Great topic! Did you have any test? When I asked my doctor they asked in return if I had any diarrhea. Huh?? Since when it's the only symptom?
Anyway, I searched in Google and what I found was :

Roundworms

Also Listed As: Ascariasis; Guinea Worm Disease; Hookworm; Loiasis; Lymphatic Filariasis; Parasitic Infection, Roundworms; Pinworm; River Blindness; Threadworm; Trichinosis; Visceral Larva Migrans; Whipworm

Treatment Approach

The use of antiparasitic medications is the primary therapy for roundworm infections; the medication prescribed depends on the specific roundworm identified. Surgical procedures may be necessary under certain circumstances; such procedures are not always readily available, however, in areas where roundworm infections are prevalent. Roundworm infections can inflame the lining of the gut and limit the absorption of and/or compete with many essential nutrients, including vitamins A and B6. Vitamin A deficiencies are believed to increase the risk of parasitic infections, so some researchers speculate that vitamin A supplementation may help prevent or reduce symptoms associated with roundworm infections. In addition, some herbal remedies, particularly fig, have been shown to limit roundworm egg production or destroy roundworms altogether. Some other studies suggest that Traditional Chinese Medicine may prove more effective than placebo in improving the symptoms of roundworm infection.

(www.healthandage.com/html/res/com/ConsConditions/Roundwormscc.html)

So, here you are. First they have to identify not only IF you have but WHICH one. The average lab is rather useless as far as I know. Parasitology in the States was given very little attention to in the medical colleges. So called 3d world coutries are more advanced in this field.
Most of the pills end with -andazole. The first side effect you have..diarrhea! the other ones:
http://www.drugs.com/index.cfm?pageID=0&htm=202339&type=cons&bn=Mebendazole&m...

Pay attention they recommend SAME herbs we take anyway. :))

Heyley, thanks for your response the other day about the
round worms--long earth worm appearing ones. According to Hulda,
we must get rid of all metal in our mouths and be chelating
to ever hope to get well from parasites. I had 13 fillings
replaced in 1999. I still did not get over my health
problems. Thanks to Huggin's books and Hulda Clark 's book,
I realized that the root canal and four crowns I had left
were bad news. I had the infected root canal out about 6 weeks
ago. I tried to research my records for what was in the
crowns and found that there was Nickel and palladium. When
I researched those metals in Hulda's book, Huggin's book
and on the Net, I found that they are very harmful to the
immune system. Long story short--I am having the last
piece of metal out of my body on Thursday. Just a thought
that you may have already addressed. Bev