A case-control study of grass sickness (equine dysautonomia) in the United Kingdom.

The research article aims to examine the cause of grass sickness in horses in the United Kingdom through case-control study conducted from 1992 to 1995.

Research Methodology

• The researchers conducted a case-control study investigating the epidemiology of grass sickness among horses in the UK from 1992 to 1995.
• Data were collected by sending postal questionnaires to the owners or veterinary surgeons of horses diagnosed with grass sickness.
• Each participant was asked to complete three questionnaires, including information about the horse with grass sickness, one healthy horse from the same premises, and another healthy horse from a different location.
• Control cases were selected based on the onset date of each infected horse to ensure similarity in environmental conditions.
• After performing univariate analyses to understand the individual effects of each variable, the team employed conditional logistic regression techniques to model the probability of grass sickness in horses.

Key Findings

• Younger horses were found to be at a higher risk of contracting grass sickness.
• Females were less likely to be affected, and the same was true for those horses that had previous contact with other sick horses.
• Horses were at a higher risk of getting grass sickness if they were on premises where there had been prior cases of grass sickness, especially if the previous case was recent.
• The researchers noted that changing fields in the preceding fortnight made horses susceptible to the disease, though the risk lessened over time.

Patterns and Contributing Factors

• Grass sickness showed a seasonal pattern, peaking from April to June.
• Access to grazing was a common factor among over 95% of the cases of grass sickness, indicating that diet or environmental factors may play a role in disease transmission.
• About 66% of the disease incidents occurred after dry weather periods extending for two weeks. This suggests that changes in weather or environmental conditions could influence the occurrence of the disease.