Quantification of the risk for introduction of virulent Newcastle disease virus into Spain through legal trade of live poultry from European Union countries

Figures & data

Table 1.  Description and source of information of variables used to parameterize a model of the risk for introduction of Newcastle disease (ND) into Spain via legal trade of live poultry.

Notation	Variable description	Parameterization and value	Source of information
f cds	Number of species s flocks in country c from which poultry were exported into a Spanish province d during the silent phase of an ND epidemic	(j cds xe cds /365)×b s	Sánchez-Vizcaíno et al. (2010)
j cds	Number of shipments of poultry of specie s sent from a country c into Spanish province d per year	Normal (µj cds σj cds )	Spanish Foreign Trade Statistics Database (2008)
e cds	Number of flocks per shipment	NA	TRACES (2008)
b s	Duration of the silent phase of an ND epidemic in the species s	Pert (3, 14, 30) for chickens and guinea fowl, Pert (6, 17, 34) for turkeys, Pert (6, 25, 40) for ducks and geese	OIE (2010a,b,c)
P Fcds	Probability of exporting fowls from an ND-infected flock of species s from country c into a Spanish province d during the silent phase of an ND epidemic	P(A 1 )xP(A 2 )	Sánchez-Vizcaíno et al. (2010)
P(A 1 )	Probability that species s from country c become ND-infected in the lapse of one year	Gamma (α cs , β)	Martínez-López et al. (2008)
α cs	Probability of having one ND epidemic affecting species s in flocks of country c with more than 100 poultry through period of time β		Sánchez-Vizcaíno et al. (2010)
E csi	Number of ND epidemics i that affected species s in flocks of country c with more than 100 poultry and that were reported to the OIE from 1992 to 2008	NA	OIE (2010a,b,c)
S csi	Probability that species s was ND-infected during the silent phase of the epidemic i in that affected country c	NA	OIE (2010a,b,c)
t	Period of time for which information regarding the occurrence of ND epidemics was available	NA	OIE (2010a,b,c)
β	Period of time considered in the assessment	NA	NA
P(A 2 )	Probability of selecting an infected species s flock for exporting poultry into a Spanish province d during the silent phase of the ND epidemic	Beta (α 1f , α 2f ) α1f =IF s +1 α2f =TF cs −IF s +1	Vose (1997); OIE (2004b); Martínez-López et al. (2008); Sánchez-Vizcaíno et al. (2010)
IF s	Number of species s flocks with more than 100 poultry in the country c infected before the detection of the epidemic	Pert (1, 1, 28) for chickens and guinea fowl, Pert (1, 1, 18) for turkeys, Pert (1, 2, 19) for ducks and geese	OIE (2010a,b,c)
TF cs	Total number of species s flocks with more than 100 poultry in country c	Normal (µ TFcs , σ TFcs )	BMELV (2008); Agreste (2009); DEFRA (2009); FAO (2009a); KSH (2009); INS (2009); CBS (2009)
n cds	Number of species s poultry exported per flock	Normal (µn cds , σn cds )	Spanish Foreign Trade Statistics Database (2008)
	Species-specific and country-specific probability that an infected bird is introduced into an agricultural operation of Spanish province d	P(B 1 )xP(B 2 )xP(B 3 )	Martínez-López et al. (2008)
P(B 1 )	Probability that an ND infected bird of species s was exported from an infected flock	Beta (α 1w , α 2w ) α1w=IA cf's +1 α2w=Z cs −IA cf's +1	Vose (1997); OIE (2004b); Martínez-López et al. (2008);
IA cf's	Number of infected poultry of species s in a infected flock of country c	Z cs xPF	Sánchez-Vizcaíno et al. (2010)
Z cs	Average size of a species s flocks with more than 100 poultry in country c	NA cs /TF cs	Sánchez-Vizcaíno et al. (2010)
NA cs	Number of species s poultry in the flocks with more than 100 poultry of country c	Normal (µ NAcs , σ NAcs )	BMELV (2008); Agreste (2009); DEFRA (2009); FAO (2009b); KSH (2009); INS (2009); CBS (2009)
PF	Expected intra-flock ND prevalence	Pert (0.1, 0.7, 1)	Gohm et al. (1999)
P(B 2 )	Probability that an ND-infected fowl of the species s survive to the infection	Pert (0, 0.33, 0.7) for chickens and guinea fowls, Pert (0, 0.65, 0.88) for turkeys, Pert (0, 0.65, 1) for ducks and geese	Onapa et al. (2006); Lee et al. (2009); OIE (2010a,b,c)
P(B 3 )	Probability that an imported bird reaches an agricultural operation in the Spanish province d	[1−P(D s )]x[1−P(S)]
P(D s )	Probability that a bird of species s dies during the shipment	Pert (minimum, most likely, maximum)	Warriss et al. (1992); Vecerek et al. (2006); Voslárová et al. (2006)
P(S)	Probability that an imported bird is shipped into a slaughterhouse	Pert (minimum, most likely, maximum)	TRACES (2008)
NA, not applicable.

Figure 1.  Geographical variation of the total risk for introduction of Newcastle disease (ND) into Spain via legal trade of live poultry (1a) estimated using a quantitative risk assessment and discriminated by species of introduction: (1b) chickens, (1c) ducks, (1d) turkeys, (1e) guinea fowl, and (1f) geese. Risk has been categorized using quartiles as nil (~0), low (5x10⁻⁷ to 2.04x10⁻⁵), medium (2.05x10⁻⁵ to 4.46x10⁻⁵), high (4.47x10⁻⁵ to 2.13x10⁻⁴), and very high (2.14x10⁻⁴ to 7.3x10⁻⁴). Provinces with nil risk and those included within the first, second, third, and fourth quartiles are shown in white, yellow, orange, red, and brown, respectively. Provinces of Catalonia, which is the region that concentrated most of the risk, are indicated with a white outline (1a).

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