Worms — they never go away

The climate and season have a major influence on the expression of worms in your sheep flocks. As you read this at the height of spring, plenty of quality pasture is allowing your sheep to cope with the worms they have. Six months ago during the drought, the lack of moisture meant sheep weren't being exposed to worms.

These parasites never go away, as the succession of droughts in Australia has shown us — they have a wonderful knack of surviving these climatic extremes. The recent MLA review of endemic livestock diseases estimated that worms cost the Australian industry more than $400 million annually. This makes them one of the biggest diseases, in dollar terms, of all those facing our industry.

It is also worth considering the likelihood of drench resistance, especially among the main worm species:

  • barber's pole worm (Haemonchus contortus)
  • brown stomach worm (Teladorsagia circumcincta)
  • black scour worms (Trichostrongylus species).

A survey of drench resistance was conducted across Australia earlier this decade. It showed that resistance to single actives available for over 30 years was widespread, and continuing to worsen (since previous surveys). Now, in spring, with young lambs present on your property, is the ideal time to conduct a drench resistance test. The results of this test will enable you to administer effective summer drenches.

Spring is the time when there are the most worms on your farm — we don't see much disease because the worms are on the pasture, rather than in your sheep. This large population is the reservoir that will allow enough to survive the summer dry period to reinfect your sheep next autumn, bringing on scours, weight loss and deaths.

Summer drenching is the key to minimising this worm carryover into next year, by making sure that there are few worms in your sheep getting a free ride to autumn.

For more information, see the WormBoss website.

Page last updated: 03 Jul 2020