Lungs, Small Intestine

Parasite: Ascarids (roundworms)
#1 parasite of concern for young horses

Lifecycle:¹

Adults are found in the small intestine and eggs are passed in the feces of infected animals, where they can live and remain infective for years in stalls, paddocks and pastures. When eggs are ingested the larvae hatch and migrate through the walls of the small intestine to the liver, and then to the lungs via the heart and pulmonary organs. The larvae invade the lungs and are coughed up and swallowed where they pass into the intestinal tract and become adults in the small intestine, where the cycle starts over.

Clinical Signs:

Signs of respiratory infection include cough, nasal discharge and low-grade fever. Signs of intestinal disease include weight loss, poor condition, loss of energy, pot belly, impaction colic and bowel rupture, which can be fatal.

Horses at greatest risk:

Foals and weanlings. Adult horses develop some immunity unless infestation is extreme and unchecked.

BIOSECURITY NOTE: Eggs can live and remain infective for years in stalls, paddocks and pastures increasing the potential for spreading ascarid infection between horses and even re-infecting the original host animal. Attention should be paid to managing and cleaning premises where foals have been shedding large numbers of ascarid eggs and contaminating stalls and surfaces.

REFERENCES

1. Handbook of Equine Parasite Control, Second Edition. Martin K. Nielsen and Craig R. Reinemeyer. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc