Drenching Information

Common Ruminant Internal Parasites

  1. Haemonchus contortus (Barber’s Pole worm)

  • Lives in the abomasum (4th stomach)
  • Summer rainfall areas with maximum numbers in February/March
  • The worms feed on the blood of the host causing anaemia and loss of protein
  • Look for
    • Anaemia
    • Oedema (fluid build-up) and Bottle Jaw
    • Weakness, listless
    • Reduced productivity
    • Death
  1. Teladorsagia (Brown Stomach worm)

  • Lives in the abomasum (4th stomach)
  • Generally found in temperate, high rainfall areas
  • Worms cause diarrhoea from maldigestion/malabsorption and increase the motility of the gut
  • Look for
    • Weight loss
    • Decreased growth rates
    • Anorexia
    • Diarrhoea
  1. Trichostrongylus (Black Scour worm)

  • Lives in the small intestine
  • Generally found in temperate winter rainfall
  • Worms cause diarrhoea from maldigestion/malabsorption
  • Look for
    • Weight loss
    • Decreased growth rates
    • Anorexia
    • Diarrhoea
  1. Fasciola hepatica (Liver Fluke)

  • Lives in the bile ducts in the liver
  • The fluke requires a specific fresh water snail to complete the life cycle
  • Look for
    • Depression (acute stage)
    • Death (acute stage)
    • Slow progressive loss of condition (chronic stage)
    • Anaemia (chronic stage)
    • No diarrhoea
  • A veterinarian will be able to look for pathology in the liver when performing a post mortem

 Drenching

Anthelmintic resistance = the ability of worms to survive treatments that are effective at the recommended dose rate

Alternating groups of drenches annually will slow down development of resistance.

Combinations of anthelmintics (e.g. BZ/Lev, BZ/Lev/Moxi) will also slow down development of resistance.

Do a Worm Egg Count (WEC) first to determine if drenching is required.

Drench at the right time (when environmental conditions are unfavourable for parasites)

Choose the right drench based on –

  • WHP
  • Route of administration
  • Cost
  • Spectrum
  • Species of parasite you’re targeting
  • Age of sheep
  • Whether resistance is already present

Ensure you read the label on the drench and drench to the weight of the largest sheep

If possible, hold sheep off feed prior to treatment for up to 24h as this will hold the drench in the gut for longer and promote more absorption

It is a great idea to perform a FEC prior to and 14d after drench to see if there is drench resistance evident

Other forms of control –

  • Grazing management : rotational grazing, paddock spelling, cross-species grazing
  • Choose rams with breeding values for worm resistance
  • Nutrition – well-nourished adult animals have considerable resistance to parasite burdens­­­.
  • Quarantine – isolate any incoming animals, drench if required