Researchers at Michigan State University are into their third year of a 10-year study of the pathogenesis and most efficacious treatments for chronic obstructive pulmonary disease (COPD). Explains Ed Robinson, MRCVS, PhD (respiratory physiology), Matilda R. Wilson Professor of Large Animal Clinical Sciences, “We’re interested in the lesser form of the disease, where horses at the racetrack and elsewhere have inflammation of their air passages that veterinarians can’t ascribe to a virus or to a bacterial infection.”

During the past several years, researchers had been concentrating on the causes of airway obstruction in seriously affected horses and the accompanying muscle spasms in the wall of the airways. “But we’re moving away from that aspect, now,” says Robinson, “and we are looking at mucous accumulation.”

Questions being investigated include these:

• Is the mucus produced in a horse affected with airway disease similar or different to the type produced in normal horses?
  
• Is it more or less viscous?
  
• Is it more or less difficult to clear from the air passages?
  
• Why is it being produced?
  
• If inflammation is relieved, will the mucus return to normal?
  
• If the horses get repeated bouts of inflammation, will the mucus eventually change permanently so that it’s more difficult to clear?

Researchers have learned that horses seriously afflicted with heaves appear fairly normal when turned out to pasture, and although they have increased amounts of mucus in their air passages, its viscosity is normal and thus easy to clear. “But 24 hours after you put that horse in the stable, the mucus becomes viscous and very difficult to clear,” Robinson explains. “We’re beginning to think that it has differences in the sugars that are associated with the mucus that make it more sticky