Scientific Opinion on the assessment of the control measures of the category A diseases of Animal Health Law: Highly Pathogenic Avian Influenza

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 Highly Pathogenic Avian Influenza (HPAI). 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 radius of the protection and surveillance zone, 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, specific details of the model used for the assessment of the laboratory sampling procedures for HPAI are presented here. Here, also, the transmission kernels used for the assessment of the minimum radius of the protection and surveillance zones are shown. Several scenarios for which these control measures had to be assessed were designed and agreed prior to the start of the assessment. In summary, sampling procedures as described in the diagnostic manual for HPAI were considered efficient for gallinaceous poultry, whereas additional sampling is advised for Anseriformes. The monitoring period was assessed as effective, and it was demonstrated that the surveillance zone comprises 95% of the infections from an affected establishment. 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 HPAI.

Keywords: Avian Influenza; Control measures; HPAI; monitoring period; protection zone; sampling procedures; surveillance zone.

Figure 1

Map of countries where outbreaks of HPAI were reported in wild birds and/or poultry between 2015 and 2020 (Data sources: ADNS and OIE)

Figure 2

Probability of detection of highly pathogenic avian influenza virus in gallinaceous poultry (left column) or Anseriformes (right column). Plots show the median probability of detection for different scenarios. For gallinaceous poultry, scenarios are short (solid lines) or long (dashed lines) infectious periods and low (red), median (blue) or high (magenta) transmission rates (see Table 2 in Section 3.1). For Anseriformes, scenarios are no (red), low (blue) or high (magenta) mortality with different transmission rates/infectious periods (solid or dashed lines) (see Table 3 in Section 3.1)

Figure 3

PRISMA diagram for the extensive literature search on monitoring period for highly pathogenic avian influenza

Figure 4

Transmission kernels for highly pathogenic avian influenza virus

Figure 5

Assessment of the radius of the protection and surveillance zone for highly pathogenic avian influenza 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 the extended Netherlands and Italian kernels in Table 8. 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 the two kernels that were assessed. The black dotted lines indicate distances of 3 km and 10 km (i.e. the proposed radius of the protection and surveillance zones, respectively)

Figure F.1

Within‐flock dynamics of highly pathogenic avian influenza virus in gallinaceous poultry. The plots show the median (solid line) and 95% prediction interval (shading) for the number of exposed birds (magenta, left column), infectious birds (red, middle column) and cumulative number of dead birds (cyan, right column) for six scenarios (rows; see Table 2 for details)

Figure F.2

Within‐flock dynamics of highly pathogenic avian influenza virus in Anseriformes. The plots show the median (solid line) and 95% prediction interval (shading) for the number of exposed birds (magenta, first column), infectious birds (red, second column), recovered birds (blue, third column) and cumulative number of dead birds (cyan, fourth column) for six scenarios (rows; see Table 3 for details)