London School of Hygiene & Tropical Medicine

There is a high probability of a new introduction of bluetongue virus serotype 3 (BTV-3) into livestock in the UK, according to a report by the UK Government’s Animal and Plant Health Agency (APHA).

Bluetongue virus is primarily transmitted by biting midges (Culicoides species) and affects cattle, sheep, and other ruminants such as goats and deer, and camelids such as llamas. Symptoms vary across species but can include fever, lesions and redness of the mouth, eyes and nose. In severe cases, it can be fatal for infected animals.

The virus does not affect humans or food safety, and meat and milk from infected animals are also safe to eat and drink.

The risk assessment warned that BTV-3 may spread due to infected midges migrating from northern Europe, where the virus has already significantly affected farming communities.

A vaccine for BTV-3 has been authorised for emergency use in the Netherlands but is yet to have authorisation in the UK.

Polly Roy, Professor of Virology at the London School of Hygiene & Tropical Medicine (LSHTM), is a world-leading expert on bluetongue and has studied the virus for over three decades. Her work has led to the first complete molecular understanding of the pathogen and researchers now know every aspect of its replication cycle, up to its engagement with the host cell.

Commenting on the concerns raised, Professor Roy said:

“The BTV-3 serotype has always been present in Africa but, in recent years, we’ve seen it move its way across Europe.

“While there are vaccines against BTV-3 already in use in other countries, they haven’t yet been authorised in the UK. This is because in some cases, this pathogen is so cunning that if the vaccine is poorly efficient, the virus can outsmart it and begin to replicate within the animal leading to unintended infection.

“To try and combat this, my team has spent many years working on a bluetongue virus vaccine which uses synthetic RNA copies of emerging strains in order to rapidly make an efficient vaccine which cannot cause disease. This type of vaccine is morphologically the same as the authentic virus but has a key protein involved in its replication, known as VP6, removed, making it unable to replicate itself.

“We believe that this vaccine will be highly effective and we’ve seen extremely promising results in animal studies so far with robust immune responses and no unintended viral replication. We hope that we will see it manufactured and authorised soon.

“The bluetongue virus has a very complicated structure compared to many other viruses, particularly other vector-borne pathogens.

“Knowing so much about how this virus replicates is allowing us to understand and target similar pathogens, such as the virus which causes African Horse Sickness, and the principles of its structure and replication cycle can also be applied to other pathogens which may infect humans.

“Even after thirty years of learning, I’m still fascinated.”