In the new version of the World Health Organization (WHO), water reuse guidelines helminth ova are considered one of the main target pollutants to be removed from wastewater reuse for agriculture and aquaculture purposes. In spite of this, along with the fact that helminth ova have been considered the main health risk to wastewater reuse for agriculture for at least 20 years, relatively little research has been done to control helminth ova in the wastewater treatment field. This paper addresses (1) characteristics of helminth ova and differences with microorganisms; (2) the most frequent helminth ova genus found in wastewater; (3) helminth ova content in developed and developing countries wastewater; (4) reasons why conventional disinfection methods cannot be applied; (5) main removal mechanisms; and (6) processes that in practice have effectively removed or inactivated helminth ova.