Large Strongyles - Horse Worms

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Large Strongyle Worms
These nematode worms are a real problem for the horse, being more damaging than the small strongyles.

Other Names
Sometimes they are also known as blood worms and also red worms due to being red in colour.

Description
Most large Strongyle types are around half to two inches in length and most are either white or red in colour.

Horses At Risk
All horses at potentially at risk, with very young horses being most at risk. Infection can also occur where there are several horses all over grazing a pasture.

Strongyle Infection

A horse who is already infected with strongyle worms will pass out strongyle eggs in their droppings.
The strongyle eggs then hatch into the infective stage of larvae within one to three weeks depending on the climate conditions.
The eggs can be found in the soil, on blades of grass, water troughs and on dew drops on blades of grass.
The eggs are then swallowed by another horse and start to migrate towards the intestines.

Symptoms

Diarrhoea
Weight loss
Anaemia
Colic
Abdominal discomfort
Enteritis
Death in some cases

Diagnosis
Horses are usually infected with both large and small strongyles and it is only by having a faecal culture done that identification of the larvae will be possible.

Prevention

The use of worming products is essential to help protect your horse, ask your veterinarian for a worming schedule to help protect your horse from the threat of these and other worms.
Regular pasture maintenance, such as harrowing and removing droppings, this will help to reduce the amount of faeces and larvae from the fields, it should be remembered that larvae can last for 1 to 5 weeks and in certain moist conditions for up to 2 years.
Where possible try not to have too many horses overgrazing one area as this increases the amount of droppings and therefore the possibility for re-infection.

Three Types Of Large Strongyle Worms
The three most common types of large strongyle worms are Strongylus vulgaris, Strongylus edentatus and Strongylus equinus

Strongylus Vulgaris
- After the eggs are eaton by the horse they travel towards the small intestine and then onto the large intestine where the larvae enter the caecum and continue to develop.
- The larvae then migrate towards the blood vessels and it is this action that often causes inflammation and blood clots to form. This action then leads to the blood clots blocking the flow of blood to parts of the intestine and thus causes parts of the bowel to die due to lack of oxygen and nutrients.
- Due to the blood loss that occurs horses affected with Strongylus vulgaris are often anaemic.
- After several months the larvae re enter the caecum and colon and become adults and start to produce eggs.
- These eggs are then passed out along with the droppings and the cycle can begin again.
Strongylus edentatus
- After being eaton by the horse the eggs enter the digestive system.
- When the larvae reach the large intestine they begin to burrow into the gut wall causing inflammation.
- From the gut wall they then enter the veins that lead towards the liver.
- The veins then lead towards to liver and it is here that the larvae continue to develop for about 8 weeks.
- They then leave the liver and go to other parts of the large intestine before eventually returning to the caecum as adults.
- As adults they produce eggs and the process begins again.
Strongylus equinus
- Once eaton the larvae travel towards the small intestine and then onto the caecum in the large intestine.
- The larvae burrow into the gut wall and pass into the veins.
- The larvae then travel around the abdomen in particular to the liver and pancreas.
- After around 9 months the larvae return to the caecum as egg producing adults.