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Genotypic detection and evaluation of the removal efficiency of Giardia duodenalis at municipal wastewater treatment plants in Northern South Africa.

Over the past decade, Giardia duodenalis has increasingly been implicated in diarrheal outbreaks and water and wastewater have been recognized as important vehicles for diseases. Although studies have reported the occurrence of these parasites in developed countries, their occurrence in water and wastewater bodies in these countries including South Africa has not been thoroughly investigated. In the present study, wastewater samples from 6 different sewage treatment plants in the Vhembe District were collected for a period of 12 months. The samples were concentrated and tested for the presence of G. duodenalis using both microscopy and polymerase chain reaction methods targeting the tpi gene. Of the 79 wastewater samples tested, 25 (31.65%) were positive. Of these, 15 (60%) were assemblage A, while 8 (32%) were assemblage B and 2 samples (8%) were positive for both genogroups. Assemblage A was more common in February 2010 while assemblage B showed two peaks in December-January and March-April and was not detected in May 2010. The general removal rate was 40% for plants using biological filters and 20% for plants using activated sludge. The present study has shown that Giardia assemblage A is more common in sewage treatment plants in the Vhembe District, but the removal efficiency was low. This represents a public health hazard since these organisms might contaminate drinking water sources. Therefore action needs to be taken for the design of more effective procedures or methods for the removal of these parasites from the environment in order to avoid potential outbreaks.