The Viability of Leptospires in the Summer Paddy Water

Abstract

In connection with the possible role played by water buffaloes in transmitting leptospiral infection, surveys of pH and temperature of paddy water in Taiwan as well as investigation of their effects upon the viability of various leptospires were performed during the summer time. The pH values of paddy water at 122 places in 37 villages distributed in the southern, central and northern parts of Taiwan were surveyed. The pH values of the water of 8 (6.6%) places ranged from 6.4 to 6.8, that of 29 (23.8%) places varied between 7.0 and 7.5, and that of 85 (69.7%) places ranged from 7.6 to 7.8. The temperature of these paddy waters was surveyed for one week between July and August. Temperatures ranging from 40 C to 43 C were obtained from 8 out of 11 places in the south, 9 out of 11 places in the central section and 5 out of 10 places in the north. L. australis A lost its viability in paddy water within one day in the experiment performed in the fields between July and August in the southern, central and northern areas, while 2 out of 21 strains of leptospires (L. semarang and L. australis A) maintained their viability for one week in the experiment performed between August and September in Taipei. In laboratory experiments, L. australis A was killed in paddy water at 42 C within 3 hours compared to 6 hours in L. semarang. The viability of both strains of leptospires was markedly influenced at −15 C, while they maintained their viability for 7 to 14 days at temperatures ranging from 0 C to 30 C. © jointly owned by Japanese society for Bacteriology and Society of Japanese Virologists