Vega Celina Guadalupe, Bok Marina, Ebinger Maren, Rocha Lucía Alejandra, Rivolta Alejandra Antonella, González Thomas Valeria, Muntadas Pilar, D'Aloia Ricardo, Pinto Verónica, Parreño Viviana, Wigdorovitz Andrés
Incuinta, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires, Argentina.
Instituto de Virología e Innovaciones Tecnológicas, Consejo Nacional de Investigaciones Científicas y Técnicas (IVIT-CONICET), Buenos Aires, Argentina.
BMC Vet Res. 2020 Jul 29;16(1):264. doi: 10.1186/s12917-020-02476-3.
Neonatal diarrhea remains one of the main causes of morbi-mortality in dairy calves under artificial rearing. It is often caused by infectious agents of viral, bacterial, or parasitic origin. Cows vaccination and colostrum intake by calves during the first 6 h of life are critical strategies to prevent severe diarrhea but these are still insufficient. Here we report the field evaluation of a product based on IgY antibodies against group A rotavirus (RVA), coronavirus (CoV), enterotoxigenic Escherichia coli, and Salmonella sp. This product, named IgY DNT, has been designed as a complementary passive immunization strategy to prevent neonatal calf diarrhea. The quality of the product depends on the titers of specific IgY antibodies to each antigen evaluated by ELISA. In the case of the viral antigens, ELISA antibody (Ab) titers are correlated with protection against infection in calves experimentally challenged with RVA and CoV (Bok M, et al., Passive immunity to control bovine coronavirus diarrhea in a dairy herd in Argentina, 2017), (Vega C, et al., Vet Immunol Immunopathol, 142:156-69, 2011), (Vega C, et al., Res Vet Sci, 103:1-10, 2015). To evaluate the efficiency in dairy farms, thirty newborn Holstein calves were randomly assigned to IgY DNT or control groups and treatment initiated after colostrum intake and gut closure. Calves in the IgY DNT group received 20 g of the oral passive treatment in 2 L of milk twice a day during the first 2 weeks of life. Animals were followed until 3 weeks of age and diarrhea due to natural exposure to infectious agents was recorded during all the experimental time.
Results demonstrate that the oral administration of IgY DNT during the first 2 weeks of life to newborn calves caused a delay in diarrhea onset and significantly reduced its severity and duration compared with untreated calves. Animals treated with IgY DNT showed a trend towards a delay in RVA infection with significantly shorter duration and virus shedding compared to control calves.
This indicates that IgY DNT is an effective product to complement current preventive strategies against neonatal calf diarrhea in dairy farms. Furthermore, to our knowledge, this is the only biological product available for the prevention of virus-associated neonatal calf diarrhea.
新生犊牛腹泻仍然是人工饲养的奶牛犊发病和死亡的主要原因之一。它通常由病毒、细菌或寄生虫源性感染因子引起。母牛接种疫苗以及犊牛在出生后6小时内摄入初乳是预防严重腹泻的关键策略，但这些措施仍然不够。在此，我们报告了一种基于抗A组轮状病毒（RVA）、冠状病毒（CoV）、产肠毒素大肠杆菌和沙门氏菌的IgY抗体产品的现场评估。该产品名为IgY DNT，已被设计为一种补充性被动免疫策略，用于预防新生犊牛腹泻。产品质量取决于通过酶联免疫吸附测定（ELISA）评估的针对每种抗原的特异性IgY抗体滴度。对于病毒抗原，ELISA抗体（Ab）滴度与用RVA和CoV进行实验性攻毒的犊牛的感染防护相关（博克M等人，2017年，阿根廷一个奶牛场中通过被动免疫控制牛冠状病毒腹泻；维加C等人，《兽医免疫学与免疫病理学》，2011年，第142卷，第156 - 69页；维加C等人，《兽医科学研究》，2015年，第103卷，第1 - 10页）。为了评估在奶牛场中的效果，30头新生荷斯坦犊牛被随机分配到IgY DNT组或对照组，并在摄入初乳和肠道封闭后开始治疗。IgY DNT组的犊牛在出生后的前2周每天两次在2升牛奶中接受20克口服被动治疗。对动物进行跟踪直至3周龄，并记录整个实验期间因自然接触感染因子而导致的腹泻情况。
结果表明，在新生犊牛出生后的前2周口服IgY DNT与未治疗的犊牛相比，腹泻发作延迟，严重程度和持续时间显著降低。与对照犊牛相比，用IgY DNT治疗的动物显示出RVA感染延迟的趋势，持续时间和病毒排出显著缩短。
这表明IgY DNT是一种有效的产品，可补充当前奶牛场预防新生犊牛腹泻的策略。此外，据我们所知，这是唯一可用于预防与病毒相关的新生犊牛腹泻的生物产品。
