Pulmonary diseases

Horses which are kept in permanent stabling are exposed to a variety of allergens and irritants, which do not occur in a natural environment. In first place is hay dust, which contains mould spores and so-called endotoxins (toxins produced by microorganisms), which can trigger allergies. Such allergens and irritants are responsible for a series of wide-spread, non-contagious pulmonary diseases. As a connection with stabling clearly exists, these diseases are in a way civilization diseases. More than half of the Swiss sports and leisure horses are affected.

The serious forms of these diseases are characterized by cramp-like constrictions of the airways, infections and increased production of mucus. They strongly restrict the quality of life and capacity of the animals. A detailed scientific confrontation with the pulmonary health of the horse is therefore not only academically relevant, but is an obligation to our animals.

Our research in pulmonary diseases engages in improved diagnosis, therapy and preventive measures.  In the process we work closely together with national and international partners. The main project engages in research of the genetic background of recurrent airway obstruction (RAO), the most important pulmonary disease, associated with stabling.  The superior goal of this research is to improve the quality of life of our horses effectively.

Genetics of RAO

RAO, previously known as COB, COPD or „heaves“, is a complex illness caused by genetic and environmental factors, which has a lot in common with human asthma. The main reason for these airway diseases are the stabling conditions, which horses are not accustomed to naturally. Horses often spend a main part of their time in stables and are exposed to different irritating and allergenic substances from hay and straw dust.  Sensitive animals and especially those with a hereditary handicap develop thereafter often RAO.

First warning signs such as a sporadic cough are often underestimated by owners. It can happen that a horse, which used to show a top performance, declines in performance, coughs more often, shows nasal discharge and finally develops a pumping breathing and respiratory distress, even when relaxed.  To protect the long-lasting health of a horse, hay has to be replaced by other roughages. If necessary, special hypoallergenic bedding has to be used and the horse should spend as much time outside as possible.

Descendants of affected parent animals have an increased risk to develop the disease

Almost a hundred years ago already, it was observed, that certain stallions and mares passed on the disease. With the help of the latest genetic methods, ISME examines the hereditary background of this airway disease. The superior goal of this research is, to improve the quality of life of these animals, with early diagnosis and prevention of high-risk pairings. As a part of these projects, two stallions suffering from RAO were identified. The descendants of these stallions were found and examined and the owners were questioned with the help of a standardized questionnaire. DNA was isolated from blood samples of the descendants. The results showed that descendants of the affected animals have about a 5 time higher risk to develop the disease themselves than other horses.

Two chromosome regions identified – Association with skin allergies and defense against intestinal parasites

As the entire genetic make-up was mapped, two chromosome regions could be identified with the so-called „whole genome scan“, which can be strongly associated with RAO. Important genes of these chromosome regions will be further examined. One of these “candidate genes” is generally related to allergies and also to the defense of parasites in humans and other animals.  Our tests showed that RAO in horses is associated to an increased occurrence of skin allergies (summer eczema, urticaria) and a decreased excretion of parasite eggs.

Further tests, which are already under way, will show how genes regulate the resistance against parasites and the sensitivity for allergies by means of even larger numbers of horses and with the help of the latest gen chip technology.

Because of the many parallels to asthma and other allergies in humans but also to parasitic diseases in third world countries, this research is not only in the interest of veterinary medicine..