Quantification of Urticating Setae of Oak Processionary Moth (Thaumetopoea processionea) and Exposure Hazards

Potential climatic and land-use changes may favor an increase in the population densities and range expansion of oak processionary moth (OPM) in Central and Western Europe in the future. This could lead to more significant threats to human and animal health, caused by the urticating setae released by OPM larvae, and more severe oak defoliation by the larvae. To cope with the public health issue, a basis for OPM hazard assessment and management was created by quantifying the setae formation potential of OPM. While a single larva forms ca. 857,000 setae during its lifespan, a single infested oak tree may be contaminated with up to 10-24 billion (10⁹) setae during an OPM outbreak. Moreover, the possible setae contamination threat to humans through airborne setae dispersal was studied in worst-case exposure simulations in the field. The highest airborne setae concentration was straight downwind, but turbulences up to 150° from the air flow were observed. The findings of this study will improve biohazard quantification as a basis for decision-making on preventive or mechanical control measures and enable an effective protection of human health. This study provides applicable information to derive warnings and recommendations for the public, as well as land managers and authorities.