Family aggregation analysis shows a possible heritable background of equine grass sickness (dysautonomia) in a Hungarian stud population.

This research investigates the possible genetic background of a fatal disease in horses known as equine grass sickness. The study suggests that the disease may have heritable factors, potentially demonstrating an X-linked recessive inheritance pattern.

Disease Overview

• The disease under consideration is equine grass sickness (EGS), also known as dysautonomia. It’s a severe disease affecting horses’ nervous system and can often result in death, with around 80% mortality rate.
• Various factors have been associated with a higher risk of EGS, including the horse’s phenotype and intestinal microbiome, along with environmental, climate, and management factors.

Research Methodology

• The study is a retrospective analysis, meaning it looks back at past data to draw conclusions.
• The researchers used pedigrees and medical records of 1,233 horses, including 49 affected by the disease, born over a 23-year period.
• They observed that certain families of horses had a higher-than-expected frequency of EGS, suggesting a genetic component to the disease.

Research Findings

• The study found potential gender differences in disease risk. Male horses seemed to have a slightly higher risk of EGS, but this result was not statistically significant, meaning it might occur by chance.
• However, the researchers did find significant familial clustering of EGS, meaning that horses with EGS were often related to each other more closely than expected by chance.
• The aggregation of the disease among close relatives was particularly significant, supporting the assumption of genetic factors in the development of EGS.

Conclusions

• The findings indicate that EGS might be caused, at least in part, by genetic factors. Specifically, the researchers suggest that an X-linked recessive inheritance pattern might be involved. This type of inheritance means a disease gene is on the X chromosome, and males (who have only one X chromosome) are more likely to express the disease than females (who have two X chromosomes and can have a normal gene on the other chromosome ‘masking’ the effect of the disease gene).
• This study is significant as it is the first to provide evidence of a possible hereditary component to EGS, providing new insight into the disease’s likely multifactorial aetiology.