REVIEW ARTICLE Parasites and pollution: the effectiveness of tiny organisms in assessing the quality of aquatic ecosystems, with a focus on Africa Beric Michael Gilbert 1 & Annemariè Avenant-Oldewage 1 Received: 26 December 2016 /Accepted: 7 June 2017 # Springer-Verlag GmbH Germany 2017 Abstract The aquatic environment represents the final repos- itory for many human-generated pollutants associated with anthropogenic activities. The quality of natural freshwater sys- tems is easily disrupted by the introduction of pollutants from urban, industrial and agricultural processes. To assess the ex- tent of chemical perturbation and associated environmental degradation, physico-chemical parameters have been moni- tored in conjunction with biota in numerous biological mon- itoring protocols. Most studies incorporating organisms into such approaches have focussed on fish and macroinverte- brates. More recently, interest in the ecology of parasites in relation to environmental monitoring has indicated that these organisms are sensitive towards the quality of the macroenvironment. Variable responses towards exposure to pollution have been identified at the population and compo- nent community level of a number of parasites. Furthermore, such responses have been found to differ with the type of pollutant and the lifestyle of the parasite. Generally, endopar- asite infection levels have been shown to become elevated in relation to poorer water quality conditions, while ectoparasites are more sensitive, and exposure to contaminated environ- ments resulted in a decline in ectoparasite infections. Furthermore, endoparasites have been found to be suitable accumulation indicators for monitoring levels of several trace elements and metals in the environment. The ability of these organisms to accumulate metals has further been observed to be of benefit to the host, resulting in decreased somatic metal levels in infected hosts. These trends have similarly been found for host–parasite models in African freshwater environ- ments, but such analyses are comparatively sparse compared to other countries. Recently, studies on diplozoids from two freshwater systems have indicated that exposure to poorer water quality resulted in decreased infections. In the Vaal River, the poor water quality resulted in the extinction of the parasite from a site below the Vaal River Barrage. Laboratory exposures have further indicated that oncomiracidia of Paradiplozoon ichthyoxanthon are sensitive to exposure to dissolved aluminium. Overall, parasites from African fresh- water and marine ecosystems have merit as effect and accu- mulation indicators; however, more research is required to detail the effects of exposure on sensitive biological processes within these organisms. Keywords Accumulation indicator . Bioindicator . Biomarkers . Effectindicator . Environmentalhealth . Metals . Parasites as indicators . Pollution sensitivity Introduction Assessment of environmental health with biota has become increasingly more attractive, and the number of identified in- dicator species has similarly increased. One of the most well- known examples of an organism’ s usefulness as an indicator of the quality of an environment is that of canaries in coal mines. Historically, canaries accompanied miners into coal mines where the sensitivity of the birds to trace amounts of noxious gases, methane and carbon monoxide (Smith and Baker 2003; Holt and Miller 2010) was used as an early warn- ing of toxic conditions to miners. As a result of their acute Responsible editor: Philippe Garrigues * Annemariè Avenant-Oldewage aoldewage@uj.ac.za Beric Michael Gilbert bericg@uj.ac.za 1 Department of Zoology, University of Johannesburg, Johannesburg, South Africa Environ Sci Pollut Res DOI 10.1007/s11356-017-9481-8