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Queensland worms, flies and lice update - February 2017

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

At this time of the year, burdens of barber’s pole worm will peak, especially if sheep have remained undrenched over the summer. Extreme day temperatures (above 35°C) would have killed worm eggs and larvae on pasture, but any infections harboured by sheep will continue to drop eggs onto pasture each and every day. As minimum temperatures drop below 20°C, eggs will remain viable. If maximums drop to between 25–30°C, then eggs stand a good chance of hatching, especially if adequate moisture is around. There are often patches of green grass or long dry ground cover that can form microclimates and hold the humidity from the morning and evening dews. Under these conditions, eggs can quickly develop into larvae infective to sheep.

Sheep and goats need to be tested for worm burdens using the worm egg count test on a couple of representative mobs to indicate whether a drench is needed. Follow drenching with another worm egg count, fourteen days later. A larval differentiation (culture for worm type) will also provide information on the levels of black scour worm, which is often present in western Queensland at this time of the year, and if it is susceptible to drenches.

The factors that attract flies to sheep are warm temperatures, moderate winds (<30 km per hour) and sheep fleece that has remained moist from rainfall over a few days.