Livestock parasite tools

August 2008
AgResearch and Massey University are working together in a joint venture in the Hopkirk Research Institute. They are developing new diagnostic tools for internal parasites in livestock, to reduce loss of production and identify host resistance to parasites and parasite resistance to treatment.

Sheep saliva parasite resistance test:

The procedure involves taking a saliva swab from inside sheep cheeks, using forceps, taking down the sheep ID and then processing the swabs using a standard Eliza diagnostic test. Many samples can be processed at once, keeping the cost down. The collection of the sample is much easier and more pleasant than faecal collection for egg counting.

Other tests such as faecal egg counting and DNA analysis are presently aimed at ram breeders. The saliva test can be done at any time and is much more suited to ewe replacement selection, for example.

The test results rank the animals for their degree of host resistance to all common internal parasites, called worms. Farmers can then breed from the more resistant individuals, because their immune response to worm challenge is faster and stronger. The ranking is a measure of the antiparasite antibodies in the mucosa, which includes the mouth and saliva.

Although the test has not been applied yet, it should also work in cattle and goats.

Detection of nematode eggs in fecal matter using fluorescence:

The fluorescence test for nematode (worm) eggs in faecal samples can be used to establish the level of drench resistance in the sheep. This is a growing problem, as parasites grow more resistant to the chemical families used in anthelmintic drenches. As resistance develops, the products become less effective and growth rate suffers.

Firstly the sheep are drenched, which should kill the resident worms and stop egg production. A sample of faeces is prepared and eggs of two main species haemonchus and trichostrongylus are stained different colours with different reagents. Under the fluorescent microscope the numbers of each species can be counted to establish the level of drench resistance in that sheep.

When commercialized, this test should provide results within 11 days, compared with 35 days currently from faecal egg counting (FEC).