African swine fever is a lethal pig disease that has been spreading rapidly across many countries. Scientists and researchers have been working tirelessly to develop an effective vaccine that can help control this disease. In this article, we discuss the progress being made on an African swine fever vaccine.
The Disease and its Impact
African swine fever is a viral hemorrhagic disease of domestic and wild pigs that was first reported in Africa in the early 1900s. Since then, it has spread to Europe and Asia. The virus that causes African swine fever is highly contagious and can spread through direct contact between infected and healthy pigs as well as indirectly through contaminated feed and contact with fomites like vehicles, clothes and shoes. The mortality rate in infected pigs approaches 100%.
Once an outbreak occurs, it is very difficult to control the spread of the disease. Countries that experience outbreaks face tremendous economic losses due to death of pigs and cost of controlling the spread and recovering from the outbreak. For example, China reported losing over a million pigs to African swine fever in 2018 alone. With increasing globalization and movement of people and goods, the spread of this disease to other regions is a major concern. Developing an effective vaccine is crucial to help control African swine fever.
Challenges of Vaccine Development
Developing a Swine Fever Vaccines African swine fever virus is challenging for several reasons. The virus lacks effective immunogenic genes and has complex mechanisms to evade the host immune system. It also exhibits considerable genetic diversity which complicates vaccine design. Furthermore, there is no small animal model for African swine fever virus pathogenesis and immune response studies. Researchers need to rely solely on expensive pig trials for vaccine testing. These challenges have significantly slowed down the pace of African swine fever vaccine development.
Promising Vaccine Candidates
Despite the challenges, progress is being made on development of African swine fever virus vaccines. Several groups across Europe and China are pursuing different vaccine strategies:
Deletion Mutants: Scientists at The Pirbright Institute in UK have developed live attenuated vaccines by deleting immunoregulatory genes from the virus genome. Pigs vaccinated with these mutants displayed some level of protection upon challenge.
Virus-Like Particles: Researchers at University of Bath constructed virus-like particles by expressing structural proteins of African swine fever virus. These sub-unit vaccines have shown protection in animal trials.
DNA Vaccines: Groups in Spain and China have designed DNA vaccines containing immunogenic genes from African swine fever virus. Pigs inoculated with these vaccines produced specific antibodies and T-cell responses.
Vector Vaccines: Recombinant vectors like vaccinia virus and adenovirus have been tried to deliver African swine fever virus antigens. One such vaccine developed by Harbin Veterinary Research Institute in China was partially protective in pigs.
Novel Delivery Systems: Novel delivery systems like polymicrobial vaccines using Salmonella or plants expressing viral antigens are also being examined to enhance immunogenicity.
Regulatory Approval and Commercialization
While the above-mentioned vaccine candidates seem promising, there is still a long way to go before commercial availability. Most vaccines will need to undergo rigorous testing through multiple pig trials under laboratory and field conditions to prove safety and efficacy as per regulatory standards. Large-scale manufacturing processes will have to be established to produce sufficient vaccine doses economically.
If future trials continue to show good protection, regulatory authorities may consider conditional licensure of African swine fever vaccines. However, full commercial rollout may still take 5-10 years given the complexity of the disease. International cooperation across research groups and regulators will also be important to standardize testing protocols and facilitate approval process. Overall, an effective African swine fever vaccine could be a game changer for the global pig industry worth billions of dollars.
To summarize, African swine fever is a challenging disease to control due to lack of vaccination. Researchers have made progress in designing various vaccine candidates using different strategies over past few years. Ongoing gene deletion mutants and subunit vaccines show most promise based on preliminary results. However, much more testing is still needed to prove efficacy under field conditions. If successfully developed, a vaccine could greatly minimize losses caused by this lethal pig disease worldwide. With sustained efforts, the goal of an approved African swine fever vaccine seems achievable in the near future.