Study of the epidemic significance of noncultivated forms of Vibrio cholerae by the polymerase chain reaction]

A specific method of the isolation of the cholera toxin gene by the directional amplification of DNA in the polymerase chain reaction (PCR) has been developed. The product of this reaction has a molecular weight of 440 sequence pairs and is a DNA fragment located on the A-subunit of V. cholerae gene vct. The sensitivity of the method permits the detection of one bacterial cell in the reaction mixture. The method is effective when V. cholerae purified DNA, cell lysates and the DNA of total microflora isolated from the water of natural springs are used. The study of water samples from natural water bodies by the method of PRC has revealed cholera toxin genes of V. cholerae noncultivated forms ni 5 out of 7 water samples taken from natural water bodies at the regions of Azerbaijan endemic for cholera and made it possible to evaluate the number of V. cholerae. The prospects of using PCR for the control of the epidemiological situation in regions endemic for cholera are discussed.     

Organization of ganglioside GM1 in phosphatidylcholine bilayers

Molecules of the ganglioside GM1 are randomly distributed in liquid-crystalline 1-palmitoyl-2-oleoyl phosphatidylcholine bilayers. This conclusion is based on a freeze-etch electron microscopic study using ferritin-conjugated cholera toxin and cholera toxin alone as ganglioside labels. The average number of GM1 molecules under a label is calculated by a novel method from the dependence of the fraction of bilayer area covered by the label on the mole fraction of GM1 in the bilayer.     

In Vitro and In Vivo Studies of Streptomycin-Dependent Cholera Vibrios

Streptomycin-dependent cholera vibrio strains were derived from Inaba, Ogawa, and NAG vibrios by the method of Mel. These phenotypes grew more slowly and attacked fermentable substances after a longer period of time than the streptomycin-sensitive parent strains. Rabbits injected with streptomycin-sensitive strains and their streptomycin-dependent forms showed homologous agglutinin production. Patas monkeys fed with 10(9) streptomycin-dependent strains shed them for 1 to 2 days without ill effect, whereas the same number of streptomycin-independent organisms caused disease. The possibility of the application of multiple doses of streptomycin-dependent organisms in oral immunization against cholera was considered.     

The case for reactive mass oral cholera vaccinations

Introduction

The outbreak of cholera in Zimbabwe intensified interest in the control and prevention of cholera. While there is agreement that safe water, sanitation, and personal hygiene are ideal for the long term control of cholera, there is controversy about the role of newer approaches such as oral cholera vaccines (OCVs). In October 2009 the Strategic Advisory Group of Experts advised the World Health Organization to consider reactive vaccination campaigns in response to large cholera outbreaks. To evaluate the potential benefit of this pivotal change in WHO policy, we used existing data from cholera outbreaks to simulate the number of cholera cases preventable by reactive mass vaccination.

Methods

Datasets of cholera outbreaks from three sites with varying cholera endemicity—Zimbabwe, Kolkata (India), and Zanzibar (Tanzania)—were analysed to estimate the number of cholera cases preventable under differing response times, vaccine coverage, and vaccine doses.

Findings

The large cholera outbreak in Zimbabwe started in mid August 2008 and by July 2009, 98,591 cholera cases had been reported with 4,288 deaths attributed to cholera. If a rapid response had taken place and half of the population had been vaccinated once the first 400 cases had occurred, as many as 34,900 (40%) cholera cases and 1,695 deaths (40%) could have been prevented. In the sites with endemic cholera, Kolkata and Zanzibar, a significant number of cases could have been prevented but the impact would have been less dramatic. A brisk response is required for outbreaks with the majority of cases occurring during the early weeks. Even a delayed response can save a substantial number of cases and deaths in long, drawn-out outbreaks. If circumstances prevent a rapid response there are good reasons to roll out cholera mass vaccination campaigns well into the outbreak. Once a substantial proportion of a population is vaccinated, outbreaks in subsequent years may be reduced if not prevented. A single dose vaccine would be of advantage in short, small outbreaks.

Conclusions

We show that reactive vaccine use can prevent cholera cases and is a rational response to cholera outbreaks in endemic and non-endemic settings. In large and long outbreaks a reactive vaccination with a two-dose vaccine can prevent a substantial proportion of cases. To make mass vaccination campaigns successful, it would be essential to agree when to implement reactive vaccination campaigns and to have a dynamic and determined response team that is familiar with the logistic challenges on standby. Most importantly, the decision makers in donor and recipient countries have to be convinced of the benefit of reactive cholera vaccinations.     

Cholera Epidemics,War and Disasters around Goma and Lake Kivu: An Eight-Year Survey

Background

During the last eight years, North and South Kivu, located in a lake area in Eastern Democratic Republic of Congo, have been the site of a major volcano eruption and of numerous complex emergencies with population displacements. These conditions have been suspected to favour emergence and spread of cholera epidemics.

Methodology/Principal Findings

In order to assess the influence of these conditions on outbreaks, reports of cholera cases were collected weekly from each health district of North Kivu (4,667,699 inhabitants) and South Kivu (4,670,121 inhabitants) from 2000 through 2007. A geographic information system was established, and in each health district, the relationships between environmental variables and the number of cholera cases were assessed using regression techniques and time series analysis. We further checked for a link between complex emergencies and cholera outbreaks. Finally, we analysed data collected during an epidemiological survey that was implemented in Goma after Nyiragongo eruption. A total of 73,605 cases and 1,612 deaths of cholera were reported. Time series decomposition showed a greater number of cases during the rainy season in South Kivu but not in North Kivu. Spatial distribution of cholera cases exhibited a higher number of cases in health districts bordering lakes (Odds Ratio 7.0, Confidence Interval range 3.8–12.9). Four epidemic reactivations were observed in the 12-week periods following war events, but simulations indicate that the number of reactivations was not larger than that expected during any random selection of period with no war. Nyiragongo volcanic eruption was followed by a marked decrease of cholera incidence.

Conclusion/Significance

Our study points out the crucial role of some towns located in lakeside areas in the persistence of cholera in Kivu. Even if complex emergencies were not systematically followed by cholera epidemics, some of them enabled cholera spreading.     

Global microbial ecology: biogeography and diversity of Vibrios as a model

An environmental source of cholera was hypothesized as early as the late nineteenth century by Robert Koch, but not proven because of the ability of Vibrio cholera, the causative agent of cholera, to enter a dormant phase between epidemics. Standard bacteriological procedures for isolation of the vibrios from the environmental samples, including water, between epidemics generally were unsuccessful. Vibrio cholera, a marine vibrio requiring salt for growth, enters into a dormant 'viable but non-culturable' stage when conditions are unfavourable for growth and reproduction. The association of V. cholera with plankton, notably copepods, provides evidence for the environmental origin of cholera, as well as an explanation for the sporadic and erratic nature of cholera epidemics. Thus, the association of V. cholera with plankton was established only recently, allowing analysis of epidemic patterns of cholera, especially in those countries where cholera is endemic. The sporadic and erratic nature of cholera epidemics can now be related to climate and climate events, such as El Ni?o. Since zooplankton have been shown to harbour the bacterium and zooplankton blooms follow phytoplankton blooms, remote sensing can be employed to determine the relationship of cases of cholera with chlorophyll, as well as sea surface temperature (SST), ocean height, and turbidity. Cholera occurs seasonally in Bangladesh with two annual peaks in the number of cases occurring each year. From the data obtained and analysed to date, when the height of the ocean is high and sea surface temperature is also elevated, cholera cases are numerous. When the height is low and sea surface temperature is also low, little or no cholera is recorded. From the examination of data for the 1992-1993 cholera epidemic in India, preliminary comparisons of cholera data for Calcutta show a similar relationship between cholera cases, ocean height and SST. In conclusion, from results of studies of SST, phytoplankton and zooplankton, and their relationships to incidence of cholera, correlation of selected climatological factors and incidence of V. cholera appears to be significant, bringing the potential of predicting conditions conducive to cholera outbreaks closer to reality.     

An Optimal Cost Effectiveness Study on Zimbabwe Cholera Seasonal Data from 2008–2011

Incidence of cholera outbreak is a serious issue in underdeveloped and developing countries. In Zimbabwe, after the massive outbreak in 2008–09, cholera cases and deaths are reported every year from some provinces. Substantial number of reported cholera cases in some provinces during and after the epidemic in 2008–09 indicates a plausible presence of seasonality in cholera incidence in those regions. We formulate a compartmental mathematical model with periodic slow-fast transmission rate to study such recurrent occurrences and fitted the model to cumulative cholera cases and deaths for different provinces of Zimbabwe from the beginning of cholera outbreak in 2008–09 to June 2011. Daily and weekly reported cholera incidence data were collected from Zimbabwe epidemiological bulletin, Zimbabwe Daily cholera updates and Office for the Coordination of Humanitarian Affairs Zimbabwe (OCHA, Zimbabwe). For each province, the basic reproduction number () in periodic environment is estimated. To the best of our knowledge, this is probably a pioneering attempt to estimate in periodic environment using real-life data set of cholera epidemic for Zimbabwe. Our estimates of agree with the previous estimate for some provinces but differ significantly for Bulawayo, Mashonaland West, Manicaland, Matabeleland South and Matabeleland North. Seasonal trend in cholera incidence is observed in Harare, Mashonaland West, Mashonaland East, Manicaland and Matabeleland South. Our result suggests that, slow transmission is a dominating factor for cholera transmission in most of these provinces. Our model projects cholera cases and cholera deaths during the end of the epidemic in 2008–09 to January 1, 2012. We also determine an optimal cost-effective control strategy among the four government undertaken interventions namely promoting hand-hygiene & clean water distribution, vaccination, treatment and sanitation for each province.     

Is HIV infection associated with an increased risk for cholera? Insights from a mathematical model

Cholera, a waterborne gastroenteric infection, remains a significant threat to public health in sub-Saharan Africa, the region most heavily affected by HIV. It is biologically plausible that immune suppression caused by HIV infection predisposes to cholera. In this paper, a simple mathematical model is developed and comprehensively analyzed to assess whether HIV infection is associated with an increased risk for cholera or not. Analytical results of the model show that the quantities R(c) and R(h), which represents the reproductive number for cholera and HIV infection, respectively, provide threshold conditions that determine cumulative new single and dual infection cases. These threshold conditions can be used to gain important insights on the epidemiological consequences of HIV and cholera coexistence in the community. Numerical results are provided to support the analytical findings. The findings suggest that in a cholera-endemic area, HIV infection is associated with an increased risk for cholera.     

Historical Epidemiology of the Second Cholera Pandemic: Relevance to Present Day Disease Dynamics

Despite nearly two centuries of study, the fundamental transmission dynamic properties of cholera remain incompletely characterized. We used historical time-series data on the spread of cholera in twelve European and North American cities during the second cholera pandemic, as reported in Amariah Brigham’s 1832 A Treatise on Epidemic Cholera, to parameterize simple mathematical models of cholera transmission. Richards growth models were used to derive estimates of the basic reproductive number (R₀) (median: 16.0, range: 1.9 to 550.9) and the proportion of unrecognized cases (mean: 96.3%, SD: 0.04%). Heterogeneity in model-generated R₀ estimates was consistent with variability in cholera dynamics described by contemporary investigators and may represent differences in the nature of cholera spread. While subject to limitations associated with measurement and the absence of microbiological diagnosis, historical epidemic data are a potentially rich source for understanding pathogen dynamics in the absence of control measures, particularly when used in conjunction with simple and readily interpretable mathematical models.     

The Burden of Cholera in Uganda

Introduction

In 2010, the World Health Organization released a new cholera vaccine position paper, which recommended the use of cholera vaccines in high-risk endemic areas. However, there is a paucity of data on the burden of cholera in endemic countries. This article reviewed available cholera surveillance data from Uganda and assessed the sufficiency of these data to inform country-specific strategies for cholera vaccination.

Methods

The Uganda Ministry of Health conducts cholera surveillance to guide cholera outbreak control activities. This includes reporting the number of cases based on a standardized clinical definition plus systematic laboratory testing of stool samples from suspected cases at the outset and conclusion of outbreaks. This retrospective study analyzes available data by district and by age to estimate incidence rates. Since surveillance activities focus on more severe hospitalized cases and deaths, a sensitivity analysis was conducted to estimate the number of non-severe cases and unrecognized deaths that may not have been captured.

Results

Cholera affected all ages, but the geographic distribution of the disease was very heterogeneous in Uganda. We estimated that an average of about 11,000 cholera cases occurred in Uganda each year, which led to approximately 61–182 deaths. The majority of these cases (81%) occurred in a relatively small number of districts comprising just 24% of Uganda''s total population. These districts included rural areas bordering the Democratic Republic of Congo, South Sudan, and Kenya as well as the slums of Kampala city. When outbreaks occurred, the average duration was about 15 weeks with a range of 4–44 weeks.

Discussion

There is a clear subdivision between high-risk and low-risk districts in Uganda. Vaccination efforts should be focused on the high-risk population. However, enhanced or sentinel surveillance activities should be undertaken to better quantify the endemic disease burden and high-risk populations prior to introducing the vaccine.     

Cholera Threat to Humans in Ghana Is Influenced by Both Global and Regional Climatic Variability

Cholera, an acute diarrheal illness, is caused by infection of the intestine with the bacterium Vibrio cholerae after ingestion of contaminated water or food. The disease had disappeared from most of the developed countries in the last 50 years, but cholera epidemics remain a major public health problem in many developing countries, most often localized in tropical areas. Cholera is an infectious disease for which a relationship between disease temporal patterns and climate has been demonstrated, but only in an endemic context and for local areas of Asia and South America. Until now, similar studies have not been done in an epidemic context, on the African continent, although the largest number of cholera cases has been reported for those countries by the World Health Organization. The wavelet method was used in order to explore periodicity in (i) a long-time monthly cholera incidence in Ghana, West Africa, (ii) proxy environmental variables, and (iii) climatic indices time series, from 1975 to 1995. Cross-analysis were done to explore links between these time series, i.e., between cholera and climate. Results showed strong statistical association (coherency) from the end of the 1980s, between cholera outbreak resurgences in Ghana and the climatic/environmental parameters under scrutiny. Further examination of the existence of common spatial and temporal patterns in infectious diseases on the continent of Africa will permit development of more effective treatment of disease.     

Identification of Hog Cholera Viral Antigen by Immunofluorescence. Application as a Diagnostic and Assay Method

In the absence of detectable cytologic changes in hog cholera virus-infected tissue culture cells, hog cholera viral antigen was readily detected by immunofluorescence. The ability to detect hog cholera viral antigen by this method allowed for determination of infectivity titers and also for titration of homologous antibody. Immunofluorescence made possible the identification, in tissue culture, of hog cholera virus from blood, serum, and spleen extracts of experimentally infected swine. Further applications of this method and its limitations are being investigated.     

The Role of Socioeconomic Status in Longitudinal Trends of Cholera in Matlab,Bangladesh, 1993–2007

There has been little evidence of a decline in the global burden of cholera in recent years as the number of cholera cases reported to WHO continues to rise. Cholera remains a global threat to public health and a key indicator of lack of socioeconomic development. Overall socioeconomic development is the ultimate solution for control of cholera as evidenced in developed countries. However, most research has focused on cross-county comparisons so that the role of individual- or small area-level socioeconomic status (SES) in cholera dynamics has not been carefully studied. Reported cases of cholera in Matlab, Bangladesh have fluctuated greatly over time and epidemic outbreaks of cholera continue, most recently with the introduction of a new serotype into the region. The wealth of longitudinal data on the population of Matlab provides a unique opportunity to explore the impact of socioeconomic status and other demographic characteristics on the long-term temporal dynamics of cholera in the region. In this population-based study we examine which factors impact the initial number of cholera cases in a bari at the beginning of the 0139 epidemic and the factors impacting the number of cases over time. Cholera data were derived from the ICDDR,B health records and linked to socioeconomic and geographic data collected as part of the Matlab Health and Demographic Surveillance System. Longitudinal zero-inflated Poisson (ZIP) multilevel regression models are used to examine the impact of environmental and socio-demographic factors on cholera counts across baris. Results indicate that baris with a high socioeconomic status had lower initial rates of cholera at the beginning of the 0139 epidemic (γ₀₁ = −0.147, p = 0.041) and a higher probability of reporting no cholera cases (α₀₁ = 0.156, p = 0.061). Populations in baris characterized by low SES are more likely to experience higher cholera morbidity at the beginning of an epidemic than populations in high SES baris.     

酪酸梭菌和婴儿型双歧杆菌对霍乱弧菌的拮抗试验

了解酪酸梭菌和婴儿型双歧杆菌单独及混合培养时对霍乱弧菌的拮抗作用。将酪酸梭菌ＬＣＬ１６６和婴儿型双歧杆菌ＬＣＬ１７２分别与霍乱弧菌Ｏ１、Ｏ１３９单独和混合培养,定时对霍乱弧菌计数,并对菌数的对数进行在检验。两株菌混合培养时对霍乱弧菌的抑制效果基本相同,单独和混合培养时对霍乱弧菌的拮抗作用主要由酪酸梭菌引起,酪酸梭菌具有抑制霍乱弧菌的作用。     

Houseflies (M. domestica L.) as transmitters of the agent of cholera

The authors present the experimental results of study of the role played by domestic flies in the spread of cholera causative agents. It was found that cholera microbes survived on the external surface of flies for 5 to 7 days, and in the insect organism--in the course of their whole life. Cholera vibrios underwent no sharp changes in the organism of flies. By means of individual infection method and keeping of flies excluding a possibility. By means of individual infection method and keeping of flies excluding a possibility of repeated autoinfection it was revealed that cholera vibrios could multiply in the organism of domestic flies. The infected insects can discharge cholera vibrios for a long time into the external environment and contaminate food.     

The effect of cholera toxin on the inhibition of vasopressin-stimulated inositol phospholipid hydrolysis is a cyclic AMP-mediated event at the level of receptor binding.

Incubation of L6 skeletal myoblasts for 16 h with cholera toxin but not with pertussis toxin, led to the inhibition of inositol phosphate generation induced by subsequent exposure to vasopressin. The effects of the toxin on inositol lipid metabolism were accompanied by the total ADP-ribosylation of the available cholera-toxin substrates within the cells. Immunological analysis demonstrated that the two polypeptides modified in vivo by cholera toxin were different forms of Gs alpha (alpha subunit of Gs). No novel cholera-toxin substrate(s) were detected. The cholera-toxin-mediated inhibition of vasopressin-stimulated inositol phosphate generation could be mimicked by both forskolin and dibutyryl cyclic AMP, but not by the separated subunits of the toxin. Receptor-binding studies demonstrated that the inhibition of agonist-stimulated inositol phosphate generation was accompanied by a decrease in cell-surface vasopressin-binding sites, with no effect on the affinity of these for the hormone. We suggest that the effect of cholera toxin and agents which increase intracellular cyclic AMP on vasopressin-stimulated inositol lipid hydrolysis is an effect on receptor number, and that there is no requirement to postulate a role for a novel G-protein, which is a substrate for cholera toxin, in the regulation of inositol phospholipid metabolism.     

The use of the gene hybridization method for the identification of epidemiologically dangerous strains of cholera vibrios

Using the labeled DNA fragments containing the genes for cholera toxin the strains of cholera vibrios were studied for the presence of cholera toxin genes. Vibrio cholerae strains isolated from natural water reservoirs under the favourable epidemic situation do not contain the cholera toxin genes. The DNA hybridization method was compared with other methods used in research and practical work for estimation of epidemic importance of cholera vibrios.     

Alteration of cholera toxin biosynthesis in Vibrio cholerae 01 as a result of temperate phage 139 integration into bacterial chromosome

Infection of V. cholerae 01 (classical and eltor biovars) cells with the temperate cholera phage 139 derived from V. cholerae serogroup 0139 followed by integration of the phage genome into the bacterial chromosome significantly increased the production of cholera toxin, the main virulence factor. The level of toxin biosynthesis in the lysogenic V. cholerae classical strain increased 3-fold and that in V. eltor thirty times in comparison with the parental strains. Increased production of cholera toxin was not associated with an increase in the number of copies of genes involved in its biosynthesis but seemed to be due to changes in toxinogenesis regulation.     

Geographic Distribution and Mortality Risk Factors during the Cholera Outbreak in a Rural Region of Haiti, 2010-2011

BackgroundIn 2010 and 2011, Haiti was heavily affected by a large cholera outbreak that spread throughout the country. Although national health structure-based cholera surveillance was rapidly initiated, a substantial number of community cases might have been missed, particularly in remote areas. We conducted a community-based survey in a large rural, mountainous area across four districts of the Nord department including areas with good versus poor accessibility by road, and rapid versus delayed response to the outbreak to document the true cholera burden and assess geographic distribution and risk factors for cholera mortality.Conclusions/SignificanceThese results highlight important geographical disparities and demonstrate that the epidemic caused the highest burden both in terms of cases and deaths in the most remote areas, where up to 5% of the population may have died during the first months of the epidemic. Adapted strategies are needed to rapidly provide treatment as well as prevention measures in remote communities.     

Experimental research on cholera vaccines. Local immunity

Parenteral immunization of rabbits with cholera vaccine decreased the number of Vibrio cholerae adhering to the mucous membrane of the small intestine. Cholera toxoid and the complex preparation ensure protection from the local action of cholera toxin on the ligated loop of the rabbit intestine, while cholera vaccine produces no effect under the same conditions. The use of three preparations under study leads to the decrease of exudative reaction to the introduction of live V. cholerae, the effectiveness of these vaccines growing in the following order: cholera vaccine, cholera toxoid, the complex preparation.