A parasitic malady is a communicable disease caused or transmitted by a parasite. Several parasites don't cause diseases. Parasitic diseases will have an effect on all living organisms, as well as plants and mammals. The study of parasitic diseases is named parasitology.
Symptoms may mimic anemia or a hormone deficiency. Parasites are responsible for many ill health conditions including diarrhoea, gastrointestinal upset, vaginal irritation, joint pain, nervous diseases, immune dysfunction and chronic fatigue. Long term, undetected infestation can cause many systemic problems.
The causal agent of soil-transmitted helminthiasis is any of the following worms: Ascaris lumbricoides, Trichuris trichiura and hookworms. Recent estimates suggest that A. lumbricoides infects over 1 billion people; T. trichiura, 795 million; and hookworms (Ancylostoma duodenale and Necator americanus), 740 million. The greatest numbers of infections occur in sub-Saharan Africa, the Americas and East Asia (including China).