The American Association of Equine Practitioners have recently updated their Parasite Control Guidelines (June 2019)
We’ve provided a brief summary of the guidelines including the updated recommendations:
It’s not about eliminating worms – its about keeping our wormers effective:
The goal of any worm control program can be summarised as:
- To minimise the risk of disease from worms
- To control worm egg shedding that keeps the infection cycle going
- To maintain the effectiveness of current worming drugs and avoid further development of wormer resistance as much as possible.
How things around worming have changed!
Important changes have occurred in equine worm populations in the last 40 years due to the introduction of new classes of wormer ingredients. Large strongyles are now rare and small strongyles are the parasites of concern in adult horses, while ascarids remain the most important parasite in foals and weanlings.
Traditional worm control programs featured rotational use of wormers at regular intervals. This strategy is 40 years old and was designed to eliminate highly dangerous large strongyles. This strategy was very successful and disease from large strongyles is now very rare.
Small strongyles are present in all horses but are relatively mild pathogens and only produce disease when present at very high levels. Frequent worming treatments are not needed to keep most adult horses healthy.
Modern Worming strategy – using Fecal Egg Counts (FECs)
The modern worm control strategy is to use wormer that are given at the appropriate time of the year based on the worm burdens of individual horses. A horse’s worm burden can be determined by a fecal egg count that measures the number of worm eggs per gram in a horses poo.
A basic foundation of worming treatments should be considered for all horses. This generally consists of one or two yearly treatments during times of peak transmission - usually Autumn through to Spring in Australia. Choose a product that provides control of strongyles, bots and tapeworms for use in Autumn.
Natural Immunity means that as little as 1 in 4 horses may need worming!
Adult horses vary greatly in immunity to worms. Most adult horses tend to have good immunity against the small strongyles that are measured in a FEC – studies over time have shown that 80% of eggs come from 20% of the horses on a property.
Adult horses tend to shed roughly the same number of eggs throughout their life time; low shedders will often remain low and high shedders have a tendency to remain high.
You can actually save money over a very short period by Fecal Egg Testing (FEC) your horses. Read more about saving money with FECs here.
Young horses and older horses need different worm control strategies
Horses less than 3 and over 20 years of age require special attention and more frequent worming since they are more susceptible to infection and developing disease.
Specifically, Foals should receive a minimum of four wormers in their first 12 months:
- 2-3 months of age, a benzimidazole wormer for ascarids.
- 4-6 months (just before weaning) At weaning, FECs are recommended to determine whether worm burdens are primarily strongyles or ascarids.
- 9 Months of age – Mectin + tapeworm based for small strongyles
- 12 months of age, Mectin based for small strongyles
Easywormer offers special programs are for foals, young horses and senior horses here
Resistance – the problem is REAL!
Wormer resistance occurs in small strongyles and ascarids. Resistance is the ability of worms in a population to survive treatment with a wormer and develops over time – eventually with continued reproduction of resistant worms, the resistant population is high enough that the wormer fails.
To reduce the rate at which resistance occurs, it is critical to maintain parasites that are not exposed to the wormer. This is known as the refugia. Parasites that are not exposed to the wormer won’t develop the resistant genes.
This means we should use wormers as little as possible and utilise other worm control measures (such as paddock management, and worming according to Fecal Egg Count result). Do not under-dose horses and foals; use weight tapes or scales to determine body weights as this is the quickest way to encourage resistance.
Evaluation of resistance on your property can be measured using a fecal egg count reduction test (like A FEC).
You can watch a video on how wormer resistance happens here.
Download the full AAEP Worming guidelines here