3 September 2002 Where do the Nematodes Live?

Infection of sheep with parasitic worms (nematodes) is a common problem for farmers in New Zealand and worldwide.

Sheep with numbers of worms in their gut do not grow as well as non-infected sheep. An added problem is that they also infect other sheep in the mob when they excrete worm eggs which then develop into larvae on the pasture.

Most parasitic infections are currently treated by drenching sheep before lambing with anthelmintics. However, there is evidence that there is a growing problem with the parasitic worms becoming resistant to anthelmintics used to provide this treatment.

In a first for New Zealand, a team of researchers from the Animal and Food Sciences Division at Lincoln University have undertaken trials to find if there are variations in nematode population of breeding ewes throughout the country.

Team member Rob McAnulty says, "Before a new ecologically sound method of treating these worms can be developed it is important to know whether the sheep are infected with a particular species of parasite. We planned that this preliminary trial will give us some baseline data so that more comprehensive trials can be undertaken."

"We are grateful to members of the Coopworth Society of NZ who have allowed us to take samples from lambing ewes from farms throughout New Zealand. In all, four areas were sampled; upper and lower North Island and upper and lower South Island."

Samples taken from ewes within two to six weeks of lambing were sent to the Parasitology Laboratory at Lincoln University where they were counted using standard faecal egg counting techniques and a bulked sample from each farm was cultured to identify general composition.

Results showed that there are differences in both the numbers and types of nematodes present in different regions of New Zealand. Statistical tests showed that these differences were significant.

"The strong geographic patterns seen provide valuable insight for the implementation of control strategies, especially for animals under greater stress such as first lambing and multiple-bearing ewes,” said Mr McAnulty.

"We are pleased with the results we obtained, but we realise that it was a small trial so we hope to undertake a much larger trial to get more comprehensive epidemiological information before country-wide recommendations on appropriate methods for management of nematode parasites in ewes can be made."

These results were presented at the NZ Society for Animal Production held in Palmerston North recently.