The Guardian view on porcine viral diarrhoea: we can’t stop it, but we can control it | Editorial

There is much to be proud of for the EU and its members. Lesson from major diseases in past, it says at the introduction of the new vaccine for porcine epidemic diarrhea virus (PEDv), which will protect swine against a devastating pathogen and help to ensure a safer future for those pigs.

From humble beginnings in the dark Atlantic hinterland of modern-day Norway, Porcine Epidemic Diarrhea virus (PEDv) was first identified by the European Food Safety Authority (EFSA) in an outbreak on the Norwegian farm in May 2015. As the virus rapidly spread throughout northern Europe, from Norway to Holland, devastating pig herds, the virus was declared a serious threat to human health and environmental and animal welfare. The interconnectedness of Europe’s livestock industries, with exports to the US, Canada and China, made a concerted response crucial, and accelerated dialogue among EU and other countries. Finally, in the summer of 2017, a widespread biosecurity zone that covered much of Europe, and those further afield, was established.

The worst-case scenario did not materialise. Human cases did not appear to be associated with the virus in the UK. But the risk of a pandemic in the European pig industry, as well as EU food exports, remained high. Although pig farms in the UK were freed from the threat of disease by a level-three biosecurity zone in April 2017, they remained heavily self-inflicted, given the virus’s mobility.

Comprehensive biosecurity measures could not, however, have kept out a virus that only took hold in a few weeks.

Fortunately, in June 2017, the first commercial-scale vaccine for PEDv was available. Fully developed in a Dutch laboratory using virus from swine in swine groups more at risk of the virus, the vaccine proved effective in various studies conducted throughout the EU. While the virus persistently lingered in pig herds, the new vaccine prevented the disease and in some areas reduced mortality.

Combating the disease

Swine influenza became a global public health threat during the Korean war in the 1950s and 1960s, when there were outbreaks in many countries. Many studies are ongoing into ways of detecting and preventing this virulent virus that affects to a low extent but can reach considerable fevers and vomiting in humans, causing fever, diarrhoea, dehydration and, in some cases, death.

Since PEDv virus can survive for up to three weeks in swine and dead pigs, it poses a major threat to pig herds. Controlling its spread requires coordination among countries and increased surveillance. An integrated approach to PEDv health care – including rapid diagnostic testing, protection against the virus, and vaccination and control measures – reduces disease transmission among pigs, and risks of severe disease within the pig population and food chain.

PEDv’s fast international spread, and the EU’s response to it, have reinforced EU leaders’ desire to lead Europe’s response to the adoption of a new global strategy on combating pandemics. Last month, a G20 summit proposed that the EU should spearhead that response through a new Pandemic Preparedness Roadmap on Public Health Emergencies. The EU is the current chair of the World Health Organisation Collaborating Centre for Pandemic Influenza, and recently launched a Strategic Plan for International Cooperation on Infectious Diseases and Emergency Preparedness.

But the success of the new PEDv vaccine depends on its sustainment. Prevention works in the long run, but humans need to be protected from their own positive behaviour – through vaccination against other viruses, as well as an understanding of how they and other viruses function in the pandemic environment. Human infection by the H7N9 virus, which began in China in 2013, is an illustration of this point. Researchers now know that the virus and the vaccines used to prevent it were virtually identical, but according to an analysis of viral mutation and host immunity during the pandemic, the virus is prone to more mutations and may continue to spread in human populations, more readily infecting people.

Without this human understanding, we have no way of fully predicting how PEDv may mutate and accelerate its spread in the future. This uncertainty will require a much more intensive global effort. Vaccination is the best prevention strategy for controlling PEDv and preventing a possible pandemic, but on its own it will not stop this virus from showing up elsewhere.

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