Hookworm are worms found in the small intestine. Infection occurs when worms found in soil bites through human skins and enters the body. Also, by ingesting the larvae of hookworms can cause infection. Symptoms are non-existence in those who are infected, except gastrointestinal issues for first-time infection. Hookwoom can cause decrease in protein and iron levels(anemia).
CDC. Parasites-Hookworm <http://www.cdc.gov/parasites/hookworm/> 10-June 2012