In the past RHD introduction events involved catching wild rabbits and manually injecting live RHD virus prior to release.   This is obviously time-consuming, expensive and cumbersome to manage.   Recent Australian Pesticides and Veterinary Medicine Authority (APVMA) approval for the spread of RHDV by the oral route on treated carrots or grain made the process simpler in the field.   However, the greatest impediment to the widespread distribution of the stock RHDV virus has been the need to ship RHD virus frozen on dry ice to ensure stability of the product.  This methodology causes the product to be classified as “Dangerous Goods” making movement, especially by airfreight, exceedingly difficult.

The implications of this are significant and include:

• A requirement for shipments to be packed by accredited staff
• More difficult logistics, sometimes resulting in the loss of all refrigerant and product
• A frequent occurrence of “failed” shipments.
  

This project is involved in the development of a freeze-dried stock of RHDV that can be easily and safely transported without the need for refrigeration - significantly reducing costs and bureaucratic impediments to uptake.  The product can be prepared for field distribution by sprinkling over carrots or oats

Progress 

Two batches of RHDV bulk virus have been produced.   The first had high levels of viral antigen (as measured by ELIZA) but its infectivity rate was relatively low.  The second batch was suitable for use.

Several freeze-drying methods (with different protective elements and drying temperatures and times) have been evaluated.

A pilot batch of freeze-dried RHDV has been incubated at different temperatures to assess stability under real-time and accelerated conditions.

To date, stability studies over 1, 3, 6, 9, 12 months have been completed.  The product will be evaluated for a further year before the data are submitted to the APVMA seeking approval for sale and distribution.

The availability of the freeze-dried RHDV stock will facilitate the movement of the virus into populations where there has been limited spread. 

A best-management code of practice will be written for a national integrated rabbit control strategy.