Bring the exterminator in, even if it's off the normal schedule; have him/her investigate for fleas and provide a written report. Assuming it shows no fleas, forward that report to your employee, sent some way or ways you can prove delivery (e.g. email and overnight delivery) and inform him/her that if he/she is not there the next day, he or she will be taken to have abandoned his/her job (e.g. quit or resigned). Phone the employee as well and keep a record of the call. If after getting an exterminator's report there are no fleas, the employee does not come in, treat it as if he/she did quit.If there were fleas, exterminate.