Reduction of cholera in Bangladeshi villages by simple filtration

Abstract

Based on results of ecological studies demonstrating that Vibrio cholerae, the etiological agent of epidemic cholera, is commensal to zooplankton, notably copepods, a simple filtration procedure was developed whereby zooplankton, most phytoplankton, and particulates >20 m were removed from water before use. Effective deployment of this filtration procedure, from September 1999 through July 2002 in 65 villages of rural Bangladesh, of which the total population for the entire study comprised Ϸ133,000 individuals, yielded a 48% reduction in cholera (P < 0.005) compared with the control. C holera is a disease that continues to ravage developing countries and reemerges sporadically elsewhere throughout the world. According to the World Health Organization (WHO), 58 countries have officially reported cholera in 2001, with a total of 184,311 cases and 2,728 deaths (1). However, there were 293,113 cases of cholera worldwide in 1998, with 10,586 deaths. These annual figures of WHO actually represent the tip of the iceberg, because the morbidity and mortality caused by Vibrio cholerae is grossly underreported owing to surveillance difficulties and also for fear of economic and social consequences (2). In fact, several cholera endemic countries, e.g., Bangladesh, are not included in the WHO report. In 1991, after almost 100 years without cholera, outbreaks in 16 Latin American countries resulted in Ϸ400,000 reported cases of cholera and Ͼ4,000 reported deaths (3).That cholera is a waterborne disease has long been known (4-6). Furthermore, surface water has been linked with transmission of cholera since the pioneering work of Snow in 1854 (7). Demonstration of the potential for water to transmit cholera was provided by Koch, who, after Pacini first described the Vibrio (8), isolated and characterized the bacterium, which he named Vibrio comma, and was able to find it in pond water used by an Indian community suffering a cholera epidemic (9).The association of pathogenic vibrios with zooplankton was reported in 1973 by Kaneko and Colwell (10) and of V. cholerae with copepods by Huq et al. in 1983 (11). Commensal occurrence of Vibrio spp. in the copepod gut was demonstrated by Sochard et al. in 1979 (12). A few years later, preferential attachment of V. cholerae to copepod surfaces, egg cases, and the copepod oral region was reported by Huq et al. (11). Extensive data have since been accumulated showing that planktonic copepods play a major role in the multiplication, survival, and transmission of cholera (13-17). That environmental V. cholerae O1 can cause cholera has been established by molecular genetic evidence (18).During spring and late summer in Bangladesh, phytoplankton blooms occur, followed by zooplankton, with heaviest blooms occurring in September and October (13,19). Each year, the seasonal zooplankton blooms, in turn, are followed by cholera outbreaks (11, 13). It has been determined that a single copepod, depending on species and size, can carry up to 10 4 cells of V. cholerae (11,17). Thus, a copepod bloom ca...

Transmissibility of cholera: In vivo -formed biofilms and their relationship to infectivity and persistence in the environment

“…Regardless of the mechanisms causing it, the fact that V. cholerae cells derived from cholera stools can have enhanced infectivity has significant epidemiological implications. A recent study in Bangladesh reported that filtering environmental water through four layers of old sari cloth material before consumption reduced the incidence of cholera among villagers by 48% (24). The authors of this study proposed that the reduction in cholera cases occurs because the filtration removes large planktonic material to which V. cholerae is likely attached (24).…”

“…A recent study in Bangladesh reported that filtering environmental water through four layers of old sari cloth material before consumption reduced the incidence of cholera among villagers by 48% (24). The authors of this study proposed that the reduction in cholera cases occurs because the filtration removes large planktonic material to which V. cholerae is likely attached (24). We assume that a similar reduction in the incidence of cholera would be observed if V. cholerae in the environment exist as CVEC, which are large clumps of cells possibly derived from human stools, because in theory such clumps can also be eliminated by sari cloth filtration.…”

Effect of TDA‐producing Phaeobacter inhibens on the fish pathogen Vibrio anguillarum in non‐axenic algae and copepod systems

“…One of the most prominent bacterial genera causing disease in aquaculture is Vibrio including Vibrio anguillarum, V. harveyi, V. vulnificus and V. splendidus (Thompson et al ., 2004; Toranzo et al ., 2005). Live feed used in aquaculture is a potential point of entry and vector for pathogenic bacteria (Olafsen, 2001), and several Vibrio species, including the human and fish pathogens V. cholerae, V. vulnificus and V. splendidus, are found in association with zooplankton, for example copepods, which in the marine environment seem to serve as natural Vibrio reservoirs (Sochard et al ., 1979; Heidelberg et al ., 2002; Colwell et al ., 2003; Vezzulli et al ., 2015). The role of copepods as hosts for V. cholerae has especially been studied extensively, and V. cholerae has repeatedly been isolated from the surface, gut and exuviae of these small crustaceans (Huq et al ., 1983; Tamplin et al ., 1990; Gugliandolo et al ., 2008).…”

The Vibrio cholerae chitin utilization program

“…Studies of this epidemiological association identified V. cholerae attached to plankton in the environment, an observation that was confirmed by microcosm coinfection experiments. The interaction of V. cholerae with zooplankton is particularly intriguing because copepods, a subclass of crustacean zooplankton, have been incriminated in the transmission of this agent from aquatic reservoirs to susceptible human hosts (3).…”