Sheep and Goat Parasites: Smart Deworming Guide

Sheep and goat parasites, particularly gastrointestinal worms, are among the leading causes of stunted growth, reduced milk production, and poor feed conversion in small ruminants. Often silent at first, parasitic infestations can build up gradually within a flock and undermine its profitability if left unmonitored. Understanding the life cycle of these parasites and adopting a targeted deworming strategy helps protect animal health while slowing down the development of resistance to dewormers.

Understanding gastrointestinal worms in sheep and goats

Sheep and goats share most of their internal parasites, which is why mixed or successive grazing of both species on the same plot can encourage transmission. The most common gastrointestinal worms settle in the abomasum, small intestine, or large intestine, where they feed on blood or digestive nutrients.

The life cycle of these parasites generally follows a similar pattern:

• Eggs are shed in the feces of infested animals.
• They develop into larvae on pasture, especially when humidity and warmth are favorable.
• Healthy animals ingest these larvae while grazing on contaminated grass.
• The larvae mature into adult worms in the digestive tract, which in turn lay new eggs.

This cycle explains why damp pastures, low-lying areas, and overgrazed watering points are prime contamination hotspots, particularly after rainfall followed by warm weather.

Impact on growth and production

Even a moderate parasitic infestation has real consequences on flock performance:

• Stunted growth in lambs and kids, delaying the time it takes to reach slaughter weight.
• Reduced milk production in nursing or lactating females.
• Progressive weight loss, sometimes accompanied by diarrhea or a dull coat/fleece.
• Anemia in cases of heavy infestation by blood-feeding worms, recognizable by pale mucous membranes.
• Weakened immunity, making animals more susceptible to other diseases.

Young animals, females in late pregnancy, and already weakened animals are generally the most vulnerable, as their immune systems are less able to keep the parasite load in check.

Recognizing the signs of an infestation

Certain signs should alert farmers and prompt closer observation of the flock:

• Weight loss despite normal access to food
• Persistent or intermittent diarrhea
• Dull-looking coat or fleece
• Pale mucous membranes (eyelids, gums)
• General drop in energy or appetite

These symptoms are not specific to parasites and may have other causes: a professional assessment is essential to confirm the exact cause before deciding on any treatment.

Dewormers for sheep and goats: principles of targeted deworming

Deworming small ruminants should no longer rely on systematic treatments repeated on a fixed schedule. This once-common approach encourages parasites to develop resistance to the active ingredients used, making treatments less and less effective over time. A targeted, evidence-based deworming approach relies on several principles:

• Treat only the animals that truly need it rather than systematically dosing the whole flock, based on body condition and clinical signs.
• Rotate dewormer classes according to professional recommendations, to limit the development of resistance.
• Respect the correct dose based on each animal's actual weight, as underdosing is one of the main drivers of parasite resistance.
• Manage pasture use by rotating plots, avoiding overgrazing, and letting the wettest areas rest.
• Isolate or prioritize treatment for newly introduced animals, a frequent source of contamination.

Rotating pastures between different species (for example with cattle, which are less susceptible to the same parasites) can also help reduce parasite pressure on a given plot.

Prevention rather than treatment

Prevention remains the cornerstone of effective, sustainable parasite management:

1. Regularly monitor the flock's overall condition (weight, behavior, coat quality).
2. Avoid overstocking pastures, especially during the wet season.
3. Provide a balanced diet to strengthen the animals' natural resistance.
4. Maintain good hygiene at watering points and feeding areas.
5. Arrange regular check-ups with a professional to adapt the treatment strategy to your flock's actual needs rather than following a fixed schedule.

Every farm has its own particularities depending on local climate, flock size, and grazing practices. Personalized guidance helps establish a deworming protocol suited to your situation and avoids unnecessary or poorly targeted treatments. It's recommended to consult veterinarians for sheep or veterinarians for goats to assess your flock's parasite load and define a targeted treatment plan.

Should deworming follow a fixed schedule or be based on need?

Systematic deworming on a fixed schedule, without prior assessment, increases the long-term risk of parasite resistance. The recommended approach is to monitor the animals' condition and, where possible, have a professional assess the parasite load before deciding on treatment, rather than treating the whole flock out of habit.

Need a professional opinion? If in doubt or in an emergency, find a veterinarian near you on TunisieVet.