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Objectives: Cholera has a long history in India and Bangladesh, the region where six out of the past seven global pandemics have been seeded. The changing climate and growing population have led to global cholera cases remaining high despite a consistent improvement in the access to clean water and sanitation. We aim to provide a holistic overview of variables influencing environmental cholera transmission within the context of India and Bangladesh, with a focus on the mechanisms by which they act., Content: We identified 56 relevant texts (Bangladesh n = 40, India n = 7, Other n = 5). The results of the review found that cholera transmission is associated with several socio-economic and environmental factors, each associated variable is suggested to have at least one mediating mechanism. Increases in ambient temperature and coastal sea surface temperature support cholera transmission via increases in plankton and a preference of Vibrio cholerae for warmer waters. Increased rainfall can potentially support or reduce transmission via several mechanisms., Summary and Outlook: Common issues in the literature are co-variance of seasonal factors, limited access to high quality cholera data, high research bias towards research in Dhaka and Matlab (Bangladesh). A specific and detailed understanding of the relationship between SST and cholera incidence remains unclear., (© 2023 the author(s), published by De Gruyter, Berlin/Boston.)

Cholera outbreaks currently account for 1.3 to 4.0 million cases and cause between 21 000 and 143 000 deaths worldwide. Cholera is preventable by proper sanitization and immunization; however, in many developing nations such as India, cholera disease is endemic. The surveillance system in India does not adequately capture the actual number of cases. As a result, it is important to utilize limited public health resources correctly in India and other developing counties more effectively to reach vulnerable communities. In this study, we analyze how studies make sense of cholera transmission and spread in India from 1996 to 2015. Furthermore, we analyze how a more sensitive surveillance system can contribute to cholera eradication by giving rise to outbreak preparedness., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

Cholera is often caused when drinking water is contaminated through environmental sources. In recent years, the drastic cholera epidemics in Odisha (2007) and Haiti (2010) were associated with natural disasters (flood and Earthquake). Almost every year the state of Assam India witnesses flood in Brahamputra River valley during reversal of wind system (monsoon). This is often followed by outbreak of diarrheal diseases including cholera. Beside the incidence of cholera outbreaks, there is lack of experimental evidence for prevalence of the bacterium in aquatic environment and its association with cholera during/after flood in the state. A molecular surveillance during 2012-14 was carried out to study prevalence, strain differentiation, and clonality of Vibrio cholerae in inland aquatic reservoirs flooded by Brahamputra River in Assam. Water samples were collected, filtered, enriched in alkaline peptone water followed by selective culturing on thiosulfate bile salt sucrose agar. Environmental isolates were identified as V. cholerae, based on biochemical assays followed by sero-grouping and detailed molecular characterization. The incidence of the presence of the bacterium in potable water sources was higher after flood. Except one O1 isolate, all of the strains were broadly grouped under non-O1/non-O139 whereas some of them did have cholera toxin (CT). Surprisingly, we have noticed Haitian ctxB in two non-O1/non-O139 strains. MLST analyses based on pyrH, recA and rpoA genes revealed clonality in the environmental strains. The isolates showed varying degree of antimicrobial resistance including tetracycline and ciprofloxacin. The strains harbored the genetic elements SXT constins and integrons responsible for multidrug resistance. Genetic characterization is useful as phenotypic characters alone have proven to be unsatisfactory for strain discrimination. An assurance to safe drinking water, sanitation and monitoring of the aquatic reservoirs is of utmost importance for combating the impending epidemic threat in the flood affected areas. Further, the management of flood through multi-prong approaches and sustainable utilization of environmental resources would be effective in disease management., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Diarrheal disease remains an unsolved problem in developing countries. The emergence of new etiological agents (non-cholera vibrios) is a major cause of concern for health planners. We attempted to unveil the seasonal dynamics of entero-pathogenic Vibrios in Gangetic riverine-estuarine ecosystem. 120 surface water samples were collected for a period of one year from 3 sampling sites on the Hooghly river. Five enteropathogenic Vibrio species, V. cholerae (35%), V. parahaemolyticus (22.5%), V. mimicus (19.1%), V. alginolyticus (15.8%) and V. vulnificus (11.6%), were present in the water samples. The vibriophages, V. vulnificus ɸ (17.5%), V. alginolyticus ɸ (17.5%), V. parahaemolyticus ɸ (10%), V. cholerae non-O1/O139 ɸ (26.6%) and V. mimicus ɸ (9.1%), were also detected in these samples. The highest number of Vibrios were noted in the monsoon (20-34°C), and to a lesser extent, in the summer (24-36°C) seasons. Samples positive for phages for any of the identified Vibrio species were mostly devoid of that particular bacterial organism and vice versa. The detection of toxin genes and resistance to β-lactam antibiotics in some environmental enteropathogenic Vibrio species in the aquatic niches is a significant outcome. This finding is instrumental in the south Bengal diarrhoeal incidence.

Climate change has the potential to influence the earth's biological systems, however, its effects on human health are not well defined. Developing nations with limited resources are expected to face a host of health effects due to climate change, including vector-borne and water-borne diseases such as malaria, cholera, and dengue. This article reviews common and prevalent infectious diseases in India, their links to climate change, and how health care providers might discuss preventive health care strategies with their patients.

Background: Despite advancement of our knowledge, cholera remains a public health concern. During March-April 2010, a large cholera outbreak afflicted the eastern part of Kolkata, India. The quantification of importance of socio-environmental factors in the risk of cholera, and the calculation of the risk is fundamental for deploying vaccination strategies. Here we investigate socio-environmental characteristics between high and low risk areas as well as the potential impact of vaccination on the spatial occurrence of the disease., Methods and Findings: The study area comprised three wards of Kolkata Municipal Corporation. A mass cholera vaccination campaign was conducted in mid-2006 as the part of a clinical trial. Cholera cases and data of the trial to identify high risk areas for cholera were analyzed. We used a generalized additive model (GAM) to detect risk areas, and to evaluate the importance of socio-environmental characteristics between high and low risk areas. During the one-year pre-vaccination and two-year post-vaccination periods, 95 and 183 cholera cases were detected in 111,882 and 121,827 study participants, respectively. The GAM model predicts that high risk areas in the west part of the study area where the outbreak largely occurred. High risk areas in both periods were characterized by poor people, use of unsafe water, and proximity to canals used as the main drainage for rain and waste water. Cholera vaccine uptake was significantly lower in the high risk areas compared to low risk areas., Conclusion: The study shows that even a parsimonious model like GAM predicts high risk areas where cholera outbreaks largely occurred. This is useful for indicating where interventions would be effective in controlling the disease risk. Data showed that vaccination decreased the risk of infection. Overall, the GAM-based risk map is useful for policymakers, especially those from countries where cholera remains to be endemic with periodic outbreaks.

Although it is well known that vaccines against many infectious diseases confer positive economic externalities via indirect protection, analysts have typically ignored possible herd protection effects in policy analyses of vaccination programs. Despite a growing literature on the economic theory of vaccine externalities and several innovative mathematical modeling approaches, there have been almost no empirical applications. The first objective of the paper is to develop a transparent, accessible economic framework for assessing the private and social economic benefits of vaccination. We also describe how stated preference studies (for example, contingent valuation and choice modeling) can be useful sources of economic data for this analytic framework. We demonstrate socially optimal policies using a graphical approach, starting with a standard textbook depiction of Pigouvian subsidies applied to herd protection from vaccination programs. We also describe nonstandard depictions that highlight some counterintuitive implications of herd protection that we feel are not commonly understood in the applied policy literature. We illustrate the approach using economic and epidemiological data from two neighborhoods in Kolkata, India. We use recently published epidemiological data on the indirect effects of cholera vaccination in Matlab, Bangladesh (Ali et al., 2005) for fitting a simple mathematical model of how protection changes with vaccine coverage. We use new data on costs and private demand for cholera vaccines in Kolkata, India, and approximate the optimal Pigouvian subsidy. We find that if the optimal subsidy is unknown, selling vaccines at full marginal cost may, under some circumstances, be a preferable second-best option to providing them for free.

We investigated two sequential outbreaks of severe diarrhoea in two neighbouring villages of Orissa, in 2005. We conducted descriptive and matched case-control studies. The attack rates were 5.6% (n=62) and 5.2% (n=51), respectively, in the first and second villages. One death was reported in the second village (case fatality 2%). We identified that consumption of milk products prepared in the household of the index case [matched odds ratio (mOR) 5.7, 95% confidence interval (CI) 1.7-30] in the first village, and drinking well water in the second village were associated with the illness (mOR 4.7, 95% CI 1.6-19). We isolated Vibrio cholerae El Tor O1 Ogawa from stool samples from both the villages. Mishandling of milk products led to a cholera outbreak in the first village, which led to sewerage contamination of a well and another outbreak in the second village. Environmental contamination should be expected and prevented during cholera outbreaks.

In many infectious diseases, an unknown fraction of infections produce symptoms mild enough to go unrecorded, a fact that can seriously compromise the interpretation of epidemiological records. This is true for cholera, a pandemic bacterial disease, where estimates of the ratio of asymptomatic to symptomatic infections have ranged from 3 to 100 (refs 1-5). In the absence of direct evidence, understanding of fundamental aspects of cholera transmission, immunology and control has been based on assumptions about this ratio and about the immunological consequences of inapparent infections. Here we show that a model incorporating high asymptomatic ratio and rapidly waning immunity, with infection both from human and environmental sources, explains 50 yr of mortality data from 26 districts of Bengal, the pathogen's endemic home. We find that the asymptomatic ratio in cholera is far higher than had been previously supposed and that the immunity derived from mild infections wanes much more rapidly than earlier analyses have indicated. We find, too, that the environmental reservoir (free-living pathogen) is directly responsible for relatively few infections but that it may be critical to the disease's endemicity. Our results demonstrate that inapparent infections can hold the key to interpreting the patterns of disease outbreaks. New statistical methods, which allow rigorous maximum likelihood inference based on dynamical models incorporating multiple sources and outcomes of infection, seasonality, process noise, hidden variables and measurement error, make it possible to test more precise hypotheses and obtain unexpected results. Our experience suggests that the confrontation of time-series data with mechanistic models is likely to revise our understanding of the ecology of many infectious diseases.

A woman aged 60 years was hospitalized for Vibrio cholerae serogroup O1 cholera. Twenty-six fellow travelers and 48 health care workers who cared for the patient were individually traced and contacted. Of the 23/27 travelers with diarrhea during the trip, 4 presented antibodies. There was no person-to-person transmission.

Background: The relevance of climatic events as causative factors for cholera epidemics is well known. However, examinations of the involvement of climatic factors in intracontinental disease distribution are still absent., Objectives: The spreading of cholera epidemics may be related to the dominant wind direction over land., Methods: We examined the geographic diffusion of three cholera outbreaks through their linkage with the wind direction: a) the progress of Vibrio cholerae O1 biotype El Tor in Africa during 1970-1971 and b) again in 2005-2006; and c) the rapid spread of Vibrio cholerae O139 over India during 1992-1993. We also discuss the possible influence of the wind direction on windborn dissemination by flying insects, which may serve as vectors., Results: Analysis of air pressure data at sea level and at several altitudes over Africa, India, and Bangladesh show a correspondence between the dominant wind direction and the intracontinental spread of cholera., Conclusions: We explored the hypothesis that winds have assisted the progress of cholera Vibrios throughout continents. The current analysis supports the hypothesis that aeroplankton (the tiny life forms that float in the air and that may be caught and carried upward by the wind, landing far from their origin) carry the cholera bacteria from one body of water to an adjacent one. This finding may improve our understanding of how climatic factors are involved in the rapid distribution of new strains throughout a vast continental area. Awareness of the aerial transfer of Vibrio cholerae may assist health authorities by improving the prediction of the disease's geographic dissemination.

During 2004 and 2005, cholera was recorded in 15 states of India, with 7 outbreaks. The newly emerged Vibrio cholerae O1 Inaba had a different antibiogram and ribotype, different pulsotypes, and different mutations in the wbeT gene. Due to the absence of serogroup O139, the Inaba serotype may have acquired the potential to affect the population at large.

The Sanskrit word Visŭcikă refers to a condition in which vitiated văta dŏşa causes pain like pricking with a needle over the body. It occurs in a person suffering with ajĭrna (indigestion) and its detailed description is available in Ayurvedic literature. This disease has its existence in India since ancient times; it has also been referred in Mahăhărata and Tripitikas. Its etiology, signs, symptoms, complications, prognosis and treatment etc. as described in Ayurveda may be correlated with the disease Cholera, which is commonly known as "Haiza" in Hindi. In Greek language, the word Cholera means a flow of bile or the bilious disease. Cholera is an acute infectious diarrheal disease, caused by comma bacillus or vibrio cholerae sero groups 01 or 0139. Aretaetus, Benjamin Rush, Chadwick, John Snow, Robert Koch, etc. were some of the pioneers in Cholera research. Medico- historical importance of Cholera, its transmission, description and references from Ayurvedic texts etc., are being presented in this article.

It is well known that diarrhoeal infections due to Vibrio cholerae are spread through fecal-oral route of transmission. In the present study an attempt was made to isolate and identify V. cholerae from houseflies, Musca domestica collected from a low socioeconomic area in Delhi, India, where an outbreak of cholera was encountered. Of the ten fly pools examined, six (60%) were positive for V. cholerae. Of these six pools, three (50%) showed V. cholerae Ogawa T2 El Tor and one (17.5%) V. cholerae non-O1. Two isolates could not be typed. During the outbreak period, V. cholerae Ogawa T2 El Tor was isolated from stools of patients suffering from diarrhoea. These findings suggest that houseflies act as mechanical vectors of V. cholerae biotype El Tor and may help in their dissemination. The present study highlights the recovery of V. cholerae El Tor from M. domestica which, to the authors knowledge, has not been reported previously.

The prevalence of Vibrio cholerae in drinking water, lakes and sewage outfalls during July and August 1996 in Vellore, India was determined. Drinking water samples were collected on single occasions from 12 sites in different geographic areas of the town where cholera had been reported. Samples of water, plankton and sediment were collected from fixed sites at three lakes on three occasions separated by at least 3 days during the course of the study. Samples from open sewers were taken from two representative sites in four areas of the town. Bacteria isolated from samples were identified by standard biochemical tests and isolated strains of V. cholerae tested for their ability to agglutinate O1 and O139 antisera. Water samples from lakes were also tested for the presence of V. cholerae O1 and O139 by fluorescent antibody staining. Non-O1, non-O139 strains of V. cholerae were detected in 41% of drinking water samples and 100% of water, sediment and plankton samples from the test lakes. Eighty-seven per cent of open sewers sampled contained viable non-O1, non-O139 V. cholerae. Fluorescent antibody staining gave positive results for V. cholerae O1 and O139 for all water samples from the three lake sites. Strains of Aeromonas spp. were isolated from 58% of drinking water samples and from 66% of sediment, 77% of plankton and 55% of water samples from lakes. All open sewers sampled contained Aeromonas spp. PCR amplification employing specific primers demonstrated that none of the non-agglutinating V. cholerae isolates contained the ctx operon. The non-O1, non-O139 V. cholerae isolates showed different patterns of antibiotic resistance to ampicillin, ciprofloxacin, chloramphenicol, tetracycline and trimethoprim.

An outbreak of V. cholerae 01 occurred in remote villages of Rohru tehsil, district Shimla, Himachal Pradesh, during June-July 1994. Seven villages were affected. Overall attack rate was 16.4 per cent in surveyed villages. Attack rate in children < 5 was significantly high. Suspected source was spring water contaminated from open air defaecation. V. cholerae was resistant to co-trimoxazole and streptomycin.

In 1993, rectal swabs from clinically suspected cases of cholera admitted to the Infectious Diseases Hospital (IDH), Delhi were examined for Vibrio cholerae O1 and O139. Epidemiological data of 396 cholera cases were collected before the patients' discharge from IDH. Of the 1528 laboratory-confirmed cholera cases, 46% and 54% were caused by serotype O1 and O139 respectively. Both serotypes appeared and disappeared simultaneously, and peaked during the same time of the year. However, the two serotypes affected persons of different age groups; about 65% of the O1 cases occurred in children aged less than 10 years, whereas this age group accounted for 40% of the cases due to V. cholerae O139. Although there were some focal outbreaks due to serotype O139, both serotypes had almost similar geographical distributions. Important risk factors for transmission of cholera were almost equally prevalent in the majority of both types of cholera cases. Since the seasonality, geographical distribution, and risk factors for transmission were similar for both serotypes, the study indicates that the preventive and control measures are also likely to be similar. The study also shows that the emergence of V. cholerae O139 in 1993 did not affect the incidence, seasonality, and epidemiology of endemic V. cholerae O1 E1 Tor strains in Delhi.

The emergence of Vibrio cholerae O139 Bengal as the second aetiologic agent of epidemic cholera in October 1992 in the south Indian coastal city of Madras has shattered the long-held notion that only V. cholerae belonging to serogroup O1 are capable of causing epidemic (and pandemic) cholera. Within months of its appearance in Madras, V. cholerae O139 engulfed the entire Indian subcontinent in a series of outbreaks of cholera. It also spread to several neighbouring countries in Asia. Several western countries also reported imported cholera cases due to this organism. In the regions of the Indian subcontinent where cholera due to V. cholerae O1 is endemic, children are mostly susceptible because adults would have acquired at least some immunity due to earlier exposure. However, when V. cholerae O139 struck people in these areas, even though all age groups were affected, the disease was more prevalent in adults, which suggested that the disease is new in this population. As with O1 cholera, water and food seemed to be the vehicles of infection. Many family contracts of index cases of O139 cholera were found to be infected with V. cholerae O139, and in many of them, the infection was asymptomatic which is reminiscent of O1 EITor infection. Again as with O1 EITor infection, individuals of blood group O were more susceptible to O139 infection than those with other blood groups. In its molecular aspects, O139 vibrio resembles O1 EITor vibrio. The virulence genes encoding cholera toxin, zonula occludens toxin, accessory cholera enterotoxin and core-encoded pilin are present in a 4.5 kb 'virulence cassette' region of the chromosome as in EITor vibrios and the expression of these virulence factors, toxin coregulated pilus (TCP) and several outer membrane proteins are found to be under the control of the master regulator ToxR as in EITor vibrios. The iron-regulated genes involved in virulence are also found in the same locus as in EITor vibrios. However, the genes involved in the somatic antigen synthesis in O1 vibrios are found to be deleted in O139 vibrios and are replaced by a new region of chromosome which encodes the new surface antigen synthesis in O139 vibrios. When V. cholerae O139 emerged and caused outbreaks, the prevailing O1 EITor vibrios virtually disappeared from most of the areas. The disappearance of EITor vibrios, the rapid spread of O139 vibrios and the resemblance of O139 vibrios to EITor vibrios seemed to suggest that O139 vibrios might be the causative agent of the 'eighth' pandemic of cholera. However, after a year of its appearance, O139 vibrios are on the wane and O1 EITor vibrios have re-emerged as the predominant organism, in the Indian subcontinent. Thus, the immediate threat of a new cholera pandemic posed by V. cholerae O139 may not be as large as it first seemed. However, whether it will follow the pattern of EITor vibrio which took approximately 60 yr since its first isolation before emerging as the seventh pandemic strain of cholera, is not clear. The factor(s) contributing to the diminished isolation of O139 vibrios and the re-emergence of O1 EITor vibrios are not understood. The vibrios might have undergone changes that would have affected their ability to survive and compete in the environment.

Hundreds of laboratory-confirmed cholera cases occur every year in Delhi. However from 1965 through 1993, no cases of cholera nor carriers of Vibrio cholerae have been detected in the months January and February of all these years. Nevertheless, two cases occurred in January 1994. Both were children who acquired their infection locally. Six hundred fifty-eight rectal swabs collected from possible contacts were negative for V. cholerae. The next isolations could be made only in April, which is the usual beginning of the cholera season. The study suggests that cholera transmission can occur during the winter months in Delhi, but that it is not sustained.

Vibrio cholerae O139 Bengal emerged on the Indian subcontinent in late 1992 and was first recognized in Thailand in 1993. To characterize the epidemiology of this disease, a hospital-based case-control study was conducted in Samutsakorn, a port city 30 km southwest of Bangkok. Between November 15, 1993, and June 3, 1994, 366 patients were confirmed to have cholera by culture, including 165 (45%) with O139 Bengal, 191 (52%) with O1 Ogawa, and 10 (3%) with both serogroups. During the same time period the previous year, 319 culture-confirmed cholera cases occurred, all serogroup O1. Questionnaires were obtained from 105 patients with O139 Bengal and 103 with O1 infections; for each case patient, two asymptomatic age- and sex-matched control persons were selected. Of the patients with O139 Bengal infections, 93% were adults (> or = 15 years) compared with 92% of patients with O1 infections. Risk factors for cholera identified by case-control comparisons were similar for the two serogroups and included consumption of untreated water, uncooked seafood, and food served at group gatherings. V. cholerae O139 Bengal has emerged in Thailand as a cause of endemic cholera, with epidemiologic features and incidence similar to those of the preexisting O1 strain.

A total of 27 families of hospitalised patients (index case families) suffering from acute watery diarrhoea caused by Vibrio cholerae O139, and 14 neighbourhood families were bacteriologically screened for 4 consecutive days to determine the extent of V. cholerae O139 infection amongst healthy contacts and other suspected vehicles of transmission at the intrafamilial level. V. cholerae O139 was isolated from faeces of 14.6% of healthy contacts in index case families as compared to none in neighbourhood families (P = 0.002). The organism could be recovered from 3.7% of handwashings of contacts of index cases and also from stored drinking water (8.0%), open well water (28.6%), flies (3.8%) and pond water (25.0%) used by the index case families and none from neighbourhood families. The large number of asymptomatic infected persons indicate an epidemiological similarity to that of eltor cholera. The organisms may be carried on hands and may act as a potential source of infection to other inmates through contamination of stored drinking water, open wells etc. The results will be useful in formulating strategies for intervention of transmission of V. cholerae O139 at the community level.

Vibrio cholerae serogroup O139 Bengal, a novel strain with epidemic potential, completely displaced V. cholerae serogroup 01 in Calcutta in January 1993, which was followed by an epidemic caused by V. cholerae O139 in March-May 1993. From November 1992 to July 1993, 95.6% of 916 V. cholerae isolates submitted to the National Institute of Cholera and Enteric Diseases from 28 locations in India were confirmed as serogroup O139. As of July 1993, V. cholerae O139 had been isolated from 13 Indian states and a union territory, and large outbreaks of cholera caused by the O139 serogroup had occurred in several cities. The extent of spread of V. cholerae O139 Bengal in India and its ability to swiftly disseminate leaves little doubt that this is the beginning of the eighth pandemic of cholera.

A new clone of non-01 V. cholerae designated as serogroup 0139, which produces cholera toxin, was detected first in south India in September 1992 and has spread to many parts of India since then. It was identified in Bangladesh in December 1992 and in Thailand in April 1993. By May 1993 it was found in Haryana and Punjab. Its clinical manifestations are typical of cholera, occurring in outbreaks. This clone has largely replaced the previously prevalent 01 V. cholerae in several cholera endemic areas indicating that a new cholera pandemic has begun.

Doxycycline was used among the family contacts of hospitalized cholera patients in Calcutta to determine its effectiveness in controlling transmission of V. cholerae infection. A total of 137 such contacts were given a single oral dose of doxycycline in graded doses according to age. A similar group of 139 contacts received a single dose of multivitamins as placebo. All 276 contacts were examined bacteriologically daily for 10 days for the presence of V. cholerae in their stools. The results showed that doxycycline was effective in significantly reducing the load of V. cholerae infection for up to 5 days following treatment.

Sulfadoxine, a long-acting sulfonamide, and tetracycline were compared as regards their effectiveness in reducing transmission of cholera infection among the contacts of cholera patients in Calcutta. A total of 109 healthy family contacts of confirmed hospitalized cholera patients were treated with a single oral dose of sulfadoxine graded according to age. Another similar group of 101 contacts received 6 divided doses of oral tetracycline over a period of 3 days. All these contacts were bacteriologically examined for 15 days. Results showed that tetracycline was effective in significantly reducing the load of cholera infection from the 2nd to 6th day, while sulfadoxine was effective from the 3rd to the 6th day. The advantages and disadvantages of the two drugs as chemoprophylactic agents in cholera are discussed.

Transmission of eltor cholera infection in endemic communities continues without diminishing because of the absence of effective intervention measures. Two methods-chlorination of stored water and the use of a narrow-necked earthenware vessel (called a 'sorai') for storing the water-were found to be effective in reducing the transmission of infection among the family contacts of cholera patients. The cholera carrier rates in the chlorination and 'sorai' intervention groups were 7.3% and 4.4%, respectively, compared with 17.3% in the control group. The 'sorai' is cheap and was well accepted by the local communities; its narrow neck prevented the introduction of the hand and contamination of the stored water.