One sub-cutaneous injection of ivermectin will kill all the critters. You can buy ivermectin and the syringes at any feed store or at a Tractor Supply store, no prescription required. I hope this is helpful, being tormented by critters is not tolerable!
Here is some info on ivermectin, most importantly notice that it is NOT toxic at standard dosage. It doesn't kill with poison.
Ivermectin inactivates parasitic nematodes, arachnids, and insects. Its action on the nematodes is by inhibiting signal transmission from the ventral cord interneurons to the inhibitory transmitter GABA from pre-synaptic nerve terminals, as well as by potentiating GABA binding to the post-synaptic receptors. The target species become paralysed and die.