Abstract
The zebra mussel (Dreissena polymorpha) is an abundant and invasive molluscan shellfish species which arrived in Ireland’s river basins in the early 1990’s. Inland and coastal surface waters can be contaminated by human waterborne zoonotic enteropathogens such as Cryptosporidium parvum, Giardia lamblia, Encephalitozoon intestinalis, E. hellem and Enterocytozoon bieneusi originating predominantly from wastewater treatment plant effluents and agricultural runoff. Bivalve species, i.e., the invasive zebra mussel, Mytilus edulis (blue mussel) and Anodonta anatina (duck mussel) were used as sentinels and also as biomonitors of the aforementioned waterborne pathogens at twelve sites located in three Irish river basin districts impacted by pollution related to various water quality pressures. A variety of advanced biomolecular techniques were utilized to assess the presence and concentration of these pathogens in molluscan shellfish. At least one pathogen species was detected in bivalves at each of the twelve sites. Cryptosporidium, implicated in several recent Irish gastrointestinal epidemics, was recorded at all sites subjected to agricultural runoff and at one treated wastewater discharge site, linking source-track directly to animal and human fecal wastes. Overall, the results demonstrated a long-term human enteropathogen contamination of Irish waters with consequent public health risk-factors for drinking water abstraction and water-based recreational activities. The study provided further solid evidence that zebra mussels can recover and concentrate environmentally derived human pathogens and therefore can be used for the sanitary assessment of surface water quality.
Highlights
Cryptosporidium parvum, Giardia lamblia, and human-virulent microsporidia such as Encephalitozoon intestinalis, E. hellem, and Enterocytozoon bieneusi are human anthropozoonotic pathogens that inflict considerable morbidity on healthy people and can cause mortality (e.g., Cryptosporidium and microsporidia) in immunosuppressed population (Wolfe et al 1992; Graczyk et al 2004)
fluorescence in situ hybridization (FISH) has been combined with direct immunofluorescent antibody (IFA) against the wall antigens of Cryptosporidium and Giardia and this approach has been successful for detection of C.parvum and G. lamblia in zebra mussels (Graczyk et al 2004; Lucy et al 2008)
One aliquot was processed for C. parvum and G. lamblia by combined FISH and direct immunofluorescent antibody (IFA), and the other for E. intestinalis, E. hellem and E. bieneusi by FISH (Graczyk et al, 2007b)
Summary
Cryptosporidium parvum, Giardia lamblia, and human-virulent microsporidia such as Encephalitozoon intestinalis, E. hellem, and Enterocytozoon bieneusi are human anthropozoonotic pathogens that inflict considerable morbidity on healthy people and can cause mortality (e.g., Cryptosporidium and microsporidia) in immunosuppressed population (Wolfe et al 1992; Graczyk et al 2004). Because Cryptosporidium, Giardia, and microsporidia can infect a variety of non-human hosts, identification of human-virulent species represents a challenge. Another challenge is determination of viability of the aforementioned pathogens as they may be non-viable and not of epidemiological importance. Recognized alignment of respective 16S rRNA regions of 22 micro-sporidia species (Hester et al 2000) allowed for the design of the E. bieneusi-specific 19 bp oligonucleotide probe (Graczyk et al 2004) for the present study. FISH has been combined with direct immunofluorescent antibody (IFA) against the wall antigens of Cryptosporidium and Giardia and this approach has been successful for detection of C.parvum and G. lamblia in zebra mussels (Graczyk et al 2004; Lucy et al 2008)
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