[Cholera]

Spatiotemporal dynamics of cholera in the Democratic Republic of the Congo before and during the implementation of the Multisectoral Cholera Elimination Plan: a cross-sectional study from 2000 to 2021

BACKGROUND

The Democratic Republic of the Congo (DRC) implemented the first strategic Multisectoral Cholera Elimination Plan (MCEP) in 2008-2012. Two subsequent MCEPs have since been implemented covering the periods 2013-2017 and 2018-2021. The current study aimed to assess the spatiotemporal dynamics of cholera over the recent 22-year period to determine the impact of the MCEPs on cholera epidemics, establish lessons learned and provide an evidence-based foundation to improve the implementation of the next MCEP (2023-2027).

METHODS

In this cross-sectional study, secondary weekly epidemiological cholera data covering the 2000-2021 period was extracted from the DRC Ministry of Health surveillance databases. The data series was divided into four periods: pre-MCEP 2003-2007 (pre-MCEP), first MCEP (MCEP-1), second MCEP (MCEP-2) and third MCEP (MCEP-3). For each period, we assessed the overall cholera profiles and seasonal patterns. We analyzed the spatial dynamics and identified cholera risk clusters at the province level. We also assessed the evolution of cholera sanctuary zones identified during each period.

RESULTS

During the 2000-2021 period, the DRC recorded 520,024 suspected cases and 12,561 deaths. The endemic provinces remain the most affected with more than 75% of cases, five of the six endemic provinces were identified as risk clusters during each MCEP period (North Kivu, South Kivu, Tanganyika, Haut-Lomami and Haut-Katanga). Several health zones were identified as cholera sanctuary zones during the study period: 14 health zones during MCEP-1, 14 health zones during MCEP-2 and 29 health zones during MCEP-3. Over the course of the study period, seasonal cholera patterns remained constant, with one peak during the dry season and one peak during the rainy season.

CONCLUSION

Despite the implementation of three MCEPs, the cholera context in the DRC remains largely unchanged since the pre-MCEP period. To better orient cholera elimination activities, the method used to classify priority health zones should be optimized by analyzing epidemiological; water, sanitation and hygiene; socio-economic; environmental and health indicators at the local level. Improvements should also be made regarding the implementation of the MCEP, reporting of funded activities and surveillance of cholera cases. Additional studies should aim to identify specific bottlenecks and gaps in the coordination and strategic efforts of cholera elimination interventions at the local, national and international levels.

Cholera in Pregnancy: A Systematic Review and Meta-Analysis of Fetal, Neonatal, and Maternal Mortality

BACKGROUND

Maternal infection with cholera may negatively affect pregnancy outcomes. The objective of this research is to systematically review the literature and determine the risk of fetal, neonatal and maternal death associated with cholera during pregnancy.

MATERIALS AND METHODS

Medline, Global Health Library, and Cochrane Library databases were searched using the key terms cholera and pregnancy for articles published in any language and at any time before August 2013 to quantitatively summarize estimates of fetal, maternal, and neonatal mortality. 95% confidence intervals (CIs) were calculated for each selected study. Random-effect non-linear logistic regression was used to calculate pooled rates and 95% CIs by time period. Studies from the recent period (1991-2013) were compared with studies from 1969-1990. Relative risk (RR) estimates and 95% CIs were obtained by comparing mortality of selected recent studies with published national normative data from the closest year.

RESULTS

The meta-analysis included seven studies that together involved 737 pregnant women with cholera from six countries. The pooled fetal death rate for 4 studies during 1991-2013 was 7.9% (95% CIs 5.3-10.4), significantly lower than that of 3 studies from 1969-1990 (31.0%, 95% CIs 25.2-36.8). There was no difference in fetal death rate by trimester. The pooled neonatal death rate for 1991-2013 studies was 0.8% (95% CIs 0.0-1.6), and 6.4% (95% CIs 0.0-20.8) for 1969-1990. The pooled maternal death rate for 1991-2013 studies was 0.2% (95% CIs 0.0-0.7), and 5.0% (95% CIs 0.0-16.0) for 1969-1990. Compared with published national mortality estimates, the RR for fetal death of 5.8 (95% CIs 2.9-11.3) was calculated for Haiti (2013), 1.8 (95% CIs 0.3-10.4) for Senegal (2007), and 2.6 (95% CIs 0.5-14.9) for Peru (1991); there were no significant differences in the RR for neonatal or maternal death.

CONCLUSION

Results are limited by the inconsistencies found across included studies but suggest that maternal cholera is associated with adverse pregnancy outcomes, particularly fetal death. These findings can inform a research agenda on cholera in pregnancy and guidance for the timely management of pregnant women with cholera.

The Vibrio cholerae colonization factor GbpA possesses a modular structure that governs binding to different host surfaces

Vibrio cholerae is a bacterial pathogen that colonizes the chitinous exoskeleton of zooplankton as well as the human gastrointestinal tract. Colonization of these different niches involves an N-acetylglucosamine binding protein (GbpA) that has been reported to mediate bacterial attachment to both marine chitin and mammalian intestinal mucin through an unknown molecular mechanism. We report structural studies that reveal that GbpA possesses an unusual, elongated, four-domain structure, with domains 1 and 4 showing structural homology to chitin binding domains. A glycan screen revealed that GbpA binds to GlcNAc oligosaccharides. Structure-guided GbpA truncation mutants show that domains 1 and 4 of GbpA interact with chitin in vitro, whereas in vivo complementation studies reveal that domain 1 is also crucial for mucin binding and intestinal colonization. Bacterial binding studies show that domains 2 and 3 bind to the V. cholerae surface. Finally, mouse virulence assays show that only the first three domains of GbpA are required for colonization. These results explain how GbpA provides structural/functional modular interactions between V. cholerae, intestinal epithelium and chitinous exoskeletons.

Vibrio cholerae is the bacterium that causes cholera, a disease endemic in developing countries with poor sanitation. The bacterium colonizes aquatic organisms that serve as a reservoir of transmission to humans. Our work has focused on GbpA, a protein that is secreted by V. cholerae and appears to facilitate growth of the bacteria both in the human intestine and on the exoskeletons of marine organisms. We show that the protein possesses an unusual three-dimensional structure consisting of four separate domains. Two of the domains are similar to proteins that are known to bind chitin, an exoskeleton biopolymer, and our data show that these domains indeed harbour the chitin binding properties of GbpA. One of these domains is also capable of binding intestinal mucus. The two remaining domains are required for interacting with the bacterium itself, creating a stable interface between the bacterium and the human/marine host, facilitating colonization. Finally, work with a cholera mouse model shows that only the first three domains of GbpA are required for colonization. These results show how GbpA provides structural/functional modular interactions between V. cholerae, the intestinal epithelium and chitinous exoskeletons.

Use of filter paper as a transport medium for laboratory diagnosis of cholera under field conditions

Confirmation of a cholera epidemic is based on bacteriological identification of the agent and requires the sending of samples to a culture laboratory, often in countries with limited resources. Comparison of the use of filter paper with the use of Cary-Blair reference medium for stool transport showed that this simple transport medium is appropriate for the recovery of Vibrio cholerae.