Benefits of Filtering
Mathematical models, employing physical-chemical parameters, including salinity, nutrient concentrations, pH, water temperature, presence of plankton, etc., have been developed showing climate and cholera correlation. Poor sanitation and lack of safe drinking water, of course, exacerbate the disease once it is initiated. Thus, environmental parameters associated with cholera can be monitored using satellite sensors and those parameters, which are monitored by satellite, such as sea surface temperature, sea surface (tidal) height, and chlorophyll, provide data for the models.
The results have provided good estimates of the number of cholera cases in Bangladesh, India, and Africa. Based on these findings, the hypothesis was developed that, since plankton carry cholera bacteria, if a simple filter is properly employed when collecting drinking water from untreated sources, such as ponds and rivers, the incidence of cholera could be reduced.
A study was conducted and several materials were tested. A field study carried out in Bangladesh, comprising 150,000 inhabitants in 50 villages, was executed over a three-year period. Bangladeshi village women trained in the use of simple cloth filters to collect water, with cooperation by village women, reinforced filtration as a method to remove particulate matter, notably plankton, since the cholera bacteria attached to the plankton would therefore also be removed. Incidence of cholera in families practicing simple filtration was reduced by approximately 50%.
A follow-up study conducted five years after the initial study ended showed filtration was sustainable, i.e., the village women continued the practice of simple filtration. Hence, it proved both sustainable and effective.
In 2000, the first genome of the cholera vibrio was sequenced. Since then, the DNAs of many additional strains of V. cholerae have been sequenced. The cholera isolates included historical strains, such as V. cholerae isolated in 1910 and geographically diverse isolates from Africa, India, the Sudan, etc. What was discovered was that the genomic sequence of these strains shows detectable variation. That is, there is a significant genetic exchange among V. cholerae, i.e., sets of genes found in V. cholerae transfer from strain to strain within V. cholerae populations. The evolution of V. cholerae was, thus, tracked by following gain and loss of sets of genes coding for pathogenic properties and serotype.
The studies conclusively showed that genes coding for serotype are laterally transferred. The cholera bacterium, in effect, undergoes genetic “drift and shift,” becoming a moving target for public health workers.
In summary, these studies of cholera in Bangladesh, India, Africa, and the U.S. have provided a model for understanding the emergence of this disease from the natural environment globally. Cholera is an excellent example of an environmental bacterium that has the potential to cause massive epidemics in human populations worldwide. It is an excellent example of how we must understand our environment and the living system it comprises.
The message, therefore, is dual: safe water is a critical necessity for humankind and the complexity of our biological world must be more fully understood for its beneficial gifts and its potential threats.