African Swine Fever (ASF)

African swine fever (ASF) is an extremely contagious ailment brought about by the African swine fever virus (ASFV), impacting both domestic swine and wild boars, including African and European wild boars. The disease is marked by abrupt hemorrhagic manifestations and is deemed a grave affliction. Susceptibility spans all pig breeds and age groups, with morbidity and mortality rates potentially reaching 100%. The World Organization for Animal Health (OIE) designates it as a notifiable animal disease due to its significant impact.

Etiology and Pathogenesis

ASFV is a large, enveloped, double-stranded DNA virus belonging to the Asfarviridae family and the genus Asfivirus. ASFV is distantly related to other virus families such as Faustoviridae and Kaumoebavirus. The main route of infection is through the upper respiratory tract, where the virus replicates in the tonsils and lymph nodes. ASFV spreads rapidly through blood, resulting in high virus concentrations in various tissues. However, it should be pointed out that ASF does not infect humans and is not a zoonotic disease.

Fig. 1 Schematic diagram of the structure of the ASFV virion.¹

Transmission

Studies have shown that there are at least 3 different circulation patterns of ASFV in the environment: bush transmission cycle, tick-swine cycle, and domestic pig (pig-pig) cycle. Currently, the main focus is on the domestic pig cycle. The ASFV transmission route is divided into direct and indirect contact transmission. Direct contact transmission is mainly transmitted by infected pigs through oral and nasal contact. Indirect contact transmission is transmitted by contaminated virus swill, tools, equipment, materials, feed, environment, etc. It can be transmitted by carrying the virus after biting infected pigs by soft ticks, mosquitoes, and flies.

Fig. 2 Diagram of the transmission cycle of ASFV in the host.²

ASF in America

ASF has had a profound impact on the global swine industry. ASF has a history of nearly a century since it was first discovered in Kenya, Africa in 1921. It spread to Europe in the 20th century and more recently to Asia. ASF has not been reported in the United States, but it is important to remain vigilant and prepare for a potential outbreak. The devastating impact of ASF in other regions highlights the need for enhanced biosecurity measures, stringent import regulations, and surveillance programs to detect any potential introduction of the virus.

Signs and Symptoms

ASF manifests in different forms, including hyperacute, acute, subacute, and chronic. The severity and distribution of lesions varied according to the virulence of the virus. The main clinical symptoms are as below.

While the symptoms are similar to classical swine fever (CSF), ASF is caused by a unique virus that is different from CSF.

Diagnosis of ASF

ASF cannot be distinguished clinically or necropsy from other febrile blood syndromes or bacterial septicemias of pigs. Therefore, laboratory testing is essential for diagnosing ASF and is key to the success of ASF surveillance campaigns. BioVenic can detect ASFV through immunodiagnostic methods and molecular diagnostic methods.

• Samples: Blood, spleen, kidney, lymph node, and tonsil samples.
• Immunodiagnostics: We help customers develop immunological laboratory diagnostic methods and kits such as lateral flow assay, ELISA, and immunofluorescence assay to detect ASFV antigens or specific antibodies in samples. Antibody testing can indicate previous exposure but may not be detected in acute cases.
• Molecular diagnostics: We use the principles of molecular diagnosis to help customers develop real-time fluorescence qPCR, LAMP, and other diagnostic methods and tools to accurately detect the ASFV gene in samples.

Prevention and Control

• Currently, there are no effective treatments or vaccines against ASF.
• Strict precautions are essential to avoid ASF.

BioVenic is at the forefront of research efforts to develop safe and effective custom vaccines for customers. Prevention and control measures mainly revolve around strict biosecurity measures, and we can develop strict and effective prevention plans for our customers, such as,

• Enforce stringent import protocols for animal products. Guarantee the exclusion of infected live pigs and pork items from entering ASF-free regions.
• Swiftly eliminate all infected pigs. Surviving animals can carry the virus, necessitating the culling of both infected and potentially infected pigs for enhanced safety.
• Adhere rigorously to on-farm biosecurity measures. Abide by established biosecurity protocols, encompassing thorough attire and footwear sanitization to prevent the ingress of viruses and bacteria.
• Control human movement. Ensure that individuals accessing the farm haven't had contact with other pigs within the previous 48 hours.
• Establish disease surveillance and monitoring. Implement comprehensive health oversight plans for pig farms. All pigs, living or deceased, should undergo an examination to detect ASF.
• Enforce rigorous quarantine procedures. Stringently apply quarantine measures in areas unaffected by ASF and those already infected, to impede disease ingress and curb its further dissemination.
• Meticulously sanitize vehicles and equipment before entry. Adequately cleanse and disinfect vehicles and equipment before permitting entry. Furthermore, refrain from using human food waste for pig feeding.

ASF poses significant obstacles to the pig industry, food safety, and international trade. Tackling this disease requires a comprehensive strategy. As a prominent player in the field, BioVenic is deeply committed to advancing ASF research and innovation. We strive to provide our customers with solutions for the development of diagnostic methods and tools, vaccine development, and enhanced biosafety protocols. If this piques your interest, please contact us directly.

References

1. Wang, Nan, et al. "Architecture of African swine fever virus and implications for viral assembly." Science 366.6465 (2019): 640-644.
2. Gaudreault, Natasha N., et al. "African swine fever virus: an emerging DNA arbovirus." Frontiers in veterinary science 7 (2020): 215.