The Michigan equine monitoring system. II. Frequencies and impact of selected health problems.

A prospective study was designed to document the frequencies of equine health problems in the state of Michigan, USA. A total of 2469 horses from a random sample of 138 equine operations were monitored in the study in two 12-month periods: 1992-1993 and 1993-1994. All the major breeds of horses in the state were proportionately represented in the sample. Using weighted annual incidence densities as measures of disease frequencies, the 10 most frequently observed groups of health problems were (from most to least frequent) leg lameness, dermatological problems, respiratory problems, hoof and foot problems, reproductive problems, systemic problems, colic, whole body lameness, neurological problems and gastrointestinal problems (other than colic). This ranking of the top 10 health problems was different from the ranking provided by equine owners/operators at the beginning of the study. Overall, very low specific mortality rates were observed in the study. However, the conditions that were associated with mortality resulted in fairly high case fatalities. The five specific illnesses that most commonly resulted in fatalities were (from greatest to least case fatality risk) systemic problems, colic, gastrointestinal problems (other than colic), neurological problems, and foot and hoof problems. Impact of disease was evaluated in terms of average duration of a case and days lost for performance. Neurological problems, lameness and dermatological problems had the longest duration per case. Neurological problems, lameness, respiratory problems and gastrointestinal problems (other than colic) had the longest average days lost per case.