Análisis del Índice Check List OCRA (ICKL)

A systematic search for published peer-reviewed research articles related to pathogens as- sociated with drinking water in New Zealand was conducted in December 2013. The search was conducted using the search engines Scopus and Web of Knowledge, available through the Massey University library. Pathogens recognised by WHO as waterborne (Table 2.1) were used as keywords for the construction of a search term. After several iterations with different combinations of keywords redundant keywords were removed resulting in the fol- lowing final search term being used: ((campylobact* OR cryptosp* OR ‘E. coli’ OR ‘es- cherichia’ OR enterovir* OR giard* OR norovir* OR salmonell*) AND (new zealand) AND (‘drinking water’ OR drinking-water)). The same search term was used in both search en- gines. The Scopus engine retrieved 40 articles while Web of Knowledge returned 67; these were combined and duplicates removed resulting in 74 unique retrievals. Each retrieved article was scanned to determine if it was relevant to the current literature review or not by examining the title and abstract. In total 24 retrieved articles were considered relevant and were included in the current review. The references of the relevant articles were scanned in order to identify more relevant articles not retrieved by the electronic search. A retrieved article was regarded as relevant if it reported a research study regarding waterborne dis- ease, waterborne pathogen(s) or indicator organism(s) in relation to drinking water in New Zealand.

The purpose of performing this review was to summarise findings of published peer reviewed research related to waterborne pathogens and drinking water in New Zealand, hence iden- tify research trends and knowledge gaps. The relevant articles were classified into two groups; the first category was composed of articles that focused primarily on human dis- ease cases and the second category on waterborne organisms. Disease case studies were further subdivided, based on their study design, into outbreak investigations, case-control and retrospective cohort studies. All of the organism-focused studies used a cross-sectional study design.

Outbreak investigations

Six studies described disease outbreak investigations; three involving campylobacteriosis, two salmonellosis and oneNorovirus infection. Campylobacteriosis (Bohmer,1997; Briese- man, 1987; Stehr-Green et al., 1991) and Norovirus (Hewitt et al., 2007) studies involved

campgrounds and a ski resort, respectively. Outbreaks at the campgrounds were due to consumption of water from untreated or inadequately treated supplies while at the ski re- sort an unusual contamination event of the water supply had occurred. The two studies investigating salmonellosis outbreaks analysed outbreak surveillance data; one over a 4 year period, 1998–2001 (Thornley et al., 2002), and another for a ten year period, 2000–2009 (King et al., 2011). Thornley et al. (2002) investigated 137 outbreaks while King et al. (2011) investigated 204 outbreaks. The largest proportion of salmonellosis outbreaks were attributed to food sources followed by person-to-person contact, water consumption and animal contact. Of the disease case studies 53 % used disease notification data, indicating that this is a very important resource for researchers. None of the retrieved articles re- ported use of metagenomic techniques exposing a new research area to be explored as far as microbial water quality is concerned in New Zealand.

Case-control studies

Of the studies that had a case-control study design, two investigated the risk of acquir- ing giardiasis (Hoque et al., 2002; Mitchell et al., 1993), another two campylobacteriosis (Eberhart-Phillips et al., 1997; Ikram et al., 1994) and one E. coli infection (Jaros et al.,

2013). Evidence from the two giardiasis studies showed that consuming drinking water other than that from regulated city supplies (probably a proxy for consumption of inad- equately treated water) resulted in an elevated risk of acquiring giardiasis. Other risk factors for acquiring giardiasis included exposure to human waste, swimming and travelling outside New Zealand. Ikram et al. (1994) reported that there was an elevated risk of acquir- ing campylobacteriosis, although statistically non-significant (marginally), associated with consumption of water other than from the city mains. Risk factors that were statistically significant for acquiring campylobacteriosis were mainly food-related, including consuming poultry at a friend’s home, consumption of undercooked poultry or barbecued chicken. In a study by Eberhart-Phillips et al. (1997), raw or undercooked chicken and consumption of chicken in restaurants were found to be strongly associated with campylobacteriosis. The likelihood of acquiring campylobacteriosis also increased with recent overseas travel, roof water at household level, consumption of dairy products, contact with puppies and contact with calves. Consumption of baked or roasted chicken appeared to protect against acquir- ing campylobacteriosis. Jaros et al. (2013) found that travel to areas in New Zealand with interrupted or no main water supply, contact with recreational water together with contact with animal manure and presence of cattle in a meshblock (smallest geographical unit in New Zealand) were risk factors for shiga toxin-producing E. coli (STEC) O157:H7. Food sources were not associated with acquiring STEC infection.

Retrospective cohort studies

Seven studies used a retrospective cohort study design. Five of these studies used New Zealand’s national disease notification data for periods ranging from 2 to 50 years: 1996–

Pathogens in drinking water — New Zealand

1998 (Duncanson et al., 2000), 1997–2006 (Britton et al., 2010b), 1996–2000 (Hoque et al., 2004), 1998–2002 (Khan et al., 2007) and 1952–2001 (Thornley et al., 2002). Cowie and Bell (2013) used disease notification data for the Waikato region (2004–2011 ) while Schousboe et al. (2013) used routine blood stream infection monitoring laboratory data belonging to the Canterbury District Health Board (2009–2011 ). The evidence from these studies suggest that consuming water from supplies that were ungraded, graded as unsat- isfactory, not complying with DWSNZ, inadequately treated water or had a poor quality water source resulted in an increased risk of acquiring waterborne infection (Britton et al.,

2010b; Duncanson et al., 2000; Khan et al., 2007). Such water supplies were likely to be those supplying small communities and probably located in rural areas. Other risk factors for gastrointestinal illness included being younger than 5 years, a history of travel outside of New Zealand, contact with persons with gastrointestinal symptoms and contact with farm animals. The evidence also showed that susceptibility to waterborne infections varied among ethnic groups, for example persons of Asian descent were more likely to acquire gia- rdiasis than others (Hoque et al.,2004) while persons of European descent were more likely to acquire cryptosporidiosis (Cowie and Bell,2013) or salmonellosis (Thornley et al.,2002). Cases of salmonellosis were reported to be more prevalent in late summer/early autumn (ibid.) while cryptosporidiosis was more prevalent in spring (Cowie and Bell,2013). Britton et al. (2010b) reported that consumption of water from supplies with the best grade had an elevated risk for acquiring giardiasis. There is no immediate explanation for this seemingly counter-intuitive finding. Schousboe et al. (2013) reported that drinking water was not a factor in the increased incidence ofE. coli bacteraemia after the 2011 Christchurch earth- quake despite land liquefaction, widespread sewer system damage and possible drinking water source contamination.

Cross-sectional studies (organism-focused)

Five studies (Close et al., 2008; Donnison et al., 2004; Savill et al., 2001; Simmons et al.,

2001; Till et al.,2008) focused on indicator organisms. Indicator organisms were regularly detected in source waters, e.g. E. coli was detected in 99 % or more of surface water samples (Close et al., 2008; Donnison et al., 2004; Savill et al., 2001; Till et al., 2008) and 50 % of roof water samples (Simmons et al., 2001). The concentration of indicator organisms was measured as MPN of organism per 100 mL of water sample and a sample was declared positive if it had one or more MPN/100 mL. Pathogens were also detected i.e. Campy- lobacter was detected in 66 % of shallow wells, 60 % of surface water samples, 37 % of roof water samples and 29 % of reticulated water samples (Savill et al., 2001). The species of

Campylobacter detected included C. jejuni,C. coli and C. lari.

Factors associated with the presence ofE. coliin surface water sources included animal graz- ing activities in the catchment and increased river flow. E. coli concentrations were highest during the spring and summer months and lowest in autumn and/or winter (Donnison et

al., 2004). Various factors, including type of roof, type of storage tank, water turbidity and season, were investigated for their association with the presence of indicator organisms in roof harvested water. Indicator organisms investigated included heterotrophs, total co- liform (TC), faecal coliform (FC) and Enterococci spp.. The presence of heterotrophs in roof water was associated with galvanised roofs and storage tanks; TC with water turbidity and galvanised roofs; FC with plastic storage tanks and Enterococci spp. with tiled roofs (Savill et al.,2001).