Victoria worms, flies and lice update - January 2018

Hamilton: Andrew Whale, Livestock Logic ( Alex Maclennan (CSU final year Veterinary Student)

Be aware of the Worms!

  • There have been many mortality events in the last fortnight from heavy worm burdens in sheep
  • Monitor all mature stock soon if not drenched in December
  • Lambs need monitoring every 3 weeks at the moment, and 5 weeks post-drenching

Over the past month in the Hamilton region, there has been a massive spike in the number of weaner deaths caused by gastrointestinal worms. I have never seen worms as bad as this at this time of the year. Many producers have been caught off guard and there has been significant losses of young sheep. This increase in deaths is due to three main reasons: weaners having low resistance to worms, adequate ground cover for larvae to survive in pasture, and a recent decrease in feed quality putting nutritional stress on the animals. We have seen lambs dying as early as 4 weeks after an effective drench, with most weaner egg counts (WormTest) rising sharply 4–6 weeks post drench across all breeds of sheep.

It takes many months for lambs to develop effective immunity against worms, which is why they are highly susceptible to disease-causing worm burdens. Highly stressful events such as weaning and periods of nutritional stress can be enough to cause fatalities in already compromised young stock. Figures 1 and 2 show the percentage of different classes of sheep that required drenching based of faecal Worm Egg Counts (WEC) submitted to Livestock Logic.

With 2017 being a wetter year, there has been an increase in ground cover, which is likely to be contributing to the survival of infective worm larvae on pasture. The recent hot dry weather has resulted in decreased pasture quality and availability. Adequate nutrition, particularly protein, is essential for weaners as it improves their ability to maintain productivity when challenged by a parasite infection. Other stock highly susceptible to nutritional stress include lactating ewes and ewes in late gestation. 

This is a timely reminder to monitor (WormTest) stock: lambs 5 weeks post drenching, and mature sheep 6­–8 weeks after drenching. Don’t allow pastures to become overly contaminated over the next few months by not assessing the worm burden in your sheep as this will cause increased worm issues in all stock this winter.

Figure 1. Average worm egg counts for weaners January (2018) compared to January (2017).

Figure 2. Percentage of faecal samples submitted from different classes of stock that required drenching in January 2018.