Trichuris trichiura is the species that infests humans. Symptoms of whipworm infection include anemia, pallor, abdominal discomfort, and dysentery. The intensity of symptoms depends upon how many parasites are carried, with individuals having only a few worms appearing to be wholly unaffected. Children are more prone to infection than adults and tend to suffer more severely. Extended infections of whipworms in the young may even cause mental and physical retardation.