[Genetics of recurrent airway obstruction (RAO)].

The research article focuses on the genetics behind recurrent airway obstruction (RAO), a complex disease affecting horses that is influenced by multiple genes and environmental factors.

Overview of Recurrent Airway Obstruction (RAO)

• Recurrent airway obstruction (RAO) is a disease that typically affects horses aged 7 and older. It is characterised by symptoms such as exercise intolerance, difficulty breathing, coughing, airway inflammation, mucus accumulation, and bronchospasm.
• Environmental triggers for RAO are primarily allergens and irritants found in hay dust. However, the exact immune mechanisms behind the disease remain unclear.

Genetic Predisposition and Inheritance of RAO

• Past studies have shown that there is a familial predisposition to RAO, indicating that the disease has a genetic basis.
• The risk of offspring developing RAO is tripled if one parent is affected. This risk increases to nearly five times if both parents have RAO.
• In high-prevalence families, segregation analysis demonstrated a significant heritability of RAO. The inheritance of RAO showed complexity with several major genes involved.

A Genetic Link for RAO

• A genomescan providing an overview of the entire genome revealed significant linkage of seven chromosomal regions with RAO. These linked regions can be considered as strong genetic candidates influencing the disease.
• In particular, a region of chromosome 13 that harbors the IL4R gene was found to be strongly associated with RAO phenotype. This association was most notable in the offspring of one RAO-affected stallion.

Genetics, Allergens and IgE Levels

• The research also found that the levels of Immunoglobulin E (IgE), an antibody often associated with allergic reactions, were influenced by hereditary factors in horses. Specifically, RAO-affected offspring of the same stallion had increased levels of specific IgE against mold spore allergens.

Benefits of Genetic Research on RAO

• Understanding the genetics of RAO can lead to better prophylaxis or prevention strategies. Early identification of susceptible individuals and the avoidance of high-risk matings can help control the spread of the disease.
• Equally, genetic insights can aid in the discovery of new therapeutic targets and the optimisation of existing treatments, ultimately improving the management and prognosis of RAO in affected horses.