This is an area of active research involving veterinary clinicians, pathologists and entomologists. It seems likely that mares inadvertently eat whole caterpillars or shed caterpillar exoskeleton (skin) while grazing in paddocks. Following the experimental administration of caterpillar/exoskeleton to mares, setae (hairs) from the caterpillar have been identified under the microscope from tissue samples throughout the … Continue reading How do processionary caterpillars cause EAFL?