Committee Report: Emerging pathogens-viruses, protozoa, and algal toxins

Techniques for inactivating Toxoplasma gondii oocysts: a systematic review

The oocyst, a resistant form of Toxoplasma gondii, plays an important role in the transmission of this protozoan. The objective of this review was to report the methods capable of inactivating oocysts through a systematic review of the literature carried out in the Scientific Electronic Library Online, Web of Science, Science Direct, PubMed and Scopus databases. The keywords searched were (((effects OR infectivity OR resistance) AND Toxoplasma) AND oocyst). We selected 16 articles that described 309 different treatments. Among all the protocols evaluated, 35.60% (110/309) were effective in inactivating oocysts. Physical methods were more effective than other methods (p <0.05). Sporulated oocysts and the T. gondii VEG strain were more resistant (p <0.05) to treatments. Although it is effective against viruses and bacteria, the use of disinfectants in water has little or no effect on T. gondii oocysts. The use of radiation and pressure were effective in inactivating oocysts, as these treatments do not include changes in temperature, they can be used in foods for raw consumption, such as vegetables, as it will not cause substantially changes in their physical and chemical characteristics. Therefore, these methods can be viable alternatives for the control of T. gondii.

Research Trends in Emerging Contaminants on the Aquatic Environments of Tanzania

The continuity for discovery and production of new chemicals, allied products, and uses has currently resulted into generation of recent form of contaminants known as Emerging Contaminants (ECs). Once in the aquatic environment ECs are carcinogenic and cause other threats to both human's and animals' health. Due to their effects this study was aimed at investigating research trends of ECs in Tanzania. Findings revealed that USA and EU countries were leading in ECs researches, little followed by Asia, South Africa, and then Zambia. Only few guidelines from USA-EPA, WHO, Canada, and Australia existed. Neither published guidelines nor regulations for ECs existed in Tanzania; rather only the occurrence of some disinfection by-products and antibiotics was, respectively, reported in Arusha and Dar es Salaam, Tanzania. As these reports had a limited coverage of ECs, henceforth, these findings constitute the first-line reference materials for ECs research in Tanzania which shall be useful for future monitoring and regulation planning.

Influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon Cryptosporidium parvum removal during riverbank filtration operations, Sonoma County, CA

This study assessed the efficacy for removing Cryptosporidium parvum oocysts of poorly sorted, Fe- and Al-rich, subsurface sediments collected from 0.9 to 4.9 and 1.7-13.9 m below land surface at an operating riverbank filtration (RBF) site (Russian River, Sonoma County, CA). Both formaldehyde-killed oocysts and oocyst-sized (3 microm) microspheres were employed in sediment-packed flow-through and static columns. The degree of surface coverage of metal oxides on sediment grain surfaces correlated strongly with the degrees of oocyst and microsphere removals. In contrast, average grain size (D(50)) was not a good indicator of either microsphere or oocyst removal, suggesting that the primary mechanism of immobilization within these sediments is sorptive filtration rather than physical straining. A low specific UV absorbance (SUVA) for organic matter isolated from the Russian River, suggested that the modest concentration of the SUVA component (0.8 mg L(-1)) of the 2.2 mg L(-1) dissolved organic carbon (DOC) is relatively unreactive. Nevertheless, an amendment of 2.2 mg L(-1) of isolated river DOC to column sediments resulted in up to a 35.7% decrease in sorption of oocysts and (or) oocyst-sized microspheres. Amendments (3.2 microM) of the anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) also caused substantive decreases (up to 31.9 times) in colloid filtration. Although the grain-surface metal oxides were found to have a high colloid-removal capacity, our study suggested that any major changes within the watershed that would result in long-term alterations in either the quantity and (or) the character of the river's DOC could alter the effectiveness of pathogen removal during RBF operations.

Are waterborne astrovirus implicated in acute digestive morbidity (E.MI.R.A. study)?

BACKGROUND

With rotavirus and Norwalk-like viruses, astroviruses are now recognized as important etiologic agents of viral gastroenteritis in all age groups. However, astrovirus is neither routinely screened for in stool samples, nor in environmental samples, and data on the health impact of waterborne astrovirus are lacking.

OBJECTIVES

To assess the potential impact of astrovirus in drinking water on the incidence of acute digestive conditions (ADC) among a panel of volunteers.

STUDY DESIGN

The Epidemiology and MIcrobial Risk Assessment (E.MI.R.A.) study combined a daily epidemiological follow-up of digestive morbidity among a panel of 544 volunteers supplied by French public water systems, and a microbiological surveillance of drinking water. Cases of digestive morbidity were collected through weekly telephone calls. The bacterial, virological and parasitic quality of tap water was assessed monthly. Additional samples were collected if the incidence of ADC increased. The relationship between incidence of ADC during a 7-day period centered about the water sampling day and astrovirus RNA prevalence in drinking water was modeled by regression techniques, taking into account several confounders.

RESULTS

12% (8/68) of the analyzed water samples were positive for astrovirus, and presence of astrovirus RNA was associated with a significant increased risk of ADC: RR=1.51 (95% CI=[1.17-1.94], P value=0.002).

CONCLUSIONS

This result suggests a role for waterborne astrovirus in the endemic level of digestive morbidity in the general population. Perhaps astrovirus is a candidate test target for viral surveillance of drinking water.

Cryptosporidium parvum and Cyclospora cayetanensis: a review of laboratory methods for detection of these waterborne parasites

Cryptosporidium and Cyclospora are obligate, intracellular, coccidian protozoan parasites that infest the gastrointestinal tract of humans and animals causing severe diarrhea illness. In this paper, we present an overview of the conventional and more novel techniques that are currently available to detect Cryptosporidium and Cyclospora in water. Conventional techniques and new immunological and genetic/molecular methods make it possible to assess the occurrence, prevalence, virulence (to a lesser extent), viability, levels, and sources of waterborne protozoa. Concentration, purification, and detection are the three key steps in all methods that have been approved for routine monitoring of waterborne oocysts. These steps have been optimized to such an extent that low levels of naturally occurring Cryptosporidium oocysts can be efficiently recovered from water. The filtration systems developed in the US and Europe trap oocysts more effectively and are part of the standard methodologies for environmental monitoring of Cryptosporidium oocysts in source and treated water. Purification techniques such as immunomagnetic separation and flow cytometry with fluorescent activated cell sorting impart high capture efficiency and selective separation of oocysts from sample debris. Monoclonal antibodies with higher avidity and specificity to oocysts in water concentrates have significantly improved the detection and enumeration steps. To date, PCR-based detection methods allow us to differentiate the human pathogenic Cryptosporidium parasites from those that do not infect humans, and to track the source of oocyst contamination in the environment. Cell culture techniques are now used to examine oocyst viability. While fewer studies have focused on Cyclospora cayetanensis, the parasite has been successfully detected in drinking water and wastewater using current methods to recover Cryptosporidium oocysts. More research is needed for monitoring of Cyclospora in the environment. Meanwhile, molecular methods (e.g. molecular markers such as intervening transcribed spacer regions), which can identify different genotypes of C. cayetanensis, show good promise for detection of this emerging coccidian parasite in water.