Effectiveness and practicality of control strategies for African swine fever: what do we really know?

African swine fever (ASF) is a major pig health problem, and the causative virus is moving closer to Western European regions where pig density is high. Stopping or slowing down the spread of ASF requires mitigation strategies that are both effective and practical. Based on the elicitation of ASF expert opinion, this study identified surveillance and intervention strategies for ASF that are perceived as the most effective by providing the best combination between effectiveness and practicality. Among the 20 surveillance strategies that were identified, passive surveillance of wild boar and syndromic surveillance of pig mortality were considered to be the most effective surveillance strategies for controlling ASF virus spread. Among the 22 intervention strategies that were identified, culling of all infected herds and movement bans for neighbouring herds were regarded as the most effective intervention strategies. Active surveillance and carcase removal in wild boar populations were rated as the most effective surveillance and intervention strategies, but were also considered to be the least practical, suggesting that more research is needed to develop more effective methods for controlling ASF in wild boar populations.

This consists in the repeated collection of data from randomly selected abattoirs and rendering plants to identify changes in pig health status (i.e. performing clinical inspections, sample collection, laboratory tests, etc.) The difference with "active surveillance of pigs at sentinel abattoirs and rendering plants " is that here, the abattoirs and rendering plants are expected to change over time 2 Active surveillance of pigs at sentinel abattoirs and rendering plants This consists in the repeated collection of data from selected abattoirs and rendering plants to identify changes in pig health status in abattoirs and rendering plants (i.e. performing clinical inspections, sample collection, laboratory tests, etc.) The difference with "active surveillance of pigs at abattoirs and rendering plants" is that here, the selected abattoirs and rendering plants are expected to remain the same over time and have been identified as high risk of disease introduction 3 Active surveillance of pigs at farms This consists in the repeated collection of data from randomly selected farms to identify changes in pig health status (i.e. performing clinical inspections, sample collection, laboratory tests, etc.) The difference with "active surveillance of pigs at sentinel farms" is that here, the farms are expected to change over time 4 Active surveillance of pigs at sentinel farms This consists in the repeated collection of data from selected farms to identify changes in pig health status in farms (i.e. performing clinical inspections, sample collection, laboratory tests, etc.) The difference with "active surveillance of pigs at farms" is that here, the selected farms are expected to remain the same over time and have been identified as high risk of disease introduction 5 Passive surveillance of pigs at farms Farmers and animal workers report voluntarily the suspicion of ASF on their farm to the competent authority. Suspicion can come from the close monitoring of pig production data (e.g. syndromic surveillance mortality at farm level). 6 Enhanced passive surveillance of pigs at sentinel farms Farmers and animal workers report voluntarily the suspicion of ASF on their farm to the competent authority The difference with "passive surveillance of pigs at farms" is that here, farms identified as high risk of disease introduction, are more likely to report a suspicion. Enhancement may come from financial incentives, improved awareness of ASF clinical signs, current legislation, etc.

Syndromic surveillance of pig mortality
Systematic collection and monitoring of pig mortality data at farm level to detect any unusual increase.

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Active surveillance of pig products at butchers, markets and supermarkets This consists in the repeated collection of data from pig products at butchers, markets and supermarkets to identify changes in pig product status (i.e. performing sample collection, laboratory tests, etc.) and to detect if infected pig products have entered the food chain 9 Active surveillance of pig products confiscated at the border This consists in the repeated collection of data from pig products at airports, ports and land borders, particularly when originating in infected countries.
10 Active surveillance of fomites This consists in the repeated collection of data from trucks that transport pigs, but also agricultural products that could be infected (feedstuff) to identify virus contamination 11 Passive surveillance based on inconclusive CSF testing Investigation of classical swine fever-suspect farms for which a confirmation or laboratory diagnosis has not been reached 12 Active surveillance of ticks in tick habitats This consists in the repeated collection of ticks in tick habitats (such as rodent burrows etc.) for being tested for ASF diagnosis 13 Active surveillance of ticks in pig farms This consists in the repeated collection of ticks in randomly selected pig farms for being tested for ASF diagnosis. 14 Active surveillance of ticks in sentinel pig farms This consists in the repeated collection of ticks in selected pig farms for being tested for ASF diagnosis The difference with "active surveillance of ticks at farms" is that here, the selected farms have been identified as high risk for ASFV maintenance in ticks because of contacts between ticks and pigs have been identified by performing serological testing against tick bite in domestic pigs (to find antibodies against the salivary glands of Ornithodoros ticks) 15 Passive surveillance of ticks at farms Farmers and animal workers report voluntarily the presence of ticks on farm to the competent authority for being tested for ASF diagnosis 16 Enhanced passive surveillance of ticks in sentinel pig farms Farmers report voluntarily the presence of ticks on selected farm to the competent authority for being tested for ASF diagnosis The difference with "passive surveillance of ticks at farms" is that here, farms identified as high risk for ASFV maintenance in ticks, are more likely to report the presence of ticks. These farms were selected because of contacts between ticks and pigs have been identified by performing serological testing against tick bite in domestic pigs (to find antibodies against the salivary glands of Ornithodoros ticks Passive surveillance of wild boar found dead Hunters (but also farmers, walkers, etc.) report voluntarily wild boar found dead to the competent authority for collection of sample being tested for ASF diagnosis 20 Enhanced passive surveillance of hunted wild boar and wild boar found dead Hunters (but also farmers, walkers, etc.) of selected areas report voluntarily hunted wild boar and wild boar found dead to the competent authority for being tested for ASF diagnosis The difference with "passive surveillance of wild boar" is that here, selected forests have been identified as high risk for disease introduction. Enhancement may come from financial incentives, improved awareness of ASF clinical signs, current legislation, etc. Culling of all infected herds All infected herds are culled. This also includes proper disposal of all dead pigs and financial compensation for culled and dead pigs 2 Intensive monitoring of neighbouring herds Herds, which are located within a defined radius around infected herds, are subjected to intensive monitoring of mortality. This is an alternative to "culling of neighbouring herds" 3 Culling of neighbouring herds Culling of herds which are located within a defined radius around infected herds. This also includes proper disposal of all culled pigs. This is an alternative to "intensive monitoring of neighbouring herds" 4 Intensive monitoring of traced herds Herds, which did trade pigs with the infected herds, are subjected to intensive monitoring of mortality. This is an alternative to "culling of traced herds" 5

Culling of traced herds
Culling of herds which did trade pigs with the infected herds. This also includes proper disposal of all culled pigs. This is an alternative to "intensive monitoring of traced herds" 6 Culling of neighbouring or traced herds followed by heat treatment and consumption This is an alternative strategy in countries where there are no funds for financial compensation and so where reporting of outbreaks by the farmers are completely discouraged. Heat processing of the culled animals into sausages, canned meat, etc. would allow some sort of compensation. 7 Movement bans for neighbouring herds Ban on animal movements (and products) for herds which are located within a defined radius around infected herds. This might be associated with intensive monitoring of neighbouring herds. 8 Movement bans for traced herds Ban on animal movements (and products) for herds which did trade pigs with the infected herds 9 Ban of swill feeding Pigs should be not fed with swill that might contain contaminated remains of pigs. This also includes proper disposal of waste food 10 Thorough cleaning and disinfection of buildings, transport vehicles and PPE From farm-to-farm and from abattoir-to-farm. PPE: Personal Protective Equipment, e.g. clothing, boots, masks, etc. 11 Health and safety regulations on farms This consists in improving the sanitary barriers: quarantine of pigs at farm entrance (i.e. physical isolation of pigs entering the farm for period of time) and measures to ensure the safe purchase of pigs, (such as vet inspection certificates, testing of pigs, adoption of basis measures of hygiene, etc.). This also implies improved awareness of farmers on ASF clinical signs. 12 Farm entrance restrictions on people Restrictions for public access in all farms. Access to farmland (via footpaths) restricted during outbreaks 13