Clostridia and equine grass sickness

Equine grass sickness, a paralysis of the gut resulting from destruction of the enteric nervous system, occurs mainly in northern Europe, especially the east of Scotland and England. A similar, possibly identical disease, mal seco, occurs in Argentina. The aetiological agent is unknown but the symptoms suggest the involvement of a toxin and a nutritional trigger. We hypothesize that C. botulinum type C may be the cause of equine grass sickness based on the modes of action of its toxins. In an ongoing study we are using serology, toxin detection and attempts to isolate the organism. C1 toxin has been identified directly in ileal specimens from seven out of 14 clinical cases, and in faeces (rectal specimens) in seven of 19 cases but also in two of 12 controls. Antibodies to C1 antitoxin and to cell-surface antigens are found in all horses but with no clear relationships between disease and antibody level.