APPLICATION AND EVALUATION OF A MAILED QUESTIONNAIRE FOR AN EPIDEMIOLOGIC-STUDY OF CORYNEBACTERIUM-PSEUDOTUBERCULOSIS INFECTION IN HORSES

The objective of this study is to describe the design, application and validity of a self-administered (mailed) questionnaire to collect dat a on potential risk factors for Corynebacterium pseudotuberculosis inf ection in California horses. Horses admitted to the UC Davis Veterinar y Medical Teaching Hospital (VMTH) between 1 July 1992 and 30 June 199 4 served as the study base for case identification and simple random s ampling of 800 control horses. A questionnaire was mailed to owners of the study horses, followed by a reminder postcard and a second copy o f a questionnaire. Data were collected on owner and horse identity and demographics, horse management and use, geographic location, and gene ral health-related issues. Return pattern over time as well as differe ntial return proportions were described. The overall return proportion was 66% (587/890), and the completion proportion 55% (491/890). The n umber of returns over time followed a negative binomial distribution, with over 90% of all returns being in by the end of the fifth week aft er mailing, and over 99% at the end of the tenth week. Some categories within the variables age (between 2 and 3 years), breed (Thoroughbred and Standardbred horses) and gender (stallions) had significantly low er return proportions than expected (differential return; p<0.05). The profile of these horses fits a section of the racehorse population th at is served by the VMTH. Age, breed and disease status information wa s available from the VMTH medical records and from the questionnaire, and was used to determine the validity of the survey data. There was g ood agreement between the data from the two sources, and we therefore concluded that the quality of the survey information was sufficient to perform a risk-factor analysis. The mailed survey provided a rapid an d cost-effective method of collecting additional information to supple ment existing medical records. (C) 1998 Elsevier Science B.V.