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Queensland worms, flies and lice update - June 2016

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

Barber’s pole outbreaks in winter—they’re certainly possible.

Crowding is the issue. In winter, the barber’s pole cycle is not greatly active but if sheep are isolated on higher ground due to minor flooding from recent rains, infections of most of the mob can develop quickly.

Sheep develop a natural immunity to worms by about 12 months of age, but it falls off in the absence of stimulation by ingested worm larvae, as happens during dry weather. After rain, larvae return onto pasture, and continuous ingestion again stimulates immunity. If sheep are crowded at high stocking rates after rain while their natural immunity is still poor, they become high-risk for infections. If rain has made conditions for handling sheep difficult, a long acting injectable drench could be the best option until sheep can moved to safer ground.

As time is of the essence in these types of conditions, assessing a ‘tail’ group of stranded sheep (they are also likely to be easier to handle) every few days for anaemia and lethargy is important to prevent deaths. Sick sheep should be treated where they are as moving them will be too stressful.

Worm burdens in ewes prior to lambing (spring lambers) need to be kept very low, as the number of worm eggs they deposit onto pasture will determine the level of worm problems in their lambs going into spring. The lambing ewe is the greatest source of infection for the lambs at foot. Worm testing is the only method of tracking movements in worm burdens to prevent production losses.

The next few weeks are predicted to be too cold for barber’s pole to progress through its life-cycle, but eggs will still be dropped onto pastures everyday by infected sheep. Most of these eggs will die, but if temperatures warm slightly and conditions are moist, they will survive and produce larvae onto pastures.