Welcome to NeuroTalk:

There is a bacterium that comes from poorly cooked chicken.
Campylobacter is the name. It results in an autoimmune PN in some people. Treatment is IVIG. This condition was illustrated on the Discovery series, Mystery diagnosis. You might be able to find the episode online. PN follows a bout of stomach "flu" therefore from this food borne infection.

Also, you are intuitively very perceptive. Vaccines can also cause a GBS in sensitive people.

The biggest problem I see is finding a doctor who will understand this progression and at least try the IVIG for your father.

Sometimes also the drugs that people take, can cause problems. What does your father take, can you tell us.

Even blood pressure drugs are not 100% safe. I am getting over a drug induced lupus from lisinopril, and ACE inhibitor.
This type of lupus does not typically raise ANA levels, so when tested this might be "normal".
Here is an article on the subject:
http://www.lupus.org/webmodules/weba...=377&zoneid=17

So people with drug induced lupus may fall thru the cracks of traditional medicine!

I would get testing done for B12 and Vitamin D. This really is the beginning for all PN type situations. Both of these nutrients can commonly be low in many people. Get the numbers of the B12 test, because doctors will accept LOWS from outdated lab ranges still as normal. So even getting testing EVALUATIONS may fail. I find this pretty disturbing, but it happens all the time, so patients have to take a proactive stance in their treatments and testings where PN is concerned.
This is our B12 thread:
http://neurotalk.psychcentral.com/thread85103.html
You will want to have at least 400pg/ml in US testing units for the lowest normal result. Most of us here keep our levels at 1000 or above.

When there is an injury to the nerves, and healing elements are not present, then the healing becomes impaired and the symptoms linger. Damage can be to the myelin that insulates the axons of the nerves, or to the mitochondria in the cell bodies. Sometimes the injury is to the dorsal ganglia in the spine. B12 is a cofactor in remyelination. So if low, then healing cannot take place. If your father uses statins for cholesterol...these drugs impair normal remyelination as a side effect, and can cause PN. One is not likely to heal therefore when these drugs are continually taken.