Hop, G.E.

Saatkamp, H.W.

English

NARCIS 

A PathWayDiagram for introduction and prevention of Avian Influenza in the Netherlands

Name not available

Wageningen Yield 

A PathWayDiagram for introduction and prevention of Avian 
Influenza in The Netherlands
G.E. Hop and H.W. Saatkamp 
Business Economics, Wageningen University 
Introduction 
Highly pathogenic avian influenza (HPAI) viruses have spread in recent years across 
broad regions of Europe, Asia and Africa (Boon et al., 2007). The number of 
outbreaks of HPAI have increased in the last decade, and the impact in terms of 
number of birds involved and the control costs of the disease have dramatically risen 
(Capua and Alexander, 2004). In recent years, three large outbreaks occurred in 
commercial poultry populations in Italy (1999), the Netherlands (2003) and Canada 
(2004) (Capua et al., 2003; Power, 2005; Stegemen et al., 2004).  
The introduction of avian influenza (AI) is a continuing threat to the poultry sector in 
The Netherlands. In times of increased risk of introduction (e.g. because of (suspicion 
of) HPAI outbreaks in neighbouring countries and/or trade partners), decision makers 
face the question whether they should establish or increase the preventive measures. 
Determining the pathways by which HPAI can be introduced has critical implication 
for preventing introduction of the virus (Webby and Webster, 2003). If the risk of 
HPAI introduction for a country is highest through the movement of migratory birds, 
surveillance at migratory stopovers and eliminating contact between wild birds and 
commercial poultry could reduce the chance of introduction. Alternatively, if the risk 
of HPAI introduction is higher via the import of poultry (products), monitoring and/or 
eliminating imports from high-risk countries should be given a high priority for 
reducing the probability of introduction (Kilpatrick et al., 2006).  
In crisis situations, a qualitative aid and decision support tool in the form of a 
PathWayDiagram would therefore be helpful in showing the theoretically possible 
pathways leading to the adverse event ‘introduction of HPAI in the domestic 
commercial poultry population’. Furthermore, the PathWayDiagram could be helpful 
in inventorizing pathways-countries-combinations, and in the qualitative assessment 
of risk and / or ranking of the pathways. As in a paper of De Vos et al. (2003) where a  
similar tree-like approach for Classical Swine Fever introduction in The Netherlands 
was developed, a PathWayDiagram for the introduction of HPAI in The Netherlands 
was developed including the procedure for using this diagram. Based on published 
scientific literature, an effort was made to describe and consolidate knowledge of (1) 
all theoretically possible pathways leading to the event ‘introduction of HPAI in the 
domestic commercial poultry population’, and (2) possible preventive measures in 
The Netherlands. 
Description of the PathWayDiagram 
In Figure 1, a general set-up of the PathWayDiagram is presented. The diagram 
consists of different layers. The first level shows the direct pathways for exogenous 
virus introduction into a region (virus outside the region), and the second level shows 
the direct escape pathways for endogenous viruses (virus inside the region). The third 
level shows the presence of virus in the four sub-populations (1) domestic migratory 
birds, (2) non-commercial poultry and birds other than poultry, (3) humans and (4) 
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mammals, whereas the fourth level shows the adverse event, an outbreak in domestic 
commercial poultry. The events leading to a primary outbreak of HPAI in domestic 
commercial poultry, as shown in the PathWayDiagram, are all conditional, i.e. the 
occurrence of an outbreak of HPAI depends on the occurrence of all the previous 
events. As shown in the detailed elaboration of the PathWayDiagram (Figure 2), for 
instance virus introduction by the pathway ‘legal import of live poultry’ will only 
occur (1) if live poultry is imported from an HPAI-affected region, (2) if the poultry is 
infected and/or contaminated with the virus, (3) if the poultry is screened 
insufficiently at the border inspection post or if the affected poultry shows no clinical 
signs, (4) if the poultry have a destination for live instead of a destination for 
slaughter, and (5) if the poultry is added to susceptible domestic commercial poultry. 
With respect to this last step, in case of e.g. contaminated livestock trucks, the virus 
dose conveyed should be at least the minimum infective dose. 
Procedure for use 
A structured way to take short term decisions in times of a possibly increased risk on 
the introduction of HPAI is given by a flow-chart of the procedure for using the 
PathWayDiagram (Figure 3). The procedure can be split up into three phases. The 
first phase, developments preceding a crisis meeting, consists monitoring the HPAI-
situation outside The Netherlands, and collecting up-to-date information. The second 
phase, crisis meeting, consists of an inventory of countries-pathways-combinations, a 
qualitative assessment of risk and / or ranking the direct and indirect pathways, 
identification and selection of preventive measures with respect to direct and indirect 
pathways, and composing a set of preventive measures based on the previous steps. 
After deciding on the set of preventive measures, phase three, the implementation of 
preventive measures can start. In case of a new situation (e.g. change in risk, and 
additional relevant information), it may be necessary to repeat phase two. The 
PathWayDiagram and the procedure were tested in a workshop in which a crisis 
meeting was simulated with AI experts from the Dutch Ministry of Agriculture, 
Nature and Food Quality (MinLNV) and the Food and Consumer Product Safety 
Authority (VWA). The PathWayDiagram and the procedure for using the diagram 
showed to be useful tools in times of (perceived) increased risk of introduction of 
HPAI. 
Conclusion 
Use of the PathWayDiagram and applying the described procedure results in a 
systematic checklist focused on (1) possibilities of (increased risk of) introduction and 
(2) possible preventive measures, resulting in a coherent and well-harmonized set of 
preventive measures covering the pathways involved. The PathWayDiagram and the 
procedure were experienced as useful qualitative aids and decision tools to support 
decision making in crisis situations. 
References 
Boon, A.C.M., Sandbulte, M.R., Seiler, P., Webby, R.J., Songserm, T., Guan, Y., 
Webster, R.G. (2007). Role of terrestrial wild birds in ecology of influenza A virus 
(H5N1), Emerg. Infect. Dis. 13:1720-1724.  
Capua, I. and Alexander, D.J. (2004). Avian influenza: recent developments, Avian 
Pathol. 33:393-404. 
Capua, I., Marangon, S., Dalla Pozza, M., Terregino, C., Cattoli, G. (2003). Avian 
influenza in Italy 1997–2001, Avian Dis. 47:839-843.
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De Vos, C.J., Saatkamp, H.W., Huirne, R.B.M., Dijkhuizen, A.A. (2003). The risk of 
the introduction of classical swine fever virus at regional level in the European 
Union: a conceptual framework, Rev. Sci. Technol. Off. Int. Epiz. 22:785-810. 
Kilpatrick, A.M., Chmura, A.A., Gibbons, D.W., Fleischer, R.C., Marra, P.P., Daszak, 
P. (2006). Predicting the global spread of H5N1 avian influenza, P. Natl. Acad. Sci. 
USA 103:19368–19373. 
Power, C. (2005). The Source and Means of Spread of the Avian Influenza Virus in 
the LowerFraserValley of British Columbia During an Outbreak in the Winter of 
2004. Available at http://www.inspection.gc.ca/english/anima/heasan/disemala/ 
avflu/2004rep/epie.shtml. Accessed on November 10, 2009.
Stegeman, A., Bouma, A., Elbers, A.R., de Jong, M.C., Nodelijk, G., De Klerk, F., 
Koch, G., Van Boven, M. (2004). Avian influenza A virus (H7N7) epidemic in The 
Netherlands in 2003: Course of the epidemic and effectiveness of control measures. 
J. Infect. Dis. 190, 2088–2095. 
Webby, R.J., Webster, R.G. (2003). Are we ready for pandemic influenza, Science 
302:1519-1522. 
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A PathWayDiagram for introduction and prevention of Avian Influenza in the Netherlands

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