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Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG responses to eight enteropathogens (Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni, norovirus) in cohorts from Haiti, Kenya, and Tanzania. We studied antibody dynamics and force of infection across pathogens and cohorts. Enteropathogens shared common seroepidemiologic features that enabled between-pathogen comparisons of transmission. Overall, exposure was intense: for most pathogens the window of primary infection was <3 years old; for highest transmission pathogens primary infection occurred within the first year. Longitudinal profiles demonstrated significant IgG boosting and waning above seropositivity cutoffs, underscoring the value of longitudinal designs to estimate force of infection. Seroprevalence and force of infection were rank-preserving across pathogens, illustrating the measures provide similar information about transmission heterogeneity. Our findings suggest antibody response can be used to measure population-level transmission of diverse enteropathogens in serologic surveillance.

Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG response to eight enteropathogens ( Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica , enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni , norovirus) using multiplex bead assays in cohorts from Haiti, Kenya, and Tanzania. By age 2 years, most children had evidence of exposure by IgG response to the pathogens studied. We discovered a shift in IgG distributions for many pathogens as children age, caused by boosting and waning from repeated exposures, which complicates interpretation of seroprevalence among older children. Longitudinal profiles revealed important variation in enteropathogen IgG response above seropositivity cutoffs, underscoring the importance of longitudinal designs to estimate seroincidence rates as a measure of force of infection. In longitudinal cohorts there was a linear relationship between seroprevalence and prospective seroincidence rates, suggesting the two measures provide similar information about variation in pathogen transmission.

Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG responses to eight enteropathogens (Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni, norovirus) in cohorts from Haiti, Kenya, and Tanzania. We studied antibody dynamics and force of infection across pathogens and cohorts. Enteropathogens shared common seroepidemiologic features that enabled between-pathogen comparisons of transmission. Overall, exposure was intense: for most pathogens the window of primary infection was <3 years old; for highest transmission pathogens primary infection occurred within the first year. Longitudinal profiles demonstrated significant IgG boosting and waning above seropositivity cutoffs, underscoring the value of longitudinal designs to estimate force of infection. Seroprevalence and force of infection were rank-preserving across pathogens, illustrating the measures provide similar information about transmission heterogeneity. Our findings suggest antibody response can be used to measure population-level transmission of diverse enteropathogens in serologic surveillance.

Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG response to eight enteropathogens ( Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica , enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni , norovirus) using multiplex bead assays in cohorts from Haiti, Kenya, and Tanzania. By age 2 years, most children had evidence of exposure by IgG response to the pathogens studied. We discovered a shift in IgG distributions for many pathogens as children age, caused by boosting and waning from repeated exposures, which complicates interpretation of seroprevalence among older children. Longitudinal profiles revealed important variation in enteropathogen IgG response above seropositivity cutoffs, underscoring the importance of longitudinal designs to estimate seroincidence rates as a measure of force of infection. In longitudinal cohorts there was a linear relationship between seroprevalence and prospective seroincidence rates, suggesting the two measures provide similar information about variation in pathogen transmission.

BackgroundMathematical models predict an exponential distribution of infection prevalence across communities where a disease is disappearing. Trachoma control programs offer an opportunity to test this hypothesis, as the World Health Organization has targeted trachoma for elimination as a public health concern by the year 2020. Local programs may benefit if a single survey could reveal whether infection was headed towards elimination. Using data from a previously-published 2009 survey, we test the hypothesis that Chlamydia trachomatis prevalence across 75 Tanzanian communities where trachoma had been documented to be disappearing is exponentially distributed.Methods/findingsWe fit multiple continuous distributions to the Tanzanian data and found the exponential gave the best approximation. Model selection by Akaike Information Criteria (AICc) suggested the exponential distribution had the most parsimonious fit to the data. Those distributions which do not include the exponential as a special or limiting case had much lower likelihoods of fitting the observed data. 95% confidence intervals for shape parameter estimates of those distributions which do include the exponential as a special or limiting case were consistent with the exponential. Lastly, goodness-of-fit testing was unable to reject the hypothesis that the prevalence data came from an exponential distribution.ConclusionsModels correctly predict that infection prevalence across communities where a disease is disappearing is best described by an exponential distribution. In Tanzanian communities where local control efforts had reduced the clinical signs of trachoma by 80% over 10 years, an exponential distribution gave the best fit to prevalence data. An exponential distribution has a relatively heavy tail, thus occasional high-prevalence communities are to be expected even when infection is disappearing. A single cross-sectional survey may be able to reveal whether elimination efforts are on-track.

BackgroundMathematical models predict an exponential distribution of infection prevalence across communities where a disease is disappearing. Trachoma control programs offer an opportunity to test this hypothesis, as the World Health Organization has targeted trachoma for elimination as a public health concern by the year 2020. Local programs may benefit if a single survey could reveal whether infection was headed towards elimination. Using data from a previously-published 2009 survey, we test the hypothesis that Chlamydia trachomatis prevalence across 75 Tanzanian communities where trachoma had been documented to be disappearing is exponentially distributed.Methods/findingsWe fit multiple continuous distributions to the Tanzanian data and found the exponential gave the best approximation. Model selection by Akaike Information Criteria (AICc) suggested the exponential distribution had the most parsimonious fit to the data. Those distributions which do not include the exponential as a special or limiting case had much lower likelihoods of fitting the observed data. 95% confidence intervals for shape parameter estimates of those distributions which do include the exponential as a special or limiting case were consistent with the exponential. Lastly, goodness-of-fit testing was unable to reject the hypothesis that the prevalence data came from an exponential distribution.ConclusionsModels correctly predict that infection prevalence across communities where a disease is disappearing is best described by an exponential distribution. In Tanzanian communities where local control efforts had reduced the clinical signs of trachoma by 80% over 10 years, an exponential distribution gave the best fit to prevalence data. An exponential distribution has a relatively heavy tail, thus occasional high-prevalence communities are to be expected even when infection is disappearing. A single cross-sectional survey may be able to reveal whether elimination efforts are on-track.

ImportanceThe World Health Organization recommends at least 3 annual mass drug administrations (MDAs) of azithromycin in places where the prevalence of follicular trachoma (FT) is greater than 10%. However, stopping MDA prior to 3 rounds, if monitoring indicates an absence of infection with Chlamydia trachomatis even if FT persists, may be more cost-effective.ObjectiveTo determine the prevalence of infection in communities randomized to 3 rounds of annual MDAs with azithromycin compared with communities randomized to a stopping rule, where MDA could cease if the infection rate was low. DESIGN A 1:1 community randomized trial comparing usual care with a cessation rule. The Partnership for the Rapid Elimination of Trachoma-Ziada Trial was conducted from February 1, 2010, through September 1, 2011.SettingSixteen communities in Tanzania with trachoma prevalence rates between 10% and 20%.ParticipantsA total of 100 children aged 5 years or younger randomly drawn from each community. Children had to reside in an eligible community, have no ocular condition that prevented trachoma grading or ocular specimen collection, and have a guardian who could provide consent for participation.InterventionsCessation of MDA with azithromycin if the community had no infection in their sample at 6 months or 18 months.Main outcome measureThe prevalence of C trachomatis at 18 months.ResultsNone of the intervention communities met criteria to stop MDA based on the 6-month or 18-month survey; all, as well as the usual care communities, were scheduled for a third MDA round. There was no difference in infection (2.9% vs 4.7%; P = .25) between the usual care and cessation rule communities at 18 months.Conclusions and relevanceIn this setting, communities with low (10%-20%) initial prevalence of active trachoma did not have MDA stopped before 3 annual rounds on the basis of monitoring for infection. Infection with C trachomatis in communities with average trachoma rates at 12% to 13% cannot be el