Analytical Epidemiology of Genomic Variation among Pan Asia Strains of Foot-and-Mouth Disease Virus

Heterogeneity and genetic variations of serotypes O and Asia 1 foot-and-mouth disease viruses isolated in Vietnam

Six field foot-and-mouth disease viruses (FMDVs), including four serotype O and two serotype Asia 1 strains, were collected from endemic outbreaks in 2005, 2006, and 2007 from four different provinces in Vietnam. The viruses were isolated and genetically characterized for their complete genomic sequences. The genetic analysis based on the complete genomic coding sequences revealed that the four serotype O FMDVs were related to each other, sharing 95.2% nucleotide (nt) identity and 97.5-97.6% amino acid (aa) identity. Genetic analysis and a phylogenetic tree, based on the VP1 gene of FMDV, showed that the four present Vietnamese serotype O strains have a high level of identity with other serotype O representatives of the Mya-98 lineage of the Southeast Asian (SEA) topotype. The four viruses were all clustered into the Mya-98 lineage of the SEA topotype, sharing 92.3-95.6% nt and 93.4-96.7% aa identity. This finding of the Mya-98 lineage was different from previous reports that the Vietnamese serotype O strains belonged to the Cam-94 lineage of the SEA topotype and two other topotypes, Middle East-South Asia (ME-SA) and Cathay. For the two serotype Asia 1 FMDVs, the genetic analysis based on the complete genomic coding sequences as well as on the VP1 gene revealed that they belonged to two genogroups, IV and V. Of note, the As1/VN/QT03/2007 strain of genogroup V, isolated in 2007, was very closely related to the pandemic Asia 1 strain which caused FMD outbreaks in China (Asia1/WHN/CHA/06, FJ906802) and Mongolia (Asia1/MOG/05, EF614458) in 2005, sharing 99.0-99.3% nt and 99.5-100% aa identity. In contrast, the second strain As1/VN/LC04/2005 of genogroup IV, isolated in 2005, was closely related to all referenced Vietnamese serotype Asia 1 strains found in the GenBank databases, sharing 86.4-100% nt and 90.9-100% aa identity with each. This study is the first description of the full-length genomic sequence of Vietnamese FMDV serotypes O and Asia 1 and may provide the evidence of the concurrent circulation of different serotypes and subtypes of FMDV in recent years in Vietnam.

Agricultural diseases on the move early in the third millennium

With few exceptions, the diseases that present the greatest risk to food animal production have been largely similar throughout the modern era of veterinary medicine. The current trend regarding the ever-increasing globalization of the trade of animals and animal products ensures that agricultural diseases will continue to follow legal and illegal trade patterns with increasing rapidity. Global climate changes have already had profound effects on the distribution of animal diseases, and it is an inevitable reality that continually evolving climatic parameters will further transform the ecology of numerous pathogens. In recent years, many agricultural diseases have given cause for concern regarding changes in distribution or severity. Foot-and-mouth disease, avian influenza, and African swine fever continue to cause serious problems. The expected announcement of the global eradication of rinderpest is one of the greatest successes of veterinary preventative medicine, yet the closely related disease peste des petits ruminants still spreads throughout the Middle East and Asia. The spread of novel strains of bluetongue virus across Europe is an ominous indicator that climate change is sure to influence trends in movement of agricultural diseases. Overall, veterinary practitioners and investigators are advised to not only maintain vigilance against the staple disease threats but to always be sufficiently broad-minded to expect the unexpected.