INTERVIEW ▶▶▶ Three vaccine candidates
The Vacdiva project is focusing on the validation of three dif- ferent ASF vaccine prototypes, described in Spain, Portugal and Russia respectively. Especially of the first two, Prof Sánchez-Vizcaíno has high hopes. The prototype description in Spain occurred at Prof Sánchez-Vizcaíno’s own Universidad Complutense in Madrid. This is based on a mutated version of the ASF natural attenu- ated virus genotype II that was found in a dead wild boar in Latvia. An oral vaccine has been made from this, which has al- ready been experimentally and successfully tried in wild boar populations. This prototype is currently under evaluation in domestic pigs in laboratories in both Madrid, Spain and Perugia, Italy. A second vaccine prototype was found in Portugal in the 1960s by the Faculty of Veterinary Medicine of Lisbon. Unlike the previous prototype, this one is based on attenuated ASF isolate, genotype I, but for the vaccine’s efficacy the genotype is not expected to make any difference. The prototype has al- ready been evaluated in domestic pigs in Madrid and Perugia with very good results; trials with wild boar are about to take place at the Visavet-UCM Center in Madrid, Spain. A third prototype is being developed in Russia by the Fed- eral Centre for Animal Health (ARRIAH) in Vladimir. This is a Russian ASF isolate called Arriah CV-1. Even though this virus is already adapted in tissue culture, only relatively few in vivo experiments have been done, so there is not much data yet.
where they lived, what densities they lived in and whether they had enough food or not. We had almost the whole wild boar pop- ulation clean in the first five years of the eradication programme. “In domestic pigs, we had got rid of the disease in the first three years of the programme. Protecting the domestic pigs was rela- tively easy; that happened by introducing much better external and internal biosecurity, plus by using ELISA to detect all the asymptomatic pigs carrying the virus. We invested a lot of money to help farmers renew their facilities, something that was very important. “Outdoor production was the last area to get rid of ASFv. And that’s because we couldn’t see where the infected ticks were. For that, ELISA was fantastic. We tested pigs for ASFv using ELISA di- agnosis, and in parallel we also did that with ticks. This showed us where the infected ticks were located and where they were able to bite the pigs. We found that the ticks were usually in little old houses that people don’t use, the zahurdas (pig sheds). Some- times these sheds were dilapidated with only a wall still standing. Using sentinel pigs we learnt that the ticks were only in these buildings. So we destroyed them all, except a few historical ones. “The eradication programme was really fantastic. I think it could be used in many scenarios, yet it is probably not well known. And
28 ▶ PIG PROGRESS | Volume 37, No. 2, 2021
because we eradicated the virus in 1995, ASF was not important for anybody, only for Spain and Portugal. Those were the only countries for whom it mattered; others weren’t interested at all.”
Hence, for many years, Spain became the centre of knowl- edge for ASF. “Yes. Spain was the ‘Cathedral’ for ASF. In Spain we had learnt that ASFv has many different faces. It is not the same to fight it in Iber- ico pigs, in ticks and in domestic pigs. Every time it’s important to take biosecurity factors into account. That is why we had more ex- perience than most of our colleagues. And it was important to do a lot of research, in order to understand how to stop the disease. After all, even despite ASF presence, swine production in Spain had become very strong. The people had learnt how to deal with and survive the disease.”
The Vacdiva project Fast forward to 2020, when ASF once more awaited him as oppo- nent. Prof Sánchez-Vizcaíno was recently appointed coordinator of Vacdiva, a European-funded ASF consortium bringing together all kinds of disciplines, companies and organisations (see also box The Vacdiva project). Its ultimate goal is to jointly find lasting solutions against the virus that has virtually 100% mortality yet for which no commercially available solutions exist. The strategy focuses on developing new diagnostic tools as well as eventually developing vaccine candidates that differentiate infected from vaccinated animals (known as the DIVA principle). These three vaccines are described in the box Three vaccines.
Why was it necessary to have a consortium like Vacdiva formed? “Because Vacdiva is a project that offers many things. We offer a safe, cross-protective vaccine, a ‘diva’ vaccine, so that implies that we have diagnostic people who know how to prepare diva vac- cines, and we also offer different vaccination strategies, depend- ing on different epidemiological scenarios, in Europe and outside of Europe. So that means we needed virologists, we needed pa- thologists, we needed immunologists, we needed epidemiolo- gists, we needed diagnosis people. Plus, we also needed one more important group, knowledgeable about wild boar behav- iour and the interaction between domestic pigs and wild boar.”
ASF has been in the EU since 2014. Do you feel that a con- sortium like Vacdiva should have been formed a lot earlier than 2020? “Yes, definitely. I sometimes have the impression that some of our administrations in general underestimated the disease… I think they don’t react quickly because they also think that they have ex- pertise and they are going to control it quickly. Sometimes in poli- tics it is difficult to assess the risk with clarity. For Europe it would have been a lot better if Vacdiva or any other group had been started earlier.”
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