Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2012
Publication Date: July 29, 2012
Citation: Brito, B.P., Perez, A.M., Jamal, S.M., Belsham, G.J., Pauszek, S.J., Ahmed, Z., Rodriguez, L.L. 2012. Foot-and-mouth disease virus serotype O phylodynamics: genetic variability associated with epidemiological factors in Pakistan. Transboundary and Emerging Diseases. DOI:10.1111j.1865-1682.2012.01366.x.
Interpretive Summary: Foot-and-mouth disease (FMD) is a highly contagious viral disease of livestock, producing losses that are insidious in endemic settings and devastating in disease-free countries. The causing virus (FMDV) is highly variable with 7 different serotypes (A, O, C, Asia, Sat 1, Sat 2, and Sat 3). Vaccines do not confer cross protection between serotypes and in many cases not even among different strains within a given serotype. In Pakistan, FMDV causes numerous outbreaks and associated economic losses to the livestock industry. Little information is available regarding the epidemiology, viral strains circulating in Pakistan and their coverage by currently available vaccines. Additionally, the role of Asian buffalo in the ecology of FMDV has not been fully characterized even though they are known to remain asymptomatically infected for prolonged periods. Little is known about FMDV infections in the absence of clinical signs (subclinical infections and carrier state), which are believed to be key to the maintenance of FMDV in mixed animal populations. The importance of Asian buffalo as reservoirs of FMDV in persistent infection therefore remains as a critical knowledge gap in understanding FMD ecology in Asia. This knowledge is necessary to guide the implementation of effective and sensible control programs. Currently, only 15% of animals are vaccinated each year and at this time no government organized vaccination plan for the country has been implemented. A pilot control program sponsored by the United States Agency for International Development (USAID) is being implemented by the Pakistani government, with support from the Food and Agriculture Organization of the United Nations (FAO). The information developed with this proposed research project will provide critical information regarding the effectiveness of FMD vaccines and the most suitable vaccination strategies leading to successful control of the disease.
One of the most challenging aspects of foot-and-mouth disease (FMD) control is the high genetic variability of the FMD virus (FMDV). In endemic settings such as the Indian subcontinent, this variability has resulted in the emergence of pandemic strains that have spread widely and caused devastating outbreaks in disease-free areas. In countries trying to control and eradicate FMD using vaccination strategies, the constantly evolving and wide diversity of field FMDV strains is an obstacle for identifying vaccine strains that are successful in conferring protection against infection with field viruses. Consequently, quantitative knowledge on the factors that are associated with variability of the FMDV is prerequisite for preventing and controlling FMD in the Indian subcontinent. A hierarchical linear model was used to assess the association between time, space, host species and the genetic variability of serotype O FMDV using viruses collected in Pakistan from 2005 to 2011. Significant (P < 0.05) amino acid and nucleotide variations were associated with spatial distance, but not with differences in host species, which is consistent with the frequent multi-species infection of this serotype O FMDV. Results from this study will con-tribute to the understanding of FMDV variability and to the design of FMD control strategies in Pakistan. Viruses sequenced here also provide the earliest reported isolate from the Pan Asia IIANT-10 sublineage, which has caused several outbreaks in the Middle East and spread into Europe (Bulgaria) and Africa (Libya).