KEEPING EQUINE INFLUENZA OUT OF AUSTRALIA

The Sydney Morning Herald has published two articles today which raise a number of issues about our quarantine management.

http://www.smh.com.au/news/horseracing/minister-fobbed-off-flu-alert/2007/11/02/1193619145628.html

http://www.smh.com.au/news/horseracing/the-cough-that-stopped-a-nation/2007/11/02/1193619145658.html?page=fullpage#contentSwap1

These articles are about the past. I want to look at the possibility of greatly improving quarantine procedures for our future protection against equine influenza (EI) being introduced to Australia again.

We have been free of EI for many years because it did not survive the boat trip to Australia. The infection would have burnt itself out on the long journey before the horses arrived. Since the introduction of air transport of horses, EI has always been the big infectious disease threat to Australia’s horses.

The protocols used by the Australian Quarantine and Inspection Service (AQIS) have not been substantially altered since we started flying horses into Australia. There are two areas that have improved greatly in the past few years that should be adopted in future.

The first improvement is the availability of better diagnostic tests. For thirty years we have really had only one tool to detect infected horses – the thermometer. Horses have been monitored in quarantine for rises in temperature that might indicate EI infection. Horses often get travel sickness after importation so an increased temperature is not specific for any particular disease. The outbreak of EI in imported stallions in Eastern Creek demonstrates the unreliability of fever as a diagnostic test. Many of the infected horses did not show a raised temperature. They were vaccinated with a killed vaccine which reduced the signs of disease, but they still excreted the virus.

The second tool that was previously used was a measure of the antibody level in the blood. Unfortunately these tests could not differentiate infection from vaccination. AQIS bleed the horses on arrival at Eastern Creek Quarantine Station (ECQS), but have saved the bloods in a freezer. The bloods were not tested unless the horse became ill, when a second test was taken to check for an increase in antibody level which would indicate the presence of infection. Previously a confirmatory test for EI would depend on growing the virus in eggs which is slow, difficult and unreliable.
Better tests are now available. With the technology now developed at the Elizabeth MacArthur Agricultural Institute (EMAI) we can test nasal swabs for presence of EI virus overnight. The test used is the Polymerase Chain Reaction (PCR) which detects the ribonucleic acid (RNA) of the EI virus. This is the type of test you see the CSI people using on TV! EMAI is running up to 1,000 of these tests daily. This test has allowed the DPI to rapidly diagnose the presence of infection, which makes eradication very feasible.

The second development is the availability of better vaccines. In the past AQIS has required that horses be vaccinated before shipment to Australia, but the killed vaccines were largely ineffective. The horses that brought EI into Australia in August, and those that developed EI, were all vaccinated with a killed vaccine.

The product that is being used in the current outbreak is a genetically modified organism (GMO) vector vaccine. The horses that had been vaccinated with the GMO vaccine did not get flu in ECQS. In addition to providing better protection, the GMO vaccine allows the blood tests to differentiate immunity that results from infection with EI from those horses that are immune after vaccination (i.e. that have not been infected). This differentiation is critical if one is to know precisely where the EI virus has been circulating within the horse herd. This ability to differentiate infected from vaccinated horses will be essential for Australia to provide proof of freedom of EI.

Therefore I suggest that we require all horses that are to be transported to Australia must have a full course of vaccination with the GMO vaccine at a suitable time before entering pre-export quarantine. These horses also must have negative PCR tests prior to them boarding the plane, on arrival into the post-arrival quarantine, and prior to release from the post-arrival quarantine.

These two measures of improved technology, introduced in addition to the other safeguards in our Quarantine policy, will make Australia much more secure against any future introduction of EI.

Rod Hoare
AHIC