Leptospirosis of Man and Animals in Urban, Rural and Jungle Areas of Southeast Asia

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  • Army Medical Service Graduate School, Veterinary Service of the Federation of Malaya, Washington 12, D. C.
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An exploratory, but systematic, serologic survey in Malaya indicated that leptospirosis is very prevalent there with about one-fourth of the human population, one-third of the domestic animals and about one-sixth of the wild rodents tested exhibiting antibodies to one or more strains of leptospiras. In the human population, the incidence of antibodies was uniformly high in urban, rural and jungle inhabitants alike while, among the domestic animals, horses, oxen, pigs, and dogs exhibited particularly high incidences.

Although evidence points to both town and rural agricultural areas as frequent sources of infection, attention has been directed in particular to the primary jungle in Malaya as an important endemic focus of leptospirosis. Here, three species of rodent which inhabit the primary forest (Rattus mülleri, R. rajah, and R. sabanus) gave evidence of leptospiral infection by serologic or cultural methods. Both serologic and cultural findings point to the presence of a multiplicity of leptospiral strains in Malaya. Thus, leptospiral strains of six different serogroups (hebdomadis, pyrogenes, icterohemorrhagiae, grippotyphosa, schüffneri and one apparently new serotype strain) were isolated from man and wild rodents bringing the total number isolated here to date to eight known serogroups and four incompletely identified strains.

A more limited survey in British North Borneo demonstrated leptospiral antibodies in about one-fourth of the indigenous population and a strain of the icterohemorrhagiae serogroup on isolation from a jungle rat (Rattus whiteheadi). The findings suggest that here, too, leptospirosis is prevalent and is caused by a multiplicity of strains.

A number of wild rodents from Thailand and Korea were cultured for leptospiras. Bandicota bengalensis and Bandicota sp. from Thailand yielded strains of the autumnalis serogroup while both Mus musculus molossinus and Apodemus agrarius from Korea yielded strains of the icterohemorrhagiae serogroup.