Essential Tips for Worming Senior Horses

Immunity and the ability to fight disease declines with age, leaving senior horses more vulnerable to parasitic infections. Older horses may not respond to parasite exposure as effectively as younger adults. However, not all will have higher parasite burdens; some may maintain a natural resistance to worms.

Tailoring Worming Programs to Your Senior Horse

A one-size-fits-all approach to equine worming is no longer recommended, especially for senior horses. Faecal egg counts are even more important in this age group to determine an appropriate worming program. This targeted approach minimizes unnecessary treatments, reduces the risk of resistance and ensures that your horse receives appropriate care.

In Australia, the worming plan should also consider seasonal changes. Understanding the local climate and its impact on parasite populations is critical for planning a worming strategy. For instance, parasite activity typically peaks during warmer and wetter months, such as spring and autumn. Very cold or very hot, dry weather is associated with lower parasite activity as the worm eggs and larvae cannot withstand these conditions. Collaborate with your veterinarian to tailor the worming plan to your region’s specific conditions.

Take a look at our article on wormer selection and use in horses to learn more about parasite control in horses.

Choosing the Right Wormer

Senior horses may have different needs when it comes to selecting a wormer. Factors that can influence this decision include the following:

• Type of Parasites: Common equine parasites affecting adult horses include small strongyles (cyathostomes), tapeworms and bots. Worming treatments should target strongyles, particularly in autumn and spring, as well as tapeworm at least once a year. If bot flies are active in your area, you should also consider treating for this right before or after winter.

• Active Ingredients: “Mectins” such as ivermectin, abamectin and moxidectin are generally the most effective against small strongyles (cyathostomes) and bot fly larvae. Moxidectin should NOT be used more than once per year, unless you are specifically told to do so by your veterinarian. Other wormers (such as pyrantel, morantel) may also be used but only if shown to be effective on your property. Praziquantel should be given at least once a year to control tapeworm burdens. It’s important to know what’s in your wormer to ensure that you are using the correct product for your senior horse.

• Safety and Tolerability: Senior horses with underlying health issues, such as liver or kidney disease, may be more sensitive to certain drugs, including wormers. Consult your veterinarian to ensure the chosen product is safe. Most importantly, don’t forget to weigh your horse to ensure that you are administering the correct dose! If you don’t have access to scales, you can use the online horse weight calculator.

Management and Environmental Control

Effective parasite control extends beyond administering a worming paste! It is important to remember that it is not the worm eggs on the pasture that are the concern, but rather the infective larvae that hatch from these eggs. When swallowed by the grazing horse, these larvae will go on to complete their life cycle and develop into adult, disease-causing worms. This is what we need to avoid! Good pasture management can significantly reduce the parasite load in a senior horse’s environment. Pasture management strategies can include:

• Regular Manure Removal: By far the most effective way of reducing larval numbers on your paddocks is via removal of the dung. If you remove the manure (and the worm eggs each pile contains) then there will be far less eggs left on the pasture to hatch into the infective larvae. Remove manure from paddocks at least twice a week to break the parasite life cycle.

• Rotational Grazing: Allow pastures to rest and recover by rotating grazing areas. By removing horses from certain paddocks, the shedding of eggs onto these pastures (and the number of infective larvae that could develop) has been reduced.

• Mixed Grazing: Grazing horses alongside other species, such as cattle or sheep, can “mop up” the worm eggs and larvae and reduce the number of infective larvae in the paddock.

• Avoid Overcrowding: Ensure paddocks are not overstocked, as this increases the risk of parasite transmission.

Account For Underlying Health Conditions

Senior horses often face health challenges such as weight loss, dental problems, arthritis or metabolic conditions like Cushing’s disease (PPID). These issues can influence the horse’s ability to tolerate a worm burden or recover from parasitic infections. Additionally, some conditions may affect how a horse processes worming medications.

Veterinary input is invaluable when managing the health of senior horses. Your vet will perform a comprehensive health check to identify any underlying conditions, then work closely with you to create a parasite control plan that considers the horse’s overall health. For example, horses with PPID may be more susceptible to parasitic infections due to suppressed immune function, necessitating a more proactive worming approach.

Follow the link for tips and further information on how to care for a senior horse.

Monitoring Body Condition and Overall Health

Pay close attention to your senior horse’s body condition, coat quality and overall health. Sudden weight loss, a dull coat, loose manure or signs of colic could indicate a high worm burden or other health issues. Promptly addressing these signs ensures the horse remains comfortable and healthy. Appropriate horse care involving an annual health check (including an FEC) and a dental exam ensures that we keep on top of any niggles and identify potential disorders before they become difficult to manage.

And Finally…

Worming senior horses in Australia requires a thoughtful, individualized approach that balances effective parasite control with the horse’s overall well-being. You can support your older horse’s health and longevity by incorporating:

• Regular FEC testing,

• Strategic use of wormers,

• Environmental management and

• Veterinary advice.

Adopting these practices not only protects your horse but also helps safeguard the efficacy of worming treatments for the entire equine population. Don’t forget to check out the Gold Standard Worming Guide for further information about sustainable and effective equine worming.