Worming Foals, Young Horses & Seniors | Age-Specific Horse Worming Australia

Worming Foals, Young Horses and Seniors: Age-Specific Strategies Every Owner Should Know

Foals: The First Year of Life

Foals may look strong and playful, but their immune systems are still developing. During this stage, they are highly vulnerable to roundworms (Parascaris equorum). Unlike adult horses, which usually develop immunity to roundworms by the age of two, foals can suffer severe consequences if these parasites aren’t controlled.

Roundworms don’t just cause a pot-bellied appearance or poor growth. In heavy infestations, they can block the intestine completely, causing life-threatening colic that sometimes requires surgery. The danger is particularly high if a young horse with a heavy burden is given a strong wormer without careful management — the sudden die-off of worms can cause a dangerous blockage.

That’s why foals need a careful, step-by-step worming plan. Most veterinarians recommend worming foals 3–4 times during the first year of life, starting from around 2–3 months of age. Products containing pyrantel or benzimidazoles are commonly used in the early doses, as they are effective against roundworms. As foals grow, broader-spectrum products can be introduced to also cover strongyles and tapeworms.

Delzani recommendation: Worm foals with Strategy-T in the early months to target roundworms, then transition to combination products like Equimax Plus Tape as the foal matures.

Yearlings and Young Horses (1–3 Years)

By the time horses reach their first birthday, their worming needs begin to shift. Roundworm risk declines as immunity develops, but strongyles (especially small strongyles, or cyathostomes) become the major concern. These worms can encyst in the gut wall and emerge en masse, causing diarrhoea, weight loss and colic.

Young horses also face risks from tapeworms, which use pasture mites as part of their life cycle. Tapeworm burdens are often highest in spring and autumn, coinciding with the mites’ activity. Left untreated, tapeworms can cause spasmodic colic, ileal impaction, and poor nutrient absorption.

Yearlings and two-year-olds generally require worming three times a year. The focus should be on products that cover strongyles, tapeworms and bots, with careful rotation between chemical classes to slow resistance. This age group benefits from regular faecal egg counts (FECs) where possible, to identify high shedders and avoid unnecessary treatments.

Delzani recommendation: For broad coverage in young horses, Virbac Ultimum is an excellent choice, offering dual-active protection. In spring and autumn, include a tapeworm treatment with Equimax Plus Tape.

Adult Horses (3–15 Years)

For healthy adult horses, the biggest mistake owners make is worming too often. Decades ago, the advice was to worm every 6–8 weeks, but we now know this approach speeds up wormer resistance and does little to improve horse health. Modern best practice recommends strategic worming, based on the season, pasture conditions, and egg count results.

Most adult horses only need 1–2 “foundation” worming treatments per year. These are usually given in spring (to target strongyles and tapeworms as conditions warm up) and in late autumn (to tackle bots, strongyles, and tapeworms before winter sets in). Horses identified as high shedders via FECs may require additional treatments, while low-shedding horses may not need more than these foundation doses.

Over-worming not only wastes money — it increases the risk of resistance, meaning wormers may stop working when you really need them. Smarter worming, not more worming, is the key.

Delzani recommendation: For spring and autumn foundation treatments, Virbac Equimax provides reliable broad-spectrum protection against strongyles, tapeworms, and bots.

Senior Horses (15+ Years)

Senior horses often enjoy a quieter pace of life, but they can face worm challenges just as serious as their younger counterparts. As horses age, their immune systems may weaken, making them more susceptible to parasites they once controlled easily. Some older horses become consistent high shedders, contaminating pastures and putting younger horses at risk.

For seniors, a tailored approach is best. Regular faecal egg counts are especially useful to monitor parasite burdens. Even if a senior horse doesn’t show obvious symptoms, signs such as weight loss, a dull coat, or recurrent colic may point to a parasite problem.

It’s also worth remembering that older horses may be more sensitive to digestive upset, so ensuring wormers are dosed correctly and accompanied by good pasture management is essential.

Delzani recommendation: Seniors benefit from comprehensive cover with Equimax Plus Tape in spring and autumn, with additional support from Strategy-T for rotational programs.

Beyond Age: Other Factors That Influence Worming Needs

While age is one of the most important factors, it’s not the only one. Other considerations include:

• Climate and geography: Coastal and tropical regions in Australia have higher year-round parasite activity than dry inland zones.
• Stocking density: Horses on heavily grazed pastures face greater exposure to worm eggs and larvae.
• Movement of horses: Competition horses that travel or new arrivals on a property can bring resistant worms.
• Pasture management: Regular poo-picking, rotation, and cross-grazing can dramatically reduce worm burdens.

The Takeaway for Horse Owners

From foals to seniors, every stage of a horse’s life brings different parasite challenges. Foals need protection against roundworms, young horses face growing risks from strongyles and tapeworms, adults thrive on strategic worming, and seniors require careful monitoring as immunity declines. There’s no universal schedule that works for every horse — but by tailoring your approach to age, environment, and individual needs, you can keep your horses healthier for longer while slowing down the development of wormer resistance.

Explore Delzani’s full range of horse wormers today, including trusted products like Equimax Plus Tape, Virbac Ultimum, Virbac Equimax and Strategy-T — designed to support Australian horses at every stage of life.