NSW Situation 23rd January 2008

It is now 49 days since the estimated last date of EI infection of a property in NSW and 31 days since the last positive laboratory test (PCR test). We are aiming for NSW freedom from EI by mid-March 2008.
NSW DPI laboratories processed 2570 EI samples yesterday, including 1180 PCR tests. All the PCR tests were negative!
Testing for EI status
Laboratory testing of samples taken from hundreds of horses each day is central to the continued success of the EI response. Results from the testing provide indications of EI infection, immunity and vaccination status. The testing helps to progress zone changes through surveillance and validation and facilitates horse movements within and between zones.
Taking the Purple Zone to green will eventually involve testing of horses on 3,000 properties and collection and processing of more than 25,000 samples.
The most common tests are the PCR (Polymerase Chain Reaction) and the ELISA (Enzyme-linked Immunosorbent Assay).
The PCR test involves samples taken as a nasal swab. The test detects the EI virus (or its remnants). A positive result indicates that a horse is infected, or has been infected, with EI in the past 30 days.
The ELISA test is carried out on blood samples and detects antibodies to the virus. Antibodies form about seven days after EI infection. A positive ELISA test is necessary to show that a horse is immune by recovery.
A combination of PCR and ELISA results can reveal additional information:

• A positive PCR and a negative ELISA indicates that the horse became infected within the previous seven days. These horses are a high risk for spreading EI to other horses.
• Where both PCR and ELISA are positive, the horse is infected with EI and has been so for more than a week. Such horses remain a high risk for spreading infection to other horses.
• A negative PCR and a positive ELISA indicates that the horse is recovered and immune to EI. A horse with these results is no longer a source of infection to other horses.

You need to allow five days from the time the samples are taken and sent before results will be available. Remember the laboratories are handling thousands of samples each day.

A third and less common test is available to show if a horse has been vaccinated. The HI (Haemagglutination Inhibition) test also involves blood sampling. It detects the antigen developed by the ProteqFlu vaccine. A positive result indicates an animal has been vaccinated. Allow 6 days turnaround for this test.

When will the Purple Zone improve?

The current proposal is for the Purple Zone to be changed to Green by mid-March. For this to happen, the following conditions will have to be satisfied:

• All infected properties, suspect properties and dangerous contact properties 'resolved' by testing, vaccination, or the expiry of set times from the date of infection or contact.
• No infections within the re-zoned area within the previous 60 days.
• A random surveillance program involving 15,000 tests across 2000 properties.
• A targeted surveillance program with a further 12,000 tests across 1000 properties.
  
• The rezoning proposal approved at a national level.

Zones

There were substantial improvements in zoning yesterday. Red Zones were progressed to Amber around Dubbo, Wellington, Narrabri, Gunnedah, Parkes, Forbes and Walcha. A part of the Red Zone around Grenfell was also progressed to Amber, while the rest remains red. Amber Zones were progressed to Green in the Queensland border area and also around Dubbo - Wellington, Young, Moss Vale, and the Illawarra region.

Statistics today

18 infected properties; 13 suspect properties; 6661 resolved cases.

Today's reminders

• There is no need to vaccinate horses that have recovered from EI or are from previously infected properties.
• From 14 January, a Travelling Horse Statement is required in the purple zone.
• From 14 January, in the Purple Zone events must be registered.
• From 4 February, you need proof of immunity to EI when moving horses in the Purple Zone.
• Proof of immunity may be a certificate of immunity, horse health certificate or certificate of vaccination showing at least two doses of ProteqFlu vaccine.
  
• The Royal Easter Show horse events are going ahead. Contact the RAS horse section on 9704 1220 for requirements.