Worm warning after early rains

Sheep producers should test drench resistance on lambs amid severe worm problems experienced after early autumn rains.

Department of Agriculture and Food principal veterinary officer Brown Besier said testing was important because drench resistance now included all available drench types except the newly-introduced monepantel.

"Testing for drench resistance is vital because if a drench doesn't work fully, the remaining worms continue to impose on sheep production, contaminating the pasture with worm eggs and adding to the level of worm larval intake by sheep," Dr Besier said.

"Although the consequences of ineffective drenches are not immediately obvious, they have a major impact on sheep health and production over the course of a year."

Tests are best conducted on lambs up to about six months of age that have not been drenched in the previous two months. An ideal time to test is from weaning to summer drenching time, while lambs are most susceptible to worms.

"Drench resistance testing is easier following the department's development of a new kit that includes everything needed for a sheep worm drench resistance test," Dr Besier said. "Tests are based on the reduction in worm egg counts in small groups of sheep after treatment with different types of drenches. A minimum count of 300 worm eggs per gram is needed.

"The department kit tests for resistance to four commonly-used drenches: abamectin, moxidectin, a white-clear drench combination, and a white-clear and abamectin combination.

"The kits contain quantities of the four drench types, sample containers, pre-addressed postage bags and clear instructions."

Drench resistance kits cost $440 with pre-payment required. This covers the kit plus laboratory costs for 60 worm egg counts and identification of worm types in five sheep groups.

Kits can be obtained by phoning department offices in Albany, Esperance, Katanning, Narrogin, Merredin, Moora and Manjimup.

The department's Albany laboratory tests the samples and forwards a report to the producer within two weeks, indicating which drenches work against which worm types, and with recommendations on good worm control with the least increase in drench resistance.

Producers are advised to discuss the test results with their veterinarian to plan their sheep management program.

Photo caption: The Department of Agriculture and Food's drench resistance kit covers laboratory costs to test 60 worm egg counts and identification of worm types in five sheep groups.