The study commissioned by the Catalan government rules out that the African swine fever outbreak originated at IRTA: "It's a strain that has never been found before."

BarcelonaThe theory that the African swine fever (ASF) outbreak in Collserola could have originated from the IRTA-CReSA laboratory is losing steam every day. This Tuesday, the Catalan government announced that the analysis it commissioned from the Institute for Research in Biomedicine (IRB) found no match between the virus strain that infected the first wild boars and the various samples of the pathogen being worked with at the Catalan laboratory. Specifically, the IRB sequenced 17 ASF virus samples that IRTA-CReSA has worked with in recent years and concluded that none of them matched the sequencing performed by the European reference laboratory on the virus strain samples taken from the first two cases. "We have found no match to indicate that the virus from the outbreak corresponds to the laboratory samples," explained ICREA research professor Toni Gabaldón, jointly affiliated with the Institute for Research in Biomedicine (IRB) and the Barcelona Supercomputing Center (BSC), and director of the Comparative Genomics group. The IRB explained that the differences observed between the samples "are too significant" to establish any direct link between the outbreak and the laboratory located in Bellaterra. The experts detailed that "the virus detected in Cerdanyola del Vallès presents dozens of specific mutations and a large genomic deletion [i.e., a loss of genetic material] that do not appear in any of the laboratory strains analyzed."

In a subsequent press conference, the Minister of Agriculture, Òscar Ordeig, announced that "according to the information we have today, pending official confirmation from the Ministry, the IRB sequencing indicates that the wild boar samples [infected with ASF] do not match those from CReSA." However, the Minister urged "caution," as this is an external study commissioned by the Catalan government and carried out in parallel with the work being done at the Central Veterinary Laboratory, the reference laboratory for the Ministry of Agriculture. This is the only center that can provide official results on the matter. The Catalan government admitted that it does not yet know when it will receive these conclusions.

Since the Catalan government commissioned the analysis, the IRB has received 19 samples of African swine fever (ASF) virus variants, which have been analyzed at the IRTA-CReSA laboratory. As of Tuesday, 17 of the 19 samples have been sequenced, a volume that the Secretary General of the Department of Agriculture, Cristina Massot, described as "significant and sufficiently relevant" to allow for the release of initial results. Among the analyzed samples are some that have been used in the last year, as well as others that are frozen and were used some time ago in other studies. In fact, the two samples awaiting sequencing have been frozen for more than five years, and Massot admitted that "the possibility of the outbreak originating from a frozen strain is very remote." However, as Ordeig did, the Secretary of Agriculture reiterated that the IRB sequencing results "are by no means conclusive" because the official reference laboratory of the Ministry is the one that must draw conclusions.

A new strain

Beyond the comparison with IRTA samples, the IRB has pointed out that the sequencing of the virus found in the dead wild boars also does not match any of the 800 African swine fever (ASF) genomic sequences that exist in public databases worldwide. "It's a strain that has never been found before; it's a new variant of the virus that hasn't been described until now," Gabaldón stated. The biomedical institute details how the sequencing of the virus's genome in the outbreak indicates that it has "general features similar to the virus detected previously, but with substantial genetic changes not previously described." In other words, the variant that has caused the death of 29 wild boars in Collserola would be a new genetic variant or, at least, a type that has not been documented until now. The IRB study suggests that this would be a new variant, as the first report from the European laboratory already indicated, because it has a unique "genetic fingerprint." Specifically, the detected virus shows a loss of a deletion or fragment of the genome—the genetic instructions in DNA—and a set of "unique" mutations that do not match the strains circulating in Western Europe. Although the characteristics of the Collserola variant do have some similarities with strains described in Eastern European and Asian countries, such as Russia, China, and Thailand, Gabaldón has insisted that the differences are significant enough to consider it a new variant.

The sandwich theory returns

One of the characteristics of the new variant of the virus, as explained by the IRB professor, is that it is "less virulent" than those previously detected. This would imply that the virus's mortality rate when it infects an animal may be lower, which is why Massot also emphasized that the Catalan government is conducting serological tests on wild boars captured alive to verify that no animals have developed resistance to the virus. The Secretary of Agriculture explained that, so far, no such cases have been detected and that they "hope not to find any." With the results of the IRB study, Minister Ordeig avoided further speculation about the possible origin of the virus. In fact, the IRB scientists also raised the possibility that the origin of the outbreak may never be known, as has already happened in other countries. However, in a statement, the government asserted that "in line with international experience," the most plausible hypothesis is the introduction of the virus through contaminated material, especially pork products. In other words, the infamous "sandwich theory" is once again being considered, a route already identified as likely in outbreaks previously detected in other European countries.

Faced with this new variant of the virus, Christian Gortázar, Professor of Animal Health at the Research Institute of Hunting Resources (IREC), warns that it may be necessary to change some protocols. In statements to SMC Spain, Gortázar cautioned: "If we have a different virus here, we will probably have to adapt to this new circumstance in some way." He insisted that "this is the most important thing, regardless of the virus's origin." In this regard, the professor pointed out that once it has been confirmed that the virus is different, "we have to see if, as expected, this different virus also has different epidemiological characteristics." If this is the case, Gortázar warns that the European Union's protocols are designed to address "highly pathogenic" variants of swine fever, the most virulent, a characteristic that the new variant detected in Collserola lacks.