Rev. sci. tech. Off. int. Epiz., 2008, 27 (3), 851-859 Foot and mouth disease in the Lao People’s Democratic Republic: II. Seroprevalence estimates, using structured surveillance and surveys of abattoirs S.D. Blacksell (1, 2) , S. Khounsy (3) , J.V. Conlan (4) , L.J. Gleeson (4)* , A. Colling (4) , H.A. Westbury (4) (1) Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand (2) Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, John Radcliffe Hospital, Oxford, United Kingdom (3) Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Lao People’s Democratic Republic (4) Commonwealth Scientific and Industrial Research Organisation, Livestock Industries, Australian Animal Health Laboratory, Private Bag 24, Geelong, Victoria 3220, Australia *Corresponding author. E-mail: axel.colling@csiro.au Submitted for publication: 19 December 2007 Accepted for publication: 22 July 2008 Summary An examination of the seroprevalence of foot and mouth disease (FMD) virus was conducted in the Lao People’s Democratic Republic (Lao PDR) from 1996 to 2005, using structured surveillance and abattoir-based studies. Under structured surveillance, seropositivity ranged from 65.7% (Vientiane Capital, 1996) to 3% (Houaphan, 2005) for cattle and buffalo; and from 2.8% (Vientiane Capital, 1998) to 0% in separate studies of pigs. In each study, species composition was significantly associated with seroprevalence rates. For abattoir surveys, the majority of samples (60.5%) came from Vientiane Capital (33.0%), Savannakhet (14.0%) and Champasak (13.5%) provinces. The overall proportion of animals testing positive for the presence of antibodies against the FMD virus was 18.7% (ranging from 50.8% in Vientiane Province to 1% in Phongsali). Generally, antibodies against serotype O were the most prevalent. Cattle and buffalo that tested as seropositive were significantly older than the seronegative animals (p < 0.00005). The overall proportional seropositivity was significantly different for different species, as was the case with the antibodies against serotypes O, A and Asia 1. Some 22% of cattle, 55% of buffalo and 23% of pigs demonstrated seropositivity but this varied significantly between provinces. Keywords Asia – Bovines – Buffalo – Cattle – Foot and mouth disease – Lao People’s Democratic Republic – Pigs – Prevalence – Serology – Swine. Introduction Foot and mouth disease (FMD) virus is a member of the genus Aphthovirus, family Picornaviridae (11) and is the causative agent of foot and mouth disease, a highly contagious virus infection of cloven-hoof animals. The FMD virus (FMDV) is endemic in the Lao People’s Democratic Republic (Lao PDR) (6, 9, 11, 12), as it is in the majority of Southeast Asia, causing severe economic losses in commercial and village (12, 13) animal production systems. The Lao PDR shares borders with Thailand, Vietnam, China, Cambodia and Myanmar, and so is a