Roadmap for the research to underpin the development of control strategies for FMD

What are we trying to achieve and why? What is the problem we are trying to solve?

To determine mechanisms of FMDV persistence in livestock and their role in disease transmission.

What are the scientific and technological challenges (knowledge gaps needing to be addressed)?

• Determine viral and host determinants of establishment and maintenance of persistence.
• Define persistence, sites of persistence, and meaning of persistent infection in nature.
• Understand the difference between carriers and not carriers.
• Identification of animals during transitional phase.
• Study mucosal responses to acute and persistent infections in cattle.
• Support research on the immunological mechanisms of cross protection in susceptible species
• Determine the role of persistent animals in FMD transmission

What approaches could/should be taken to address the research question?

What else needs to be done before we can solve this need?

Existing knowledge including successes and failures

In domestic and wild ruminants, FMDV may persist (i.e. carrier state) with intermittent viral shedding in the oral-pharyngeal fluid for extended periods of time. Persistence may result from symptomatic or asymptomatic infection of naïve, convalescent or vaccinated animals. Evidence suggests that the sites of viral persistence are in the pharyngeal region, specifically the dorsal soft palate, dorsal pharyngeal area, and associated lymph nodes.
The mechanisms mediating the establishment and maintenance of persistent infections in ruminants remain unclear, but it is noteworthy that both primary and persistent infections with FMDV have been associated with pharyngeal tissue in ruminants. The role of persistence in the transmission of FMDV is poorly understood, although some evidence indicates that persistently infected African buffaloes (Syncerus caffer) can serve as a source of infection to cattle. Despite the uncertainty surrounding the true threat posed by FMDV carriers, it is clear that the perception of
threat from these animals is one of the main driving forces dictating FMDassociated trade issues. Thus, one of the long-term goals of novel FMD countermeasures must be prevention or cure of the carrier state.
Experimental studies evaluating persistent infections have demonstrated that only some ruminant species exposed to FMDV become carriers, irrespective of whether they are fully susceptible or immune; i.e., protected from disease as a result of vaccination or recovery from infection.