Small Strongyles In Horses/ Cyathostomins 

9-30-24

Samantha Young 

• Reservoir: Horses – Pasture acts as a secondary reservoir: here, larvae develop and survive harsh conditions until another horse ingests them 

• Portal of exit: Contaminated horse feces 

• Mode of transmission: Direct: Fecal-oral transmission 

-Adult small strongyles in a horse’s large intestine lay eggs, which then exit the horse via feces into the horse’s environment 

- Eggs hatch into infective larvae (L1,L2,L3) in the environment. It can be days or weeks, depending on the conditions

- Horses graze in a field where infective larvae (L3) are located 

- Ingested larvae then migrate to the horse’s large intestine, where they burrow in the walls or encyst, mature into adult worms (L4), and the cycle continues 

• Portal of entry: Ingestion through the mouth. Grazing on contaminated pastures, water, or food with infective larvae 

• Susceptible host: Mainly prolific in equines

-Foals and yearlings are more vulnerable and immunocompromised horses  

• How can we control the spread of this disease: 

-Deworming schedule, but be careful not to over-treat because these parasites can build up resistance to anthelmintics.  

-Fecal testing 

-Routine cleaning and maintenance of pastures and stalls

-Reduce overcrowding on pastures   

-Be aware of climate conditions- due to the survival rate of these parasites in extreme conditions

References:

• Corning, S. (2009, September 25). Equine Cyathostomins: A Review of Biology, clinical significance and therapy. Parasites & vectors. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2751837/

• Small strongyles. Merck Animal Health USA. (2024, April 19). https://www.merck-animal-health-usa.com/condition/small-strongyles-2

• Strongyles in horses. Extension Horses. (n.d.). https://horses.extension.org/strongyles-in-horses/

Photo Citation:

• User, S. (n.d.). Strongyles. Bimectin. https://www.bimectin.com/disease-information-us/horses/small-strongyles