My guess, no zapper. But I'd almost see this as more toxicity than parasites. The toxin, which they are sensitive to, perhaps unusually so, could be from any number of things--personal care items, cleaning agents, petro-carbon stuff from oil based products, like gas fumes.
Obviously from something they use frequently as it's building up and not getting a chance to be cleared out. Or even some source in their environment--leaky gas pipe or heating/cooling unit, or refrideratior or whatever.
They really need to check those things too. But a good parasite cleanse with zapper never hurts, and could help ease symptoms as the body's immune system become less overloaded and able to process out the toxin faster.