Molecular epidemiology of environmental leptospira in Udon Thani, Thailand, and in vientiane, lao peoples democratic republic

Abstract

Leptospirosis is an acute febrile illness caused by pathogenic bacteria of the genus Leptospira. The bacteria are regularly excreted into the environment by carrier animals, and infection in man mainly results from indirect contact with contaminated water or soil, for example during rice farming. A single clone of bacteria called Leptospira interrogans sequence type (ST) 34 caused an outbreak of human leptospirosis in northeast Thailand and also frequently caused leptospirosis in the Lao PDR (Laos). Little is known about the presence and molecular epidemiology of Leptospira in these two endemic areas. This is mainly due to the difficulty of isolating pathogenic Leptospira species from the environment. With a new bacteria culture medium called Leptospira VW agar, isolation is more robust. A total of 103 environmental water samples were collected from Udon Thani, Thailand (n=86) and Vientiane, Laos (n=17) in the dry and wet seasons. 19/86 (22%) samples from Udon Thani and 2/17 (12%) from Vientiane contained Leptospira species. Single colonies of Leptospira were screened for pathogenic and intermediate group markers. Pathogenic (n=1, novel species) and intermediate (n=3, Leptospira licerasiae and Leptospira wolffii) isolates were identified only from Thai samples. Leptospira interrogans ST 34 or other pathogenic Leptospira species were not identified in samples from water in Thailand or Laos.