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Queensland worms, flies and lice update - June 2017

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

It was rather warm in May, but temperatures have now dropped and the cold weather has arrived – and a welcome relief from drenching, you would hope. While barber’s pole activity does slow during cool weather, most days in southern Queensland reach temperatures of above 18°C, the temperature at which barber’s pole eggs start to hatch.  Even on the Granite Belt day temperatures mostly reach 16-18°C, borderline for egg hatch.   

Rainfall is often very light during winter, but when dews are heavy enough they can provide enough moisture to allow development of barber’s pole worm eggs to larvae. The majority of larvae on pasture will die from hunger over a few months as they have limited energy reserves, but some will still be present at August lambing. Mature worms in sheep are protected from adverse weather conditions and have the potential to initiate infection when conditions become favourable again.   

WormTest at recommended times (so that you don’t have to keep wondering, “are they wormy?” or get any nasty surprises when you check your sheep):
From March to October, 4–6 weeks after significant rain (20+ mm) and especially if rain falls again in the next 3–4 weeks. If grass is long and dry, and covering shorter green pick you will need to WormTest. Take faecal samples from the poor doers (often also the most wormy in the mob) to determine if you need to drench.

The incidence of nodule worm in sheep is now quite low due to the efficiency of modern drenches that kill the adults in the gut lumen as well as the immatures encysted in the wall of both the small and large bowel. Nodule is occasionally seen in the older sheep, and often, albeit in small numbers, in larval differentiations (worm typing) conducted on WormTest submissions. Nodule worm larvae on pastures are very cold-sensitive and probably die within 10 weeks.  May/June has always been considered the time to treat (use a short acting, multi-active drench as these contain either BZ or MLs that are effective against worm stages in the gut wall) for nodule but WormTest first to make sure you are not wasting your time and money.