Coxsackie viruses as causes of epidemic pleurodynia and on the behaviour of Toxoplasma gondii in tissue culture.    From Wordnik.com.  [Thomas H. Weller - Biography] Reference

Horses suffering with pleurisy, pleurodynia, or rheumatism, and other affections accompanied with much pain, will grunt when moved, or when the pain is aggravated, but grunting under these circumstances does not justify the term of "grunter" being applied to the horse, as the grunting ceases when the animal recovers from the disease that causes the pain.    From Wordnik.com.  [Special Report on Diseases of the Horse] Reference