Worming Foals: Significant and potentially life-threatening problems may occur from worm infections in foals. Foal Worming: Foals do not have a natural immunity to worms and need regular support with wormers and rigorous paddock hygiene measures to grow them to their potential.

In short:

• Foals have do not have a natural immunity to worms and need regular support with wormers as they mature and develop this immunity.
• Effects of a heavy worm burden in foals can include: pneumonia, stunted growth, diarrhoea, constipation and obstructions including potentially fatal colic
• A targeted foal worm control program is needed for foals to reach their physical potentiale
• Fecal egg counts and paddock hygiene is recommended in addition to using wormers to keep worms under control

Worms affecting foals:

Threadworm

Threadworm is usually the first worm a foal encounters -  commonly transmitted from mare to foal through nursing in the mares milk, but can also come from the environment, so foals should not be exposed to wet yards or muddy paddocks.

The majority of foals show no clinical signs when infected.

Control: Routine worming of the broodmare during pregnancy and strategic worming 4 weeks prior to foaling will decrease the transmission of Threadworms to the foal. 

Roundworms

It's almost inevitable that foals will be exposed to roundworm eggs. These are the most significant worms to infect foals as they target the immune systems of horses less than 18 months old and can cause pneumonia, stunted growth, diarrhoea, constipation and obstructions, including potentially fatal colic. 

External signs of infection are poor weight gain, rough hair coat, pot-belly appearance, nasal discharge and cough.

Control: From 60 days of age treat every 60 days with Revolve (BZ group) until 9 months.  Leaving treatment longer than 60 days could allow Roundworms to mature and contaminate the surrounding paddocks and stables with eggs which can survive for a decade or longer.

Tapeworms

In recent years, parasitologists have observed that weanlings and yearlings experiencing their first tapeworm infection might be particularly at risk for developing colic.

Control: Begin tapeworm treatment with Evolve (Ivermectin/praziquantel) right around or shortly after weaning. Use a weight tape to estimate your foal's weight and to ensure accurate dosing of all wormers.

Non-Chemical Controls

Fecal Egg Counts

Fecal egg counts should be performed on a representative sample of the foals at five months and 10 months to monitor the ongoing effectiveness of the worm control program.

Paddock Hygiene

Reserving the cleanest pastures available for weanlings, yearlings, and mares with foals. Clean pastures include those that have been vacant for at least two months during the height of summer, paddocks that were used recently to produce hay, or pastures that were grazed by an alternate livestock species, such as cattle or sheep.

Wherever possible, horses should not be fed off the ground. Soil is an excellent spot for worm eggs.

Stable & yard hygiene

Stalls should be cleaned thoroughly and disinfected prior to any introduction of new stock, manure should be removed daily, and all bedding should be replaced regularly.

Sources: DEWORMING FOALS - Patrick M. McCue | The Horse: Age related parasites of foals  |  De-worming young horses.