Combating African Swine Fever: A Comprehensive Guide to Prevention, Control, and Management
Shikhakrati Negi* and Tamal Chandra Dhara
ICAR – Indian Veterinary Research Institute, Bareilly, Uttar Pradesh 243122
* Corresponding Author Email Id- shikhakrati_negi@ymail.com
Abstract
African swine fever (ASF) is a devastating viral disease affecting domestic and wild pigs, posing severe socioeconomic and environmental consequences worldwide. This comprehensive guide provides an in-depth exploration of ASF, focusing on prevention, control, and management strategies tailored for the Indian context. It elucidates the epidemiology, transmission dynamics, and clinical manifestations of the disease, emphasizing the critical role of biosecurity measures, farm hygiene, and quarantine protocols in mitigating outbreaks. The guide outlines a robust outbreak response framework, including surveillance, zoning, culling, disposal, and decontamination procedures. Additionally, it addresses the challenges of farm restocking and repopulation after an outbreak, highlighting the importance of thorough cleaning, disinfection, and monitoring protocols. By encouraging collaborative efforts, continuous education, and capacity-building initiatives, this guide aims to strengthen swine sector’s preparedness and resilience against the formidable threat of ASF.
Keywords: African swine fever, biosecurity, outbreak management, pig farming.
Introduction
African swine fever (ASF) is an infectious, deadly, transboundary, hemorrhagic viral disease that affects farmed and wild pigs with a staggering 100% mortality rate. Despite having a narrow host range limited to pigs and lack of zoonotic potential to infect humans, the socioeconomic impact of this disease has been immense. ASF outbreaks have decimated pig populations across multiple regions, severely disrupting the pork supply chain and trade flows. This has resulted in billions of dollars in economic losses for pig farmers, processors, exporters, and allied sectors like feed suppliers and transporters. In areas where pork is a staple protein source, the shortage has threatened food security and access to affordable meat, potentially contributing to malnutrition. The culling of millions of pigs to contain ASF’s spread has placed a heavy environmental burden in terms of safe disposal of carcasses and contaminated materials. But perhaps the most acute impact has been on smallholder pig farmers and rural communities heavily reliant on swine for their livelihoods. The complete loss of pig herds has pushed many into unemployment, debt traps, and poverty cycles that are difficult to escape. Despite its limited host range, ASF has proven to be a formidable transboundary threat with severe ramifications.
Understanding African Swine Fever
African Swine Fever (ASF) is caused by the African Swine Fever Virus (ASFV), a large, double-stranded DNA virus belonging to the Asfarviridae family. The virus is remarkably resilient, capable of surviving for extended periods in various environments and matrices, posing significant challenges for its containment. Transmission of ASFV can occur through direct contact with infected live or dead pigs, as well as indirect exposure to contaminated materials, such as food, water, equipment, or clothing. Additionally, potential carriers and vectors, including wild boar populations, soft ticks, and even human activities, can contribute to the spread of the disease across geographic boundaries.
The clinical manifestations of ASF can vary depending on the virulence of the viral strain and the immune status of the host. Early signs may include fever, loss of appetite, lethargy, and reddening of the skin, particularly around the ears, snout, and lower limbs. As the disease progresses, more severe symptoms may arise, such as respiratory distress, diarrhea, vomiting, and neurological disorders. In acute cases, the mortality rate can approach 100%, devastating entire swine populations. The devastating impacts of ASF extend beyond animal health, with significant economic repercussions for the swine industry, including production losses, trade disruptions, and the implementation of costly control measures.
Preventing ASF Outbreaks
As of now, there are no approved vaccines or therapeutic treatments specifically developed for African Swine Fever (ASF). Consequently, the primary approach to combating this disease relies heavily on preventive measures and stringent biosecurity protocols. Prevention is the key to mitigating the risks associated with African Swine Fever. By understanding the transmission routes, potential carriers, and implementing effective biosecurity practices, farmers can significantly reduce the chances of their farms becoming infected. Early detection and rapid response are also critical in containing the spread of the virus and minimizing its impact. Ultimately, a proactive and vigilant approach to prevention can protect not only individual farms but also the broader swine industry from the devastating consequences of an ASF outbreak.
- Farm hygiene and sanitation: Proper cleaning and disinfection protocols are crucial for preventing the spread of African Swine Fever virus (ASFV) in pig farms. This involves removing all movable objects and thoroughly cleaning surfaces with detergents and high-pressure water to eliminate visible dirt and organic matter. After thorough cleaning, the pig sheds and premises should be disinfected using solutions specifically approved for inactivating the African Swine Fever virus. Effective disinfectants include sodium hydroxide at a concentration of 8 parts per 1000 for 30 minutes, formalin at 3 parts per 1000 for 30 minutes, sodium hypochlorite at 1-2% for 30 minutes, iodine compounds at 2-3%, ortho-phenylphenol at 3% for 30 minutes, and multi-constituent products like Virkon, Verocid and Lysofromin.
Farm personnel must wear dedicated clothing and footwear, which should be disinfected upon entry and exit. Foot dips containing disinfectants like potassium permanganate, sodium hydroxide or bleaching powder, should be placed at the main gate and entrances to individual pig sheds. After completing work, workers should properly wash and disinfect their boots and clothing and store them in a separate area. Strict adherence to these cleaning and disinfection measures is essential for preventing ASFV transmission and protecting swine populations.
The practice of swill feeding, which involves using kitchen waste, hotel waste, hostel waste, or meat meal as feed for pigs, should be strictly prohibited. If swill feeding is practiced, the waste material must be properly boiled before being fed to the pigs.
Additionally, farm utensils used for feeding diseased pigs should be designated exclusively for that purpose and should never be used for feeding healthy pigs. Cross-utilization of feeding equipment between infected and uninfected animals can facilitate the spread of ASF within the farm premises.
- Restricting movement and quarantine protocols: Implementing proper fencing measures is essential to safeguard pig farm complexes from the potential introduction of African swine fever (ASF) by wild animals. To effectively prevent the access of wild boars and other wild fauna that could carry the virus, it is crucial to establish robust fencing surrounding the entire farm premises.
Pigs should only be sourced from authorized and reputable suppliers with thorough health screening processes in place. Acquiring pigs from unauthorized or unknown sources poses a significant risk of disease transmission and should be strictly avoided. Import of pigs and pig meat should be prevented from the nations affected by the disease. When introducing new pigs to a farm, it is essential to follow quarantine protocols. Newly purchased pigs should be isolated from the existing herd for a period of 30-45 days. During this time, their health should be closely monitored on a daily basis for any observable signs of illness. After the quarantine period, the pigs should be screened for the presence of diseases, and only those testing negative should be introduced to the main farm population.
Controlling access to the farm premises is another critical biosecurity measure. Visitors and vehicles should be restricted from entering the farm unless absolutely necessary. If entry is required, proper disinfection procedures must be followed. This includes disinfecting vehicle tires and wheels, as well as visitors’ shoes or boots, using approved disinfectants such as 2% sodium hypochlorite or 3:1000 potassium permanganate solutions. A comprehensive visitor log should be maintained, and visitors should be limited to designated areas near the entrance, such as an office or meeting room. Farms should also have dedicated areas for vehicle tire washing and unloading arrangements at the entrance to prevent vehicles from entering the premises. Veterinarians and high-risk visitors from ASF outbreak areas should only be allowed on the farm after taking necessary precautionary measures.
Furthermore, the sharing of equipment among farms or villages should be discouraged unless proper cleaning and disinfection procedures are followed. Cross-contamination can occur through the transfer of equipment, posing a significant risk of disease transmission. If equipment must be shared, it is imperative to thoroughly clean and disinfect it before moving it from one location to another.
- Vector control: The only documented insect-borne DNA virus is ASFV, which is mostly transmitted by Ornithodoros ticks, while it can also be carried by other insects such as swine lice, kissing bugs, leeches, and stable flies. The implementation of vector management measures is crucial in reducing the transmission of African Swine Fever (ASF) and safeguarding swine populations. Chemical control approaches use insecticides and acaricides strategically to suppress vector populations, whereas biological control methods use natural predators and parasitoids to lower vector numbers. Furthermore, several control techniques are used in integrated vector management (IVM) approaches to maximize efficacy and minimize environmental impact. Vector control activities play a major role in the prevention and control of ASF outbreaks by promoting community education and awareness campaigns and executing targeted interventions, such as adult vector suppression and larval management, in high-risk areas.
Outbreak Response and Management
Farmers are mandated to promptly notify the Department of Animal Husbandry & Dairying (DAHD) of any abnormal mortality rates observed in domestic, wild, or feral pigs. Upon receiving such reports, the state department will assemble a dedicated task force to initiate further action. This action will encompass virological and clinical surveillance measures outlined by the OIE, including documenting and reporting pathognomonic gross lesions and clinical signs in deceased and affected pigs, gathering data on the availability of susceptible pigs in the area, collecting and shipping samples for testing, and delineating zones within the reported area. Samples for laboratory diagnosis of ASF are sent to the referral disease diagnosis laboratory for ASF (Regional Disease Diagnostic Laboratory, RDDL and National Institute of High Security Animal Diseases, Bhopal) with proper labelling like Name of owner, locality, brief history, animal No., date of collection, Age, Sex, Breed etc. To facilitate bio-containment efforts, infected and surveillance zones will be declared, accompanied by stringent controls on the movement of pigs and vehicles associated with pig farms. The zoning criteria are as follows:
- a) Infected Zone (IZ) – A 1 km radius surrounding the infected premises (IP)
- b) Intermediate/Surveillance Zone (SZ) – A 10 km radius extending from the infected premises, with a 9 km buffer outside the IZ
- c) Disease-Free Zone/Non-Infected Area (FZ) – The area beyond the SZ
Immediate steps will include sealing and disinfecting affected animal sheds and premises, culling pigs within the infected zone that have direct or epidemiological links to the outbreak, and providing appropriate on-site compensation. Deceased pigs must be disposed of through deep burial or incineration, and not discarded in rivers, canals, streams, or other water bodies. Proper disposal of litter during an outbreak, along with effective sterilization of garbage, is crucial. Strict biosecurity and quarantine measures must be enforced, restricting animal movement within and to/from affected areas. Personal hygiene for animal owners and handlers, as well as disinfection of the area, is essential.
Farms should be maintained under strict hygienic and biosecured conditions at all times, including proper fencing to prevent disease transmission between domestic and wild pigs. It is imperative to ensure that no waste material from pig meat shops and pig farms is improperly dumped. All waste material should be destroyed or disposed of through community disposal centers.
Thorough inspection and quarantine of all live pigs and pork products entering the state are advised to be diligently carried out, leaving no room for lapses that could potentially compromise the region’s animal health status. Within the designated “infected zone,” all trade and distribution of fresh pork meat and pork products are strictly prohibited. While the entry of fresh pork meat and pork products into the “infected zone” is permitted solely from “free zones” where no outbreaks have been reported, the exit of any such products from the “infected zone” is strictly forbidden.
Culling and disposal
As a critical measure to contain the outbreak, all pigs residing within a 1-kilometer radius of the infected premises will be humanely culled as swiftly as practicable by qualified personnel contracted by the State or District veterinary authorities. This culling operation, overseen by registered veterinary practitioners, is implemented irrespective of whether the animals currently exhibit overt signs of the disease or not.
Carcasses of animals culled for disease control purposes remain within the infected premises (IP) and undergo disposal on-site. Any unauthorized movement of these carcasses outside the designated area is strictly prohibited to mitigate the risk of further viral dissemination. Adhering to the guidelines outlined in the FAO manual, all deceased and culled pigs must be disposed of solely through deep burial method.
In case pigs from an ASF infected farm/ premise have been moved for slaughter before restrictions were imposed, the infected meat and products can still be a source of spread and dispersal of ASF as the virus can remain active for months or years in infected meat. Therefore, the meat from these pigs may be affected by African Swine Fever and should be traced, withdrawn and disposed of.
Farm Restocking and Repopulation After an Outbreak
The cleaning and disinfection of an infected farm involves two phases: preliminary and secondary. Preliminary disinfection is carried out immediately after culling and disposal, under the Designated Veterinary Authority’s (DVA) direction and government’s expense. It involves surface application of approved disinfectants in areas housing infected animals and culling zones. Preliminary disinfection is complete 24 hours after the final disinfectant application.
Secondary cleansing and disinfection are the owner’s responsibility and cost, following DVA’s directions. The DVA can issue a notice mandating secondary cleaning and disinfection, irrespective of plans for reintroducing pigs. If the owner fails to comply, the DVA can arrange for it at the owner’s expense.
New stock on a pig farm after the ASF infected pigs have been culled cannot be brought in immediately. The farm should be left destocked for at least 40 days. New pigs can be brought in an ASF affected farm/premise 40 days after secondary Cleaning and disinfection have been satisfactorily completed. The number of sentinel pigs to be used is specified by the Veterinary authority and should not increase a maximum of 10 % of the stocking capacity of the infected zone. The sentinel pigs are kept under observation after reintroduction on an ASF affected farm, for a period of 6 weeks to ensure that they are free from ASF.
Conclusion
Effectively controlling the spread of African Swine Fever (ASF) requires a collaborative and multifaceted approach driven by teamwork, education, and heightened vigilance. Farmers, veterinarians, and authorities must forge a strong partnership, actively sharing information and coordinating their efforts. Authorities should prioritize conducting extensive awareness campaigns and specialized training programs to equip farmers and veterinary professionals with the knowledge to maintain biosecurity, promptly identify early signs of ASF, and report suspected cases without delay. Moreover, staying updated with the latest developments, research findings, and updated guidelines is paramount. By fostering a culture of continuous learning and knowledge-sharing, communities can take proactive steps to prevent outbreaks, safeguard the swine population, and ensure food security. Vigilance must extend beyond border checks, with increased coordination and efficient communication channels among relevant agencies and stakeholders to rapidly disseminate critical updates and enable swift, coordinated responses to emerging challenges. Capacity-building initiatives, such as specialized training programs for frontline personnel, should be prioritized to ensure a well-equipped and knowledgeable workforce capable of effectively implementing biosecurity measures. Regular drills, simulations, and refinement of protocols can further enhance preparedness and strengthen the collective resilience against this devastating disease.
Authors’ declaration
All authors certify that they have participated sufficiently in the work to take public responsibility for the content, including participation in the concept, design, writing, and/or revision of the manuscript. Furthermore, each author certifies that this material has not been and will not be submitted to or published in any other publication before its appearance in Pashudhan praharee.
References
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- Ministry of Fisheries, Animal Husbandry and Dairying, Department of Animal Husbandry and Dairying, Government of India. (2020, June). National Action Plan for control, containment and eradication of African Swine Fever.
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