Researchers have developed genetically modified pigs that are protected from classical swine fever virus.

The infectious agent responsible is a virus CSFV (previously called hog cholera virus) of the genus Pestivirus in the family Flaviviridae. CSFV is closely related to the ruminant pestiviruses that cause bovine viral diarrhea and border disease.

The effect of different CSFV strains varies widely, leading to a wide range of clinical signs. Highly virulent strains correlate with acute, obvious disease and high mortality, including neurological signs and  hemorrhages  within the skin.

Less virulent strains can give rise to chronic infection that may escape detection, while still causing abortions and stillbirths. In these cases, herds in high-risk areas are usually tested on a thorough statistical basis.

Infected piglets born to infected but subclinical sows help maintain the disease within a population. Other signs can include lethargy, fever, immunosuppression, chronic diarrhea, and secondary respiratory infections. The incubation period of CSF from 2 to 14 days, but clinical signs may not appear until after 2 to 3 weeks. Preventive state regulations usually assume 21 days as the outside limit of the incubation period. Animals with an acute infection can survive 2 to 3 months before their eventual death.

As noted by the authors, these pigs offer potential benefits over commercial vaccination and could reduce economic losses related to classical swine fever. CSFV is responsible for a highly contagious, often fatal disease that causes significant economic losses. Due to the economic importance of this virus to the pig industry, the biology of CSFV has been investigated extensively.

Many efforts to stamp out the disease from pig populations, it is widespread, and it is only a matter of time before the virus is reintroduced, and the next round of disease outbreaks occurs. There is an urgent need to develop effective approaches to eradicate CSFV.

CSFV-resistant

To address this challenge, Ouyang and colleagues generated CSFV-resistant pigs by combining a gene-editing tool called CRISPR / Cas9 with RNA interference (RNAi), a technique that silences gene expression.

The researchers demonstrated that these pigs could effectively limit the replication of CSFV and reduce CSFV-associated clinical signs and mortality. Moreover, disease resistance could be stably transmitted to the first-generation offspring. Currently, the researchers are conducting long-term studies to monitor the safety and effectiveness of this approach to these animals.

According to the authors, generating anti-CSFV pigs using a genome editing-based strategy could be a direct and practical approach to facilitate the permanent introduction of novel disease resistance traits into the mass population of production pigs via conventional breeding techniques. Besides,