Seasonal development and survival of equine cyathostome larvae on pasture in south Louisiana.

This research studied the development and survival of Cyathostome larvae in horses, focusing specifically on pastures in Southern Louisiana. The researchers found that specific climatic conditions as well as carefully timed anthelmintic treatments can help in reducing the parasite in horses.

Research Methodology and Findings

• The researchers closely observed pony mares and their foals maintained on a naturally infested pasture in Southern Louisiana. This observation took place over two periods: January 1986 through December 1988 and September 1996 through October 1997.
• Fecal egg counts (FEC) and numbers of infective larvae at the third stage (L3) per kg of dried herbage were recorded biweekly over these specified periods.
• The researchers noted an increase in FEC during the late summer through early autumn, which preceded the peak of L3 on pasture during the winter season. In other words, the FEC was higher before the number of harmful larvae peaked in the winter seasons.
• The numbers of Cyathostome larvae were noticeably reduced during the hottest months of the year. The primary reason for this reduction was daily minimum temperatures above 18 degrees Celsius.
• They also observed a reduction in the winter when freezing conditions occurred, specifically when the daily minimum temperatures fell below 0 degrees Celsius.
• Anthelmintic treatments given to horses before returning them to the pasture combined with tilling of the pastures further reduced the number of Cyathostome larvae in the early winter months. The effectiveness of this method apparently depends on both measures being performed together.

Recommendations Based on the Findings

• Based on the collected data, the authors suggested that a parasite reduction program in Southern Louisiana, covering the end of September through the end of March, could be an effective way of controlling the Cyathostome population in horses.
• An equally important recommendation is the combination of effective veterinary care—specifically, the administration of anthelmintic treatments—and good pasture management practices such as tilling to enhance the chances of reducing the Cyathostome larvae present on pastures.