Crossley Beate M, Miramontes Craig C, Rejmanek Daniel, Gallardo Rodrigo, Pereira Richard
California Animal Health & Food Safety Laboratory System (CAHFS), University of California, Davis, Davis, CA 95616.
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616.
J Dairy Sci. 2025 Mar;108(3):2264-2275. doi: 10.3168/jds.2024-25985. Epub 2025 Jan 30.
Avian Influenza virus H5N1 2.3.4.4.b has recently been detected in cattle, with milk from infected animals reported to contain a high viral load, serving as a potential source for shedding and dissemination of this virus. Currently, pasteurization is the only widely recognized method for on-farm inactivation of H5N1 in milk. A current concern is that according to USDA data, less than 50% of large dairy farms pasteurize nonsaleable milk, with a much lower percentage occurring in medium and small dairy farms. The objective of this pilot study was to evaluate the effect of milk acidification to a pH of ∼4.0 to 4.4 and lactoperoxidase system (LP system) on the inactivation of low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI) in raw whole milk. Initial trials in our study used the LPAI H6N2 virus as a surrogate for HPAI H5N1. For the acidification trials, citric acid was used to acidify milk. For evaluation of milk acidification and LP system, milk samples were inoculated with LPAI H6N2, with samples collected before and after treatment at various times. Evaluation of virus viability was conducted using specific-pathogen-free embryonated chicken eggs and viral quantification using real-time quantitative PCR. Three acidification experiments were conducted using milk spiked with LPAI H6N2. Given the positive outcome observed in the inactivation of LPAI with citric acid, a fourth trial was conducted with milk containing a high load of H5N1 originating from actively infected cows. Our results indicated that milk acidification with a pH between 4.1 and 4.2 resulted in the inactivation of LPAI H6N2 and HPAI H5N1 virus in milk after 6 h of treatment. Milk treatment with the LP system was not effective for the inactivation of the H6N2 virus, and no further trials were conducted for this treatment option. This is the first study reporting the effectiveness of milk acidification for the inactivation of HPAI H5N1 in milk originating from animals infected with H5N1. Milk acidification is an effective, accessible, and easy-to-use alternative to milk pasteurization, and future studies should evaluate the on-farm effectiveness of acidification of nonsaleable milk to inactivate H5N1.
最近在牛身上检测到了H5N1 2.3.4.4.b亚型禽流感病毒，据报道，受感染动物的牛奶中病毒载量很高，这成为该病毒传播和扩散的一个潜在来源。目前，巴氏杀菌法是农场中对牛奶中的H5N1进行灭活的唯一广泛认可的方法。目前令人担忧的是，根据美国农业部的数据，大型奶牛场中不到50%对非销售用牛奶进行巴氏杀菌，中小型奶牛场的这一比例则低得多。这项初步研究的目的是评估将牛奶酸化至pH值约为4.0至4.4以及使用乳过氧化物酶系统（LP系统）对原料全脂牛奶中低致病性禽流感（LPAI）和高致病性禽流感（HPAI）的灭活效果。我们研究中的初步试验使用LPAI H6N2病毒作为HPAI H5N1的替代物。在酸化试验中，使用柠檬酸对牛奶进行酸化。为了评估牛奶酸化和LP系统，将LPAI H6N2接种到牛奶样本中，并在不同时间对处理前后的样本进行采集。使用无特定病原体的鸡胚评估病毒活力，并使用实时定量PCR进行病毒定量。使用添加了LPAI H6N2的牛奶进行了三次酸化实验。鉴于用柠檬酸灭活LPAI取得了阳性结果，对含有高载量源自活跃感染奶牛的H5N1的牛奶进行了第四次试验。我们的结果表明，在处理6小时后，将牛奶酸化至pH值在4.1至4.2之间可使牛奶中的LPAI H6N2和HPAI H5N1病毒失活。用LP系统处理牛奶对灭活H6N2病毒无效，因此未对该处理方法进行进一步试验。这是第一项报道牛奶酸化对灭活源自感染H5N1动物的牛奶中的HPAI H5N1有效的研究。牛奶酸化是一种有效、可行且易于使用的替代牛奶巴氏杀菌的方法，未来的研究应评估对非销售用牛奶进行酸化以灭活H5N1在农场中的有效性。
