The epidemiology of the parasites Giardia, Cryptosporidium and Entamoeba - The wastewater discharge nexus.
Work is on-going to investigate the causes and distribution of three important parasites: in the Elbe and Rhine rivers. Whereas the water medium has attracted considerable research efforts, waterborne transmission of these life-threatening microorganisms still constitutes a serious public health risk. In the on-going investigation, 97 mussels of Dreissena polymorpha and Corbicula fluminea have been analysed for the presence of protozoan parasites using microbiological and molecular techniques. Cryptosporidium spp have been detected in 53% E. histolytica in 30% Giardia spp in 48% of the mussels sample examined. Thus evidence is accumulating in support of a link between wastewater treatment plants (WWTPs) discharge and the occurrence and distribution of protozoan parasites in river courses. This ‘nexus’ is the focus of this investigation. Up to now, research has only been able to provide partial answers to the contribution of WWTPs to microbial pollution of water bodies and recreational sites, underscoring the need for a significant expansion of known epidemiological approaches and their harnessing as bio-monitoring tools. The purpose of this work is mainly two-fold: 1) to establish the link between the wastewater discharges and the spread of parasites; 2) to catalyze basic research effort that enables a correct understanding of the dynamics of these organisms, which is vital for the development of prevention strategies against disease outbreaks.In epidemiological studies, it is important to take into account all factors that could interfere with biological results. Parasitism and disease dynamics are known to be strongly influenced by environmental conditions. Effects of factors such as temperature, nutrients and salinity on the mussel-protozoa interaction and the ultimate transmission of the pathogens need to be investigated as fluctuations can have far-reaching implications on disease outbreaks.The first phase of this work which targeted the Rhine river has generated interesting data that needs to be verified and validated through replicated work as foreseen in the original project plan. Thus the next phase in the work will involve an intensive sampling of the Elbe river and analysis of raw data from Hamburg WWTPs.This study will generate a complete understanding of the epidemiology of the three pathogens. How they: enter the environment, invade and are transmitted. The study will provide leads as to how protozoa diseases scale up from individuals to populations and communities. Furthermore, findings of the study will contribute to on-going efforts to develop an effective tool, with Mussel as the choice biological model, for sanitary biomonitoring of water bodies. In addition, findings will have relevance to the Ministry of Health’s department of infectious disease control, which establishes water-quality standards for pathogens to protect public health.