Over time our confidence that processionary caterpillars are the major cause of EAFL has progressively grown stronger, based on:
- experimental studies where administration of processionary caterpillars and caterpillar exoskeleton has reliably caused abortion in pregnant mares with the same signs as in field cases.
- observations of processionary caterpillars in trees either in or adjacent to paddocks where EAFL cases have been previously identified
- observations of very low incidence of EAFL cases on properties that do not appear to have processionary caterpillars
- observations of a reduction in incidence of EAFL cases on properties where active measures have been implemented to detect and remove caterpillars