. The mare was running on a 33ha property west of Macksville. There was a 16 year old gelding in the same paddock as the deceased mare and 2 younger brumbies running in a separate paddock well separated from the affected animal. Also on the property was a small beef herd of approximately 30 breeders and 2 cats. There were several fig trees on the property, however none in the paddock the horses were currently grazing and the owners reported only occasional bat sightings. The paddock was bordered on one side by a river, along which are growing numerous species of native eucalypts which may attract flying foxes.
The mare was noted by the owner to be slightly off colour on the afternoon of the 1st July. Initially the owners reported that the mare appeared to be slightly lame on the right hind leg and appeared depressed. Over the course of the following day there was progression of neurological signs with the horse appearing blind, walking through fences and becoming increasingly ataxic. Head pressing was also noted. The horse died during the night of the 2nd-3rd July. The owners had contacted their local private vet and the emergency animal disease hotline late on the night of the 2nd July to discuss the horses condition as they were significantly concerned about the animals behaviour. I was called on the morning of the 3rd July and a property visit took place.
The owners had put the horse in a small yard on the previous night and she had died pushing through a wire gate (Figure 1). Personal protective equipment including P2 mask, disposable overalls, glasses and double gloves were worn during examination of the dead horse. There was a small amount of blood from the nose suspected to be associated with trauma of pushing through a gate and the membranes appeared very congested. Nasal swabs were collected and stored in PBGS virus transport media. EDTA, Lithium heparin and plain blood tubes were collected from the clinically normal paddock mate.
The dead horse was buried on site that day.
Samples were submitted to the State veterinary Diagnostic Laboratory the following day (Monday 4th July).
A phone call was received late on Wednesday 6th July advising that the results of the swabs were positive for Hendra virus. At this point I began to question my PPE and property exit procedure hoping that I had done everything correctly.
The phone call advising of the positive result triggered several hours on the phone. After notifying the owner of the result a discussion with NSW health was had identifying all in contact people. My personal risk level was considered negligible given that PPE had been worn, however self monitoring through daily temperature taking was recommended. Two people who had had contact with the horse were tested for Hendra virus with negative results.
This case was the second in NSW in 2011 following a case at Wollongbar in June and unbeknown to me at the time triggered the activation of a disease control centre. This property is some 4 hours south of the disease control centre so I became site supervisor. A 42 day quarantine was issued under section 35 of the Animals Diseases (Emergency outbreaks) Act 1991.
A property visit the following day took place disinfecting areas near the house where the horse had been. A quaternary ammonium compound was used to disinfect the environment immediately adjacent the house yard. The in contact horse was now in a small 'quarantine' paddock and owners were advised that there should be no contact within 2 metres. The horse was thrown hay daily and observed by the owner twice daily, with observations recorded on a checklist and forwarded to the disease control centre.
Nasal swabs and blood were collected from the 2 brumbies as the owner requested that they be tested, both were negative.
The in contact horse, 2 brumbies and both cats were bled on days 16 and 32 - with all samples being negative. Following the negative results on day 32 the quarantine was revoked.