Developing a National Surveillance System of Strangles

Summary of the new research project

Doctor Richard Newton, Animal Health Trust.

Monitoring the menace: development & implementation of a nationwide strangles surveillance system.

Strangles in horses, caused by infection with S. equi, is characterised by fever, loss of appetite and swelling and abscessation of lymph nodes of the head/neck and occurs across most of the world, affecting many thousands of horses, with hundreds of outbreaks in the UK annually. However, despite its significance globally, in most countries including the UK, there are no meaningful national surveillance data accurately monitoring the extent and progress of the disease through the horse population. This project will develop and implement a system for clinical and laboratory surveillance of strangles, the most important equine infectious disease in the UK. We will establish two surveillance networks (comprising veterinary practices and laboratories, respectively), with methods introduced for regular submission of anonymised information. AHT already uses networks of veterinary practices and laboratories in its long-established equine influenza and Defra/AHT/BEVA quarterly equine disease surveillance initiatives; these will form the basis of this proposed surveillance system. Once developed, this initiative will regularly collate information on clinical and laboratory-confirmed strangles cases across the UK, allowing ongoing assessment of its true welfare impact and highlighting trends over time and in different geographical areas. The system will also conduct genetic sequencing of S. equi provided by collaborating laboratories and representing the national strangles picture. These data will allow unprecedented genetic surveillance of the causative organism of strangles in the UK, confirming or refuting links between outbreaks and flagging emerging strain diversity, which may result in altered disease severity or future vaccine efficacy. In time the system will facilitate monitoring of strangles control initiatives, including future vaccines, especially those with DIVA-capability (Differentiating Infected from Vaccinated Animals).