Glass K, Barnes B, Scott A, Toribio J-A, Moloney B, Singh M, Hernandez-Jover M
Research School of Population Health, Australian National University, Australia.
Research School of Population Health, Australian National University, Australia.
Prev Vet Med. 2019 Apr 1;165:8-14. doi: 10.1016/j.prevetmed.2019.02.002. Epub 2019 Feb 5.
As of 2018, Australia has experienced seven outbreaks of highly pathogenic avian influenza (HPAI) in poultry since 1976, all of which involved chickens. There is concern that increases in free-range farming could heighten HPAI outbreak risk due to the potential for greater contact between chickens and wild birds that are known to carry low pathogenic avian influenza (LPAI). We use mathematical models to assess the effect of a shift to free-range farming on the risk of HPAI outbreaks of H5 or H7 in the Australian commercial chicken industry, and the potential for intervention strategies to reduce this risk. We find that a shift of 25% of conventional indoor farms to free-range farming practices would result in a 6-7% increase in the risk of a HPAI outbreak. Current practices to treat water are highly effective, reducing the risk of outbreaks by 25-28% compared to no water treatment. Halving wild bird presence in feed storage areas could reduce risk by 16-19% while halving wild bird access of potential bridge-species to sheds could reduce outbreak risk by 23-25%, and relatively small improvements in biosecurity measures could entirely compensate for increased risks due to the increasing proportion of free-range farms in the industry. The short production cycle and cleaning practices for chicken meat sheds considerably reduce the risk that an introduced low pathogenic avian influenza virus is maintained in the flock until it is detected as HPAI through increased mortality of chickens. These findings help explain HPAI outbreak history in Australia and suggest practical changes in biosecurity practices that could reduce the risk of future outbreaks.
自1976年以来，截至2018年，澳大利亚家禽业已经历了7次高致病性禽流感（HPAI）疫情，所有疫情均涉及鸡。人们担心，由于已知携带低致病性禽流感（LPAI）的鸡与野生鸟类之间接触的可能性增加，散养养殖的增加可能会提高HPAI疫情爆发的风险。我们使用数学模型来评估转向散养养殖对澳大利亚商业养鸡业中H5或H7型HPAI疫情爆发风险的影响，以及干预策略降低这种风险的可能性。我们发现，25%的传统室内养殖场转向散养养殖方式将导致HPAI疫情爆发风险增加6%-7%。目前的水处理措施非常有效，与不进行水处理相比，可将疫情爆发风险降低25%-28%。将饲料储存区的野生鸟类数量减半可将风险降低16%-19%，而将潜在桥梁物种进入鸡舍的机会减半可将疫情爆发风险降低23%-25%，并且生物安全措施的相对小幅改善可以完全弥补由于该行业散养养殖场比例增加而带来的风险增加。鸡肉鸡舍的短生产周期和清洁措施大大降低了引入的低致病性禽流感病毒在鸡群中持续存在直至通过鸡的死亡率增加被检测为HPAI的风险。这些发现有助于解释澳大利亚的HPAI疫情爆发历史，并提出生物安全措施方面的实际改变，以降低未来疫情爆发的风险。
