Effects of high temperature and disinfectants on the viability of Sarcocystis neurona sporocysts.

This research investigates the effects of high temperature and several disinfectants on a dangerous parasite called Sarcocystis neurona. The findings suggest that heat treatment is the most effective method of killing this parasite in horse feed or the environment.

Understanding Sarcocystis neurona

• Sarcocystis neurona is a protozoan parasite that can infect horses and other animals, causing a severe neurological disease known as equine protozoal myeloencephalitis (EPM).
• Poorly understood and difficult to control, researchers are keen to devise methods to reduce the threat of S. neurona in the environment, particularly where horses are kept.

Research Methodology and Findings

• The scientists exposed Sarcocystis neurona sporocysts (the infective stage of the parasite) to various temperatures, ranging from 50 – 70 degrees Celsius for different time durations. They then tested the viability of these sporocysts by bioassaying them in special interferon gamma gene knockout (KO) mice. This type of mice is deficient in specific immune responses and is commonly used in such bioassays.
• They found that sporocysts heated to 50 C for 60 min and 55 C for 5 min were still infective to KO mice. However, sporocysts exposed to temperatures of 55 C for 15 min and 60 C or above for at least 1 min lost their ability to infect mice, indicating that they had been rendered nonviable.

Disinfectant Evaluation

• Next, the researchers exposed the sporocysts to a variety of disinfectants including bleach, chlorhexidine, betadine, o-benzyl-p-chlorophenol, phenol, benzyl ammonium chloride, formalin, and ammonium hydroxide.
• Surprisingly, most did not kill the sporocysts. Undiluted ammonium hydroxide (29.5% ammonia) was the only exception, killing off the sporocysts after 1 hour of exposure. In contrast, a 10x dilution of this solution (2.95% ammonia) failed to kill the sporocysts after 6 hours of exposure.

Conclusion

• These findings demonstrate that high temperature (55 C for 15 min or 60 C and above for at least 1 min) is effective in killing S. neurona sporocysts.
• Of the tested disinfectants, only undiluted ammonium hydroxide proved effective. Consequently, heat appears to be the most promising method for reducing the prevalence of this parasite in horse feed or the environment.