Nasheri Neda, Alkie Tamiru N, Cutts Todd, Pama Lemarie, Romero-Barrios Pablo, Catford Angela, Hooper-McGrevy Kathleen, Berhane Yohannes
Bureau of Microbial Hazards, Health Canada, Ottawa, ON, Canada; Department of Biochemistry Microbiology, and Immunology, University of Ottawa, Ottawa, ON, Canada.
National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Winnipeg, MB, Canada.
Food Microbiol. 2025 Dec;132:104853. doi: 10.1016/j.fm.2025.104853. Epub 2025 Jun 24.
The recent spillover events of highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b to dairy cattle, and high viral shedding in the milk from infected animals, has created concern that milk and dairy products could be a route for human infection. It has been demonstrated that pasteurization is effective in inactivating A(H5N1) in milk. However, multiple dairy products are made with unpasteurized but thermised milk. Thermisation is a subpasteurisation heat treatment applied to raw milk, and the aim of this study was to examine whether commonly used conditions for thermisation are effective against inactivation of A(H5N1) in whole milk. For this purpose, we artificially inoculated whole raw cow milk with 6.5 log EID A(H5N1) and heated for 15 s at 60, 63 and 66 °C, the viral infectivity was tested using embryonated chicken eggs. We observed over 4 and 5 log reduction in viral infectivity at 60 and 63 °C, respectively (p < 0.0001) compared to the titre in untreated milk. The viral infectivity was reduced to below the detection limit at 66 °C. We also calculated the D-values, the time required to reduce the viral titer by one log, for each treatment and as expected, we observed a decrease in D-values with increasing thermisation temperature. These data demonstrate that thermisation is effective in reducing the viral load and thus they allow for informed risk assessment of A(H5N1) contaminated dairy products made from thermized milk.
近期高致病性禽流感（HPAI）A（H5N1）2.3.4.4b亚分支毒株向奶牛的溢出事件，以及受感染动物乳汁中病毒的高滴度排放，引发了人们对牛奶及奶制品可能成为人类感染途径的担忧。已证实巴氏杀菌法可有效灭活牛奶中的A（H5N1）病毒。然而，多种奶制品是用未经过巴氏杀菌但经过热杀菌处理的牛奶制成的。热杀菌是对生牛奶进行的低于巴氏杀菌温度的热处理，本研究的目的是检验常用的热杀菌条件是否能有效灭活全脂牛奶中的A（H5N1）病毒。为此，我们用6.5 log EID的A（H5N1）人工接种全脂生牛奶，并分别在60、63和66℃加热15秒，使用鸡胚检测病毒感染力。与未处理牛奶中的病毒滴度相比，我们观察到在60℃和63℃时病毒感染力分别下降了4个对数和5个对数以上（p < 0.0001）。在66℃时病毒感染力降至检测限以下。我们还计算了每种处理的D值，即病毒滴度降低一个对数所需的时间，正如预期的那样，我们观察到随着热杀菌温度的升高，D值降低。这些数据表明，热杀菌能有效降低病毒载量，从而有助于对由热杀菌牛奶制成的受A（H5N1）污染的奶制品进行可靠的风险评估。
