Seasonal translation of equine strongyle infective larvae to herbage in tropical Australia.

This research article investigates how well horse strongyle infective larvae, a type of parasite, can survive in horse faeces, migrate to and survive on herbage in the dry tropical climate of North Queensland, Australia.

Longevity of Strongyle Infective Larvae in Faeces

• The study looks into the lifespan of the strongyle infective larvae in horse faeces deposited in different weather conditions, for up to two years.
• Results showed that larvae from mixed strongyle (70% cyathostomes and 30% large strongyles) could survive up to 12 weeks in hot, dry weather, as long as 32 weeks in cool conditions, and less than 8 weeks during the hot, wet summer.

Migration of Larvae to Herbage

• The study also examined the translation, or migration, of these larvae to herbage (or pasture) under different climatic conditions.
• The results showed that larvae migration is mainly limited to the hot, wet season (December-March), except when unseasonal winter rainfall of 40-50 mm per month was observed during July and August, which allowed for some additional migration.

Larvae Survival on Pasture

• The survival of the strongyle infective larvae on pasture was estimated to be between 2-4 weeks during the summer wet season and 8-12 weeks in the autumn-winter dry season (April-August).
• The research found that hot, dry spring weather (pre-wet season) was the most unfavourable for the larvae’s development, migration, and survival.
• During the research, peak counts of up to 60,000 larvae per kilogram of dry herbage were recorded.

Impact on Anthelmintic Control Programs

• The findings of this study have significant implications for the development of rational anthelmintic control programs – strategies aimed at controlling parasitic worms.
• Understanding the seasonal nature of pasture contamination by strongyle infective larvae allows for more effective and targeted control measures based on their lifecycle and ecology.