Cylicocyclus nassatus

Cylicocyclus nassatus is a species of parasitic nematode belonging to the family Cyathostominae. Known as small strongyles, these worms are among the most prevalent internal parasites in equines worldwide. While not an agricultural crop pest, they are a significant concern for the equestrian industry and equine husbandry, causing substantial health issues for horses, ponies, and donkeys.

The lifecycle of this parasite involves both an environmental phase and a host-dependent phase. Eggs are shed in the feces of infected animals and hatch into larvae on pasture. These larvae develop into an infective third stage, which is ingested by the horse while grazing. Once ingested, the larvae undergo a complex maturation process within the gastrointestinal tract, specifically targeting the colon and cecum.

A distinctive biological feature of Cylicocyclus nassatus is its ability to undergo mucosal encystment. The larvae penetrate the intestinal lining and form cysts, where they can enter a period of arrested development known as hypobiosis. This phase is critical because these encysted larvae are notoriously difficult to target with many standard anthelmintic medications, allowing them to persist in the host for long periods.

The damage caused by these parasites is primarily due to the mass emergence of larvae from the intestinal wall. This process leads to severe inflammation of the gut lining, which can result in clinical symptoms such as chronic weight loss, diarrhea, dull coat, and colic. In severe infestations, the sudden emergence can cause acute inflammatory bowel disease, which poses a serious threat to the life of the animal.

Effective control measures require an integrated approach to break the parasite cycle and manage host health:

• Regular fecal egg count testing to monitor infection levels and ensure appropriate treatment.
• Strategic use of anthelmintics, rotating chemical classes to prevent the development of drug resistance.
• Pasture management, including regular removal of manure and rotating grazing areas to reduce larvae density.
• Maintaining healthy stocking density to prevent heavy pasture contamination.