Effect of composting on Parascaris equorum eggs

The eggs of the large roundworm of horses, Parascaris equorum, are particularly resistant to extremes of climate and may survive for many years in stables and on pasture. Composting is becoming a popular method of dealing with waste from equine premises. How likely are P. equorum eggs to survive in composted manure?

A study carried out by researchers from the University of Kentucky Department of Animal and Food Sciences on a central Kentucky horse farm investigated the viability of P. equorum eggs in manure subjected to windrow composting.

For the purposes of this study, a single windrow approximately 42.3m in length, 2.7m in width, and 0.9m in height was built. It contained equine manure, soiled bedding and other waste material, which came from stables occupied by adult stallions and mares. Temperature and carbon dioxide levels within the row were monitored daily. The compost would be mechanically turned and aerated as necessary to maintain optimum conditions. Previous experience had shown that it took 10-12 weeks for the windrow to decompose completely.

Sentinel chambers were used to expose 3g samples of feces to the composting process. The faeces, collected from a weanling foal, had an average of 2216 P. equorum eggs per gram.

The chambers were made of mesh that kept the P. equorum eggs inside, whilst allowing liquids and bacteria to pass through.

 

Chambers were exposed to one of three treatments.

1. Constant exposure. These were placed within the centre of the windrow. Each day after the windrow had been turned, the chamber was placed back in the centre of the windrow.
2. Intermittent exposure. The chambers were placed in the centre of the windrow. On alternate days, after the windrow had been turned, the chamber was placed back in the centre, or placed on the outside of the windrow.
3. Control chambers were kept at 4°C.

Every two days, one chamber from each group was removed and incubated at room temperature for 21 days, at which stage the eggs were examined microscopically to assess if they were viable. (Viable eggs contained larvae.)

Chambers treated with constant exposure contained about 10% viable eggs on day 2 and 0% by day 8. Intermittent treatment resulted in 16% viable eggs on day 2 and 0% by day 6. In contrast , control chambers had average P. equorum egg viabilities of 79% throughout the 18 days of the study.

The researchers concluded that not only was the windrow composting system effective in eliminating viable P. equorum eggs, it did so rapidly. 

 For more details see: http://www.equinescienceupdate.com/articles/ecpee.html