Internal parasites, or endoparasites, are a silent threat lurking within livestock, causing weight loss, poor growth, reproductive challenges, and even death if left unchecked. For South African farmers, managing these parasites is not just a health issue but an economic imperative.
With the right knowledge, treatment options, and a well-timed deworming schedule, farmers can control parasite loads and protect their herds’ productivity.
Kevin Pieterse, an experienced farm manager and Kyron Agri representative, shares practical and expert advice on how to treat and manage endoparasites effectively within a herd.
Endoparasites, commonly known as worms, infest various parts of an animal’s digestive and organ systems. According to the Merck Veterinary Manual, endoparasites in ruminants are categorised into three groups: roundworms, tapeworms and liver flukes. Left untreated, these parasites can cause severe damage, including weight loss, stunted growth, and reproductive failure.
“There are many different types of endoparasites, let’s call them worms, and they’re found in different parts of the animal’s body. Some are in the stomach, some in the small or large intestines. Liver flukes, for example, target the liver, and each type can have a serious effect on the animal,” says Pieterse.
Parasites like wireworm and liver fluke deprive animals of vital nutrients, deteriorating body condition and damaging organs. This not only compromises livestock health but also reduces their market value.
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Dewormers: Contact vs long-acting treatments
South African farmers can choose from up to 11 classes of deworming agents, each defined by its active ingredient and mode of action. Pieterse simplifies this by grouping them into two categories: contact (short-acting) treatments and long-acting injectables.
Contact dewormers: Fast-acting and effective
“You get what we call contact remedies or contact dewormers, levamisole is one such popular option. These go into the intestinal tract, pass through the stomach lining into the bloodstream, and kill parasites on contact.”
Short-acting dewormers such as albendazole and triclabendazole interfere with the parasite’s metabolism or nervous system: “They eventually run out of energy, become paralysed, detach from where they’re feeding, and die.”
Levamisole-based drenches, commonly referred to as yellow drenches, function by overstimulating the parasite’s nervous system, ultimately leading to its death and detachment from the host. Farmers are advised to keep a close eye on young animals’ droppings, as the presence of small, rice-grain-like particles is often a sign of a tapeworm infestation.
Long-acting injectables: Convenience and sustained protection
Long-acting dewormers, especially injectables, are popular for their ease of application and extended effect.
“It’s much quicker and easier to inject it than to dose animals orally, especially with large animals like cattle,” explains Pieterse.
Products with closantel and macrocyclic lactones (such as ivermectin, doramectin, moxidectin, and abamectin) are particularly effective. “They’re excellent for controlling roundworms and fall into a class called insecticides, which treat both internal (endoparasites) and external parasites (ectoparasites).”
These injectables provide broad-spectrum coverage, even targeting pests like blue ticks and nasal botworms.
“If you drench your animals with something like moxidectin, you get up to 35 days of residual activity, especially helpful against wireworm, which is a major concern for many farmers.”
Management is just as crucial as treatment
Successful parasite control goes beyond medication; it requires good management practices.
“You need to know which parasites are on your farm so you can adapt your grazing and treatment plans accordingly,” Pieterse says.
Strategic steps for controlling endoparasites
- Observation and body condition scoring
Regular observation and body condition scoring (BCS) help detect early signs of parasitic stress. Pieterse encourages farmers to learn this simple yet powerful skill: “I think farmers should educate themselves about doing a body conditioning score.”
Animals with poor condition, such as visible weight loss or dull coats, could be carrying a heavy parasitic burden. Early detection allows for timely intervention with either contact treatments like levamisole or longer-lasting injectables such as moxidectin.
Pieterse adds, “It helps identify underperforming or infected animals early, before problems escalate.”
- Post-mortems to investigate the cause of death
Post-mortems offer crucial insights into which parasites are affecting your livestock. Pieterse encourages farmers to get hands-on. “I think every farmer should be curious enough to want to know why [their animals] died. Go through the entire intestinal tract.” - Address resistance through strategic culling
Overusing dewormers on the same animals can result in resistant parasite strains. Pieterse warns, “If you are constantly deworming a certain animal, at some stage you’re going to have to think about maybe culling those animals.”
Strategic culling of animals with persistent worm loads helps reduce resistance in the herd and improves overall productivity.
- Ensure correct dosage
Underdosing is a key driver of resistance. Pieterse stresses the importance of proper weight estimation:
“It all starts with the weight of the animal. Underdosage is very dangerous. You’re actually starting to build up resistance within your herd…”
If a livestock scale isn’t available, Pieterse recommends using a weight belt to help estimate the animal’s weight more accurately. Getting the dosage right is essential for both short-acting treatments like levamisole and longer-lasting options such as Ivermex Platinum LA or Moxieject.
- Consult professionals
Parasite control should be tailored to each farm’s unique needs. Pieterse encourages farmers to make use of the support available from state veterinarians, extension officers, or Kyron Agri representatives. These professionals can help choose between fast-acting or residual solutions, depending on parasite type and risk levels.
Suggested deworming timelines
For cattle
To maintain herd health and prevent parasite build-up, Pieterse recommends the following schedules:
- Six weeks before breeding
Deworm and provide vitamin/mineral supplements. - Six weeks before calving
Repeat deworming and supplementation, with a focus on vitamins A and E. - Calves aged 2–3 months
Administer the first deworming treatment. - Around 6 months old (pre-weaning)
Provide the second deworming dose and treat specifically for tapeworms. - In liver fluke-prone areas
Consider using targeted treatments such as Ivermex Plus Fluke or Endotect Plus Fluke to manage this specific parasite.
For sheep and goats
A consistent schedule can help protect ewes, rams, and their offspring:
- Four weeks before breeding
Routine deworming to reduce parasite load before mating. - Four weeks before lambing/kidding
Repeat treatment to protect both the mother and newborns. - Lambs and kids
Deworm at 2–3 months, and again at 6 months to ensure ongoing protection during early development.
Pieterse stresses that parasite control plans should not be static; they must evolve with new observations and outcomes.
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