Waterborne outbreak of Campylobacter enteritis after outdoors infantry drill in Utti, Finland

The military as a neglected pathogen transmitter, from the nineteenth century to COVID-19: a systematic review

Background

The risk of outbreaks escalating into pandemics has soared with globalization. Therefore, understanding transmission mechanisms of infectious diseases has become critical to formulating global public health policy. This systematic review assessed evidence in the medical and public health literature for the military as a disease vector.

Methods

We searched 3 electronic databases without temporal restrictions. Two researchers independently extracted study data using a standardized form. Through team discussions, studies were grouped according to their type of transmission mechanism and direct quotes were extracted to generate themes and sub-themes. A content analysis was later performed and frequency distributions for each theme were generated.

Results

Of 6477 studies, 210 met our inclusion criteria and provided evidence, spanning over two centuries (1810–2020), for the military as a pathogen transmitter, within itself or between it and civilians. Biological mechanisms driving transmission included person-to-person transmission, contaminated food and water, vector-borne, and airborne routes. Contaminated food and/or water were the most common biological transmission route. Social mechanisms facilitating transmission included crowded living spaces, unhygienic conditions, strenuous working, training conditions, absent or inadequate vaccination programs, pressure from military leadership, poor compliance with public health advice, contractor mismanagement, high-risk behaviours, and occupation-specific freedom of movement. Living conditions were the most common social transmission mechanism, with young, low ranking military personnel repeatedly reported as the most affected group. Selected social mechanisms, such as employment-related freedom of movement, were unique to the military as a social institution. While few studies explicitly studied civilian populations, considerably more contained information that implied that civilians were likely impacted by outbreaks described in the military.

Conclusions

This study identified features of the military that pose a significant threat to global health, especially to civilian health in countries with substantial military presence or underdeveloped health systems. While biological transmission mechanisms are shared by other social groups, selected social transmission mechanisms are unique to the military. As an increasingly interconnected world faces the challenges of COVID-19 and future infectious diseases, the identified features of the military may exacerbate current and similar challenges and impair attempts to implement successful and equitable global public health policies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41256-021-00232-0.

A systematic review and meta-analysis on the incubation period of Campylobacteriosis

Accurate knowledge of pathogen incubation period is essential to inform public health policies and implement interventions that contribute to the reduction of burden of disease. The incubation period distribution of campylobacteriosis is currently unknown with several sources reporting different times. Variation in the distribution could be expected due to host, transmission vehicle, and organism characteristics, however, the extent of this variation and influencing factors are unclear. The authors have undertaken a systematic review of published literature of outbreak studies with well-defined point source exposures and human experimental studies to estimate the distribution of incubation period and also identify and explain the variation in the distribution between studies. We tested for heterogeneity using I 2 and Kolmogorov-Smirnov tests, regressed incubation period against possible explanatory factors, and used hierarchical clustering analysis to define subgroups of studies without evidence of heterogeneity. The mean incubation period of subgroups ranged from 2·5 to 4·3 days. We observed variation in the distribution of incubation period between studies that was not due to chance. A significant association between the mean incubation period and age distribution was observed with outbreaks involving only children reporting an incubation of 1·29 days longer when compared with outbreaks involving other age groups.

Risk Factors for Sporadic Domestically Acquired Campylobacter Infections in Norway 2010-2011: A National Prospective Case-Control Study

Background

Campylobacteriosis is the most frequently reported food- and waterborne infection in Norway. We investigated the risk factors for sporadic Campylobacter infections in Norway in order to identify areas where control and prevention measures could be improved.

Methods

A national prospective case-control study of factors associated with Campylobacter infection was conducted from July 2010 to September 2011. Cases were recruited from the Norwegian Surveillance System of Communicable Diseases (MSIS). Controls were randomly selected from the Norwegian Population Registry. Cases and controls were mailed a paper questionnaire with a prepaid return envelope. Univariable analyses using logistic regression were conducted for all exposures. A final parsimonious multivariable model was developed using regularized/penalized logistic regression, and adjusted odds ratios were calculated.

Results

A total of 995 cases and 1501 controls were included in the study (response proportion 55% and 30%, respectively). Exposures that had significant increases in odds of Campylobacter infection in multivariable analysis were drinking water directly from river, stream, or lake (OR: 2.96), drinking purchased bottled water (OR: 1.78), eating chicken (1.69), eating meat that was undercooked (OR: 1.77), eating food made on a barbecue (OR: 1.55), living on a farm with livestock (OR: 1.74), having a dog in the household (OR: 1.39), and having household water supply serving fewer than 20 houses (OR: 1.92).

Conclusions

Consumption of poultry and untreated water remain important sources of Campylobacter infection in Norway, despite ongoing control efforts. The results justify the need for strengthening education for consumers and food handlers about the risks of cross-contamination when preparing poultry and with consuming raw or undercooked chicken. The public should also be reminded to take precautions when drinking untreated water in nature and ensure continued vigilance in order to protect and maintain the quality of water from small-scale water supply systems.

Environmental determinants of campylobacteriosis risk in Philadelphia from 1994 to 2007

Campylobacter species infections are a common cause of acute gastroenteritis, and may uncommonly be complicated by renal, neurological, and rheumatologic sequelae. Although excess summertime campylobacteriosis has been observed, environmental mechanisms driving disease seasonality are poorly understood. We sought to evaluate the relationship between environmental factors and campylobacteriosis risk in a major North American metropolitan area. We evaluated 1532 cases of campylobacteriosis reported in Philadelphia between 1994 and 2007. We constructed Poisson regression models with oscillatory smoothers, and also used case-crossover design, to evaluate the associations between environmental exposures and disease risk on weekly and daily time scales. Both methods control for confounding by seasonally oscillating environmental factors. Incidence was greatest in June and July, with annual periodicity. Weekly incidence was associated with increasing relative humidity, (incidence rate ratio (IRR) per % 1.017, 95% CI 1.008-1.025), temperature (IRR per degrees C 1.041, 95% CI 1.011-1.072), and decreasing Delaware River temperature during the same week (IRR per degrees C 0.922, 95% CI 0.883-0.962), and at 4-week lags (IRR per degrees C 0.953, 95% CI 0.919-0.990). No acute associations were identified in case-crossover analyses. Our findings affirm the summertime seasonality of campylobacteriosis in Philadelphia, and the link between warm, humid weather and disease risk. However, the link between low river temperatures and enhanced campylobacteriosis risk in humans described here is novel, consistent with known links between watershed temperature and Campylobacter survival, and implicates local watersheds as epidemiologically important reservoirs for foodborne pathogens.

A community outbreak of Campylobacter jejuni infection from a chlorinated public water supply

An outbreak of Campylobacter jejuni infection occurred in a South Wales Valleys housing estate. Illness in estate residents was associated with tap water consumption [population attributable risk (PAR) 50%, relative risk (RR) 2.53, 95% confidence interval (CI) 1.9-3.37] and residence in the upper estate (PAR 49%, RR 2.44, 95% CI 1.83-3.24). Amongst upper estate residents, rates of diarrhoeal illness increased with rates of water consumption (OR 18, 95% CI 3.5-92.4 for heaviest consumers, chi2 trend P<0.0001). The upper estate received mains water via a covered holding reservoir. A crack in the wall of the holding reservoir was identified. Contamination with surface water from nearby pasture land was the likely cause of this outbreak. Service reservoirs are common in rural communities and need regular maintenance and inspection. The role of water in sporadic cases of campylobacter enteritis may be underestimated.

Campylobacter jejuni multilocus sequence types in humans, northwest England, 2003-2004

MLST can be used to describe and analyze the epidemiology of campylobacteriosis in distinct human populations.

Detailed understanding of the epidemiology of Campylobacter is increasingly facilitated through use of universal and reproducible techniques for accurate strain differentiation and subtyping. Multilocus sequence typing (MLST) enables discriminatory subtyping and grouping of isolate types into genetically related clonal complexes; it also has the advantage of ease of application and repeatability. Recent studies suggest that a measure of host association may be distinguishable with this system. We describe the first continuous population-based survey to investigate the potential of MLST to resolve questions of campylobacteriosis epidemiology. We demonstrate the ability of MLST to identify variations in the epidemiology of campylobacteriosis between distinct populations and describe the distribution of key subtypes of interest.

A robotic DNA purification protocol and real-time PCR for the detection of Campylobacter jejuni in foods

Primers designed to amplify a Campylobacter jejuni cadF gene sequence were used in an SYBR Green I real-time PCR assay as an alternative to conventional bacteriological methods for the rapid detection of C. jejuni in foods. Twenty-five grams of chicken skin (breast and thigh) was contaminated by adding approximately 1, 10, or 50 CFU of C. jejuni ATCC 35560. Twenty-five grams of pork and 25-ml aliquots of milk were also inoculated with 1 and 10 CFU of the pathogen. The samples were incubated in Bolton broth for different periods at 37 and 42 degrees C under microaerophilic conditions. Using a commercial robotic DNA purification system, DNA was extracted and purified from 1-ml aliquots of the enrichment cultures before and after centrifugation of the 250-ml enrichment broth at 15,900 x g for 10 min at 4 degrees C. The DNA was used as the template in a real-time PCR assay. C. jejuni was detected after 12 h of enrichment from samples inoculated with about 50 CFU/25-g sample. After centrifugation, an enrichment step of 8 h was sufficient to allow detection of pathogen in samples inoculated with 10 CFU/25 g. However, 24 h of enrichment was necessary to detect pathogen in samples inoculated with approximately 1 CFU/25 g. The real-time PCR protocol developed in this study significantly reduced the detection time of C. jejuni in foods.

Risk factors associated with Campylobacter jejuni infections in Curaçao, Netherlands Antilles

A steady increase in the incidence of Guillain-Barré syndrome (GBS) with a seasonal preponderance, almost exclusively related to Campylobacter jejuni, and a rise in the incidence of laboratory-confirmed Campylobacter enteritis have been reported from Curaçao, Netherlands Antilles. We therefore investigated possible risk factors associated with diarrhea due to epidemic C. jejuni. Typing by pulsed-field gel electrophoresis identified four epidemic clones which accounted for almost 60% of the infections. One hundred six cases were included in a case-control study. Infections with epidemic clones were more frequently observed in specific districts in Willemstad, the capital of Curaçao. One of these clones caused infections during the rainy season only and was associated with the presence of a deep well around the house. Two out of three GBS-related C. jejuni isolates belonged to an epidemic clone. The observations presented point toward water as a possible source of Campylobacter infections.

Campylobacter spp., Giardia spp., Cryptosporidium spp., noroviruses, and indicator organisms in surface water in southwestern Finland, 2000-2001

A total of 139 surface water samples from seven lakes and 15 rivers in southwestern Finland were analyzed during five consecutive seasons from autumn 2000 to autumn 2001 for the presence of various enteropathogens (Campylobacter spp., Giardia spp., Cryptosporidium spp., and noroviruses) and fecal indicators (thermotolerant coliforms, Escherichia coli, Clostridium perfringens, and F-RNA bacteriophages) and for physicochemical parameters (turbidity and temperature); this was the first such systematic study. Altogether, 41.0% (57 of 139) of the samples were positive for at least one of the pathogens; 17.3% were positive for Campylobacter spp. (45.8% of the positive samples contained Campylobacter jejuni, 25.0% contained Campylobacter lari, 4.2% contained Campylobacter coli, and 25.0% contained Campylobacter isolates that were not identified), 13.7% were positive for Giardia spp., 10.1% were positive for Cryptosporidium spp., and 9.4% were positive for noroviruses (23.0% of the positive samples contained genogroup I and 77.0% contained genogroup II). The samples were positive for enteropathogens significantly (P < 0.05) less frequently during the winter season than during the other sampling seasons. No significant differences in the prevalence of enteropathogens were found when rivers and lakes were compared. The presence of thermotolerant coliforms, E. coli, and C. perfringens had significant bivariate nonparametric Spearman's rank order correlation coefficients (P < 0.001) with samples that were positive for one or more of the pathogens analyzed. The absence of these indicators in a logistic regression model was found to have significant predictive value (odds ratios, 1.15 x 10(8), 7.57, and 2.74, respectively; P < 0.05) for a sample that was negative for the pathogens analyzed. There were no significant correlations between counts or count levels for thermotolerant coliforms or E. coli or the presence of F-RNA phages and pathogens in the samples analyzed.

Detection and typing of Campylobacter jejuni and Campylobacter coli and analysis of indicator organisms in three waterborne outbreaks in Finland

Waterborne outbreaks associated with contamination of drinking water by Campylobacter jejuni are rather common in the Nordic countries Sweden, Norway, and Finland, where in sparsely populated districts groundwater is commonly used without disinfection. Campylobacters, Escherichia coli, or other coliforms have rarely been detected in potential sources. We studied three waterborne outbreaks in Finland caused by C. jejuni and used sample volumes of 4,000 to 20,000 ml for analysis of campylobacters and sample volumes of 1 to 5,000 ml for analysis of coliforms and E. coli, depending on the sampling site. Multiple samples obtained from possible sources (water distribution systems and environmental water sources) and the use of large sample volumes (several liters) increased the chance of detecting the pathogen C. jejuni in water. Filtration of a large volume (1,000 to 2,000 ml) also increased the rate of detection of coliforms and E. coli. To confirm the association between drinking water contamination and illness, a combination of Penner serotyping and pulsed-field gel electrophoresis (digestion with SmaI and KpnI) was found to be useful. This combination reliably verified similarity or dissimilarity of C. jejuni isolates from patient samples, from drinking water, and from other environmental sources, thus confirming the likely reservoir of an outbreak.

Prevalence of thermophilic Campylobacter spp. in ready-to-eat foods and raw poultry in Northern Ireland

Although there have been numerous studies investigating the prevalence of campylobacters in animals and raw meats, there are limited data on the persistence of these organisms in ready-to-eat (RTE) foodstuffs. Although poultry is now well established as a major reservoir of thermophilic campylobacters, it is widely assumed that hazard analysis critical control point (HACCP) controls in commercial and industrial settings are effective in eliminating this hazard through thorough cooking of RTE products. Therefore, it was the primary aim of this study to investigate the effectiveness of HACCP controls in eliminating campylobacters in such cooked RTE foods by attempting to isolate viable organisms from product. Concurrently, the results of this study demonstrate that local poultry is highly contaminated with campylobacters. Commercially available RTE foodstuffs (n = 2,030) consisting of 1,061 poultry-related cooked products and 969 other products were analyzed and were not found to contain thermophilic Campylobacter spp. In addition, 107 raw chickens (63 fresh birds and 44 frozen birds) were sampled, and 94% of the fresh birds and 77% of the frozen birds examined were demonstrated to be contaminated with campylobacters, with Campylobacter jejuni, Campylobacter coli, and Campylobacter lari accounting for 69, 30, and 1% of the contaminating organisms, respectively. In general, commercially available RTE foodstuffs, including cooked poultry, are not commonly contaminated with campylobacters and thus do not appear to represent a significant cause of clinical infection of Campylobacter spp. in Northern Ireland. However, raw poultry produce, including fresh and frozen chicken, frequently tested positive for campylobacters. Implementation of HACCP systems by food processors will help to minimize and/or eliminate the risk posed by this organism to the consumer.

Detection of Campylobacter jejuni and Campylobacter coli in environmental waters by PCR enzyme-linked immunosorbent assay

A PCR enzyme-linked immunosorbent assay (ELISA) assay was applied to the detection of Campylobacter jejuni and Campylobacter coli in environmental water samples after enrichment culture. Bacterial cells were concentrated from 69 environmental water samples by using filtration, and the filtrates were cultured in Campylobacter blood-free broth. After enrichment culture, DNA was extracted from the samples by using a rapid-boiling method, and the DNA extracts were used as a template in a PCR ELISA assay. A total of 51 samples were positive by either PCR ELISA or culture; of these, 43 were found to be positive by PCR ELISA and 43 were found to be positive by culture. Overall, including positive and negative results, 59 samples were concordant in both methods. Several samples were positive in the PCR ELISA assay but were culture negative; therefore, this assay may be able to detect sublethally damaged or viable nonculturable forms of campylobacters. The method is rapid and sensitive, and it significantly reduces the time needed for the detection of these important pathogens by 2 to 3 days.

Water as a reservoir for Campylobacter jejuni infection in cows studied by serotyping and pulsed-field gel electrophoresis (PFGE)

The occurrence of campylobacters was studied in the faecal samples of a dairy herd with about 20 animals and in the lake which was their source of drinking water during the grazing period from June to September. Of the total of 141 faecal samples studied, 0-21% were found to be positive for C. jejuni at various sampling times throughout the year. More cows were found to be campylobacter-positive in summer or in autumn after the grazing period than after the winter, when the animals were inside and their drinking water source was municipal chlorinated tap water. C. jejuni was isolated from most of the lake water samples. Serotyping with heat stable antigens and molecular typing with PFGE using SacII- and SmaI-digested DNA revealed that an animal that was permanently infected with C. jejuni sero-/PFGE-type PEN 0:6, 25/I/ND most probably contaminated the lake water in summer 1987. This was the only sero/PFGE-type isolated from the lake water in summer and autumn 1987 and in spring 1988. This sero/PFGE-type was also isolated from four other cows in autumn 1987, suggesting that lake water was the source of the infection. This study is first to employ molecular methods to assess the possible role of contaminated drinking water in the transmission of campylobacter infection within a dairy herd.

Water-borne Campylobacter jejuni infection in a Danish town---a 6-week continuous source outbreak

OBJECTIVE: To determine the cause and characteristics of illness of a Campylobacter jejuni outbreak in Denmark in 1995--96. METHODS: A retrospective follow-up study was designed for culture-confirmed cases and for residents without a bacteriologic diagnosis. Stored clinical and environmental isolates were analyzed by serotyping and genotyping with restriction endonuclease analysis (REA), pulsed-field gel electrophoresis (PFGE) and ribotyping. RESULTS: Campylobacter jejuni was isolated from 110 residents and visitors to the area. However, an estimate based on a telephone survey indicated that some 2400 people were affected by the outbreak. Water samples obtained from the community waterworks contained Campylobacter jejuni serotype O2, the same serotype as in all but one of the 30 stored isolates from the outbreak. The water and clinical isolates also showed the same DNA profile, except for the single strain showing the distinct serotype. The contamination of the water supply was traced back to contamination of ground water due to a break in a sewage pipe. CONCLUSIONS: A retrospective and demographic epidemiologic investigation of both culture-confirmed and non-culture-confirmed cases in the town combined with typing of the isolates was crucial in defining the extent and cause of the outbreak.

Assessment of the dose-response relationship of Campylobacter jejuni

Mathematical relations describing the risk of infection after exposure to enteropathogens are important tools for the evaluation of the potential health risk from exposure via food and water. A quantitative description of the dose-response relation for Campylobacter jejuni with the Beta-Poisson model was fitted to experimental data of infection with Campylobacter jejuni (as determined by shedding of C. jejuni) obtained in human feeding studies performed by Black et al. (1988). The maximum likelihood estimates for the Beta-Poisson model parameters based on these data are: alpha = 0.145 and beta = 7.59. The fit of the model on the experimental data was good: the difference between the likelihood obtained with the Beta-Poisson model and the maximum possible likelihood was not significant. The occurrence of symptoms of intestinal illness did not follow a similar dose-related trend. Overall, 22% of the infected volunteers developed symptoms (diarrhea, fever). The highest illness-to-infection ratio was found at an intermediate dose (9 x 10(4)). The dose-response relation and the illness-to-infection ratio appeared to differ between different C. jejuni isolates. The dose-response relation derived from feeding studies with a single isolate should therefore be considered indicative. The absence of experimental data in the low dose range resulted in a relatively large confidence interval at low doses. However, in cases where the dose-response relation has been applied so far to estimate the health risk of exposure to C. jejuni in water, the uncertainty in the dose-response relation was insignificant compared to the uncertainty in the exposure estimate.

Antibiotic susceptibility of campylobacter isolates from sewage and poultry abattoir drain water

In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11-18% quinolone resistance for SPB isolates to 17-33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.

Food-borne bacterial infections

The number of episodes of diseases caused by bacterial contamination of food has shown a real increase by about threefold in the last decade in the U.K. The numbers for 1992 are estimated to be 2 million. The causes are multifactorial and complex, and 4 representative pathogens are reviewed. The main increase in diseases due to salmonella has been caused by Salmonella enteritidis, especially from eggs. The commonest bacterial food pathogen is campylobacter, which causes an illness with specific season peaks in May and June. This may be related to the activities of birds and mammals. Both these bacteria cause common diseases that are rarely fatal. In contrast, Listeria and E. coli are ubiquitous but rarely produce disease; however, the consequences of any such illness are often dire. Procedures and techniques are available for the control of most of these diseases, but society does not seem determined to implement them.

Survey of thermotolerant Campylobacter spp. and Yersinia spp. in three surface water sources in Norway

We investigated the occurrence of thermotolerant Campylobacter and Yersinia spp. in three surface water sources in Norway which represented different levels of pollution and eutrophication. Samples were collected every fortnight during a 14-month period. In addition, samples from 100 private wells were examined for campylobacters only. Campylobacter was recovered from 42 (43.8%) of the 96 samples of surface water, whereas Yersinia spp. were isolated from four (4.2%) of the samples. Campylobacter was not isolated from the well water samples. The highest isolation rate of Campylobacter was obtained from the two most polluted water sources. The proportion of positive samples was significantly higher in the autumn (71.4%) than in the spring (36.4%) or summer (22.2%). The highest overall isolation rate was obtained at water temperatures ranging from 2.1 to 8.0 degrees C, and the lowest at temperatures greater than 15 degrees C. Logistic regression analysis showed a highly significant relationship between the prevalence of Campylobacter and the number of three types of indicator bacteria: faecal coliforms, faecal streptococci and sulphite-reducing clostridia. Of the 60 Campylobacter isolates obtained, 51.7% belonged to C. jejuni biotype 1, 20.0% belonged to C. jejuni biotype 2, 21.7% to C. coli, 3.3% to C. lari and 3.3% were non-typable. All four Yersinia isolates were non-pathogenic variants.

Survival of Escherichia coli and Campylobacter jejuni in untreated and filtered lake water

The survival of Campylobacter jejuni and Escherichia coli in lake water was studied using viable counts. Escherichia coli survived better than C. jejuni in all the test conditions studied. Both the species survived better in filtered than in untreated water. This suggests that predation and/or competition for nutrients affect the survival of both the species in an aquatic environment. Campylobacter jejuni survived less well in filtered autoclaved water and in 0.9% NaCl than in filtered water without autoclaving. The lack of some essential nutrients, which may be degraded by autoclaving, might explain these results.

Thermophilic campylobacters in surface waters around Lancaster, UK: negative correlation with Campylobacter infections in the community

The incidence of campylobacter enteritis in Lancaster City Health Authority is three times the UK average for similar sizes of population and has marked seasonal peaks in May and June. Environmental monitoring of surface waters around Lancaster showed that thermophilic campylobacters were absent from drinking water from the fells and from the clean upper reaches of the River Conder but were present in the main rivers entering Morecambe Bay, the lower reaches of the River Conder, the Lancaster canal, and seawater from the Lune estuary and Morecambe Bay. All the surface waters tested showed the same seasonality, namely, higher numbers in the winter months and low numbers or none in May, June and July. The absence of thermophilic campylobacters in the summer months may be due to high sunshine levels because experiments on the effects of light showed that campylobacters in sewage effluent and seawater were eliminated within 60 and 30 min of daylight respectively but survived for 24 h in darkness. As the concentrations of campylobacters in surface waters were at their lowest precisely at the time of peak infections in the community it is unlikely that surface waters form Lancaster's reservoir of campylobacter infection for the community.