Small Strongyles. Big problem.
Deworming has come a long way in the past 40 years – from products that were nearly toxic and required complicated tubing to the easy-to-administer dewormers we know now. As more and more people recognize the value of regular deworming, past troublemakers such as large strongyles (bloodworms) have become much less of a threat.

But there is one worm that regular deworming may not
eliminate – small strongyles. Parasitologists consider it the
number one nematode problem in horses today.

Signs of trouble.
Horses are exposed to small strongyles by grazing on pasture that contains larvae. These worms become dangerous when the larval stage enters the horse’s digestive system, burrows into the intestinal lining and forms cysts. Encysted small strongyles can remain in this state for up to three years. Unfortunately, there’s no way of knowing how heavy of an encysted small strongyle load your horse is carrying, since fecal analysis cannot measure worms in the encysted state. What’s worse, since your horse may show no outward signs of a parasite problem, you may not notice the damage until it is too late. Encysted small strongyles can cause severe clinical signs and even death when thousands to millions of the fourth stage larvae (L₄) emerge simultaneously from the intestinal wall. The resulting damage to the intestinal mucosa shows up in your horse as:

• Listlessness, weakness
• Anorexia
• Recurring colic
• Diarrhea
• Weight loss
• Peripheral edema (swelling)
• Death

In less severe cases, you may notice decreased performance, poor food utilization, dull hair coat and an overall feeling that your horse just isn’t doing right.

The life cycle of small strongyles.

1. Adult small strongyles lay eggs that are passed in the horse’s feces and deposited into pastures, paddocks, etc.
2. While in the pasture, these eggs hatch and develop into third-stage larvae (L₃).
3. L₃’s are ingested by grazing horses and migrate into the lining of the horse’s colon in as little as six hours.
4. Cysts form around L₃’s in the intestinal wall. The encysted L₃ has two stages: early (EL₃) and late (LL₃).
5. EL₃’s may remain in the intestinal tract for up to three years before becoming LL₃’s and then fourth-stage larvae (L₄).
6. L₄’s emerge from the cyst and enter the lumen of the colon where they become fifth-stage larvae (L₅) and then the adult form.
7. Adults pass eggs in the feces and the cycle starts again.