Idiopathic Focal Eosinophilic Enteritis (IFEE), an emerging cause of abdominal pain in horses:the effect of age, time and geographical location on risk

Background: Idiopathic focal eosinophilic enteritis (IFEE) is an emerging cause of abdominal pain (colic) in horses that frequently requires surgical intervention to prevent death. IFEE lesions were first identified in the late 1990’s and the incidence of this form of colic has continued to increase in certain equine hospital populations. The epidemiology of IFEE is poorly understood and it is difficult to diagnose pre-operatively. In addition, the aetiology of this condition and methods of possible prevention are also currently unknown. Based upon a UK equine hospital population the aims of this study were to investigate temporal and spatial heterogeneity in IFEE risk and to ascertain the effect of horse age on the risk process. Methodology/Principal Findings: A retrospective, nested case-control study was undertaken. Data were extracted and pertained to 85 observed IFEE cases and 848 randomly selected controls (non-cases) admitted to a UK equine hospital for exploratory laparotomy to investigate the cause of colic over a 10-year period. Spatial clustering was investigated via K-function analysis, and generalised additive models (GAM's) were used to quantify temporal and age effects on the odds of IFEE and to provide mapped estimates of ‘residual’ risk over the study region. The relative risk of IFEE increased over the study period (p=0.001) and a seasonal pattern was evident (p<0.01) with greatest risk of IFEE being identified between the months of July-November. Age was found to be a contributory factor (p<0.001) with IFEE risk decreasing with increasing age and younger (0 - 5 years old) horses being at greatest risk. Spatial clustering of cases was significantly different to that of controls (p<0.001) over a wide range of spatial scales (from 4km to at least 50km). The mapped surface estimate exhibited significantly atypical sub-regions (p