zoonoses and communicable diseases common to ... - PAHO/WHO

118 BACTERIOSESThere are various schemes that classify non-O1 V. cholerae in serovars (orserotypes). One of them (currently used in the US) is the Smith scheme (Smith,1977), which distinguishes more than 70 serovars. Serotyping is limited to referencelaboratories for epidemiologic studies.Geographic Distribution: Worldwide. The presence of non-O1 V. cholerae hasbeen confirmed on all inhabited continents, either in the environment (particularlyin bodies of water), or in man and animals. In Asia, serogroup O139 has spread fromBangladesh and India to China, Malaysia, Nepal, Pakistan, and Thailand, and mayspread further. The first case introduced into the US was a California resident whohad traveled to India. There was also a case in the UK.Occurrence in Man: In man, it appears as sporadic cases or small outbreaks. Inareas where cholera is endemic, patients have frequently suffered a disease similarto cholera, but caused by non-O1 V. cholerae. In India and Pakistan, nonagglutinablevibrios were isolated (i.e., non-O1 V. cholerae) from a small percentage ofpatients with choleriform symptoms. In 1968, an outbreak attributed to this agentoccurred in Sudan and caused gastroenteritis in 544 people, 31 of whom died(Kamal, 1971). In the former Czechoslovakia, an outbreak of gastroenteritis affected56 young people at a training center. NAGs were isolated from 42 of the 56, but notfrom 100 controls. The disease was attributed to this etiologic agent and the vehicleof infection was thought to be potatoes (possibly contaminated after cooking) thatthe patients ate. The disease was mild and short lived (Aldová et al., 1968). Therewas also an outbreak on a flight from London to Australia that was attributed to anasparagus and egg salad (Dakin et al., 1974). Sporadic cases are more common andhave occurred in several countries.The appearance of serogroup O139 completely changed the scenario. Thisserogroup is not distinguished from serogroup O1 as an epidemic agent of cholera.The epidemic it is causing has affected tens of thousands of people, with approximatelya 5% mortality rate (WHO, 1993). The fear is that this new agent has thepotential to cause a pandemic. The epidemic wave has already moved from India toThailand, Bangladesh, and other countries.Occurrence in Animals: Non-O1 V. cholerae has been isolated from manydomestic and wild mammalian species, as well as from birds. In India, 14% of morethan 500 dogs harbored “noncholeric vibrios” in their intestines. In the same geographicarea, the same vibrios were found in ravens (Sack, 1973). In another area ofIndia, far from the endemic cholera area, 195 domestic animals were examined(goats, cows, dogs, and birds) in a search for an animal reservoir for V. cholerae.Fifty-four strains were isolated, 8 of which were O1 V. cholerae and 46 of whichwere non-O1. Serotype O1 was found only during the months when cholera washighly prevalent in the population, whereas the other serotype was found throughoutthe year (Sanyal et al., 1974).The Disease in Man: It appears in two forms: intestinal, which is prevalent, andextraintestinal.Gastroenteritis caused by non-O1 V. cholerae is usually of short duration and thesymptoms are mild to moderate. The disease is only occasionally severe, as occursin epidemic cholera (Morris, 1990). The clinical picture is usually variable. In agroup of 14 patients in the US, 100% had diarrhea (25% of the patients had bloody