An outbreak of gastroenteritis from a non-chlorinated community water supply

Clinical features of gastroenteritis during a large waterborne Campylobacter outbreak in Askøy, Norway

Purpose

Outbreaks of Campylobacter infection are common, but studies exploring the clinical features of acute illness in the outbreak setting are scarce in existing literature. The main purpose of the present study was to investigate the clinical features of self-reported acute illness in gastroenteritis cases during a large waterborne Campylobacter outbreak in Askøy municipality, Norway, in 2019.

Methods

A web-based self-administered questionnaire, and invitation to participate was sent by the municipality of Askøy as text message to mobile phones using the municipality’s warning system to the inhabitants during the ongoing outbreak.

Results

Out of 3624 participants, 749 (20.7%) were defined as cases, of which 177 (23.6%) reported severe gastroenteritis. The most common symptoms were loose stools (90.7%), abdominal pain (89.3%) and diarrhea (88.9%), whereas 63.8% reported fever, 50.2% joint pain and 14.2% bloody stools. Tiredness, a symptom non-specific to gastroenteritis, was the overall most common symptom (91.2%).

Conclusion

About one in four of the cases reported symptoms consistent with severe gastroenteritis. We found more joint pain and less bloody stools than reported in published studies of laboratory confirmed campylobacteriosis cases. Tiredness was common in the current study, although rarely described in previous literature of acute illness in the outbreak setting.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01652-3.

Large waterborne Campylobacter outbreak: use of multiple approaches to investigate contamination of the drinking water supply system, Norway, June 2019

On 6 June 2019, the Norwegian Institute of Public Health was notified of more than 50 cases of gastroenteritis in Askøy. A reservoir in a water supply system was suspected as the source of the outbreak because of the acute onset and geographical distribution of cases. We investigated the outbreak to confirm the source, extent of the outbreak and effect of control measures. A case was defined as a person in a household served by Water Supply System A (WSS-A) who had gastroenteritis for more than 24 h between 1 and 19 June 2019. We conducted pilot interviews, a telephone survey and an SMS-based cohort study of residents served by WSS-A. System information of WSS-A was collected. Whole genome sequencing on human and environmental isolates was performed. Among 6,108 individuals, 1,573 fulfilled the case definition. Residents served by the reservoir had a 4.6× higher risk of illness than others. Campylobacter jejuni isolated from cases (n = 24) and water samples (n = 4) had identical core genome MLST profiles. Contamination through cracks in the reservoir most probably occurred during heavy rainfall. Water supply systems are susceptible to contamination, particularly to certain weather conditions. This highlights the importance of water safety planning and risk-based surveillance to mitigate risks.

Waterborne outbreaks: a public health concern for rural municipalities with unchlorinated drinking water distribution systems

OBJECTIVES

The objective of this study is to describe an important waterborne outbreak of gastrointestinal illness observed in a rural municipality of Quebec.

METHODS

A population-based retrospective cohort study was conducted to identify risk factors associated with acute gastroenteritis. Indirect surveillance data were used to estimate the extent and the resolution of the epidemic.

RESULTS

The cohort consisted of 140 randomly selected individuals of whom 22 met the illness case definition (15.7% attack rate). The epidemic curve was similar to the evolution of antidiarrheal products sold by the only pharmacy in town and calls made to the Health Info Line. Bivariate analysis led to identifying five risk factors of gastrointestinal illness: consumption of municipal water, contact with someone with acute gastroenteritis (within and outside of the household), contact with a child in daycare, and being less than 35 years of age. Drinking municipal water had the highest risk ratio (RR = 24.31; 95% CI = 1.50-393.4). Drinking water from a private artesian well was a protective factor (RR = 0.28; 95% CI = 0.09-0.90).

CONCLUSION

This study highlighted that managing the risks associated with the consumption of untreated drinking water remains an important public health challenge, particularly in small rural municipalities vulnerable to climate variability.

Human campylobacteriosis: A public health concern of global importance

Campylobacter species are among the leading cause of bacterial foodborne and waterborne infections. In addition, Campylobacter is one of the major causative agent of bacterial gastrointestinal infections and the rise in the incidence of Campylobacter infections have been reported worldwide. Also, the emergence of some Campylobacter species as one of the main causative agent of diarrhea and the propensity of these bacteria species to resist the actions of antimicrobial agents; position them as a serious threat to the public health. This paper reviews Campylobacter pathogenicity, infections, isolation and diagnosis, their reservoirs, transmission pathways, epidemiology of Campylobacter outbreaks, prevention and treatment option, antibiotics resistance and control of antibiotics use.

Ruminant and chicken: important sources of campylobacteriosis in France despite a variation of source attribution in 2009 and 2015

Pathogen source attribution studies are a useful tool for identifying reservoirs of human infection. Based on Multilocus Sequence Typing (MLST) data, such studies have identified chicken as a major source of C. jejuni human infection. The use of whole genome sequence-based typing methods offers potential to improve the precision of attribution beyond that which is possible from 7 MLST loci. Using published data and 156 novel C. jejuni genomes sequenced in this study, we performed probabilistic host source attribution of clinical C. jejuni isolates from France using three types of genotype data: comparative genomic fingerprints; MLST genes; 15 host segregating genes previously identified by whole genome sequencing. Consistent with previous studies, chicken was an important source of campylobacteriosis in France (31-63% of clinical isolates assigned). There was also evidence that ruminants are a source (22-55% of clinical isolates assigned), suggesting that further investigation of potential transmission routes from ruminants to human would be useful. Additionally, we found evidence of environmental and pet sources. However, the relative importance as sources varied according to the year of isolation and the genotyping technique used. Annual variations in attribution emphasize the dynamic nature of zoonotic transmission and the need to perform source attribution regularly.

Epidemiological and serological investigation of a waterborneCampylobacter jejunioutbreak in a Danish town

Following an unusually heavy rainfall in June 2009, a community-wide outbreak ofCampylobactergastroenteritis occurred in a small Danish town. The outbreak investigation consisted of (1) a cohort study using an e-questionnaire of disease determinants, (2) microbiological study of stool samples, (3) serological study of blood samples from cases and asymptomatic members of case households, and (4) environmental analyses of the water distribution system. The questionnaire study identified 163 cases (respondent attack rate 16%). Results showed a significant dose-response relationship between consumption of tap water and risk of gastroenteritis.Campylobacter jejunibelonging to two relatedflaAtypes were isolated from stool samples. Serum antibody levels againstCampylobacterwere significantly higher in cases than in asymptomatic persons. Water samples were positive for coliform bacteria, and the likely mode of contamination was found to be surface water leaking into the drinking-water system. This geographically constrained outbreak presented an ideal opportunity to study the serological response in persons involved in aCampylobacteroutbreak. The serology indicated that asymptomatic persons from the same household may have been exposed, during the outbreak period, toCampylobacterat doses that did not elicit symptoms or alternatively had been exposed toCampylobacterat a time prior to the outbreak, resulting in residual immunity and thus absence of clinical signs.

Survival in water of Campylobacter jejuni strains isolated from the slaughterhouse

Campylobacter jejuni cause gastroenteritis in humans. The main transmission vector is the consumption or handling of contaminated chicken meat, since chicken can be colonized asymptomatically by C. jejuni. However, water has been implicated as the transmission vector in a few outbreaks. One possibility is the contamination of water effluent by C. jejuni originating from chicken farm. The ability of C. jejuni to be transmitted by water would be closely associated to its ability to survive in water. Therefore, in this study, we have evaluated the ability of reference strains and chicken-isolated strains to survive in water. Defined water media were used, since the composition of tap water is variable. We showed that some isolates survive better than others in defined freshwater (Fraquil) and that the survival was affected by temperature and the concentration of NaCl. By comparing the ability of C. jejuni to survive in water with other phenotypic properties previously tested, we showed that the ability to survive in water was negatively correlated with autoagglutination. Our data showed that not all chicken isolates have the same ability to survive in water, which is probably due to difference in genetic content.

A community-based gastroenteritis outbreak after Typhoon Haiyan, Leyte, Philippines, 2013

BACKGROUND

Three weeks after Typhoon Haiyan, an increasing number of acute gastroenteritis cases were reported in Kananga, Leyte, an area where evacuated residents had returned home two days after the disaster. An outbreak investigation was conducted to identify the source and risk factors associated with the increase of gastroenteritis.

METHODS

A case was defined as any person in Kananga who developed acute diarrhoea (≥ 3 times/24 hours) and any of the following symptoms: fever, nausea, vomiting or abdominal pain from 11 November 2013 to 10 December 2013. Active case finding was conducted by reviewing medical records, and a case-control study was conducted. Rectal swabs and water samples were tested for bacteriological examination.

RESULTS

One hundred and five cases were identified. Multivariate analysis revealed that consumption of untreated drinking-water was associated with illness (adjusted odds ratio: 18.2). Both rectal swabs and municipal water samples tested positive for Aeromonas hydrophila. On inspection of the municipal water system, breaks in the distribution pipes were found with some submerged in river water.

CONCLUSION

This acute gastroenteritis outbreak was most likely caused by Aeromonas hydrophila and transmitted through a contaminated water source. This study highlights that areas less damaged by a disaster that do not require ongoing evacuation centres can still have acute gastroenteritis outbreaks. All affected areas should be monitored during a disaster response, not just those with evacuation centres. Boiling or chlorinating of water should also be recommended for all areas affected by disaster.

Genome analysis of Campylobacter jejuni strains isolated from a waterborne outbreak

BACKGROUND

Waterborne Campylobacter jejuni outbreaks are common in the Nordic countries, and PFGE (pulsed field gel electrophoresis) remains the genotyping method of choice in outbreak investigations. However, PFGE cannot assess the clonal relationship between isolates, leading to difficulties in molecular epidemiological investigations. Here, we explored the applicability of whole genome sequencing to outbreak investigation by re-analysing three C. jejuni strains (one isolated from water and two from patients) from an earlier resolved Finnish waterborne outbreak from the year 2000.

RESULTS

One of the patient strains had the same PFGE profile, as well as an identical overall gene synteny and three polymorphisms in comparison with the water strain. However, the other patient isolate, which showed only minor differences in the PFGE pattern relative to the water strain, harboured several polymorphisms as well as rearrangements in the integrated element CJIE2. We reconstructed the genealogy of these strains with ClonalFrame including in the analysis four C. jejuni isolated from chicken in 2012 having the same PFGE profile and sequence type as the outbreak strains. The three outbreak strains exhibited a paraphyletic relationship, implying that the drinking water from 2000 was probably contaminated with at least two different, but related, C. jejuni strains.

CONCLUSIONS

Our results emphasize the capability of whole genome sequencing to unambiguously resolve the clonal relationship between isolates of C. jejuni in an outbreak situation and evaluate the diversity of the C. jejuni population.

Role of environmental survival in transmission of Campylobacter jejuni

Campylobacter species are the most common cause of bacterial gastroenteritis, with C. jejuni responsible for the majority of these cases. Although it is clear that livestock, and particularly poultry, are the most common source, it is likely that the natural environment (soil and water) plays a key role in transmission, either directly to humans or indirectly via farm animals. It has been shown using multilocus sequence typing that some clonal complexes (such as ST-45) are more frequently isolated from environmental sources such as water, suggesting that strains vary in their ability to survive in the environment. Although C. jejuni are fastidious microaerophiles generally unable to grow in atmospheric levels of oxygen, C. jejuni can adapt to survival in the environment, exhibiting aerotolerance and starvation survival. Biofilm formation, the viable but nonculturable state, and interactions with other microorganisms can all contribute to survival outside the host. By exploiting high-throughput technologies such as genome sequencing and RNA Seq, we are well placed to decipher the mechanisms underlying the variations in survival between strains in environments such as soil and water and to better understand the role of environmental persistence in the transmission of C. jejuni directly or indirectly to humans.

The role of environmental reservoirs in human campylobacteriosis

Campylobacteriosis is infection caused by the bacteria Campylobacter spp. and is considered a major public health concern. Campylobacter spp. have been identified as one of the most common causative agents of bacterial gastroenteritis. They are typically considered a foodborne pathogen and have been shown to colonise the intestinal mucosa of all food-producing animals. Much emphasis has been placed on controlling the foodborne pathway of exposure, particularly within the poultry industry, however, other environmental sources have been identified as important contributors to human infection. This paper aims to review the current literature on the sources of human exposure to Campylobacter spp. and will cover contaminated poultry, red meat, unpasteurised milk, unwashed fruit and vegetables, compost, wild bird faeces, sewage, surface water, ground water and drinking water. A comparison of current Campylobacter spp. identification methods from environmental samples is also presented. The review of literature suggests that there are multiple and diverse sources for Campylobacter infection. Many environmental sources result in direct human exposure but also in contamination of the food processing industry. This review provides useful information for risk assessment.

Binational outbreak of Guillain-Barré syndrome associated with Campylobacter jejuni infection, Mexico and USA, 2011

In June 2011, a cluster of suspected cases of Guillain-Barré syndrome (GBS), which can follow Campylobacter jejuni infection, was identified in San Luis Río Colorado (SLRC), Sonora, Mexico and Yuma County, Arizona, USA. An outbreak investigation identified 26 patients (18 from Sonora, eight from Arizona) with onset of GBS 4 May-21 July 2011, exceeding the expected number of cases (n = 1-2). Twenty-one (81%) patients reported antecedent diarrhoea, and 61% of 18 patients tested were seropositive for C. jejuni IgM antibodies. In a case-control study matched on age group, sex, ethnicity, and neighbourhood of residence, all Arizona GBS patients travelled to SLRC during the exposure period vs. 45% of matched controls (matched odds ratio 8·1, 95% confidence interval 1·5-∞). Exposure information and an environmental assessment suggested that GBS cases resulted from a large outbreak of C. jejuni infection from inadequately disinfected tap water in SLRC. Binational collaboration was essential in investigating this cross-border GBS outbreak, the first in mainland North America since 1976.

Quality of piped and stored water in households with children under five years of age enrolled in the Mali site of the Global Enteric Multi-Center Study (GEMS)

Water, sanitation, and hygiene information was collected during a matched case-control study of moderate and severe diarrhea (MSD) among 4,096 children < 5 years of age in Bamako, Mali. Primary use of piped water (conditional odds ratio [cOR] = 0.45; 0.34-0.62), continuous water access (cOR = 0.30; 0.20-0.43), fetching water daily (cOR = 0.77; 0.63-0.96), and breastfeeding (cOR = 0.65; 0.49-0.88) significantly reduced the likelihood of MSD. Fetching water in > 30 minutes (cOR = 2.56; 1.55-4.23) was associated with MSD. Piped tap water and courier-delivered water contained high (> 2 mg/L) concentrations of free residual chlorine and no detectable Escherichia coli. However, many households stored water overnight, resulting in inadequate free residual chlorine (< 0.2 mg/L) for preventing microbial contamination. Coliforms and E. coli were detected in 48% and 8% of stored household water samples, respectively. Although most of Bamako's population enjoys access to an improved water source, water quality is often compromised during household storage.

Excess healthcare costs of a large waterborne outbreak in Finland

Background: The economic effects of waterborne outbreaks have rarely been reported. A large waterborne outbreak occurred in the town of Nokia in Finland in 2007 with half of the population in the contaminated area suffering from gastroenteritis. We studied the healthcare costs of this outbreak. Methods: Healthcare costs were studied using register data from the Nokia Health Care Centre, data collected in the regional university hospital, and data from laboratory register on stool samples. Results: Total excess healthcare costs were EUR 354,496, which is approximately EUR 10 per resident of Nokia. There were 2052 excess visits because of gastroenteritis in Nokia Health Care Centre, 403 excess episodes in the university hospital, and altogether over 2000 excess stool samples due to the outbreak. Care in the Nokia Health Care Centre accounted for 44% and care in the university hospital for 42% of the excess healthcare costs while stool samples accounted for only 10%. Conclusions: Despite the high morbidity, the total cost was low because most patients had a relatively mild illness. The situation would have been worse if the microbes involved had been more hazardous or if the financial situation of the community had been worse. Prevention of waterborne outbreaks is important, as there is a risk of severe short- and long-term health effects and substantial health-economic costs.

Isolation of Campylobacter sp in surface waters of Taiwan

BACKGROUND

Campylobacter sp is one of the main causes of human acute enteritis and diarrhea. It is commonly found in bird intestinal canal and pollutes water bodies through bird droppings. Clinically, detection of Campylobacter sp is by culture method and most are fecal samples. The objective of this study is to investigate the distribution of Campylobacter sp in river water of Taiwan.

METHODS

The detection of campylobacters in water by the United Kingdom Health Protection Agency was adopted and simplified. Water samples (1L) were enriched through membrane filters and selective enrichment Bolton broth. The mCCDA medium was used for culturing Campylobacter sp. In addition to using the selective media, DNA sequencing for species' identification was also included in this study.

RESULTS

Campylobacter sp was detected in only 2 of 75 water samples, and 72 suspected strains were isolated from the selective mCCDA medium, in which several pathogenic bacteria included Escherichia coli O157.

CONCLUSIONS

Not only there was pollution of Campylobacter sp in water environment but also other antibiotics-resistant pathogenic bacteria, which may cause public health risk.

An extensive gastroenteritis outbreak after drinking-water contamination by sewage effluent, Finland

An inappropriate cross-connection between sewage- and drinking-water pipelines contaminated tap water in a Finnish town, resulting in an extensive waterborne gastroenteritis outbreak in this developed country. According to a database and a line-list, altogether 1222 subjects sought medical care as a result of this exposure. Seven pathogens were found in patient samples of those who sought treatment. To establish the true disease burden from this exposure, we undertook a population-based questionnaire investigation with a control population, infrequently used to study waterborne outbreaks. The study covered three areas, contaminated and uncontaminated parts of the town and a control town. An estimated 8453 residents fell ill during the outbreak, the excess number of illnesses being 6501. Attack rates were 53% [95% confidence interval (CI) 49.5-56.4] in the contaminated area, 15.6% (95% CI 13.1-18.5) in the uncontaminated area and 6.5% (95% CI 4.8-8.8) in the control population. Using a control population allowed us to differentiate baseline morbidity from the observed morbidity caused by the water contamination, thus enabling a more accurate estimate of the disease burden of this outbreak.

Outbreaks of campylobacteriosis in Australia, 2001 to 2006

The objective of this study was to examine the frequency of Campylobacter outbreaks in Australia and determine common transmission routes and vehicles. Summary and unit data on Campylobacter outbreaks that occurred between January 2001 and December 2006 were systematically collected and analyzed. Data from Campylobacter mandatory notifications for the same period were used for comparison. During the study period there were 33 Campylobacter outbreaks reported, affecting 457 persons. Of these, 147 (32%) had laboratory-confirmed infections, constituting 0.1% of notified Campylobacter cases. Campylobacter outbreaks most commonly occurred during the Australian Spring (September to November; n = 14, 45%), when notifications generally peaked. Transmission was predominantly foodborne or suspected foodborne (n = 27, 82%), commercial settings (n = 15, 55%) being most commonly involved. There were eight foodborne outbreaks (30%) attributed to food prepared or eaten at institutions; four (15%) at aged care facilities and three (11%) at school camps. A vehicle or suspected vehicle was determined for 16 (59%) foodborne outbreaks; poultry (chicken or duck) was associated with 11 (41%) of these, unpasteurized milk and salad were associated with two outbreaks each. Three potential waterborne outbreaks were detected, and one was due to person-to-person transmission. Campylobacter outbreaks were more commonly detected during this study period compared to a previous 6-year period (n = 9) when prospective recording of information was not undertaken. However, outbreak cases continue to constitute a very small proportion of notifications. Improved recognition through subtyping is required to enhance outbreak detection and investigation so as to aid policy formulation for prevention of infection. In addition to detection of chicken as a common source of outbreaks, these data highlight the importance of directing policy at commercial premises, aged care facilities, and school camps to reduce Campylobacter disease burden.

Comparison of PCR binary typing (P-BIT), a new approach to epidemiological subtyping of Campylobacter jejuni, with serotyping, pulsed-field gel electrophoresis, and multilocus sequence typing methods

To overcome some of the deficiencies with current molecular typing schema for Campylobacter spp., we developed a prototype PCR binary typing (P-BIT) approach. We investigated the distribution of 68 gene targets in 58 Campylobacter jejuni strains, one Campylobacter lari strain, and two Campylobacter coli strains for this purpose. Gene targets were selected on the basis of distribution in multiple genomes or plasmids, and known or putative status as an epidemicity factor. Strains were examined with Penner serotyping, pulsed-field gel electrophoresis (PFGE; using SmaI and KpnI enzymes), and multilocus sequence typing (MLST) approaches for comparison. P-BIT provided 100% typeability for strains and gave a diversity index of 98.5%, compared with 97.0% for SmaI PFGE, 99.4% for KpnI PFGE, 96.1% for MLST, and 92.8% for serotyping. Numerical analysis of the P-BIT data clearly distinguished strains of the three Campylobacter species examined and correlated somewhat with MLST clonal complex assignations and with previous classifications of "high" and "low" risk. We identified 18 gene targets that conferred the same level of discrimination as the 68 initially examined. We conclude that P-BIT is a useful approach for subtyping, offering advantages of speed, cost, and potential for strain risk ranking unavailable from current molecular typing schema for Campylobacter spp.

Description and sources of contamination by Campylobacter spp. of river water destined for human consumption in Brittany, France

Presence or absence of Campylobacter spp. in water of five rivers upstream from an intake point for drinking water production was investigated, and isolates genetically compared with human, pig and poultry isolates in order to determine their source. River water and drinking water obtained from these rivers were sampled one time per month, over a period of one year, and tested for Campylobacter. Isolates were typed by PFGE. Campylobacter was not detected in treated drinking water, but 50% of the river samples were contaminated. Contamination was observed on the four seasons. In total, 297 Campylobacter isolates were collected and generated 46 PFGE profiles. Campylobacter jejuni was the most frequently detected species in samples (74.1% of the isolates), followed by Campylobacter coli (17.8%) and Campylobacter lari (8.1%). Forty-two of the 46 PFGE profiles were unique. Only one genotype was detected three times in a river during the year and four genotypes in two different rivers. When compared to animal and human Campylobacter PFGE profiles, 14, 11 and one Campylobacter genotypes from water were genetically closed to human, poultry, and pig Campylobacter genotypes, respectively. The Campylobacter population displayed a high level of genetic diversity, suggesting that contamination originated from various origins. Human, poultry and pig were sources of contamination of the river by Campylobacter. Finally, no Campylobacter were detected in drinking water, indicating that the risk of outbreaks due to consumption of drinking water is low.

Pediatric emergency department visits for diarrheal illness increased after release of undertreated sewage

CONTEXT

Contamination of local waterways may occur through release of partially treated sewage. The Environmental Protection Agency has recently reviewed regulatory standards for this practice. However, the health effects of these events have not been well studied.

OBJECTIVE

Our goal was to identify any increase in visits to a pediatric emergency department for diarrheal illness after sewage bypass into Lake Michigan.

METHODS

The study was conducted as a retrospective, observational time-series analysis in a tertiary care children's hospital emergency department with an annual volume of approximately 45,000 visits. We collected data for 2002-2004 pertaining to the daily number of emergency department visits for children (aged <19 years) for diarrheal illness (using specified International Classification of Diseases, Ninth Edition codes as a reference). Daily diarrheal illness visits were the dependent variable in a time-series model. The primary independent variable was the occurrence of a sewage-bypass event in the 3 to 7 preceding days. Potential confounders included the season and daily rainfall. Separate models were created for visits from people living in zip codes that used Lake Michigan drinking water and those who used other water sources.

RESULTS

Over the 3-year study period, there was a mean of 5.0 +/- 3.8 (SD) daily visits for diarrheal illness from people who lived in zip codes that used Lake Michigan drinking water and 1.2 +/- 1.4 (SD) from outside that area. There were 6 sewage-bypass events identified. After adjusting for the season and rainfall, there was a significant increase of 2.5 to 2.7 visits only from people who lived in zip codes that used Lake Michigan drinking water after the 2 largest of the 6 bypass events.

CONCLUSIONS

Emergency department visits for diarrheal illness increased significantly after 2 events of release of partially treated sewage into area waterways. These data suggest a potentially harmful effect of such practices.

A Waterborne Outbreak of Gastroenteritis with Multiple Etiologies among Resort Island Visitors and Residents: Ohio, 2004

BACKGROUND

The implementation of treated municipal water systems in the 20th century led to a dramatic decrease in waterborne disease in the United States. However, communities with deficient water systems still experience waterborne outbreaks. In August 2004, we investigated an outbreak of gastroenteritis on South Bass Island, Ohio, an island of 900 residents that is visited by >500,000 persons each year.

METHODS

To identify the source of illness, we conducted a case-control study and an environmental investigation. A case was defined as diarrhea in a person who traveled to the island during the period from May 1 through 30 September 2004 and became ill within 2 weeks after the visit. Healthy travel companions served as matched control subjects. We also performed an environmental assessment and extensive testing of island water sources.

RESULTS

Among the 1450 persons reporting illness, Campylobacter jejuni, norovirus, Giardia intestinalis, and Salmonella enterica serotype Typhimurium were identified in 16, 9, 3, and 1 persons, respectively. We interviewed 100 case patients and 117 matched control subjects. Case patients were more likely to drink water on the island than control subjects (68% vs. 35%; matched odds ratio, 4.3; 95% confidence interval, 2.2-9.3). Sampling of ground water wells indicated contamination with multiple fecal microbes, including Escherichia coli, C. jejuni, Salmonella species, and Giardia species. Irregularities in sewage disposal practices that could have contaminated the underground aquifer were noted.

CONCLUSIONS

The combined epidemiological and environmental investigation indicated that sewage-contaminated ground water was the likely source of this large outbreak. Long-term changes to the island's water supply and sewage management infrastructure are needed.

Estimated Numbers of Community Cases of Illness Due to Salmonella, Campylobacter and Verotoxigenic Escherichia Coli: Pathogen-specific Community Rates

OBJECTIVE

To estimate the annual number of cases of illness due to verotoxigenic Escherichia coli (VTEC), Salmonella and Campylobacter in the Canadian population, using data from the National Notifiable Disease registry (NND), estimates of under-reporting derived from several National Studies on Acute Gastrointestinal Illness, and the literature.

METHODS

For each of the three pathogens (VTEC, Salmonella and Campylobacter), data were used to estimate the percentage of cases reported at each step in the surveillance system. The number of reported cases in the NND for each pathogen was then divided by these percentages. In cases where the pathogen-specific estimates were unavailable, data on acute gastrointestinal illness were used, accounting for differences between those with bloody and nonbloody diarrhea.

RESULTS

For every case of VTEC, Salmonella and Campylobacter infection reported in the NND, there were an estimated 10 to 47, 13 to 37, and 23 to 49 cases annually in the Canadian population, respectively.

CONCLUSIONS

The authors estimate that a significant number of infections due to VTEC, Salmonella and Campylobacter occur each year in Canada, highlighting the fact that these enteric pathogens still pose a significant health burden. Recognizing the significant amount of under-reporting is essential to designing appropriate interventions and assessing the impact of these pathogens in the population.

Spatial distribution and registry-based case-control analysis of Campylobacter infections in Denmark, 1991-2001

Using data from an 11-year period (1991-2001), the authors analyzed available information on location of residence for all registered, laboratory-confirmed, domestically acquired cases of campylobacteriosis in Denmark. Patient data were merged with data from a national register on housing and addresses, and a population density index was constructed using the Danish population register. The study was performed as a register-based case-control study; 15 age-matched controls for each case were selected from the national population register. A total of 22,066 cases were compared with 318,958 controls in logistic regression analysis. Living in types of housing found in rural areas and living in areas with a low population density were both associated with an increased risk of infection. This relation concerned children in particular and explained one third of cases among children in the countryside. Furthermore, in some counties there was an association between infection and type of drinking-water company serving the home. This study indicated that contact with animals or the environment is the source of a substantial proportion of sporadic Campylobacter infections in the Danish countryside, particularly among children.

Survival of Campylobacter jejuni in water: effect of grazing by the freshwater crustacean Daphnia carinata (Cladocera)

Environmental studies of the human-pathogenic bacterium Campylobacter jejuni have focused on linking distributions with potential sources. However, in aquatic ecosystems, the abundance of C. jejuni may also be regulated by predation. We examine the potential for grazing by the freshwater planktonic crustacean Daphnia carinata to reduce the survival of C. jejuni. We use a system for measuring grazing and clearance rates of D. carinata on bacteria and demonstrate that D. carinata can graze C. jejuni cells at a rate of 7% individual(-1) h(-1) under simulated natural conditions in the presence of an algal food source. We show that passage of C. jejuni through the Daphnia gut and incorporation into fecal material effectively reduces survival of C. jejuni. This is the first evidence to suggest that grazing by planktonic organisms can reduce the abundance of C. jejuni in natural waters. Biomanipulation of planktonic food webs to enhance Daphnia densities offers potential for reducing microbial pathogen densities in drinking water reservoirs and recreational water bodies, thereby reducing the risk of contracting water-borne disease.