Both horses and sheep have internal parasites.
Deworming medication is used to manage these parasitic infections.
But can a horse dewormer be used in sheep?
Key Takeaway:
Multiple dewormers are available for horses and sheep, but ivermectin and moxidectin are options for both species. Sheep and horse dewormers contain different concentrations of the active ingredient. We must exercise caution when calculating the correct volume to administer.
Intestinal worms are inevitable in livestock.
Dewormers are available to help keep these parasites at a manageable level.
However, anthelmintic resistance is a growing problem.
Keep reading to learn what dewormers are available and how good management practices can help keep your sheep healthy.
Parasites in Sheep and the Goal of Deworming
Sheep have gastrointestinal parasites, which can potentially cause negative health effects like low body condition scores.
Unfortunately, this can decrease productivity and has financial implications for livestock producers.
These parasites live within the digestive system of sheep and steal sustenance from their hosts.
Depending on the life stage of the individual animal host and the number of parasites present, these worms may cause deadly diseases in severe cases.
Although parasites take nutrients from their hosts, sheep can tolerate a small number of intestinal worms without significant health problems.
It is also important to acknowledge that it is unrealistic to completely eliminate intestinal parasites from sheep.
The goal of deworming is to prevent parasitic infection from reaching a point that causes decreased productivity or illness.
Intestinal worms become problematic when there is a high parasite burden.
Additionally, animals with compromised immune systems are at greater risk, such as old, young, pregnant, or nursing sheep.
Common Parasites in Sheep:
- Haemonchus contortus (barber pole worm)
- Teladorsagia (Ostertagia) circumcinta (brown stomach worm)
- Ostertagia trifurcata (brown stomach worm)
- Trichostrongylus axei (bankrupt worm)
- Trichuris ovis (whipworm)
- Moniezeia expansa (tapeworm)
- Oesophagostomum columbianum (nodule worm)
- Eimeria (coccidia)
- Cryptosporidium
Main Types of Sheep Dewormer
Dewormers for sheep fall into different categories.
The types of medications include benzimidazoles and macrocyclic lactones.
These anthelmintics, or dewormers, have different mechanisms of action.
Benzimidazoles work by targeting a parasite’s ability to metabolize energy.
In contrast, macrocyclic lactones cause muscle paralysis.
Sheep Dewormers Approved by the FDA
- Thiabendazole
- Albendazole
- Levamisole
- Ivermectin
- Moxidectin
Common Horse Dewormers
The type of medication indicated for a certain horse depends on his age, the season, and the number of intestinal parasites he is shedding.
Based on fecal egg counts, horses are classified as low, moderate, or high shedders.
In adult horses, the common horse dewormers include ivermectin and moxidectin, with or without the addition of praziquantel.
For foals, the dewormers commonly indicated are fenbendazole or oxibendazole.
Why Would You Want to Use Horse Dewormer in Sheep?
Some sheep owners are curious if they can use a horse dewormer on their sheep as an alternate medication.
Most commonly, sheep owners are inquiring about using horse ivermectin in sheep.
Horse ivermectin comes in a paste, whereas ivermectin labeled for sheep comes in a liquid, oral drench formulation.
Some owners feel sheep have a lower risk of choking with a horse paste wormer.
A liquid drench for sheep may be more likely to inadvertently get into a sheep’s lungs, putting them at risk for pneumonia.
Is Horse Dewormer Effective in Sheep?
There is some overlap in comparing the common horse dewormers listed above with those approved for sheep.
Specifically, ivermectin and moxidectin are potentially effective deworming options in sheep and horses.
While horse dewormers may contain the same active ingredient as some sheep dewormers, the concentration and label dose are different.
For example, as reflected by the product labels, the concentration of ivermectin in this horse wormer found on Amazon is 1.87% compared to 0.08% in this Ivermectin sheep drench.
Therefore, we must be careful when calculating to get the anthelmintic dosage correct.
Additionally, the equine dosage and the dose for sheep are different.
A deworming product labeled for horses in sheep is considered extra-label drug use.
Therefore, you must consult a licensed veterinarian.
Your veterinarian can help you calculate an appropriate dosage given the variation in concentration of the products.
Deworming Strategies for Sheep
There are multiple different deworming strategies for sheep.
The most appropriate deworming strategy for a particular flock depends on the parasite burden as well as the geographic region of the farm.
This is because certain intestinal worms are more prevalent in particular regions.
Furthermore, intestinal parasites in certain regions are more likely to be resistant to deworming medication.
Different classes of deworming medication are better at targeting different types of intestinal worms.
Therefore, combining different classes of drugs can provide a broader spectrum of activity against a wider variety of parasites.
Tips to Ensure Proper Deworming:
- Check the expiration date of the dewormer
- Follow storage guidelines for the dewormer
- Ensure equipment (e.g., drench gun) is clean
- Follow the instructions to calibrate equipment
- Administer deworming medication as directed by your veterinarian
The Growing Problem of Resistance in Sheep
Unfortunately, dewormers are losing effectiveness over time.
Anthelmintic resistance is largely attributed to the overuse and inappropriate use of dewormers.
Ideally, fecal counts of parasite eggs should be performed on sheep before deworming to assess the degree of parasite infection.
Then, we can restrict the use of dewormers to cases of high parasite load.
Additionally, sheep should be weighed before deworming so a proper dosage may be calculated.
Failure to dose by weight accurately contributes to parasite resistance.
Good Management Practices for Your Sheep
Regardless of which deworming strategy you use, we must all strive to consistently implement good management practices to ensure we only deworm sheep when necessary.
Overusing dewormers is irresponsible because it contributes to parasite drug resistance, which is already a serious problem.
An example of management practice to consider adding to your approach to parasite management is using a confinement system to rear your sheep flock.
Additionally, forage strategies like rotational grazing and strip grazing take advantage of certain environmental conditions to decrease the number of viable worms on pasture.
Like all animals, sheep require appropriate nutrition for good overall health.
Therefore, I recommend consulting your veterinarian to see if mineral supplementation might benefit your sheep’s immune system, strengthening them against intestinal parasites.
Additionally, I recommend feeding forages containing tannins since this acts as a natural dewormer.
