Top 10 pitfalls in small ruminant parasite management

By Melissa Holahan, Veterinary Medicine Extension, and Laura Williams, Parasitology Section Head WADDL

Gastrointestinal parasitism is a major health concern affecting small ruminants and therefore preventive care should be directed towards parasite management. This seminar will review the top ten pit falls of parasite management and present evidence based recommendations and research from WADDL covering quantitative fecal results from the past 10-years.

1. Deworming based on a schedule rather than the patient
   Deworming based on a calendar schedule is an old school of thought that was adopted from equine parasite management that can quickly lead to dewormer resistance. Instead, the author recommends running fecals on a calendar schedule (spring & fall), especially with smaller herds/flocks. Another time to consider running targeted fecals are during times of stress (2 weeks post kidding, late pregnancy, during the first few months of transition for new arrivals, young stock (< 6 months), persistent diarrhea, illness and/or poor body condition. Testing individual animals is more specific because you can establish the parasite burden in each animal and evaluate the effect of the treatment.
2. Using injectable or topical dewormers rather than oral dewormers
   Topical dewormers, while favorable because most have little to no milk/meat withdrawals, they have a high level of resistance. Injectable dewormers are also easier to administer but they also carry a high risk of dewormer resistance, especially with injectable ivermectin.
3. Not utilizing copper oxide wire particles (COWP) and/or over utilizing COWP
   COWP administered orally passes through the rumen and lodges in the abomasum or true stomach, where the adult H. contortus resides. COWP appears to cause damage to the adult worm and likely death, but does not affect immature larvae, which can also feed on blood from the animal. The copper oxide from COWP is poorly absorbed, but will increase the concentration of copper in the liver. Sheep, and to a lesser degree goats, are susceptible to copper toxicity and too much copper from feed, minerals (loose, block, or as COWP), or forages can lead to death. Therefore, care should be taken with how much and how often COWP is administered and should be reserved for individuals determined to be anemic for control of barber pole worm. Treatment can be repeated in six weeks if necessary, but it is recommended to not use more than four COWP treatments within a worm season. COWP should not be used in sheep breeds sensitive to copper toxicity or when other sources of dietary copper are available, in areas of low soil molybdenum or high copper, or in sheep grazing pastures fertilized with poultry waste (high in copper), all of which may augment copper toxicity.
4. Missing Coccidiosis in healthy kids
   Young stock should be closely monitored especially during the weaning period. While fecals should be evaluated on those with clinical signs of coccidia, treatment should not be delayed. However, it is important to perform follow-up fecals on these animals and spot check other young stock housed within these groups as marked coccidia can commonly present in non-clinical animals, resulting in heavy environmental contamination rates.
5. Using an inappropriate dewormer dosage
   Whenever dosing dewormers for small ruminants it’s important to use the appropriate products at the appropriate dosages. The author recommends utilizing www.wormx.info for current dosage charts and using liquids intended for small ruminants. The use of equine paste dewormers is not recommended as it is difficult to appropriately dose and toxicity is more commonly seen. The use of large dog scales can be a feasible option to get accurate body weights for small ruminants and camelids.
6. Deworming based on the number not the patient
   The most common pitfall involves producers deworming based on a number and not the patient. Most first time producers believe that small ruminants should have little to no parasites, which is a common misconception. A general guideline to deworming animals: > 800 eggs per gram (epg) monitor every 2-3 weeks and reassess, >2000 eggs per gram in warm months and >1000 eggs per gram of feces in the colder months. It’s important that a McMaster’s fecal with quantitative results is performed so that veterinarians can compare results with each other and overtime. Results should be reported in eggs per gram (epg) or oocysts per gram (opg) of feces. Not all parasites are created equally as some are more concerning than others. After treating individual animals, separate them from those that are not treated.
7. Not utilizing a combination of dewormers and switching dewormers often
   Current literature supports the use of two dewormers given concurrently when deworming an animal to reduce the incidence of dewormer resistance. The other common concern with dewormers is the use of rotational dewormers, un-necessarily exposing the farm to multiple different dewormers within each drug class. The best practices include using the same dewormers on the farm until resistant is seen. This is another reason why intermittent fecals (esp. follow-up fecals after deworming) are important to determine when resistance is seen.
8. Treating the entire herd instead of utilizing secondary markers of parasite load
   Body condition scoring, FAMACHA scoring and the 5-point check are the main indicators of parasitism2. Other clinical signs that can be associated with a heavy parasite load can include: weight loss, diarrhea, rough hair coat, weakness, anemia (FAMACHA scoring), bottle jaw (low protein), jaundice, etc.
9. Inappropriate grazing management
   Parasites in the pasture can go from egg to infective stage in as little as six days to go from egg to infective stage. Therefore, producers using grazing rotations need to stay ahead of this cycle and the main key to this is to subdivide fields so that the animals have enough to eat for four to five days. Rotating animals into a new field within five days helps to ensure the parasite larva reach the infective stage after the sheep or goats have moved out of that field. A good rule of thumb is to prevent grazing below 4 inches of growth; if you can see their hooves the pasture is too short.
10. Not isolating/quarantining new arrivals to the farm
    This is the only time that the author recommends aggressive deworming protocols. While submitting a fecal is still recommended to evaluate the new arrival for baseline parasite levels, this is one incidence where deworming should be strongly considered, esp. if the animal is coming from another state/region. There is a higher likelihood that the new arrival may have a different species of coccidia and/or resistant strongyles.