What is Strongyloides sp ?
The strongyloides westeri parasite can be present in the intestines of the mare at foaling and can be passed from the mare to the foal through the milk ingested from the mare after birth. The parasite can be successfully treated and, if found quickly enough, the foal need not suffer significantly permanent disability.
Strongyloides sp in horses is a parasitic nematode called strongyloides westeri (also known as threadworm) and it is the first parasite of which a new foal can be infected.
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Symptoms of Strongyloides sp in Horses
As noted above, this parasite can infect a newly born foal and can occur within 4 days of birth. These are the most noticeable symptoms that you will likely see in your infected foal:
- Diarrhea - Can be severe and won’t respond to normal treatments for diarrhea
- Weight loss
These symptoms may begin as a mild state but can progress to more severe stages in a matter of days. Since the diarrhea doesn’t respond to the usual treatments, dehydration can occur in a young foal quickly and systemic issues can quickly become problematic, even to the extent that they can cause death in the young foal.
There are several types of strongyloides parasites but not all of them are germaine to equids:
- Strongyloides papillosus is particularly serious for calves up to 6 months of age (can cause lung damage and gut damage)
- Strongyloides westeri commonly found in foals as early as 4 days old and infestations beginning within two weeks of birth (severe infections can be responsible for severe diarrhea, blood loss, weight loss, severe dehydration, a number of respiratory problems and dermatitis; these conditions, when severe, can be fatal to the foal)
- Strongyloides ransomi is a strain that is found in piglets (severe infections can cause hemorrhagic or mucous diarrhea, anemia, coughing, abdominal pain and even sudden death in the piglet)
- Strongyloides avium is the strain that is found in young birds (most commonly found in birds that either live or are kept outside; symptoms are weakness, weight loss and diarrhea that can be hemorrhagic or mucus)
Causes of Strongyloides sp in Horses
Strongyloides in horses is caused by the infestation of the nematode strongyloides westeri. This parasite gets into the horse’s system via oral means and contact with skin. Frequently, the mare can be a carrier and not exhibit symptoms of the disease but she can shed the parasite through her feces. However, upon the birthing of a foal and the subsequent nursing, she can pass the parasite to her newborn foal through the milk. The newborn foal can also pick up the parasite from the bedding or pasture as the strongyloides westeri is a free-living nematode which means it can survive outside a living host for a fairly long period of time.
Once the parasite gets into the young foal, it will travel to the intestines and continue its life cycle and will reproduce rapidly. This will allow the infestation to grow exponentially and will cause physical harm to the young foal. The parasite can cause damage to lung tissue and the digestive system of the young foal, conditions which, if left untreated, can kill the foal.
Diagnosis of Strongyloides sp in Horses
Your veterinary professional will need to do a thorough physical examination of the afflicted foal. He will need to assess the overall condition of the young foal as his main concern, even before diagnosis, will be whether the young foal is in a state of severe dehydration. Especially in the more severe cases, the dehydration will need to be dealt with to keep the young foal alive while diagnoses are obtained and treatments are administered. There will need to be laboratory evaluation done on the feces of the foal to determine the presence of parasites and to identify which parasites are responsible for the condition of the foal. The specimen collection of feces will likely not be limited to just a single specimen but, instead, your vet may require several to get an accurate analysis. Once that analysis is obtained, your vet will be able to develop an appropriate and effective treatment plan.
Treatment of Strongyloides sp in Horses
Aside from the rehydration of the young foal with fluids and electrolytes, de-worming treatments will likely be recommended. Severe diarrhea caused by these parasites doesn’t respond to the usual diarrheal interventions because the cause of the diarrhea is still alive and actively doing its damage within the intestinal system of the young foal. The parasites must be deactivated and eliminated before the diarrhea and subsequent dehydration, blood loss, weight loss and potential lung and intestinal damage will be stopped.
It will likely require two dewormings, each approximately 4 weeks apart to ensure that all of the larvae in all of their various life cycles have been killed. Additionally, deworming the mare before foaling and even a month before birthing would reduce the parasite’s opportunity to infect the young foal. If there are other systemic problems which have ensued due to the presence of the parasite, your vet may need to prescribe and administer other medications to treat those system issues as the foal heals.
Recovery of Strongyloides sp in Horses
Once the parasites have been eliminated, either by virtue of the deworming or by the natural immune process, the young foal should return to normal feeding and growing. Your veterinary professional may recommend periodic retesting of the feces of the foal to inhibit future infestations of the parasite. The foal’s immune system should naturally build up a resistance to the parasite which will also help to protect the foal as it grows and matures. Catching and treating the disease as early as possible will limit any potential damage to lung and intestinal tissue on a permanent basis. For future breeding and foaling purposes, it would be wise to adopt a regular deworming regimen both before foaling and about a month prior to the expected birth to reduce the chance that the parasite will be a factor in the survival of your young foal.