abortion, goats; parasites; ewes

Livestock production: Treating against parasites during winter

Question: Are there any parasites I can’t see that can cause problems? Do I need to treat against parasites during winter?


  • One parasite that does cause a problem, but can’t be seen, is the liver fluke.
  • Its distribution depends on rainfall and the availability of open water sources.
  • During very wet years cases of liver fluke can increase dramatically.
  • Although cattle are more resilient than sheep, neither develops a very good resistance to this specific parasite.
  • In South Africa, the high rainfall of last spring and summer meant conditions were probably optimal for heavy infestations during autumn.
  • Animals get infested when they graze in wet areas where plants are growing in a water source, such as the edge of water pans.
  • Immature flukes are ingested with the grazing.
  • They work their way through the intestines to the abdomen and then to the liver.
  • For the next 2 months they tunnel through the liver, eating the tissue and growing to adults. The adults move on to the bile ducts where they survive for a long time.
  • This process destroys the normal functioning of the liver, which leads to a reduction in feed intake and metabolism, causing anaemia and lowering blood protein levels.
  • The worse effect on the animal occurs during late winter, when grazing is scarce and of a poor quality.
  • Bottle jaw (accumulation of fluid below the skin under the lower jaw) can be seen in affected sheep, but cattle show very few signs of disease apart from losing condition.
  • Usually, the farmer only realises there is a liver fluke problem when the first animals die.
  • The big adult liver flukes can be seen in the bile ducts when the liver of the dead animal is cut in half.
  • Any product that works against liver fluke can be used in late winter to treat the adult flukes. This is called a strategic treatment because it gets rid of the adult flukes that produce eggs which lead to the next generation during the following spring and summer.
  • It takes about a month for animals to improve after treatment if damage to the liver was severe.

Also read: Small stock production: The five-point check for internal parasites in small stock


  • If you supplement using a commercially produced lick you won’t need to supplement further for most vitamins.
    1 vitamin that can cause a problem is vitamin A.
  • It is produced by cattle and small stock from the green grass that they eat and stored in the liver.
  • About 3 months after the last available green grass was eaten, the store in the liver will all have been used up.
  • Another problem is that vitamin A is light-sensitive and breaks down in the supplementary lick provided.
  • The best way to supplement with this vitamin during late winter is by injecting cattle with the vitamin and dosing small stock with a vitamin A product.
  • The vitamin is essential for the health of membranes in the eye and nose, and the uterus of a pregnant animal.
  • If animals are healthy, the vitamin protects against diseases such as eye infections and pneumonia.

Also read: Livestock production: Why is vitamin A important for animals?


I haven’t seen any ticks on my animals during this cold winter. Do I still need to dip them?

  • During a very cold winter we see very few adult ticks on cattle.
  • The blue tick survives winter in the form of eggs that will hatch and get onto the cattle again in spring.
  • Multi-host ticks like the bont tick are in the immature stage during winter and feed on small game and ground birds.
  • External parasites that do cause a problem during cold winters are blue lice.
  • They have this name because they suck blood and look like very small ticks.
  • They are usually attached to the animal around the base of the tail, but can also occur on other parts of the body.
  • These lice don’t move around and cannot survive off the animal.
    1 treatment with an injectable Ivermectin would get rid of the entire infestation.
  • In many cases it is not necessary to treat animals against ticks during a very cold winter, but it is very important to start dipping early in spring when the first adult blue ticks are seen.
  • If dipping is repeated every three weeks throughout spring it will significantly reduce the number of blue ticks in summer.

Also read: Goat production: Act against abortions in your goat flocks

  • This article was written by Dr. Danie Odendaal and first appeared in Farming SA.


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