During the winter of 2011 the North Coast of NSW had multiple properties diagnosed with Hendra virus (7 Infected Premises) and an unprecedented number of Hendra exclusions (over 60). The events of 2011 have demonstrated that the region is prone to Hendra virus. The reason behind the sudden increase in Hendra virus cases on the North and Mid-coast is still not understood.
Since 2006 the North Coast LHPA has always been involved in the occasional Hendra virus exclusion. However, the vast majority of Hendra exclusions are serviced by private veterinarians because they can carry out diagnostic procedures and administer treatments that the LHPA is not legislated to perform.
During the 2011 outbreaks the author undertook the following roles:
The experiences gained during these roles are summarised by two case studies and the discussion. Three other staff from the North Coast LHPA also undertook roles with Hendra virus. For these staff, 170 out of 700 available work hours were spent on Hendra virus activities in the month of August 2011.
Some Hendra cases studies focus on attempts to understand the epidemiology of the outbreak. The included case studies instead outline situations where Hendra virus was diagnosed in circumstances where a private veterinarian was not employed or LHPA assistance was required. The case studies also highlight that Hendra virus needs to be considered when a horse is found dead in a fence. The second case study also summarises the challenges confronted when manageing an Infected Premise (IP).
In July 2011 a cattle producer near Lismore contacted their private veterinarian about one of their horses that had died with its head stuck through a wire fence. The horse was observed by the owner to have no signs of disease 12-18 hours earlier. The paddock that the horse had been in contained a fig tree. Flying foxes were suspected to visit the property but were not thought to be overly common. The private veterinarian indicated that it was unlikely to be Hendra virus but advised the producer to contact the LHPA. After collecting a history from the farmer, two district veterinarians in the LHPA independently considered that the case was likely to be an accident. Despite this a district veterinarian attended the farm to investigate.
ON FARM EXAMINATION
A single dead horse was observed by the district veterinarian with its head and neck through a fence line. The fence line was at the bottom of a hill. The head and neck were on the ground underneath the bottom fence wire. Another horse was in the paddock with no signs of disease. This horse had been observed to 'sniff' at the face of the dead horse. Using appropriate personal protective equipment an oral and nasal swab was taken from the horse. It was noted that there was significant blood stained froth in the nasal cavities. Swabs were placed in PBGS viral transport medium.
Both oral and nasal swabs were positive for Hendra virus on a N Gene TaqMan Assay done at the Australian Animal Health Laboratory (AAHL) and on a PCR test done at NSW EMAI State Diagnostic laboratory. All subsequent testing on the live horse was negative.
A neighbour to a sugar- cane property near Ballina reported to NSW DPI that they had observed two dead horses in their neighbour's paddock. The owner of the property was currently away. A district veterinarian from the North Coast LHPA was tasked by NSW DPI to investigate.
ON FARM EXAMINATION
Wearing appropriate PPE the district veterinarian observed and examined two dead horses in a house paddock. One horse was dead attached to a fence wire and the other horse was dead in the middle of the lawn near the house. This horse appeared to have prolapsed material from both the rectum and vulva but the district veterinarian considered that this may just be from decomposition. The house paddock contained some native trees and an old orchard. Four live horses were observed without any obvious signs of disease. The initial field diagnosis by the district veterinarian was an accident for the horse attached to the fence and a reproductive incident for the other horse. Both swabs and jugular blood was collected from both dead horses.
All samples collected from the horses were positive for Hendra virus on testing done at both the NSW State Diagnostic Laboratory and AAHL.
MANAGEMENT OF INFECTED PREMISE
Staff from the North Coast LHPA were tasked to carry out the initial management of this IP and to carry out ongoing observations of the live horses.
The management of this IP was complicated by the following issues:
The author carried out the following steps to initially manage this IP:
A significant challenge in the initial management was the inability to find, at short notice, the necessary contractors to appropriately dispose of the carcases. The carcasses could not be buried where they were because they were right next to the house. There was also a concern that if the aged carcases were dragged or lifted they would fall apart spreading contamination en route. The preferred option was to source large enough machinery to simply lift the horses and dirt beneath the horses to a suitable burial site. Only a bobcat and small excavator was available. Ongoing communication between the IP manager and contractor was complicated by the use of PPE. This unfortunately led to the author having to use PPE to attach chains to the carcasses and then remove them from the horses once they were in the burial pit. In hindsight, despite the distance involved, the horses should probably have been dragged and then pushed into the burial site.
The owners' absence created difficulties in that LHPA rangers needed to be involved in feeding the live horses. Additional experience on other Hendra IPs on the North Coast has shown that once agricultural services take responsibility for the care of horses it creates significant problems when that care cannot meet owner expectations. The RSPCA also became involved in this case because of the delay between the horses death and the discovery of the carcasses.
These case studies demonstrate the following:
The NSW livestock health system that combines the use of private veterinarians, LHPA and NSW DPI veterinarians and staff to undertake surveillance and control activities for disease proved effective in the case of the Hendra virus outbreaks in northern NSW.
Advisory messages to horse owners should include that horses stuck in fences should not be assumed to be an accident. The neurological damage that Hendra virus can do may predispose horses to becoming stuck in fences.
LHPA management considers that the risk of exposure to Hendra virus by their veterinarians is increased from 'low' when no sharps are used to 'high' if sharps are used. These case studies suggest that if adequate bodily fluid in a dead horse can be found then the use of sharps may not be required. Multiple swabs of bodily fluid is likely to detect infection. However if nasal cavities and other orifices are dry, without obvious discharge it would be recommended to collect jugular blood or possibly a superficial lymph node.
When Hendra policy and procedures are reviewed the experiences of field staff should be considered. The resources required to undertake twice daily observation of live horses and to undertake horse husbandry tasks should be justified.
Livestock diseases that are mainly significant because of their zoonotic potential create challenges for agricultural agencies. In developing countries, Rabies is a relevant example. As regions such as the North Coast of NSW become prone to Hendra virus, agricultural field staff can spend a considerable amount of time on the disease. The long term objectives of agricultural services being involved in tasks that are principally about protecting human health should be debated in consultation with human health agencies. The role of the LHPA, a ratepayer funded organisation, also needs to be continually reviewed because ongoing questions are asked by rate paying sheep and cattle producers as to why it is relevant for LHPA staff to be involved in Hendra virus.
Overall, staff of the North Coast LHPA found their experiences with the 2011 Hendra outbreaks valuable and relevant. They provided useful experience to prepare for future biosecruity incidents in any species.