by Swine fever, also known as classical swine fever (CSF), is a highly contagious viral disease affecting pigs. While historically swine fever outbreaks have caused huge economic losses to pig farmers globally, recent developments in vaccine research provide hope that this disease can effectively be controlled through vaccination. In this article, we explore the landscape of swine fever vaccine research and development and how an effective vaccine can potentially eliminate the threat of this dreaded pig disease.
Emergence of deadly swine fever strains
Swine fever is caused by the classical swine fever virus (CSFV) which is a pestivirus belonging to the Flaviviridae family. While the disease was first reported in the early 19th century, recent decades have witnessed the emergence of more virulent strains. In 1997-1998, a highly pathogenic variant caused widespread outbreaks across several European and Asian countries leading to the culling of over 10 million pigs. More recently in 2018-2019, outbreaks of virulent CSFV in China, North Korea and other parts of Asia resulted in losses estimated at over a billion dollars. These large outbreaks highlighted the economic devastation possible from swine fever epidemics and underscored the need for improved control strategies including vaccination programs.
Advances in swine fever vaccine research
Traditional Swine Fever Vaccines based on live attenuated viruses helped control the disease for many years. However, issues with reversion to virulence and difficulty in differentiating infected from vaccinated animals led researchers to develop new generation vaccines. In the last decade, major advances have been made with the development of subunit and marker vaccines against CSFV.
Subunit vaccines containing targeted viral proteins like E2 glycoprotein induce strong immune responses without risk of reversion. Marker vaccines are designed to allow differentiation between naturally infected and vaccinated animals through inclusion of genetic markers. Promising experimental studies have demonstrated the efficacy of several subunit and marker vaccine candidates against virulent CSFV challenge. Some of these second generation vaccines have also received conditional licenses in Europe and other regions in recent years.
Challenges in developing an effective global vaccine
While progress on swine fever vaccines looks very encouraging, key challenges still remain before a globally effective vaccine can be deployed. Ensuring adequate cross-protection against the diverse genotypes of CSFV circulating worldwide is a major hurdle. Extensive field trials simulating real world conditions are still needed to validate vaccine efficacy and safety. Large-scale manufacturing capabilities also need to be established to meet global demand at affordable costs, especially for developing countries where swine fever takes the biggest toll. Regulatory guidelines for licensing and differentiating vaccinated from infected animals also differ between jurisdictions and need better harmonization. Addressing issues of vaccine cold-chain storage and delivery in remote rural pig farming communities poses additional logistical challenges.
Role of vaccines in swine fever control programs
If an effective global swine fever vaccine satisfying all regulatory approvals becomes available, it could transform control programs for this dreaded pig disease. Mass vaccination campaigns periodically supplemented with serological surveillance testing could eliminate the threat of epidemics in previously affected regions and help ease trade restrictions. Vaccination of maternal herds could facilitate the development of “vaccinated-only” pig farming industries increasing food security. Combined use of emergency ring vaccination along with stringent movement controls and culling during outbreaks may even help eradicate the last vestiges of the disease globally over time. This could relieve pig farmers worldwide from the enormous economic hardships and mental agony arising from recurrent CSF outbreaks.
Swine fever remains one of the most significant viral diseases of pigs worldwide. However, recent vaccine research advances provide real hope that through targeted vaccination programs, this scourge can potentially be controlled and eventually eliminated globally. While significant challenges still remain, effective licensing and coordinated global deployment of new generation swine fever vaccines hold the promise to transform current disease control strategies. Making such a vaccine widely available especially to small farmers in endemic developing nations should be an international priority. Continued progress on this front could well be a potential game changer in the fight against this calamitous pig pandemic.
