Encysted cyathostomin larvae in foals – progression of stages and the effect of seasonality.

This research focuses on the development and progression of cyathostomin larvae, a common internal parasite in horses, in foals. The findings show that the infection’s progress in foals significantly differs from mature horses.

Study Aim

• The study aimed to understand the development and progression of Cyathostomins (commonly known as small strongyles) larvae in foals, young horses. The objective was to ascertain how infection varies in foals compared to mature horses since foals don’t have a well-developed immune response to the infestation of cyathostomin larvae.

Research Subjects and Methodology

• Thirty-seven foals born between 2013 and 2015 were used in the study.
• The foals were part of a parasitology research herd and were not treated with any anti-parasitic drugs.
• The foals were euthanized between 50 and 293 days of age as part of an ongoing parasite transmission research, and the larvae encysted in the gut walls were counted.
• A digestion technique was deployed to classify and quantify early third stage (EL3) and late third stage/fourth stage (LL3/L4) larvae in various sections of the intestines.
• Statistical analysis was performed to evaluate the effect of foal age, gender, and seasons on the larvae counts.

Key Findings

• Total larvae counts, as well as LL3/4 counts in particular, were significantly higher during the grazing seasons (March-November).
• There was no statistical difference in larvae counts between the defined age groups.
• Male foals had significantly higher total larvae counts than females, which was a newly observed phenomenon.
• Contrary to adult horses where larvae arrested development, the study did not find any evidence suggesting larval arrestment in foals indicating that the cyathostomin larvae infection in foals have a different trend compared to mature horses.
• Around 41% of the larvae recovered were early third stage (EL3).

Conclusion

• The findings underscore the significant role of host immune system in governing the parasite life cycle.
• A different approach may be necessary to tackle cyathostomin infection in foals, as their physiological response slightly varies from adult horses.