2013 Annual Report
1a.Objectives (from AD-416):
The goal of this project is to conduct phylogenetic, temporal and spatial analysis and modeling of viral strains circulating in Central Asia, Southeast Asia and Africa. Specific objectives include:
1. Gain a better understanding of the epidemiology of Foot-and-Mouth Disease Virus (FMDV) strains circulating in selected endemic regions of Asia and Africa.
2. Determine the phylogenetic relationships of FMDV strains in endemic settings and the nature and extent to which such relationships are associated with epidemiological factors or the settings.
3. Determine the antigenic relationship of FMDV strains circulating in select regions with currently available vaccine strains.
1b.Approach (from AD-416):
1. Data from FMD outbreaks and active (non-outbreak) surveillance of infected populations will be collected through ongoing field activities in Vietnam, Pakistan and Cameroon. The samples will be tested by rRT-PCR and virus isolation. Sequencing will be conducted and the data generated will be incorporated with known epidemiological data to determine differences between spatial and temporal variables in an effort to determine virus distribution and gain an understanding of viral – host genomic factors. A longitudinal field study will be conducted to determine the viral and host genomic factors influencing viral persistence in local livestock to gain a better understanding of the mechanisms of FMDV persistence.
2. Genetic characterization of viral strains obtained over a 2 -3 year period in three endemic regions of Africa, Central and Southeast Asia will be conducted. The strain information will be coupled with associated geographic and temporal data, case history and animal demographics to determine associations between the pair-wise genetic distances of FMDV isolates and epidemiological factors.
3. Vaccine-strain matching studies will be conducted, which may lead to the recommendation of adding new vaccine antigens to the existing vaccine bank. Determination of the ratio of heterologous vs. homologous titers will be conducted by neutralization with reference sera to relevant predicted vaccine strains and by ELISA. Antigenic cartography will be conducted using serological data to visualize and quantify antigenic relationships among viruses and sera.
As a member of the Global Foot-and-Mouth Disease Research Alliance (GFRA) ARS has international collaborative research projects in various countries including Vietnam, Pakistan, and Cameroon. Valuable field Foot-and-Mouth Disease (FMD) samples, such as clinical disease samples, subclinical disease and serological surveys, are collected on a regular basis under these projects, including detailed epidemiological data such as geo-localization and animal demographics. This project supports analysis of viral strains and associated information of field research projects on FMD in Pakistan, Vietnam and Cameroon.
During FY13 numerous outbreak samples were received from all three study sites. In Vietnam, we identified numerous carrier steers and buffalo through antemortem screening by ELISA and swab/probang testing. Some of these animals for selected for inclusion in transmission studies whereas others were chosen for necropsy and tissue collection. Serial screenings were conducted and numerous samples were delivered to ARS, PIADC and are being processed for presence of virus as well as tissue localization at the molecular level. In addition outbreak strains were sent to ARS, PIADC for sequence characterization and vaccine matching studies. Serotypes A and O were indentified in Vietnam, with virus activitiy most prevalent in northern Vietnam.
In Pakistan sampling continued in 40 infected premises containing persistently infected buffalo and cattle. In addition over 100 samples from outbreak investigations were transferred from Pakistan to ARS, PIADC for further investigation. Sequence analysis showed that serotypes A, O and Asia 1 caused outbreaks throughout Pakistan. Genotypes were widely distributed indicating widespread movement of infected animals.
Cameroon presents a unique opportunity for epidemiological studies in that the country does not vaccinate FMD. Therefore, the antigenic and genetic behavior of FMD virus (FMDV) strains circulating “naturally” among different livestock production systems in the Far North of Cameroon were studied to give insight into the ecology of the virus. We found serological evidence of FMDV infection in over 80% of the animals sampled with no significant differences observed among the sampled groups i.e. market, sedentary, and nomadic. We also found antibodies reactive to five FMDV serotypes namely serotypes A, O, Sat 1, Sat2 and Sat 3 among the animals sampled. Finally, we were able to genetically characterize viruses obtained from clinical and subclinical FMD infections in Cameroon. Serotype O viruses grouped into two topotypes, West and East Africa. Sat-2 viruses grouped with viruses from Central and Northern Africa, particularly the sublineage causing the large epidemic in Northern Africa in 2012, suggesting a common origin for these viruses. This research will guide future interventions for the control of FMD such as improved diagnostics, guidance for vaccine production, and epidemiological understanding in support of the progressive control of FMD in Cameroon.
No technologies were transferred or publications produced during FY 2013.