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Table 2 Differences in farm characteristics between IAV-S-positive and IAV-S-negative farms

From: Effect of herd size on subclinical infection of swine in Vietnam with influenza A viruses

Variable   IAV-S-positive farms, IAV-S-negative farms, Odds ratio 95 % CI p valuea
no. (%) no. (%)    
Farm typeb Family-operated farm 6 (27.3 %) 183 (86.3 %)   reference  
Corporate farm 16 (72.7 %) 29 (13.7 %) 16.83 6.09 to 46.52 <0.001
Total number of pigs <50 4 (18.2 %) 108 (47.8 %)   reference  
50 to 500 1 (4.5 %) 83 (36.7 %) 0.33 0.04 to 2.97 0.319
501 to 1000 1 (4.5 %) 14 (6.2 %) 1.93 0.20 to 18.50 0.569
1000 16 (72.7 %) 21 (9.3 %) 20.57 6.25 to 67.70 <0.001
Shower-in facility for humansc No 5 (26.3 %) 195 (85.9 %) 17.06 reference  
Yes 14 (73.7 %) 32 (14.1 %)   5.75 to 50.62 <0.001
Disinfection facility for vehiclesc No 7 (31.8 %) 194 (85.8 %) 12.99 reference  
Yes 15 (68.2 %) 32 (14.2 %)   4.92 to 34.34 <0.001
Other animals on farmd No 9 (42.9 %) 33 (16.1 %) 0.26 reference  
Yes 12 (57.1 %) 172 (83.9 %)   0.10 to 0.66 0.005
Type of operation Not farrow-to-finishe 5 (22.7 %) 91 (39.9 %)   reference  
Including farrow-to-finish 17 (77.3 %) 137 (60.1 %) 2.26 0.81 to 6.34 0.12
Type of pig housef Open- or semi-open-sided house 20 (90.9 %) 178 (78.1 %) 0.36 reference  
Windowless 2 (9.1 %) 50 (21.9 %)   0.08 to 1.58 0.173
Introduction of pigs No 1 (5.6 %) 30 (19.7 %) 4.18 reference  
Yes 17 (94.4 %) 122 (80.3 %)   0.54 to 32.67 0.173
Vaccinationg No 1 (5.3 %) 32 (15.1 %) 3.20 reference  
Yes 18 (94.7 %) 180 (84.9 %)   0.41 to 24.82 0.266
Respiratory diseases history in pigh No 15 (68.2 %) 208 (91.2 %)   reference  
Yes 7 (31.8 %) 20 (8.8 %) 4.85 1.77 to 13.29 0.002
Respiratory diseases history in working staffh No 20 (90.9 %) 225 (98.7 %)   reference  
Yes 2 (9.1 %) 3 (1.3 %) 7.50 1.18 to 47.54 0.032
Livestock farm No 14 (68.2 %) 116 (91.2 %)   reference  
within 100 mi Yes 6 (31.8 %) 111 (8.8 %) 0.45 0.17 to 1.21 0.112
Pig farm within 100 m No 14 (68.2 %) 157 (91.2 %) 0.96 reference  
Yes 6 (31.8 %) 70 (8.8 %)   0.35 to 2.61 0.938
  1. aLogistic regression analyses were performed to calculate odds ratio of IAV-S-positive vs -negative farms for each variable
  2. bCorporate farm managed by a company, and family-operated farm managed by owner’s family
  3. cDisinfection facilities for humans or vehicles at the farm entrance
  4. dPoultry (chickens, ducks), dogs, cats, cattle, etc
  5. eFarrow-to-wean or wean-to-finish farms
  6. fWindowless house or (semi-) open-sided house
  7. gVaccines for diseases other than swine influenza. Swine influenza vaccine is not available in Vietnam
  8. hRespiratory symptoms observed in pigs or working staff within the 6 months before our sampling
  9. iPresence of livestock farms including pig farm within 100 m