Oreiby Atef, Seada Ayman S, Abou Elazab Mohamed F, Abdo Walied, Kassab Mohamed, Hegazy Yamen, Khalifa Hazim O, Matsumoto Tetsuya
Department of Animal Medicine (Infectious Diseases), Faculty of Veterinary Medicine, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
Bacteriology Department, Animal Health Research Institute, Tanta Branch, Egypt.
Animals (Basel). 2022 Aug 15;12(16):2084. doi: 10.3390/ani12162084.
This study aimed to investigate a sheeppox outbreak in a highly susceptible naive sheep population in Kharsit village, Gharbia Governorate, Egypt. Moreover, to compare commercial sheeppox vaccines, the Romanian strain and RM-65 vaccines, as emergency vaccination against sheeppox under field conditions. In December 2018, a sheeppox outbreak occurred in a flock of 65 sheep upon the purchase of an apparently healthy ewe from outside the village. This ewe showed a systemic disease with cutaneous lesions after a few days, thereafter more cases began to appear. Cutaneous lesions in other sheep in the flock in the form of macules, papules, and scabs were common in wool-less areas of the body, in addition to fever and respiratory disorders. Postmortem findings revealed the congestion of visceral organs with apparent gross pathology of the lung. Biopsies of cutaneous lesions and visceral organs were collected, and sheeppox was identified by histopathology and transmission electron microscopy, which showed the existence of sheeppox cells and intracytoplasmic brick-shape sheeppox virions. The Romanian strain and RM-65 vaccines were used for the emergency vaccination for two different groups of animals and the third group was left as a control group. Serum samples were collected before vaccination as well as 21 days post-vaccination, and serum protein fractionation analysis was performed for all groups. The outbreak ended after 2.5 months, the cumulative incidence was 66.2%, and the overall case fatality was 51.1%. There was significantly higher protection against sheeppox infection and mortalities among RM-65 vaccine immunized group compared to Romanian strain vaccine-immunized animals at p < 0.05. RM-65-vaccinated animals did not show sheeppox cases or mortalities, compared to Romanian strain-vaccinated animals, which had mild pox signs in 78% of animals and case fatality of 35.7%. The serum protein analysis also indicated the superior performance of the RM-65 vaccine; it increased the level of α1-globulin and β-globulin compared to the Romanian strain, which increased the level of β-globulin only. The current study shows a better performance of the tested RM-65 than the Romanian strain vaccine for emergency vaccination against sheeppox under field conditions. These findings point to the validity of emergency vaccination against sheeppox and the importance of the comparative field evaluation of vaccines; however, wide-scale studies are required for further evaluation. Future investigation of whether the Romanian strain itself or vaccine-production-related issues are responsible for these findings is required.
本研究旨在调查埃及盖尔比亚省哈尔西特村一个高度易感的未接触过羊痘的绵羊群体中发生的羊痘疫情。此外，为比较商业羊痘疫苗、罗马尼亚毒株疫苗和RM - 65疫苗，在现场条件下作为羊痘紧急疫苗接种进行对比。2018年12月，从村外购买了一只看似健康的母羊后，一个65只羊的羊群中爆发了羊痘疫情。这只母羊几天后出现了伴有皮肤损伤的全身性疾病，此后更多病例开始出现。羊群中其他羊的皮肤损伤表现为斑疹、丘疹和结痂，常见于身体无毛部位，此外还伴有发热和呼吸道疾病。尸检结果显示内脏器官充血，肺部有明显的大体病理变化。采集了皮肤损伤和内脏器官的活检样本，通过组织病理学和透射电子显微镜鉴定出羊痘，显示存在羊痘细胞和胞质内砖形羊痘病毒粒子。罗马尼亚毒株疫苗和RM - 65疫苗用于对两组不同的动物进行紧急接种，第三组作为对照组。在接种疫苗前以及接种后21天采集血清样本，对所有组进行血清蛋白分级分析。疫情在2.5个月后结束，累计发病率为66.2%，总体病死率为51.1%。与罗马尼亚毒株疫苗免疫的动物相比，RM - 65疫苗免疫组对羊痘感染和死亡的保护作用显著更高（p < 0.05）。与接种罗马尼亚毒株疫苗的动物相比，接种RM - 65疫苗的动物未出现羊痘病例或死亡，接种罗马尼亚毒株疫苗的动物中78%有轻度痘疹症状，病死率为35.7%。血清蛋白分析也表明RM - 65疫苗性能更优；与仅增加β -球蛋白水平的罗马尼亚毒株疫苗相比，它增加了α1 -球蛋白和β -球蛋白的水平。当前研究表明，在现场条件下，用于羊痘紧急接种时，受试的RM - 65疫苗比罗马尼亚毒株疫苗表现更好。这些发现表明羊痘紧急接种的有效性以及疫苗对比现场评估的重要性；然而，需要进行大规模研究以作进一步评估。未来需要调查是罗马尼亚毒株本身还是与疫苗生产相关的问题导致了这些结果。
