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

MELIOIDOSIS 185bacteria that lives in surface waters and in soil. P. pseudomallei can survive in moist,clayey soil; under laboratory conditions; at ambient temperature; and in shade for 30months (Thomas and Forbes-Faulkner, 1981).P. pseudomallei has several possible virulence factors, including an endotoxin, anexotoxin, and various digestive enzymes that can attack tissue. The role that each ofthese virulence factors plays in pathogenesis is still unknown. The exotoxin is themost toxic substance produced by the bacteria and can inhibit intracellular proteinsynthesis (Dance, 1991; Ismail et al., 1991).Geographic Distribution: Most human and animal cases have been recorded inSoutheast Asia (Indonesia, Malaysia, Myanmar [Burma], and Thailand), which isconsidered the main endemic area. The disease has also been diagnosed in northeasternAustralia, Guam, Iran, Korea, Madagascar, Papua New Guinea, Sri Lanka,and Turkey. Cases have also occurred in Bangladesh, India, and Pakistan. In theAmericas, the infection has been confirmed in Aruba, the Bahamas, Ecuador, ElSalvador, Mexico, Panama, and Puerto Rico. More recent investigations haverevealed the agent’s presence in other areas (Brazil, Burkina Faso, Côte d’Ivoire,Haiti, and Peru) by isolating it from people, animals, or soil and water samples.Sporadic cases have also occurred in human in Kenya and the Gambia, in swine inBurkina Faso and Niger, and in goats in Chad. The agent’s distribution is predominantlytropical. The epizootic that occurred in the “Jardin des Plantes,” in Paris, isthe first reported outbreak in a temperate climate. In Europe, in addition to France,there have been cases in horses in Spain (Benenson, 1990; Galimard and Dodin,1982; Dance, 1991a).Occurrence in Man: Clinically apparent infection caused by P. pseudomallei isnot very common. During the war in Indochina, several hundred French, American,and Vietnamese soldiers became ill with melioidosis. From 1965 to 1969, threecases per month occurred among US Army soldiers in Vietnam (Piggott, 1976).According to a serological survey, 9% of the 3 million US personnel participating inthe Vietnam conflict were exposed to the agent. Cases confirmed in the US duringthe 1970s were almost all military personnel or travelers returning from SoutheastAsia (CDC, 1977).The numerous cases that occurred among military personnel during the VietnamWar provoked interest in the disease among medical professionals in Thailand. Priorto 1965, only three cases of melioidosis had been recorded in that country, whilethere were a total of about 1,000 cases between 1967 and 1988 (Kanai andDejsirilert, 1988).Melioidosis is currently recognized as the most common cause of pneumoniaoccurring in the Top End region in the Northern Territory of Australia(Currie, 1993).Occurrence in Animals: In endemic zones, sporadic cases have been reported indifferent animal species. Occasional outbreaks have occurred among sheep (inAustralia and Aruba), in swine (Vietnam), in goats, cattle, horses, dogs, dolphins,tropical fish, and zoo animals, as well as in monkeys imported for laboratories. Acase occurred in macaques of the species Macaca fascicularis imported to GreatBritain from the Philippines. There were a total of 13 confirmed or suspected casesin 50 imported animals. Most had splenic abscesses, but their general condition was