BACK TO BASICS: THE ACUTE ABDOMEN IN THE FIELD


The water source may not necessarily freeze but become cold during the cooler months; water tem- perature was found to affect consumption during cold but not hot weather.19,20 During cold weather, horses with only warm water available drink a greater volume each day than if they have only icy cold water available; however, if they have a choice between warm and icy water, they drink almost exclusively from the icy water and drink less vol- ume than if they have only warm water available. While the higher incidence of impactions occurring during the winter months15 may be associated with housing and diet, inadequate water intake during these months may also be a contributing factor. Mineral content of water should also be considered in areas where horses are predisposed to enteroli- thiasis.10,11 All horses should have a readily available source of fresh, palatable water avail- able and water intake monitored when possible. An increase in the number of hours in a stall and decrease in exposure to pasture and recent change in exercise regimen increased the risk for colic and simple colonic obstruction and distention.9,14 Horses that are housed for 19–24 hours a day are at a partic- ular risk for colic compared to horses at pas- ture.9,10,14,17 Pasture access and duration of access, however, have been associated with risk of equine grass sickness in non-US geographical regions.21 Recent transportation has been associated with


colic. Horses that had a history of travel in the previous 24 hours had an increased risk of simple colonic obstruction and distention compared to horses that had not been transported.14 Stress, change in diet/water consumption, and possibly re- stricted movement are likely related to the associa- tion between travel and colic. There has also been an association between transportation and salmo- nellosis. Transportation had a major role in reactivating Salmonella sp. infection in carrier po- nies22 and horses with a travel time to the hospital 1 hour were at an increased risk for shedding salmonella compared to horses with a shorter travel time.23


Knowledge of where the horse has previously re-


sided as well as when and for how long the horse was in that region may help with diagnosis. While there may not be an association between geograph- ical region and occurrence of colic,16 specific types of colic tend to occur in different regions:


● Enterolithiasis is particularly common in California.7,8


● Ileal impaction is associated with horses resid- ing in the southeastern United States.5


● Sand colic occurs in horses residing in regions with sandy soil such as Arizona, California, Florida, New Jersey, and Delaware.


● Duodenitis-proximal jejunitis is geographi- cally variable with California having a lower incidence compared to other regions and the disease seeming to occur with greater severity


in the southeastern compared to the northeast- ern United States.24,25


History of anthelmintic therapy including the an- thelmintic(s) used, frequency of administration, and results of monitoring of parasite burden need to be obtained. While historically Strongylus vulgaris (large red worm) was associated with colic, with the development of ivermectin-based anthelmintics the role of S. vulgaris in colic has diminished.4 Anaplo- cephala perfoliata (tapeworms) have been associated with gas colic, ileal impaction, ileocecal, cecocecal, and cecocolic intussusceptions, and cecal impac- tion4,26 and treatment with praziquantal tartrate or pyrantel pamoate (double dose) should be part of the anthelmintic regimen. Cyathostomes (small red worms) have been associated with cecal and large colon lesions4,27,28 and Parascaris equorum (round worms) have been associated with intestinal ob- struction, rupture, peritonitis, intussusception, or abscessation in foals.4,29 Monitoring of resistance of these parasites to routinely used anthelmintics is recommended on large farms. Horses that were not treated with an ivermectin- or moxidectin-based anthelmintic within the previous 12 months12 or were not on a regular deworming program6 were predisposed to colic and horses recently adminis- tered an anthelmintic were at a decreased risk of colic.9 Recent anthelmintic administration, how- ever, within 7–8 days was associated with colic10 and ascarid impactions.29 Vaccination history is also important particularly in cases where it may not be clear that the horse is showing signs of colic.


7. Medical History


Horses that have had previous colic surgery and previous episodes of colic are predisposed to col- ic.10,11,14,16–18 Horses with a large colon volvulus and displacement necessitating surgical correction were significantly more likely to colic after surgery if they had more than one episode of colic prior to the one necessitating surgery.30,31 The specific diagno- sis and procedure performed during a previous colic surgery often provides an indication of the cause of colic e.g., colonic displacements and large colon vol- vulus have a tendency to recur and horses having had small intestinal or small colon surgery are pre- disposed to adhesions. Often owners/caregivers may be aware of previous colic or colic surgery but with no knowledge of the specific lesion. Owners/ caregivers should be encouraged to keep records of the horses under their care so that this information is readily available to the attending veterinarian. The frequency and severity of previous colic episodes should be recorded. Recurrent colic warrants a more in-depth diagnostic work up, albeit not neces- sarily on an emergency basis. Knowledge of current or recent medication includ-


ing dose rate, route, and frequency of administration that the horse is or was receiving is critical so that treatment can be continued should the horse become


AAEP PROCEEDINGS  Vol. 66  2020 91


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