Pathogenic Parasites in Raw and Treated Wastewater in Africa: A Review

Wastewater is reused for irrigation in agriculture in many African cities. However, the use of partially/untreated wastewater may result in the transmission of infectious organisms such as parasites. This article reviews the prevalence and concentrations of parasites in raw and treated wastewater in African countries and the efficiency of the wastewater treatment systems used. This will highlight the burden of parasitic infections in African communities and suitability of reusing wastewater in these communities. The following databases: PUBMED, HINARI and Google Scholar were searched for any article presenting information on the occurrence and concentration of parasites in wastewater in any African country. No restrictions were set on date of publication, study design or language. Thirty publications were identified. These publications presented works related to parasites in wastewater in 12 African countries. A total of 23 parasite species were identified throughout the 5 African regions. Eggs of Ascaris lumbricoides predominated followed by Hymenolepis species, Trichiuris trichiura, Hookworm, Taenia species, Enterobius species, Toxocara species and Schistosoma species. Cysts of Giardia species, Entamoeba histolytica and Entamoeba coli were the most commonly identified protozoa. Waste stabilization ponds and activated sludge systems are the common wastewater treatment systems used in Africa with the former being more efficient for parasites removal than the later. The review results show that wastewater in Africa contains a variety of pathogenic parasites with protozoa predominating helminth and putting public health at risk. Despite the fact that wastewater treatment systems removed helminths, some of them did not meet the WHO standard. Moreover, these systems do not clear protozoa and there is no standard concentration established for safe reuse of wastewater. Therefore, there is a need for improving treatment systems design and management. Moreover, standards for protozoa should be set.