Curbing cholera

FOR the long-suffering people ofBangladesh, India and more recentlyLatin America, who have to contendwith frequent outbreaks of cholera, hereis a message of hope from Rita Colwell,a researcher at the Maryland Universit),Washington. Her research has revealedthat a major outbreak of cholera can beprevented by keeping a watch on thegrowth of a type of aquatic plant knownas the phytoplankton.

Cholera is a threat whenever cleanwater is scarce and is caused by a kindof bacteria called -,qbrio cholerae. Colwellhas discovered that a kind of microscopic aquatic animal, the zooplanktonwhich also thrives in cold water, is the primary carrier of the cholera virus. An individual zooplankton can carry asmany as 10,000 vibrios and can enter ahuman body through water or eventhrough fish or shellfish picked upfrom a pond or river. Colwell hasfurther observed that the populationof zooplankton increases - usually inthe summers - when an aquaticplant, the phytoplankton, whichforms the primary diet of the littleanimals, grows in abundance. This isinevitably followed by an outbreakof cholera. Colwell suggests thatthe bloom of phytoplankton shouldbe monitored by keeping a closewatch on the satellite images of theearth. And the alarm signals should besent vigorously ringing whenever thereis a significant change in the growth ofthe phytoplanktons.