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Queensland worms, flies and lice update - April 2016

Brisbane: Maxine Murphy, Veterinary Parasitologist (maxine@paraboss.com.au)

It’s still dry everywhere. Lack of feed and higher grain prices may force many properties to destock coming into winter. Worm counts are generally low but monitoring worm susceptible classes of stock will track any increases in worm burdens if sheep are crowding onto patches of green pick.

In the higher rainfall tablelands and slopes regions, it’s still dry, but it’s time to start preparing paddocks for spring lambing. The idea is to give time for eggs and larvae already on pasture to die, and reduce further contamination by continuing to spell pastures, and/or grazing only with adult cattle, and/or only with sheep that were drenched in the last 18-21 days.

This 18-21 day period after an effective short acting drench is when no worm eggs are passed by the sheep. This regimen needs to be continued until August, as it appears unlikely that maximum daytime temperatures will remain much below 18°C for any length of time. Eighteen degrees centigrade is the magical number above which barber’s pole worm eggs will start to hatch.

For drier regions, spelling paddocks for between 3-6 months should suffice. Also consider the likelihood of rainfall during winter and if combined with daily maximum temperatures of above 18°C for more than a day or two, the worm cycle could be initiated.

See this article from earlier this month to appreciate the conditions that will allow larvae to develop.

In set-stocked systems, worm egg counting of weaner mobs and pregnant ewes at about 6 weekly intervals will reveal any active infections and identify which paddocks pose potential worm risks. Older dry mobs can remain undrenched if dry conditions persist. In younger stock even a low worm burden can reduce weight and wool growth during periods of poor nutrition. Use short acting drenches in dry seasons.

But all this could change as some are predicting winter rains. If so, then increase worm testing of pregnant ewes and weaners to every 4 weeks, check that dense tall dry grasses are not restricting sheep from moving through to fresh grazing, and check sheep for any visible signs of barber’s pole infections.