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Volume 23, Number 9—September 2017

Research

Risk for Low Pathogenicity Avian Influenza Virus on Poultry Farms, the Netherlands, 2007–2013

Ruth Bouwstra12, Jose L. Gonzales2, Sjaak de Wit, Julia Stahl, Ron A.M. Fouchier, and Armin R.W. Elbers2Comments to Author 
Author affiliations: Wageningen Bioveterinary Research, Lelystad, the Netherlands (R. Bouwstra, J.L. Gonzales, A.R.W. Elbers); GD Animal Health, Deventer, the Netherlands (S. de Wit); Sovon Dutch Center for Field Ornithology, Nijmegen, the Netherlands (J. Stahl); Erasmus Medical Center, Rotterdam, the Netherlands (R.A.M. Fouchier)

Main Article

Table 1

LPAIV surveillance data collated from poultry farms, the Netherlands, 2007–2013*

Type of farm No. farms positive Total no, farms Median time at risk, mo Median distance to wild water bird areas, m Median distance to medium- sized waterway, m† Probability of introduction‡ RR§
Indoor-layer 60 5,600 7.3 4,227 769 0.001 1
Outdoor-layer 143 2,549 6.3 3,996 670 0.009 6.0
Layer-breeder 14 2,174 9.5 4,157 738 0.001 0.5
Broiler 2 5,409 1.2 3,292 576 0.000 0.2
Broiler-breeder 14 2,718 8.5 4,002 824 0.001 0.4
Meat-turkey 30 469 3.7 3,208 1,042 0.017 11.7
Turkey-breeder 2 18 5.7 2,035 659 0.019 13.1
Meat-duck 16 267 1.2 3,477 1,180 0.050 33.9
Duck-breeder 14 70 5.8 4,107 767 0.034 23.4

*LPAIV, low pathogenicity avian influenza virus; RR, relative risk.
†Distance to clay soil and distance to small- and large-sized waterways also included in the multivariate analysis (data not shown). They did not have a significant effect on the risk for LPAIV introduction. Waterway sizes were defined as follows: small, 0.5–3 m wide; medium, 3–6 m wide; large, >6 m wide.
‡Unadjusted probabilities of LPAIV introduction per farm months at risk.
§These are the unadjusted RR estimates obtained by dividing the unadjusted probabilities of LPAIV introduction of each type of poultry farm by that of indoor-layer farms.

Main Article

1Current affiliation: GD Animal Health, Deventer, the Netherlands.

2These authors contributed equally to this article.

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