An international project led by scientists in the World Reference Laboratory for Foot-and-Mouth Disease (WRLFMD) at The Pirbright Institute has tracked the evolution of FMD virus (FMDV) over nearly 20 years to reveal how different factors affect its spread across countries of Western and Southern Asia.
FMD is a highly contagious disease that affects over 50 million animals every year, with an estimated annual cost of US$1.2-2.3 billion in livestock production losses in regions where it is widespread. The disease is caused by seven different types of FMDV (known as serotypes), which each require a specific vaccine since immunity raised against one serotype does not provide protection against others.
In their study recently published in Molecular Biology and Evolution, Pirbright scientists analysed nearly 2,500 viruses of three FMD serotypes (O, A and Asia1) circulating in Western and Southern Asia between 2001 and 2018, documenting important evolutionary events driving patterns of virus infections in the region.
A key finding was the recognition that certain countries in Southern Asia play a central role in the creation of new virus variants that subsequently spread in a westerly direction across the region. This observation is important because it helps us to understand the origins of FMD viruses that pose the greatest risks to neighbouring countries via trade connections.
This study also showed for the first time, that the “molecular clock” that drives evolutionary changes in FMD viruses is similar across different virus serotypes. This clock generates virus variants that are genetically different from the original serotypes, which are introduced in waves that typically lasted three years in the study region. The scientists suggest that this oscillatory pattern is influenced by three key factors: immunity, since this is specific to each virus type, the “fitness” of these viruses to replicate and be transmitted in livestock and the opportunities for the virus to spread through international trade.
Dr Antonello Di Nardo, lead author of the paper at Pirbright, said: “Our work highlights the importance of data-sharing and exchange of samples between countries where FMD is endemic. These results offer vital insights about the spread of FMD across Asia, which has been influenced not only by factors such as geography and trade, but also by differences in the way that FMD viruses evolve and are transmitted between cattle and sheep. Our results help us to understand the risks of FMD spread between countries to enable improved prevention and intervention strategies to be implemented.”
This study was funded by the Department for Environment, Food and Rural Affairs (Defra), the Biotechnology and Biological Sciences Research Council (BBSRC), part of UKRI and the European Commission for the control of Foot-and-Mouth Disease (EuFMD).