Threadworms in Donkeys: Strongyloides Infection in Young Donkeys

Threadworms in donkeys usually refers to infection with Strongyloides westeri, a tiny parasitic worm that lives in the small intestine of very young equids. It is best known in foals, and the same pattern is expected in donkey foals: adults usually carry little to no active intestinal disease, while nursing young animals are the group most likely to shed eggs and show signs.

This parasite is most often discussed when a young donkey has loose manure, poor growth, or a generally unthrifty appearance. That said, not every foal with threadworms becomes sick, and not every foal with diarrhea has threadworms. In many cases, your vet will consider threadworms as one possible piece of a larger parasite and neonatal health picture.

The good news is that many cases are manageable. Early recognition, a fecal check, and a practical parasite-control plan can help reduce reinfection and support healthy growth during the first months of life.

Threadworms are caused by infection with Strongyloides westeri. In young equids, the most important route is transmission from the mother shortly after birth. Dormant larvae in the jenny’s tissues can become active around foaling and then pass to the foal through milk during nursing.

Foals may also be exposed from contaminated bedding, stalls, or pasture. Eggs passed in manure develop into larvae in the environment, and those larvae can contribute to ongoing exposure, especially in warm, moist, heavily stocked areas with poor manure removal.

Young age is the biggest risk factor. Foals have immature immunity, so they are more likely to become infected and shed eggs than older donkeys. Overcrowding, inconsistent parasite monitoring, and delayed manure cleanup can all increase environmental contamination and make reinfection more likely.

Diagnosis usually starts with a physical exam and a careful history. Your vet will want to know the foal’s age, whether the jenny was dewormed around foaling, how long diarrhea has been present, whether growth seems normal, and what the housing and pasture conditions are like.

A fecal flotation is the most common test used to look for Strongyloides eggs. In some cases, your vet may repeat testing because parasite shedding can vary, and young foals can have more than one problem at the same time. Fecal testing is helpful, but results still need to be interpreted alongside the foal’s age and clinical signs.

If the foal is sick, your vet may also recommend checking hydration, bloodwork, or testing for other causes of diarrhea. That matters because threadworms are only one possible explanation for loose manure in a young donkey, and treatment choices depend on the whole picture.

Prevention starts before the foal shows signs. Because Strongyloides westeri can pass through the jenny’s milk, your vet may recommend treatment of the mother around foaling as part of a broader parasite-control plan. The right timing and product depend on the individual donkey, local parasite patterns, and the rest of the herd.

Good hygiene matters too. Prompt manure removal from stalls, foaling areas, and small paddocks helps reduce larval buildup. Clean, dry bedding is especially important for young foals, since warm and damp environments support parasite development.

Fecal monitoring is useful for herd-level control, but it should be paired with practical management. Avoid overcrowding, quarantine new arrivals when appropriate, and work with your vet on a targeted deworming schedule rather than treating on guesswork alone. That approach supports parasite control while also helping slow drug resistance.

Young donkeys can look bright even when they are starting to fall behind. Regular weight checks, growth monitoring, and early attention to loose manure can help catch problems before they become more serious.