Assessment of the control measures of the category A diseases of Animal Health Law: Classical Swine Fever

Abstract

EFSA received a mandate from the European Commission to assess the effectiveness of some of the control measures against diseases included in the Category A list according to Regulation (EU) 2016/429 on transmissible animal diseases ('Animal Health Law'). This opinion belongs to a series of opinions where these control measures will be assessed, with this opinion covering the assessment of control measures for Classical swine fever (CSF). In this opinion, EFSA and the AHAW Panel of experts review the effectiveness of: (i) clinical and laboratory sampling procedures, (ii) monitoring period and (iii) the minimum radii of the protection and surveillance zones, and the minimum length of time the measures should be applied in these zones. The general methodology used for this series of opinions has been published elsewhere; nonetheless, details of the model used for answering these questions are presented in this opinion as well as the transmission kernels used for the assessment of the minimum radius of the protection and surveillance zones. Several scenarios for which these control measures had to be assessed were designed and agreed prior to the start of the assessment. Here, several recommendations are given on how to increase the effectiveness of some of the sampling procedures. Based on the average length of the period between virus introduction and the reporting of a CSF suspicion, the monitoring period was assessed as non-effective. In a similar way, it was recommended that the length of the measures in the protection and surveillance zones were increased from 15 to 25 days in the protection zone and from 30 to 40 days in the surveillance zone. Finally, the analysis of existing Kernels for CSF suggested that the radius of the protection and the surveillance zones comprise 99% of the infections from an affected establishment if transmission occurred. Recommendations provided for each of the scenarios assessed aim to support the European Commission in the drafting of further pieces of legislation, as well as for plausible ad hoc requests in relation to CSF.

Keywords: CSF; disease control; intervention; monitoring period; protection zone; sampling procedures; surveillance zone.

Figure 1

Map of countries with reported outbreaks of CSF in domestic swine and wild boar between 2015 and 2021 (Data sources: ADNS and OIE)

Figure 2

Map of countries with the OIE official free status for Classical swine fever, 2021 (Source: OIE; © OIE)

Figure 3

Within‐herd dynamics of CSFV in pigs. The plots show the median (solid line) and 95% prediction interval (shading) for the number of exposed pigs (magenta), infectious pigs (red), recovered pigs (blue) and cumulative number of dead pigs (cyan) for the six scenarios considered in Table 1; these scenarios differ in terms of R ₀ and infectious period (rows; see Table 1 for details)

Figure 4

Decision tree of the diagnostic procedure for CSF confirmation

Figure 5

Simulated time (days post introduction) in order to detect CSFV in a pig herd when testing of two dead pigs each week is implemented. The plots show the time to detection in a herd of 50 100, 200 or 1,000 pigs (indicated at the top of each column) for six scenarios which differ in transmission parameters and infectious period. The vertical dotted lines demarcate the weekly sampling periods for a period up to 8 weeks

Figure 6

PRISMA diagram CSF Monitoring period ELS

Figure 7

Kernels for the transmission of classical swine fever virus

Figure 8

Assessment of the radius of the protection and surveillance zone for classical swine fever virus. The top panel shows the probability of transmission beyond a given distance (if transmission were to occur from an infected establishment) computed using the estimates (blue circles) and the lower and upper 95% confidence limits (error bars) for each kernel (and in the same order as) in Table 15. The thick black line indicates the median probability for all kernels. The black dotted lines indicate threshold probabilities of 0.05 and 0.01. The bottom panel shows the distances at which a threshold probability of transmission beyond that distance is reached calculated using the estimates (circles) and lower and upper 95% confidence limits (error bars) for each kernel. The thick black line indicates the median distance for all kernels. The black dotted lines indicate distances of 3 km and 10 km (i.e. the proposed radius of the protection and surveillance zones, respectively)