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. 2017 Mar 23;15(3):e04732.
doi: 10.2903/j.efsa.2017.4732. eCollection 2017 Mar.

Epidemiological analyses on African swine fever in the Baltic countries and Poland

European Food Safety Authority (EFSA); José Cortiñas Abrahantes, Andrey Gogin, Jane Richardson, Andrea Gervelmeyer

Epidemiological analyses on African swine fever in the Baltic countries and Poland

European Food Safety Authority (EFSA) et al. EFSA J. .

Abstract

African swine fever virus (ASFV) has been notified in the Baltic countries and the eastern part of Poland from the beginning of 2014 up to now. In collaboration with the ASF-affected Member States (MS), EFSA is updating the epidemiological analysis of ASF in the European Union which was carried out in 2015. For this purpose, the latest epidemiological and laboratory data were analysed in order to identify the spatial-temporal pattern of the epidemic and a risk factors facilitating its spread. Currently, the ASF outbreaks in wild boar in the Baltic countries and Poland can be defined as a small-scale epidemic with a slow average spatial spread in wild boar subpopulations (approximately from 1 in Lithuania and Poland to 2 km/month in Estonia and Latvia). The number of positive samples in hunted wild boar peaks in winter which can be explained by human activity patterns (significant hunting activity over winter). The number of positive samples in wild boar found dead peaks in summer. This could be related to the epidemiology of the disease and/or the biology of wild boar; however, this needs further investigation. Virus prevalence in hunted wild boar is very low (0.04-3%), without any apparent trend over time. Apparent virus prevalence at country level in wild boar found dead in affected countries ranges from 60% to 86%, with the exception of Poland, where values between 0.5% and 1.42%, were observed. Since the beginning of the epidemic, the apparent antibody prevalence in hunted wild boar has always been lower than the apparent virus prevalence, indicating an unchanged epidemiological/immunological situation. The risk factor analysis shows an association between the number of settlements, human and domestic pigs population size or wild boar population density and the presence of ASF in wild boar for Estonia, Latvia and Lithuania.

Keywords: African swine fever; epidemiology; wild boar.

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Figures

Figure 1
Figure 1
Notifications of ASF in the Eastern Europe region in 2007–2016

  1. Sources: ADNS, WAHIS, Official web site of the Federal Service for Veterinary and Phytosanitary Surveillance of Russia; period covered 1 January 2007–31 August 2016.

Figure 2
Figure 2
Number of tests for ASF, from January 2014 to August 2016, submitted by the Member States to the DCF
Figure 3
Figure 3
Number of wild boar tested per 100 square km in 2014–2016 at NUTS 3 level. (A) hunted wild boar, (B) wild boar found dead

  1. Source: DCF.

Figure 4
Figure 4
Evolution of ASF in wild boar in the Baltic states and Poland from July 2014 to September 2016 (note that map E covers the period 1 July–16 September 2016)

  1. Source: ADNS.

Figure 5
Figure 5
Number of positive samples (PCR) identified in wild boar (hunted and found dead) between December 2013 and August 2016 in the Baltic countries and Poland submitted to the DCF

  1. formula image Start of active selective hunting of female wild boars and formula image removal of dead animals in Latvia;

    formula image Start of active selective hunting of female wild boars and formula image removal of dead animals in Estonia;

    formula image Start of active selective hunting of female wild boars and formula image removal of dead animals in Lithuania;

    formula image Start of active selective hunting of female wild boars and formula image removal of dead animals in Poland (Appendix D).

Figure 6
Figure 6
Temporal distribution of tested and positive samples in wild boar found dead (A) and in hunted wild boar (B) in the Baltic States and Poland (January 2014–September 2016)

  1. Note that the scales of the tested and the positive hunted wild boar in Figure B are different from the corresponding scales in Figure A.

    Source: DCF.

Figure 7
Figure 7
Temporality of clusters of notifications in the four affected EU Member States in the period from July 2014 to May 2015 (A) and in the period from June 2015 to September 2016

  1. Red clusters: ASF clusters involving wild boar or domestic pigs which were preceded by an outbreak in the domestic pig sector and had a notification before the domestic pig outbreak had been resolved; Blue clusters: ASF clusters which are not preceded by outbreaks in the domestic pig sector and had no notification before the domestic pig outbreak had been resolved.

Figure 8
Figure 8
Temporal distribution of ASF notifications in wild boar (blue) and domestic pigs (orange) on spatial clusters in the four affected EU Member States from January 2014 to September 2016

  1. Source: ADNS.

Figure 9
Figure 9
Mean centres and standard distances (1 standard deviation of distances between individual notifications and the centre of a cluster) of the notifications of ASF in wild boar in Estonia, January 2014–August 2016

  1. Source: ADNS.

Figure 10
Figure 10
Modelling outputs, fitted values for each region and timepoint. Mean estimated probability for the temporal profiles for each LAU2 region (time evolution of the estimated probability of observing ASF cases for each LAU2 region, B) and their estimated spatial pattern for each year (yearly map of the estimated probability of observing ASF cases in each region, A)
Figure 11
Figure 11
Mean centres and standard distances (1 standard deviation from the centre of a cluster) between notifications of ASF in wild boar in Latvia during the period of January 2014–August 2016

  1. Source: ADNS.

Figure 12
Figure 12
Mean centres and standard distances (1 standard deviation from the centre of cluster) between notifications of ASF in wild boar in Lithuania in the period of 2014–2016
Figure 13
Figure 13
Mean centres and standard distances (1 standard deviation from the centre of cluster) between notifications of ASF in wild boar in Poland during the period 2014–2016
Figure 14
Figure 14
Average monthly apparent virus (PCR) prevalence in the Baltic countries and Poland in hunted wild boar and wild boar found dead, January 2014–December 2016

  1. Source: DCF.

Figure 15
Figure 15
Apparent virus (PCR) prevalence in wild boar that were found dead during the period from January 2014 to August 2016 in Estonia

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 16
Figure 16
Apparent virus (PCR) prevalence in hunted wild boar in Estonia (2014–2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 17
Figure 17
Apparent ASFV‐antibody prevalence in hunted wild boar in Estonia (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 18
Figure 18
Apparent virus (PCR) prevalence in found dead wild boar in Latvia (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 19
Figure 19
Apparent virus (PCR) prevalence in hunted wild boar in Latvia (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 20
Figure 20
Apparent ASFV‐antibody prevalence in hunted wild boar in Latvia (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 21
Figure 21
Apparent virus (PCR) prevalence in wild boar found dead in Lithuania (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 22
Figure 22
Apparent virus (PCR) prevalence in hunted wild boar in Lithuania (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 23
Figure 23
Apparent ASFV‐antibody prevalence in hunted wild boar in Lithuania, 2014–2016

  1. Grey colour: 95% confidence interval (CI‐95%).

    Source: DCF.

Figure 24
Figure 24
Apparent virus (PCR) prevalence in wild boar found dead in Poland (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 25
Figure 25
Apparent virus (PCR) prevalence in hunted wild boar in Poland (2014–2016, DCF)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 26
Figure 26
Apparent ASFV‐antibody prevalence in hunted wild boar in Poland (January 2014–August 2016)

  1. Grey colour: 95% confidence interval (CI‐95%).

Figure 27
Figure 27
Apparent virus (PCR) prevalence in wild boar found dead in the Baltic countries (January 2014–August 2016)
Figure 28
Figure 28
Apparent virus (PCR) prevalence in hunted wild boar in the Baltic countries (2014–2016, DCF)
Figure 29
Figure 29
Apparent ASFV‐antibody prevalence in hunted wild boar in the Baltic countries (January 2014–August 2016)
Figure 30
Figure 30
Probability tree and relative importance of variables for detection of ASF in wild boar in Estonia (for 2015)
Figure 31
Figure 31
Probability tree and relative importance of variables for detection of ASF in wild boar in Estonia (for 2016)
Figure 32
Figure 32
Probability tree and relative importance of variables for detection of ASF in wild boar in Latvia (for 2014)
Figure 33
Figure 33
Probability tree and relative importance of variables for detection of ASF in wild boar in Latvia (for 2015)
Figure 34
Figure 34
Probability tree and relative importance of variables for detection of ASF in wild boar in Latvia (for 2016)
Figure 35
Figure 35
Probability tree and relative importance of variables for detection of ASF in wild boar in Lithuania (for 2014‐2016)
Figure C.1
Figure C.1
Wild boar population density in Estonia in 2014–2016, ind./10 km2

  1. Source: Ministry of the environment (Estonia)

Figure C.2
Figure C.2
Wild boar population density in Latvia in 2015–2016, ind./10 km2

  1. Source: State Forest Service of Latvia

Figure C.3
Figure C.3
Estimated wild boar density in hunting rounds of Poland (2014–2016)

  1. Source: General Directorate of the State Forests (Poland)

See this image and copyright information in PMC

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