Helminths (Figure 12) are parasitic worms that can cause ill health in humans. They range from a millimetre long to more than a metre (Baron, 1996).
Helminths can cause morbidity, and sometimes death, by compromising the nutritional status of the infected person. They can also affect cognitive processes, induce tissue reactions and provoke intestinal obstruction or rectal prolapse (WHO, 2013).
Infection occurs through ingestion of helminth eggs that are present in food. For example, helminth eggs may be present in the meat of cattle grazing on land that is contaminated by poorly treated sewage effluent or sludge.