ridecamp@endurance.net: Re: Colic Survey

Re: Colic Survey

Trish Dowling (dowling@skyway.usask.ca)
Thu, 7 Aug 1997 10:50:10 -0700 (PDT)

I didn't keep the email address of the person that was compiling the practices of the list members, but I told
them that I knew that I had seen this addressed by a veterinary study funded by the Morris Animal
Foundation. I was cleaning my files, getting ready for school to start back, and I found the abstract. While a
survey of list members is somewhat interesting, it lacks enough power to be statistically significant. This
study does, so here it is for anyone who is interested.

Risk Factors for Equine Colic Identified by Means of a Multicentered Case-Control Study*
Mathew J. Reeves BVSC, PhD and Mo Saiman BVMS, PhDt

INTRODUCTION
Despite the large amount of basic and clinical research conducted regarding the equine colic syndrome,
little is known about the exact cause of intestinal obstructions in horses. Many different variables have been
suggested as possible causes of colic -e.g., diet, exercise, parasites, and environmental factors. However,
there have been very few epidemiologic studies conducted to identify risk factors forequine colic. The
objective of this study was to identify risk factors by using a multicenter case-control study.
MATERIALS AND METHODS
Horses were selected from the veterinary hospitals located at Comell, Guelph, Ohio State, Pennsylvania,
and Tufts universities. Each institution was instructed to select up to 100 cases and 100 controls between
March and November 1991. Horses admitted with a history of abdominal pain that had a final diagnosis of
either medical colic, strangulated obstruction, obstipation or nonstrangulated obstruction were included in
the study. For each colic case identified, a control horse was selected at random from a list of all non-colic
equine admissions seen at the same hospital.The person(s) responsible for the day-to-day care of the horse
during the 4-week period prior to admission was contacted and asked to complete a telephone survey. The
questionnaire collected a wide range of information, including details concerning housing, stable or farm
environment, pasture access, diet, exercise, breeding history, travel history, health history and veterinary
care. Data were analyzed using standard multivariable logistic regression methods. A bivariate screening
(using a P=0.20 significance level) was first employed to reduce the number of explanatory variables. A
purposeful forward selection method was used to identify a final model. Variables included in the model were
selected on the basis of statistical significance (using a P=0.05 significance level), biological plausibility,
and goodness-of-fit given the data.
RESULTS
A total of 812 surveys, 406 colic cases and 406 control horses, were included in the analysis. Thirty-four
subjects either refused to participate, could not be contacted, or provided unacceptably poor information,
giving an overall response rate of 96% (812/846). The results of the final logistic regression model are
presented in Table 1. Because of space limitations, not all the results are presented.
DISCUSSION
To our knowledge, this is one of the very first investigations designed to identify colic risk factors. In some
instances the results appear to confirm previous clinical impressions. For example, breeding horses had
almost twice the colic risk as pleasure horses. Standardbreds had a significantly lower colic risk compared
with Thoroughbreds, whereas Arabian horses were more than twice as likely to be colic cases. Neither of
these findings have been reported previously. Horses cared for by a trainer ora famVstabIe managerhad a
significantly highercolic risk (odds ratio = 2.8 and 1.8, respectively) compared to horses cared for by their
owners. This result is intriguing and may be related to important differences in the way horses are cared for
on a routine basis. Horses that had access to two or three pastures during the month prior to presentation
had a significantly lower colic risk, compared with horses that had no pasture access. Again, this result is
intriguing since it may imply that regular access to fresh pasture might reduce colic risk. Finally, although
the use of a daily worming product was associated with a significantly lower colic risk, only 13 horses used
the product during the last 12 months. This finding should therefore be interpreted with some caution at this
stage. Further research is obviously required before these findings can be regarded as true colic risk factors.
However, this epidemiologic study has served to confirm some previous notions regarding colic risk factors,
as well as to identify several important new areas of study.

This work was partially supported by the Morris Animal Foundation, Englewood, CO
>From the 39th Annual Convention Proceedings of the American Association of Equine Practitioners, 1993

Trisha Dowling, DVM, MS, Diplomate ACVIM & ACVCP
Associate Professor, Veterinary Clinical Pharmacology
Western College of Veterinary Medicine
Saskatoon, SK S7N 5B4
306-966-7359/FAX 306-966-7376

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