The most common ones found in North America include Giardia infections (through contaminated water) and toxoplasmosis (spread by cats). Primary: Mebendazole (Vermox), 100 mg orally once Secondary: Pyrantel pamoate (Pin-Rid), 11 mg per kg (maximum of 1 g) orally once; or albendazole (Valbazen), 400 mg orally once If persistent, repeat treatment in two weeks. Some of the most common symptoms and signs of intestinal parasites include: Digestive problems, including unexplained constipation, diarrhea, or persistent gas. Skin issues, including unexplained rashes, eczema, hives, and itching. Muscle and joint pain.