Worms are internal parasites of cattle, sheep and goats and almost all the ruminants and non-ruminants. They do not have any negative impact on the livestock until their population increases and causes harm to them. Worms survive in different parts of the livestock and feed on what the animal eats. The animals get infected if they ingest the larvae in the grass/rangeland. The older animals are mostly affected by worms and the weaners except for the suckling calves.

Life cycle of worms

  1. Larvae enter the gut, as the host eats infected grass
  2. Larvae mature into egg producing adults and eggs are excreted by the host
  3. Eggs are then spread by hooves and rain
  4. Eggs develop into larvae after 24 hours
  5. At 3-4 days old larvae become infectious
  6. Larvae move throughout pasture and attach to grass

Different types of worms affect livestock. We will discuss 4 types of worms which mostly affect livestock:

  • Tapeworms 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 fecal matter and can become overly concerned.
  • Roundworms: worms that lives in the abomasum and small intestine of sheep and goats. There are several types of roundworms that infect sheep and goats. The most dangerous parasite affecting small stock is the gastrointestinal roundworm (barber pole worm).The parasite sucks blood and it reproduces through egg laying.
  • Stomach worms: In cattle, brown stomach worm (Ostertagia ostertagi)is by far the most important worm. Disease only occurs in first and sometimes second season grazing stock as immunity is developed over this period. Two types of disease occur; Type I during the summer, as larvae are picked up from the pasture and Type II in early spring when the larvae start to develop into worms. Symptoms of the two types of disease are very similar.
  • Lung worms: Lungworm is more serious in cattle than in sheep. In areas where the worms are more prominent, first season cattle can be vaccinated before they affected.


Factors affecting worm infection levels

  • Worms present.  Some roundworms produce thousands of eggs daily, others only a few hundred.
  • Stock management. Higher stocking rates produce greater contamination, especially in the right conditions for egg or larval development, such as the spring and summer.
  • Immune status of animals.  The influence of stocking density will be greatest if all the stock are fully susceptible, or if the ratio of susceptible to immune stock is high.

Symptoms of worm infection

  • Stomach and intestinal worms cause diarrhoea, appetite loss and weight loss
  • Lung worms cause coughing and unthriftiness
  • Barbers pole worm causes anaemia and bottle jaw due to blood sucking
  • Rough coat/skin
  • Poor milk production

Treatment and control of worms

Controlling worms means to avoid the animals from high infections of worms and it can be done in the following ways:

  • Use of wormers: these are chemicals and vaccines that are used to deworm the livestock. They are very vital to control worm populations and infections, as they help the farmer save from economic losses from infection by worms.
  • Practice clean grazing: this is when the pasture can be treated to minimize the larvae population in the grazing area and it is left for about 6 months without being grazed by any livestock. Also it is land that harvesting of legumes has just been done.
  • Integrated systems: This is where the farmer uses both the two other methods of controlling worms at the same time.
  • Manage grazing: do not overgraze the grazing land

When to dose/deworm livestock

Dosing livestock depends on the age of the livestock. As the livestock grows it ends up developing immunity over worms, and mature animals tend to become immune to them. Weaners are the most susceptible to worms because they have not yet developed immunity hence they need to be dewormed. Deworming should be done regularly especially since most people use the extensive system of grazing. Every end of season it is advisable to deworm especially after the wet season. This will reduce worm populations and also reduce the larvae that would have hid in the livestock`s body.