Identification of environmental factors affecting the prevalence of insect bite hypersensitivity in Shetland ponies and Friesian horses in the Netherlands

Abstract

It is expected that climate and habitat factors influence the prevalence of culicoides and, therefore, the prevalence of insect bite hypersensitivity (IBH), but very little is described in the literature to prove the association of these factors. Prevalence varies widely from 3% in certain areas of Great Britain to 60% in certain parts of Australia. To describe the influence of environmental factors on the prevalence of IBH in Shetland ponies and Friesian horses in The Netherlands. Data on 3284 Shetland and 2824 Friesian mares (n = 6108) were collected in The Netherlands, based on 90 regions, according to postal codes. The climate components, amount of rainfall, number of warm days, number of cold days, and habitat components of soil type and type of vegetation were collected for each region. Prevalence of IBH varied widely from 0-71.4% per region. The results showed that the environment with low IBH-prevalence had high rainfall, many cold days and few warm days per year. Habitats with a low IBH-prevalence were based along the coast line. Habitats with increasing prevalence of IBH had soils of clay with heather and woody vegetation. Friesian mares had a higher IBH prevalence than Shetland mares, which could indicate an effect of genetic background or an effect of year. There is an environmental effect on IBH prevalence within The Netherlands, which is caused by climate and habitat factors. The results provide a more accurate description of environmental factors and their impact on development of IBH; and should help better to understand habitat and climate effects, and to distinguish these from other effects, such as animal factors (genetics, age or sex).