Chronic diarrhea is a frequent problem that’s extremely difficult to treat successfully. We gathered four typical cases with successful treatment outcomes as examples. In addition, our chart will help guide you to likely causes and help you and your veterinarian determine the best treatment route.
Case 1: A 13-month-old Thoroughbred colt had returned home from a Canadian breeding farm at the age of 4.5 months in poor condition and with chronic diarrhea. No parasite or pathogenic bacterial problem could be found, and no treatments had any good or lasting results.
A Lawsonia infection was discounted initially because his serum protein level was normal (it’s usually low with Lawsonia infections in foals), but when some checking around found that Lawsonia can also cause chronic diarrhea this was finally investigated and Lawsonia did turn out to be the cause. Treatment improved him 80%.
Case 2: A 22-year-old Arabian mare had loose manure for two years. No other horses on the farm had this problem, and their deworming program was believed to be good, with negative fecals. Manure exams and cultures turned up no cause, although the mare was found to have Cushing’s disease. Larvicidal deworming with fenbendazole firmed up her manure within the first three days of the five-day double-dose treatment.
Case 3: An eight-year-old Standardbred, who was given to his current owner after having had chronic diarrhea for over a year, was unresponsive to all treatments tried. His owner wasn’t having much luck with controlling it either, until he followed suggestions to ease up on exercise load (no speed work), substitute beet pulp for grain for a while and give him free-choice grass hay. The diarrhea resolved completely within a month and hasn’t returned, with the horse back in full training and on grain again.
Case 4: A 12-year-old Palomino mare had assorted skin problems, lung allergies and a lifelong history of long bouts of diarrhea. Careful questioning of the owner revealed a pattern of the diarrhea appearing only when on commercial grain mixes. On hay alone, she was OK. The mare was put on a mixture of beet pulp and oats instead of a grain, which she did well on, then was “challenged” by adding individual ingredients, and it was found she couldn’t tolerate corn or soybean meal without having diarrhea.
Chronic diarrhea is a complicated problem. Except for the relatively rare cases of lymphosarcoma or a genetic immune deficiency, most cases get their start with either parasitism (especially immature tissue forms of parasites), viral/bacterial/protozoal/rickettsial infections, or an allergy to a specific dietary component.
The inflammation and gut damage the initial problem causes lead to diarrhea directly and set the stage for altered immune function and increased sensitivity to a variety of allergens/irritants that a healthy, intact intestinal tract would handle without problems. Populations of gut organisms can also be negatively affected.
By the time a vet sees a horse with chronic diarrhea, the original cause may not still be there. And eliminating a parasite burden or infection may not solve the problem. A return to normal may take time and involve one or more of these steps:
• Larvicidal deworming to eliminate possible high-tissue levels of immature parasites.
• Support the establishment of normal intestinal “bugs” through use of Ration Plus, high-dose live organisms and exposure to the manure of normal horses.
• Aggressive efforts to identify infectious organisms of all types.
• Trials of oral antimicrobial drugs, even if an organism cannot be identified.
• Use of oral equine serum or colostrums products.
• Implementing a simple diet, such as only grass hay.