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Alasdair King

One of the challenges of working with emerging diseases is how little is often known. How do we best implement control programmes when we don't fully understand the epidemiology of a disease? Vaccines are clearly an aid, but we need a broader understanding in order to reduce the risks.

Lumpy skin disease is a clear demonstration of this issue. When the virus broke free of its traditional geographic restraints and rapidly spread into Southern Europe, there were a lot of questions around the subject of transmission, especially: "Exactly what role does the vector play?" Although we know that good quality Neethling-like vaccines can control the disease, it is important that we don't simply rely on these and that we know what advice to give to farmers. As part of our commitment to be a part of the community and to control this disease, we decided to support two projects from The Pirbright Institute that address this area.

We were therefore very excited to see two posters at the International Meeting on Arboviruses and Their Vectors (IMAV19) held in Glasgow, Scotland, this September as a result of this work. Overseen by Pip Beard, Lumpy Skin Disease Virus Does Not Replicate Productively in Insect Cell Lines by Charlotte Cook and Lumpy Skin Disease Virus: Transmission to Dipteran Vectors Using Animal and Ex-Vivo Models by Beatriz Sanz Bernardo, are groundbreaking.

Considering that lumpy skin disease has been recognized since 1929, it is perhaps surprising that the exact transmission route has not been fully understood before now. That vectors were involved was clear, but to what extent and how had not been answered. The results of these two studies give us a clearer picture of what is happening. This is important for countries trying to assess risk and determining what to communicate to farmers.

Some of the findings are really interesting. For instance, while the virus does not replicate within the insects (in itself a critical finding), all the Diptera species tested, including mosquitos, stable fly, and midges, became positive for the virus genome. And while I would think of mechanical spread as being a short term, the virus can actually be recovered from mosquitos for at least 8 days after feeding. However, non-clinical cattle are significantly less likely to pass virus to the vectors. My personal take on this—and I must stress "my take" because this isn't in the posters—is that the risk of spread is greater than we could expect from mechanical transmission, but even non-sterile immunity will inhibit transmission enough to break the infection cycle as long as cattle show no signs of disease. This hints at why vaccination has been so successful where used in Europe.

What is at least equally impressive with these posters is that they were able to develop an ex-vivo model in order to study the transmission of the virus. At MSD Animal Health we are firmly committed to the 3R's (Replacement, Reduction and Refinement) principle and believe it is essential to find methods of research which avoid using animals wherever possible. This is a big component of my role as Animal Welfare Lead, so being part of a study which has successfully managed to use a membrane feeding system to replicate what happens in the field is especially pleasing.  

Over the last 5 years we have worked hard to ensure our support goes into the community to further knowledge of transboundary and emerging diseases. It is an area where we believe we can add value and that will change the future. Work such as this by Charlotte and Bea goes a long way to convince us this is the right route. We are looking forward to hearing more from them as they delve deeper into this area.

Alasdair King
Director, Intergovernmental Veterinary Health

Beatriz Sanz Bernardo, The Pirbright Institute, presenting her work on the role of vectors in lumpy skin disease virus (LSDV) transmission at the IMAV19, Glasgow, Scotland.

Charlotte Cook, The Pirbright Institute, with her poster on the LSDV transmission and replication in insect cell lines, IMAV19, Glasgow, Scotland.

 

 

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