Controlling Internal Parasites in your Horse
Parasite control is a critical aspect of equine health when caring for your horses. Historically, recommendations for deworming have centered around frequently treating horses and rotating de-worming products.
We know now, unfortunately, that both practices have led to the development of resistance to our deworming products. Meaning, if we treat horses, there can be parasites that aren’t effectively killed by the drench. Fortunately, we do have a test (called a "Faecal Egg Count Reduction Test") available to assess how efficacious drenches are if you aren’t sure if resistance is on your farm.
As horses age, optimal worm management strategies adapt. Young horses (up to 3 years old) don’t have a fully mature immune system, making regular interval treatment necessary to keep internal parasites under control.
Mature (5-15 years) horses have a more established immune system, and the focus should be on treating only when necessary. Generally speaking, 20% of horses in a herd carry around 80% of the total parasite load. This emphasises that we are likely treating horses unnecessarily throughout the year. We should, where possible, identify ‘high shedding’ horses by performing regular faecal egg counts (FECs) seasonally. Low egg-shedding horses may only need 1-2 treatments per year, while 3-4 drenches may be required when managing high egg shedders.
Older horses (15+ years) may develop diseases such as Cushing’s/Pituitary Pars Intermedia Dysfunction, which can predispose them to shedding more eggs. Or, they may just naturally begin shedding more eggs, even if they hadn’t previously. It is recommended that we perform more FECs in our older patients so we can determine whether they may need more drenching.
The table below outlines recommendations for each age category so you can best care for your horse
| Age | Recommended Treatment |
| 2 months | Product containing either Oxfendazole or Fenbendazole +/- Pyrantel |
| 5 months | As per 2 months |
| 7-8 months | Perform a FEC to identify current parasite burden. If no roundworms are found, a product containing Ivermectin/Abamectin/Moxidectin and Praziquantel should be given to target Strongyles and Tapeworm |
| 12 months | Treat with an Ivermectin/Abamectin/Moxidectin-based product |
| Young (1-3 years) & maturing (3-5 years) | Initially administer drenches seasonally (particularly in spring/autumn), including a Praziquantel-based product in one of the drenches. Gradually move to performing FECs seasonally to help your vet categorise the horse as a high or low shedder. |
| Mature (5-15 years) | Low shedders: Give 1-2 drenches per year, during autumn/spring Moderate/high shedders: Perform FECs seasonally and treat accordingly. This may mean treating 3-4 times per year. *Include Praziquantel in one of the drenches (per year) |
| Aged (15+ years) | Perform seasonal FECs to find out whether your horse is shedding more parasite eggs, adjust treatment frequency accordingly. *Include Praziquantel in one of the drenches (per year) |
If you have any questions regarding parasite control on your farm, please don’t hesitate to reach out today by calling 03 5725 1464.
