Imported Dogs as Possible Vehicles of Vibrio Cholerae O1 Causing Cholera Outbreaks in Northern Vietnam

Strains of V. cholerae O1 were isolated from the sewage and a pond near the first patient's house and also from domestic vegetables obtained at a neighboring market. From 24 October 2007 to 25 June 2009, 1,505 cases were confirmed positive for V. cholerae O1 (biotype El Tor, serotype Ogawa) in 22 cities and provinces in northern Vietnam. On May 8 and May 12, 2009, epidemic strains of V. cholerae O1 were isolated from dogs in slaughter houses in Hanoi and from dogs in cages in Thanh Hoa, respectively. Isolates of V. cholerae O1 in Laos and Thailand were found to be the same clone as those isolates from dogs, patients and environmental water samples in northern Vietnam. Although the transmission routes of cholera differed between the northern and southern provinces of Vietnam, the same clonality was observed among isolates from 2007 to 2010.