Sooner or later, most horse, dog and cat owners ask themselves the same question: Should I be deworming my animals?
And if so, when and how often? And does it make sense to test faeces beforehand? Do I really have to use to use chemicals to treat worms or can natural remedies like garlic, onions or herbs help?
“People are constantly asking me if deworming is really necessary,” says Ralph Rückert, a vet based in the German city of Ulm. "Deworming is the safest option for both animal and human health."
Parasites in dogs and cats can be transmitted to humans, and children in particular are at risk. The fox tapeworm can cause serious internal diseases and is particularly dangerous. That can happen suddenly and without warning: "It can take 10 to 15 years between the ingestion of its eggs and the first symptoms," Rückert says.
Often hard to spot
An infection with the most common parasites is transmitted through faeces. Thus, pick up your dog's faeces when you go for a walk, if only to prevent worms, Rückert recommends. Worms can be very persistent and remain in the soil long after the rain has washed away the faeces. If a dog or cat walks over them and licks their paws, they can become infected.
Worm larvae, such as those of the roundworm, hatch in the intestine and spread throughout the body. "They attack the gastrointestinal tract and can cause severe diarrhoea or vomiting," says Rückert. A patchy coat or bloated stomach can indicate a severe worm infestation. However, animals are not visibly infested with parasites.
An animal's immune system can defend itself from worms, but there are limits. "If the body has to fight off infections and the dog or cat is old and has worms, the immune system will eventually be overwhelmed," he says.
Deworming with herbs or garlic is pointless as the risk is too high, says Rückert: "Medicine should be based on evidence and there is no evidence for this. Selective deworming, ie., examining the animal's faeces and then deciding whether worming is necessary, is not a viable alternative."
While that may be a good idea, a negative result does not prove that the dog or cat is worm-free. The eggs of the very common roundworms are not shed regularly but in batches. They are found in the body rather than in faeces.
Therefore, if an animal owner chooses to have the test done, the faeces should be collected on three consecutive days. If done correctly, a faecal sample has a 90% success rate.
Worm infestations are common in dogs and cats and are almost a permanent fixture in horses - especially young animals whose immune systems are not yet fully developed. Although a worming treatment may initially remove all worms, the parasite usually reappears after 13 weeks at the latest, according to vet and horse breeder Carmen Obach-Schröck.
A horse with a patchy coat or mane may be showing signs of severe worming. Their ribs are often visible because the worms are gobbling up their food. At the same time, the belly may be fat as the parasites spread all over the intestines.
Clean the stable thoroughly after feeding
The frequency of worming depends on how the horses are kept. "If horses are kept in a poorly dung stable or on small pastures, they tend to have a lot of worms," says the vet. The most sensible strategy for controlling parasites in horses is broad-spectrum and selective worming.
“The two essential worming treatments are done in spring and at the end of the year," she says. In spring, the horses are injected with a paste against all types of parasites three days before they are let out into the paddock. That gives them enough time to get rid of any worms. The stable should then be thoroughly cleaned. At the first frost in November or December, another worming treatment is a must - because of botflies.
These pests can cause a very painful inflammation of the stomach lining and ulcers. High infestations can even cause lameness as they can damage the blood vessels. Botflies cannot be detected in faeces, so any prior examination is useless.
Some worms resistant to some products
During the grazing season, Obach-Schröck then relies on selective deworming and collects faecal samples every two to three months, on three consecutive days, as the worms are not excreted evenly in horses. If the worm load is above a set limit, deworming is then carried out. "This hasn't been necessary for the mares and geldings so far, but is a must for our group of stallions, which has a lot of young animals," she says.
The vet recommends alternating between different active ingredients when deworming, as worms are already resistant to some products - especially the most commonly used cheap wormers.
To prevent worms, muck out thoroughly and manage pastures rigorously. Remove faeces from small pastures regularly. Large meadows are ideal. If they have enough space, horses tend to avoid manure-covered spaces ie., worm-infested areas.
