African swine fever (ASF) is a highly infectious viral disease affecting pigs. It was first reported as an acute haemorrhagic fever in East Africa in the early 1900s (Dixon et al. 2020; Montgomery 1921). The virus infects domestic pigs and wild suids such as bush pigs or warthogs and Ornithodoros species ticks. Warthogs and soft ticks maintain ASF virus (ASFV) through the sylvatic cycle, which does not cause any pathogenic effects in these hosts. Understanding these dynamics is essential for managing and preventing outbreaks in naïve pig populations (Van Rensburg et al. 2020b). Direct transmission of ASFV occurs between infected and susceptible pigs, whereas indirect transmission occurs when pigs encounter contaminated food, bedding and utensils (Brown & Bevins 2018).

African swine fever is a controlled disease in South Africa (SA) in terms of the Animal Diseases Act, 1984 (Act 35 of 1984), and has been reported to the World Organisation for Animal Health (WOAH). The Department of Agriculture (DOA), which was previously known as the Department of Agriculture, Forestry and Fisheries (DAFF), has produced a detailed veterinary procedural notice (VPN) standard for ASF control, which clearly outlines control of ASF. The control area in SA was instituted in 1935 in Limpopo, northern parts of North West and KwaZulu-Natal and north-eastern parts of Mpumalanga, as indicated in the Animal Diseases Act of South Africa (Act 35 of 1984). A control zone is defined within a part of the country to distinguish between infected and disease-free zones, and this is done to progressively control diseases and allow trade in livestock and their commodities (Fujita 2004). Pig production in SA is practised in all nine provinces, with Limpopo, North West, Gauteng and KwaZulu-Natal having the highest numbers of pig farmers (Munzhelele, Oguttu & Fasina 2016). According to Stats SA (2016), in Gauteng province, agricultural households that farm with a combination of livestock (cattle, sheep, goats, pigs and chicken) make up only 29.0% of all farmers, and 1.1% of these households are engaged in a combination of pig and poultry farming.

The Animal Diseases Act, 1984 (Act 35 of 1984) was initially proven effective for SA in controlling ASF within the control zone. However, since 2016 ASF outbreaks in domestic pigs have not been linked to the recent transfer of infected animals or materials from within the controlled area (Van Rensburg et al. 2020b). Outbreaks of ASF outside the control zone cause significant losses to farmers because of its high mortality rate, trade restrictions and severe socio-economic impact (Van Rensburg et al. 2020b). According to Penrith (2020), smallholder and backyard farms provide conditions that facilitate ASFV circulation. The control of ASF includes biosecurity measures and movement control, but challenges remain when it comes to smallholder (subsistence) farmers, as they do not always have the financial means and understanding to effectively implement the biosecurity measures that will aid in the prevention and control of ASF (Dione et al. 2020).

The effects of ASF infection in the pig industry are overwhelming because they restrict trade and production, whereas for smallholder farmers in developing countries, livelihoods are affected as they use pigs as income sources (Sánchez-Cordón et al. 2018). Minimum standards for accredited piggeries should include access control (fencing, personnel and visitors, vehicle access, animal access), internal biosecurity, pest control, feed and feed quality, a farm plan, care and management, transport (loading, vehicle and vehicle hygiene) and records for new pig introductions as well as pig movements (DAFF 2018). The objective of this study focuses on providing specific, local data on biosecurity gaps and knowledge deficits regarding ASF in Gauteng. This is the first systematic biosecurity assessment in Gauteng province, SA’s most economically important and densely populated region. Gauteng’s peri-urban production landscape – characterised by high population density, market integration, informal settlements and complex urban-rural interfaces – differs from the rural Limpopo settings of prior SA studies (Fasina et al. 2015; Mokoele et al. 2014) and East African contexts. These contextual differences necessitate location-specific assessment rather than generalisability.

A total of 137 farmers were interviewed across the Gauteng study areas (27 from ASF-free areas + 110 from HRA = 137 total). Notably, participation was significantly lower in ASF-free areas compared to HRA: 27/137 (19.7%) versus 110/137 (80.3%), p < 0.05.

The significant difference in the sample composition between ASF-free areas and HRA aligns with the established behavioural theory regarding leverage-salience and survey participation (Groves, Singer & Corning 2000). Several factors may contribute to this disparity: stakeholders in disease-free areas may perceive ASF-related surveys as less applicable to their immediate circumstances, reducing motivation to participate (Dillman, Smyth & Christian 2014), the absence of local ASF cases may result in lower disease awareness and reduced engagement with ASF-related communications (Jurado et al. 2018), psychological distance from the threat may diminish perceived personal relevance, a known predictor of survey participation in agricultural health studies (Brewer et al. 2007; Weinstein 1989) and farmers facing active threats demonstrate heightened information-seeking behaviour and greater engagement with research initiatives addressing their immediate challenges (Hernández-Jover et al. 2012; Mankad 2016; Racicot et al. 2011).

A census of pigs was conducted on farms included in the study to quantify the number of pig farmers in the selected regions of Gauteng. However, because of COVID-19 restrictions and voluntary participation of farmers, a full census of the areas was not completed. It is recommended that a comprehensive census be conducted to determine the approximate number of pigs and/or farms in each municipality, as some farmers reported recently establishing piggeries. The demographic profile of pig farmers in Gauteng aligns with trends observed across SA, where older individuals dominate smallholder pig production (Mokoele et al. 2014). While younger people often prefer formal employment, their engagement in pig farming could address unemployment and enhance productivity, given their adaptability to innovative management practices (Madzimure et al. 2012). Male farmers predominate in the sector, which is consistent with prior national studies (Matabane et al. 2015).

Emerging farmers represent a significant proportion of smallholder pig producers, highlighting the need for clear classification criteria to avoid potential bias in identifying farmer groups (Zantsi, Greyling & Vink 2019). Across all production systems, biosecurity practices are crucial to mitigating the risk of exposure to ASF. Permanent housing reduces exposure to disease, whereas unfenced or free-range systems increase vulnerability (Maoba, Manyakanyaka & Mamaregane 2022; Penrith 2013). The movement of pigs – particularly for trade or during outbreaks – remains a key factor in ASF transmission, necessitating regulatory measures such as movement permits and strict monitoring of auctions (Dione et al. 2016; Olugasa & Ijagbone 2007; Van Rensburg, Penrith & Etter 2022).

Knowledge gaps regarding ASF symptoms and biosecurity measures exacerbate disease risks. Limited awareness delays early detection, facilitating outbreaks (Aliro et al. 2022; Arvidsson et al. 2022; Casal et al. 2007). As described in Uganda (Dione et al. 2020), most of the training efforts in SA are often sporadic and project-specific, with no systematic evaluation of effectiveness. Evidence from Uganda suggests that increased awareness correlates with improved management practices, underscoring the importance of continuous farmer education (Nantima et al. 2015).

Effective hygiene and disinfection are pivotal in controlling ASF, particularly in the absence of a commercial vaccine. Practices such as routine cleaning of piggeries, handwashing, changing boots, and the use of footbaths have been shown to reduce biosecurity risks (Kouam, Jacouba & Moussala 2020; Maoba et al. 2022). Cleaning and disinfection of equipment and transport vehicles is especially important given the virus’s environmental resilience in organic material (Gao et al. 2023). Comparisons with regions lacking such practices, such as Tanzania’s Southern Highlands, demonstrate a direct link between poor hygiene and high ASF incidence (Fasina et al. 2020).

Feeding strategies also influence ASF risk. Use of untreated swill containing pork products is a well-documented transmission route (Nantima et al. 2015; Van Rensburg et al. 2020a). Economic constraints have led some farmers to supplement commercial feed with alternative sources, highlighting the need for affordable, safe feeding practices. Similarly, the use of pig waste as fertiliser can contribute to ASF spread if improperly managed, which is a common concern in integrated crop-livestock systems (Kabuuka et al. 2014).

Although in this study slaughtering has not been thoroughly investigated, the few farmers who reported slaughter did mention slaughtering at home and at abattoirs. Food safety may be jeopardised by improper slaughtering facilities and methods used in the unorganised sector (Rani et al. 2017). Meat from smallholder or backyard slaughter is often tainted and unsanitary. The Meat Safety Act No. 40 of 2000’s rules, which are intended to safeguard consumer health, are not always followed in the informal sector (Rani et al. 2017). Meat safety issues related to handling meat during distribution continue to be a source of worry, even if these standards are implemented in the official sector. Safe handling and disposal of sick or deceased pigs is essential to prevent virus dissemination. Isolation, veterinary consultation, and supervised disposal – including burial, incineration or burning – are recommended to minimise environmental contamination (Bellini, Rutili & Guberti 2016). Inappropriate handling poses a high risk of indirect transmission and compromises biosecurity.

The multiple comparison adjustment (Online Appendix 1, Table 1-OA1) demonstrates most of the biosecurity practice differences reported in the original data (Table 2-OA1, Table 3-OA1, and Table 4-OA1) may be false positives (Type I errors) arising from conducting multiple statistical tests without adjustment. The phenomenon of ‘multiple testing’ is well-established. When conducting 31 tests at α = 0.05, it is expected that ~1.5 of the tests will be significant by chance alone even if no true differences exist (Sterne & Smith 2001).

The key finding is that handwashing behaviour varies significantly according to ASF status, displaying a paradoxical pattern: farmers in ASF-free areas exhibit better hand hygiene than those in HRA without prior ASF experience. This counterintuitive finding warrants further investigation and suggests that factors beyond proximity to ASF outbreaks drive biosecurity adoption.

Overall, the study underscores that management practices, farmer knowledge and resource limitations critically shape ASF risk in smallholder systems. Even low-cost interventions, such as footbaths, routine cleaning and controlled pig movement, can substantially mitigate outbreak risk. These findings reinforce that preventive biosecurity remains the cornerstone of ASF control. The potential availability of vaccines would complement, rather than replace, sound biosecurity practices, as vaccination programmes are most effective in healthy, well-managed herds. This further underscores the importance of targeted education, accessible infrastructure and regulatory oversight in safeguarding pig health.

This study indicated that fewer biosecurity practices were implemented in HRA areas, posing a potential risk of ASF spreading into Gauteng. Knowledge gaps are a plausible explanation for poor biosecurity adoption that requires verification through targeted follow-up research. This implies that farmers in Gauteng require training on ASF disease symptoms and piggery management, encouragement to practise safe feeding and adoption of appropriate husbandry practices. The research offers valuable insight into stakeholder engagement regarding disease risk perception, with higher engagement with populations at high risk for ASF outbreaks, which could lead to enhanced practical applicability of the biosecurity and risk management findings. This context-specific focus provides a possible model for outbreak-prone regions, although it limits generalisability. In addition, this study provides baseline data for Gauteng-specific policy development and describes a framework that other provinces can adapt.