Poultry Diagnostic and Research Center, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
Merck Animal Health, De Soto, KS 66018.
Avian Dis. 2023 Jun;67(2):145-152. doi: 10.1637/aviandiseases-D-23-00010.
Infectious laryngotracheitis (ILT) is a respiratory disease that causes significant economic losses to the poultry industry. Control of the disease is achieved by vaccination and implementation of biosecurity measures. The use of bivalent and trivalent recombinant herpesvirus of turkey (rHVT) vaccines expressing infectious laryngotracheitis virus (ILTV) genes has increased worldwide. In the United States, vaccination programs of long-lived birds (broiler breeders and commercial layers) against ILT include immunizations with either HVT recombinant vector vaccines, or at hatch, or live attenuated vaccines administered via drinking water (chicken embryo origin [CEO]) or eye drop (tissue culture origin [TCO]). The efficacy of bivalent rHVT-LT at hatch followed by drinking water or eye-drop CEO vaccination has been shown to provide more robust protection than rHVT-LT alone. The objective of this study was to evaluate the protection efficacy of a commercial trivalent rHVT-ND-LT when administered at 1 day of age followed by TCO vaccination via eye drop at 10 wk of age. Groups vaccinated with only rHVT-ND-LT or TCO, the combination of rHVT-ND-LT + TCO, and one nonvaccinated group of chickens were challenged with a virulent ILTV strain at 15 wk of age. After challenge, mortalities were prevented only in the group of chickens vaccinated with the rHVT-ND-LT + TCO. Clinical signs of the disease and challenge virus replication in the trachea were significantly reduced for both the rHVT-ND-LT + TCO- and TCO-vaccinated groups of chickens. To assess challenge virus transmission, contact-naive chickens were introduced to all vaccinated groups immediately after challenge. At 8 days postintroduction, infection of contact-naive chickens was evidenced in those introduced to the rHVT-ND-LT and TCO group but prevented in the rHVT-ND-LT + TCO group. Overall, these results indicated that compared to rHVT-ND-LT or TCO when administered alone, the rHVT-ND-LT + TCO vaccination strategy improved protection against disease and reduced shedding of the challenge virus.
传染性喉气管炎（ILT）是一种呼吸道疾病，给家禽业造成了重大经济损失。该疾病的控制通过疫苗接种和实施生物安全措施来实现。双价和三价重组火鸡疱疹病毒（rHVT）疫苗在全球范围内的使用有所增加，这些疫苗表达传染性喉气管炎病毒（ILTV）基因。在美国，针对 ILT 的长寿禽类（肉鸡种鸡和商品蛋鸡）免疫接种方案包括使用 rHVT 重组载体疫苗或在孵化时进行免疫接种，或者通过饮用水（鸡胚来源[CEO]）或滴眼（组织培养来源[TCO]）进行活毒疫苗接种。孵化时接种双价 rHVT-LT 然后通过饮用水或滴眼 CEO 疫苗接种的效果已被证明比单独接种 rHVT-LT 提供更强大的保护。本研究的目的是评估在 1 日龄时接种商业三价 rHVT-ND-LT，然后在 10 周龄时通过滴眼接种 TCO 的保护效力。仅接种 rHVT-ND-LT 或 TCO、rHVT-ND-LT + TCO 组合以及一组未接种疫苗的鸡在 15 周龄时用强毒 ILTV 株进行攻毒。攻毒后，仅在接种 rHVT-ND-LT + TCO 的鸡群中预防了死亡。接种 rHVT-ND-LT + TCO 和 TCO 的鸡群的疾病临床症状和攻毒病毒在气管中的复制均显著减少。为了评估攻毒病毒的传播，在攻毒后立即将接触性无知的鸡引入所有接种组。在引入后 8 天，在接种 rHVT-ND-LT 和 TCO 组的接触性无知鸡中证实了感染，但在 rHVT-ND-LT + TCO 组中预防了感染。总的来说，这些结果表明，与单独接种 rHVT-ND-LT 或 TCO 相比，rHVT-ND-LT + TCO 接种策略提高了对疾病的保护作用，并减少了攻毒病毒的脱落。
