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Volume 15, Number 12—December 2009

Research

Risk for Infection with Highly Pathogenic Avian Influenza Virus (H5N1) in Backyard Chickens, Bangladesh

Paritosh K. BiswasComments to Author , Jens P. Christensen, Syed S.U. Ahmed, Ashutosh Das, Mohammad H. Rahman, Himel Barua, Mohammad Giasuddin, Abu S.M.A. Hannan, Mohammad A. Habib, and Nitish C. Debnath
Author affiliations: Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh (P.K. Biswas, S.S.U. Ahmed, A. Das, M.H. Rahman, H. Barua, N.C. Debnath); Copenhagen University, Copenhagen, Denmark (J.P. Christensen); Bangladesh Livestock Research Institute, Dhaka, Bangladesh (M. Giasuddin); Department of Livestock Services, Dhaka (A.S.M.A. Hannan, M.A. Habib)

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Table 1

Matched-pair analysis of potential risk factors for highly pathogenic avian influenza virus (H5N1) in backyard chickens, Bangladesh, 2007

Risk factor Case farms
(n = 25), no. (%) Control farms
(n = 75), no. (%) Matched OR 
(95% CI)* p value
Farm <5 km from nearest veterinary hospital 15 (60.0) 41 (54.7) 1.3 (0.5–3.2) 0.636
Nearby (<0.1 km) body of water 16 (64.0) 23 (30.7) 3.7 (1.5– 9.5) 0.004
Farm <0.5 km from larger body of water 15 (60.0) 50 (66.7) 0.7 (0.3–1.9) 0.543
Commercial farm within 0.5 km 9 (36.0) 44 (58.7) 0.3 (0.1–0.9) 0.028
Migratory birds seen around farm 6 (24.0) 5 (6.7) 7.5 (1.5–38.7) 0.010
Local live bird market within <5-km radius 24 (96.0) 73 (97.3) 0.7 (0.1–7.4) 0.747
Farm <1 km from live bird market 17 (68.0) 50 (66.7) 1.1 (0.4–3.0) 0.895
Contact with ducks 22 (88.0) 55 (73.3) 4.0 (0.8–20.1) 0.062
Contact with pigeons 16 (64.0) 21 (28.0) 5.5 (1.9–16.0) 0.001
Presence of rodents 12 (48.0) 9 (12.0) 5.8 (2.0–16.8) 0.001
Chickens and ducks on the same farm 11 (44.0) 40 (53.3) 0.7 (0.3–1.7) 0.415
Chickens and ducks in different night shelters 2 (8.0) 31 (41.3) 0.1 (0.1–0.5) 0.001
Frequent (≈1×/wk) cleaning of shelter 18 (72.0) 44 (58.7) 1.8 (0.7–4.9) 0.221
No disinfection in shelter 4 (16.0) 10 (13.3) 3.0 (0.2–48.0) 0.448
Disposal of bird in open space 19 (76.0) 58 (77.3) 0.9 (0 .3– 3.2) 0.869
Recently purchased chickens brought in† 5 (20.0) 10 (13.3) 1.7 (0.5–5.7) 0.421
Offering slaughter remnants of purchased chickens† 8 (32.0) 2 (2.7) 22.1 (2.7–177.7) 0.000
Death of neighbor’s chickens 7 (28.0) 20 (26.7) 1.1 (0.4–2.8) 0.900
Source of chicks = own hatched 5 (20.0) 20 (26.7) 0.4 (0.1–2.0) 0.226

*Matched-pair analysis using McNemar (Mantel-Haenszel) test statistics. OR, odds ratio; CI, confidence interval.
†Within 21 days of the onset clinical signs on case backyard farms.

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