Spotlight

Hooked on Parasites

By Lynda Gray

Belonging to different research institutions has proved no barrier to co-operation between a student and a deer specialist. Stuart Parsons, from the Zoology Department at Otago University, and Dr Colin Mackintosh, a vet at the Mosgiel-based MAF Invermay research centre, have joined forces to combat parasitical lungworm in farmed deer.

Parsons finds the study of parasites and the way they interact with their hosts fascinating. He became interested in developing a lungworm vaccine after doing a BSc Honours project comparing parasites in wapiti and red deer.

Approximately one million deer are commercially farmed in New Zealand. Between 200-300,000 weaners are bred annually, and these are the most at risk from lungworm attack, especially during late summer and autumn. Apart from good husbandry practices, the only guard against lungworm at present is drenching.

"Ultimately, what we're looking to develop is a vaccine we can innoculate deer with before they are exposed to the parasite in the autumn. This will save farmers both time and money by reducing the need for drenching," says Parsons. It is estimated that anthelmintics, lungworm related deaths, and associated production losses cost the deer industry more than $1,000,000 per year.

Mackintosh advised Parsons on his BSc project, and is now jointly supervising the post-graduate's PhD research. Mackintosh has been involved in vaccine development before, and he is under no illusions as to the time the lungworm research could take.

"It could take three years or more to determine if it's possible to produce a vaccine, and as long again to develop it into a commercially viable product," he says.

Adding to the time problem is the seasonality of lungworm infections. Because lungworm larvae are dormant during the winter, it is difficult to get sufficient lungworm at that time to continue research. The only way to get large numbers of lungworm is to allow animals to become heavily infected, which is "very risky" according to Parsons.

A commercial lungworm vaccine exists for cattle and, assuming everything goes according to plan, Parsons will use this as a basis for comparison for the experimental deer vaccine, and as a template for development.

Currently, Parsons and Mackintosh are conducting laboratory tests to determine if deer immune systems can distinguish between deer and cattle lungworm.

"If we find the immune system does distinguish between the two lungworms, it's likely we can develop a successful vaccine. If no distinction is apparent, the research will change course and we'll concentrate instead on the genetics of the lungworm and try and identify reasons why the immune system doesn't recognise the parasite," says Parsons.

Parsons says that although his research is proving to be challenging and difficult, he is determined to prove one way or another if a deer lungworm vaccine is possible.

Lynda Gray is a writer for Otago University's Zoology Department.