Pseudomonas pseudomallei: danger in the paddy fields.

'Whitmore's diScSlSe', 'morphia injector'8 septi-caemia', 'the great mimicker' and 'Vietnamese time-bomb' are some of the more colourful names which have been given to melioidosis since it was lirst described inBurma by WHITMORE & KRISHNASWAMI (1912). Pzz&monus pseudmllei has caused outbreaks of infection amongst animals in such diverse settings as a Hong Kong dolphinarium and zoos in Paris (GALIMAND & DODIN, 1982). It received considerable attention as a cause of illness amongst French and American soldiers in Vietnam (HOWE et al., 1971), and at one stage was considered as a potential agent for bacteriological warfare (LEVI, 1960). Until relatively recently, however, melioidosis was usually regarded as a rare and esoteric tropical disease, found only in southeast Asia and northern Australia. The provision of modern microbiological facilities in rural areas of Thailand has unearthed large numbers of both mild and life-threatening P. pseudo-mallei infections (CHAOWAGUL et al., 1989: LEELAR-ASAMEE & BOVORNKITTI, 1989), suggesting that melioidosis may be greatly under-diagnosed where laboratory facilities are less well developed. In addition to southeast Asia, sporadic cases have been diagnosed in the Indian subcontinent, central Africa and central and south America (LEELARASAMEE & BOVORNKI-~TI, 1989). The factors which influence the local incidence of clinical melioidosis are poorly understood, and the true worldwide distribution and incidence of the disease are therefore unknown. Melioidosis is a strikingly seasonal disease, with annroximatelv 80% of cases in northeast Thailand presenting during the rainy season from June to November (CHAOWAGUL et al.. 1989: DANCE et al.. 1989a). These infections are *presumably recently acquired, since P. pseuahallei is an environmental saprophyte, and is most easily isolated from soil and water during the rainy season (LEELARASAMEE & BOVORNKITTI, 1989). In Thailand, most patients are rice-farmers, who are thought to contract infection through cuts and abrasions sustained whilst working in flooded rice-paddy Ex: perimental animals can be infected by inhalation and ingestion of P. pseuahmalZei, but the importance of these routes in naturallv acauired infection is uncertain. Iatrogenic infections &e occasionally reported (IENKINS et al.. 1990). but human-human transmis-Bon has been reported only once (MCCORMICK et al., 1975), which questions the value of the barrier-nursing and chemoprophylaxis of contacts that are sometimes recommended (SHEPPARD et al., 1990). Infection is seen in all age groups, whilst males outnumber females 3:2. Relatively little is known about the pathogenesis of P. pseudomallei infection. Although melioidosis may affect apparently healthy individuals, the disease behaves predominantly as an opportunistic …