Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses.

The research investigates the likelihood and timing of exposure in young horses to two parasites, Sarcocystis neurona and Neospora hughesi, as well as the decay time for maternally acquired antibodies against these parasites. The study finds that exposure is relatively low in foals under 2.5 years, and that antibodies from the mother may cause false positive results for a few months after birth.

Research Objective and Methodology

• This study aimed to estimate the risk of exposure in foals (young horses) to two specific parasites, namely Sarcocystis neurona and Neospora hughesi. The research also monitored the time taken for foals to lose their inherited maternal antibodies to these parasites.
• The study’s subjects included 484 Thoroughbred and Warmblood foals from four farms in California. To collect data on the horses’ exposure to the parasites and the decay of their maternal antibodies, serum was drawn from the foals before and after they ingested colostrum, and then every three months.
• The serum samples were evaluated using the indirect fluorescent antibody test. Threshold titers (the dilution of serum at which antibodies can be detected) were established at > or = 40 for S. neurona and > or = 160 for N. hughesi.

Study Findings

• The study discovered that the risk of foals being exposed to S. neurona and N. hughesi during the research period were 8.2% and 3.1% respectively, with an annual exposure rate of 3.1% and 1.7% respectively.
• The researchers found a significant disparity in exposure risk to S. neurona among different farms, though this was not the case with N. hughesi.
• The median age for first-time exposure to these parasites was 1.2 years for S. neurona and 0.8 years for N. hughesi.
• The highest ratios of antibodies against these parasites were found at a mean age of 1.7 years for S. neurona and 1.4 years for N. hughesi; these were 6% and 2.1% respectively.
• Researchers found that the median time for the decay of maternal antibodies was comparable for both parasites: 96 days for S. neurona and 91 days for N. hughesi.
• No instances of Equine Protozoal Myeloencephalitis (EPM), a common disease caused by these parasites, were found amongst the horses studied.

Study Conclusions

• The research concluded that young horses up to 2.5 years old had a relatively low risk of exposure to S. neurona and N. hughesi.
• The study also suggested that maternally derived antibodies could lead to false positive results in the foals for three to four months after birth.
• The research further affirmed that EPM was a rare condition in horses aged 2.5 years or younger.