Equine Colic: I. Introduction by N.A. White II in the Annual Convention of the AAEP, 2006

Colic, defined as any abdominal pain, has resulted in the death of horses throughout recorded history. The earliest treatments may have been acupuncture. The use of drugs for treatment of associated pain and ileus has only applied recently. A definition offered in a book entitled Diseases of Livestock (1880) by a human physician states that the spasmodic colic gripes is caused by “improper food, sudden changes in diet, exhaustion from overwork, drinking cold water when heated or exhausted, constipation, worms, and ulcers of the stomach.” Flatulant colic was “attributed to easily fermented food, such as raw potatoes, green clover, brewers’ slop and the like.” Recommended treatments included drenches such as chloroform, laudanum, sulphuric ether (1 oz each in 8 oz of linseed oil), and were reported to “never fail” in a genuine case of colic. Later texts separated simple colic such as spasmodic colic and tympany from more severe colic caused by intestinal strangulation, which was considered uniformly fatal. The causes of many types of colic were discussed and, in some cases, with equal accuracy, compared with what is known today. Research on equine gastrointestinal disease was not mentioned in early veterinary texts. Initial research was mostly observational with conclusions about the cause of colic based only on lesions found at necropsy or a response to treatment. Some of the first observations about causes of colic by Udall are still professed today. Proposed etiologies included changing of food (from oats to corn), overeating, damaged feed, irregular work, fatigue, drinking excessively after work, stormy weather, increased temperatures, idiosyncrasy, and faulty mastication. Dietary factors, including the feeding of concentrates or poor quality roughage, were considered primary causes of colic. Parasites were recognized as a major cause of colic, and Strongylus vulgaris blamed as the chief cause of simple and thromboembolic colic in horses. Recently, small strongyles, rather than Strongylus vulgaris, were determined to be the main cause of increased colic incidence on farms. Verminous colic was reproduced by infecting foals with Strongylus vulgaris larva; however, vascular lesions were observed in 90% of horse necropsies, and few of these horses suffered from colic. Therefore, the actual risk of colic associated with this parasite was questioned. Not until the widespread use of ivermectin was it clear that the decrease in thromboembolic colic paralleled