When should I deworm my sheep/goat(s)?


When they need it.

No longer is it recommended that sheep/goats be dewormed prophylactically or based on the calendar. Nor is it recommended that all animals in a group be dewormed at the same time. These approaches have caused the worms (especially the barber pole worm) to develop resistance to the dewormers. Dewormers (called anthelmintics) are antiparasitic drugs. They should be given to treat clinical disease, not prevent it. Good management is what prevents clinical disease.

There are various decision-making tools available to help sheep/goat producers decide if/when to deworm an animal. In barber pole worm prevalent areas (moist climates), the FAMACHA© score card can be used to determine which animals need deworming or would benefit most from treatment. The card estimates the level of anemia (blood loss; packed cell volume) in the animal. Anemia is the primary symptom of barber pole worm (Haemonchus contortus) infection. The card depicts five eye scores and treatment recommendations.

The Five Point Check© builds on the FAMACHA© system by adding criteria for the other parasites that commonly affect small ruminants, not just the blood-feeding ones. It’s also useful for deciding whether or not to deworm an animal with a FAMACHA© score of 3, as the FAMACHA© card has a question mark (?) next to category 3.

The Five Point Check© includes five check points on the animal’s body: eye, jaw, back, tail, and nose. You check the eye for FAMACHA© score, the jaw for submandibular edema (“bottle jaw”), the back for body condition score, the tail for fecal soiling (scours), and the nose for nasal discharge (nasal bots). Sometimes, hair coat is used as an additional check point for goats. A poor quality hair coat can be indicative of poor health, including parasitism. All of the criteria of the Five Point Check© should be considered together when making deworming decisions.

In areas where the barber pole worm is not the primary parasite, scientists have developed the “Happy Factor” model. It uses target weights to determine deworming needs. If an animal fails to meet its weight objective (ADG), it is dewormed. In the tropics, they have etermined weight gain along with FAMACHA© to be the best criteria for making deworming decisions. In our research program at the Western Maryland Research & Education Center, we use weight gain (or loss) to help make deworming decisions, especially for FAMACHA© 3s.

Fecal egg counts are generally not a good tool for making deworming decisions (for individual animals). For one, they are not a chute-side decision-making tool. They take time to do. Fecal egg counts can be combined with other criteria, but by themselves are not very reflective of the worm load an animal is carrying. Nor are there any agreed-upon thresholds for treatment. Better uses of fecal egg counts are determining dewormer resistance, monitoring pasture contamination, and identifying resistant (or susceptible) animals.

Ultimately, what’s important is that you have a good reason for deworming. Selecting animals for treatment (or non-treatment) will go a long way towards preserving the effectiveness of dewormers and keeping our sheep/goat farms sustainable and profitable.


Additional reading

Targeted Selective Treatment: Best Management Practices (WormX)