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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Understanding Fmd Disease Viral Ecology and Landscape Epidemiology Toward Control and Eradication

Location: Foreign Animal Disease Research

Project Number: 8064-32000-057-60
Project Type: Reimbursable

Start Date: Aug 15, 2013
End Date: Sep 30, 2014

Objective:
This collaborative research project is aimed at improving the understanding of Foot-and-Mouth Disease (FMD) ecology in endemic regions to provide the basis for effective control strategies. The possible role of persistently infected ruminants in initiating new outbreaks remains highly controversial and the inability to quantify the real risk posed by such animals could preclude control of FMD in India. The role of Asian Buffalo, cattle and small ruminants in FMDV ecology will be studied in endemic settings in India. This project focuses on epidemiology, viral ecology and pathogenesis of the virus. Specific objectives include: 1. Monitor FMDV circulating sub-clinically in endemic areas of India obtained by probang samples. 2. Conduct virus isolation and molecular characterization of these viruses. 3. Predict antigenic characteristics and conduct vaccine matching studies utilizing current vaccine strains to identify potential new emerging viruses. 4. Quantify epidemiological dynamics of FMDV transmission in India including rate of transmission from persistently infected cattle to susceptible animals and the genetic variation of the virus in the country and its association with epidemiological factors. 5. Conduct necropsy study of persistently infected Asian buffalo and small ruminants to identify localized anatomic sites of FMDV persistence in the animals. Conduct sequence analysis to contribute to the understanding of the role of carriers in FMDV ecology in India.

Approach:
1. To monitor FMDV circulating sub-clinically in endemic areas of India 20-40 farms sites containing FMD-susceptible species with high incidences of FMD outbreaks will be identified. Sera and oropharyngeal fluid samples (probang) will be collected. The sera will be tested for antibodies against non-structural proteins of FMDV and the probang will be tested by rRT-PCR for viral RNA and /or virus isolation. 2. Molecular characterization of these viruses will be conducted through high resolution analysis of all FMDV isolates identified by probang from surveillance well as archival strains. Phylogenetic trees will be drawn depicting results. 3. To predict the antigenic characteristics and conduct vaccine matching studies, FMDV isolates will be compared to vaccines currently in use in the study area. Virus neutralization tests will be conducted to determine the relationship coefficient between the field virus and vaccine virus. 4. To quantify the epidemiological dynamics of FMDV transmission and genetic change in India a susceptible-infectious-recovered (SIR) model will be used. Theoretical distribution of the transmission and recovery rates will be fitted to data and a SIR model will be developed by collaborators from UC Davis to quantify the spread of the virus from carriers to susceptible populations. The association between FMDV evolution and epidemiological factors hypothesized to influence the change will be assessed by Bayesian regression models and the distribution of FMDV clades will be mapped using geostatistical analysis, maximum entropy or Bayesian modeling. 5. Animals (specifically small ruminants and Asian Buffalo) identified as asymptomatic carriers will be procured and euthanized. Necropsy studies will include targeting pharyngeal mucosal tissues and lymph nodes. These tissues will be screened by rRT-PCR and virus isolation for macroscopic localization of the virus. Immunohistochemistry will be performed on the tissues to localize FMDV microscopically. The harvested viruses will be sequenced and compared phylogenetically to other FMDVs characterized within the study.

Last Modified: 10/25/2014
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