In New Zealand most Health Insurance Policies will exclude cover for treating GBS and CIDP or related conditions with IVIg or Plasmapheresis as these fall into the excluded category of
“Renal dialysis or specialised transfusions of blood and blood products and derivatives”
Under “pre-existing conditions clauses most providers will expect a previous episode of GBS or CIDP to be declared.
In the case of travel insurance advice varies with some companies accepting that following recovery from GBS a re-occurrence is most unlikely whilst CIDP has an increase re-occurrence risk. Cover may be provided at an enhanced premium. It is always best to check the situation with your Insurance provider.