Internal and External Parasites

Parasites pose a significant threat to the health of small ruminants. Parasites can damage the gastrointestinal tract and result in reduced reproductive performance and even death. Factors that may affect an individual’s susceptibility to parasitism include natural genetic resistance, age, and reproductive stage. Goats are generally more susceptible to internal parasites than sheep. The groups most susceptible to parasitism are young animals, lactating ewes and does, and those in late gestation or around the time of parturition.

Internal Parasites

Several types of internal parasites affect sheep and goats and all sheep and goats have a low level of parasite activity. Internal parasite that commonly affect small stock are:

  • Roundworm: that lives in the abomasum and small intestine of sheep and goats.There are several types of roundworms that infect sheep and goats including Telodorsagia (Ostertagia) circumcincta, Haemonchus contortus, and Trichostrongylus colubriformis. The most dangerous parasite affecting small stock is the gastrointestinal roundworm Haemonchus contortus (barber pole worm).The parasite sucks blood and it reproduces through egg laying.
  • Coccidia: are protozoan parasites that damage the lining of the small intestine. Fly strike and secondary infections can also result from coccidiosis. Coccidia are usually found in animals in confinement or intensive grazing systems as a result of poor sanitation, overcrowding, and stress. Animals between one and six months of age in feedlots or intensive grazing systems are at highest risk for coccidiosis.
  • Tapeworm: Lambs and kids become resistant to tapeworms quickly, so infections are most common in animals younger than four or five months of age. The biggest problem with tapeworms is that producers can actually see the segments in faecal matter and can become overly concerned.

External parasites

External parasites may damage the fleece (woolly coat of goats and sheep). External parasites are especially common in the winter when sheep or goats are in closer confinement. Parasites common to sheep or goats include:

  • Lice: there are two kinds of lies that affect small stock being chewing lice which feed from the dead skin cells and the blood suckling lies which sucks blood. They can be detected by the presence of the eggs (nits). Small stock showing signs of wool or hair loss should be checked for lice
  • Keds: they pierce the skin and sucks blood and are usually found on the neck, shoulders, and flanks. Ked bites are very irritating to sheep causing them to scratch, rub, and bite themselves which damages the wool. Keds also cause wool discolouration, which further reduces the value of the fleece. Ked bites affect the hide quality as well.
  • Mites: mites burrow beneath the skin instead of living on the surface. This irritates the skin causing the sheep and goats to itch, which results in wool or hair loss and lesions or scabs. Mites can be diagnosed by doing a skin scraping.


  • General clinical signs that an animal is suffering from a parasitic infestation include diarrhoea, weight loss
  • Unthriftiness (failure to grow or put on weight but feed is present and in abundance)
  • loss of appetite and reduced reproductive performance.
  • anaemia (pale mucous membranes)
  • skin is usually seen as swelling of the lower jaw (Bottle jaw)
  • protein loss, and death.
  • weak and lethargic (often straggling at the back of the herd when driven a distance).
  • gastrointestinal upset.
  • A tapeworm infection can be diagnosed by yellowish-white segments in the faeces
  • dehydration, fever and breaking of wool or hair.

Treatment and control

  • Outbreaks of coccidiosis can be controlled by implementing good sanitation techniques, providing clean water, rotating pastures, and avoiding overstocked pens. Outbreaks of coccidiosis can be treated with sulfa drugs. Coccidiostats can be administered to inhibit coccidial reproduction
  • Pour-on treatments are a common form of management for many external parasites, and are more effective
  • Shearing sheep (process of cutting off fleece in sheep) will remove most adult keds and larvae, and is especially important before lambing.
  • Administering injectable Ivermectin or topical insecticides can help infected animals.