[The urticating hairs of the oak processionary caterpillar (Thaumetopoea processionea L.), a possible problem for...

Since 1991 the urticating hairs of the oak processionary caterpillar (Thaumetopoea processionea L.) have caused a lot of nuisance to the population and animals in a growing number of provinces in the Netherlands from June to August. Favourable climatic and nutritional factors may contribute to the mass gradation of this caterpillar. Larvae develop their urticating hairs from the third larval stage. The poisonous hairs serve as a defence mechanism against predators such as birds and small rodents. Human contact with these hairs (setae) induces dermatitis, strong cutaneous reactions (weal and flare reaction), ocular lesions and upper respiratory tract reactions by a mechanic and toxic mechanism (lepidopterism). When animals, like dogs and horses, are in direct contact with the urticating hairs due to ingestion and inhalation, the most important complaints are labial angiooedema, ptyalism, sloughing, tongue swelling, stomatitis, conjunctivitis and respiratory distress. This article describes three cases, in which animals are possibly exposed to the urticating hairs of the oak processionary caterpillar.