Foot and mouth disease: impact of preclinical diagnosis on farm-to-farm transmission

Preclinical detection of Foot-and-mouth disease virus (FMDV) during outbreaks has the potential to allow earlier culling of infected herds and thereby reduce transmission and aid the control of epidemics.

During an outbreak of foot and mouth disease, current control and eradication methods rely on rapid clinical detection and the removal of infected herds.

In a study published in the Journal of Clinical Microbiology, scientists at The Pirbright Institute and Wageningen Bioveterinary Research evaluated the methods and effects of preclinical diagnosis during surveillance (as would be in place during an outbreak), in order to reduce the risk of transmission between herds of cattle on neighbouring farms.

Transmission experiments in cattle were used to collect samples taken from individual animals such as blood, saliva and nasal swabs, and at herd level such as air samples, on a daily basis during the course of infection. The sensitivity of each of these types of samples for the detection of infected cattle during different phases of infection was then quantified.

Dr. Simon Gubbins, Head of Transmission Biology at Pirbright said: “Our results were incorporated into a mathematical model for FMDV transmission in a cattle herd in order to evaluate the impact of early detection and removal of an infected herd on the reduction in the amount of infectious output which could enable transmission of the virus to cattle on a neighbouring farm.

“By using weekly surveillance, clinical inspection alone was found to be ineffective at blocking transmission. This was in contrast to the impact of weekly sampling using saliva swabs of at least ten animals per farm or daily air sampling (for housed cattle), both of which were shown to reduce the risk of transmission substantially.”

Dr. José Gonzáles from Wageningen Bioveterinary Research added: “These findings provide a new approach to disease control which could be added to our emergency preparedness programmes. A potential benefit of applying this strategy is a reduction in the number of animals culled unnecessarily, which is likely to happen when traditional strategies such as pre-emptive culling are implemented.”

The Pirbright-Wageningen research team plan to test their approach in field trials.

Article: Predicting the Ability of Preclinical Diagnosis to Improve Control of Farm-to-Farm Foot-and-Mouth Disease Transmission in Cattle by Noel Nelson, David J. Paton, Simon Gubbins, Claire Colenutt, Emma Brown, Sophia Hodgsona and Jose L. Gonzales, published in Journal of Clinical Microbiology (2017) vol. 55, no. 6, pp. 1671-1681, doi: 10.1128/JCM.00179-17

[SOURCE: The Pirbright Institute]