Investigations into the incidence of field colic

Abstract

SummaryThis investigation was undertaken to compare the accuracy of different methods of collecting data on the incidence of colic. The results of an historical cohort technique and a questionnaire survey were compared with those obtained from a prospective cohort study. In a separate analysis, the practical application of the historical cohort method was used to estimate the incidence of colic in horses owned by regular clients of a general equine practice.Horses from 14 herds were used in Part 1 of the study, to gather the prospective cohort, historical cohort and questionnaire data. The prospective cohort method recorded 91 episodes of colic in 349.1 horse years, generating an incidence of 0.26 cases/horse‐year at risk. The historical cohort method, based on an analysis of billing records, identified 82 colic cases in 370 horse‐years at risk, under‐counting colic cases and overestimating the population at risk. However, the summary estimate of 0.22 cases/horse‐year at risk did not differ significantly from that generated by the prospective cohort study (P / 0.18). The questionnaire based survey identified 112 colic cases in 313 horse‐years at risk, over‐counting cases and under‐counting the population at risk. The incidence estimate was 0.36, which differed significantly from that found in the prospective cohort survey (P = 0.008).The second part of this investigation used the validated historical cohort method to estimate the incidence of colic in animals owned by clients of a University field service practice. The incidence estimated in this population was 0.19 cases/horse year at risk. This incidence may be generalised to groups of mature performance and pleasure horses using veterinary services regularly for herd health activities.