Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, MS, United States.
Department of Population and Pathobiology, College of Veterinary Medicine, Mississippi State University, MS, United States.
Vet Microbiol. 2019 Apr;231:246-253. doi: 10.1016/j.vetmic.2019.03.027. Epub 2019 Mar 25.
Bovine respiratory disease (BRD) is economically significant, and influenza D virus (IDV) is commonly identified in cattle with BRD. Mannheimia haemolytica (MHA) is an opportunistic bacterial contributor to BRD; surveillance data suggest that MHA and IDV co-infection occurs in cattle. The objective of this study was to evaluate the synergistic pathogenesis in cattle co-infected with IDV and MHA. Sixteen dairy calves were randomly assigned to four groups of four calves. The IDV + MHA + group received D/bovine/C00046 N/Mississippi/2014 (D/46 N) intranasally at 0 days post-inoculation (DPI) and Mannheimia haemolytica D153 (MHA D153) intratracheally at 5 DPI. The IDV + MHA- group received only D/46 N at 0 DPI; the IDV-MHA + group received only MHA D153 at 5 DPI; and the IDV-MHA- group received neither agent. Clinical scores were calculated twice daily. At 10 DPI, IDV + MHA+, IDV-MHA+, and IDV-MHA- calves were euthanized and evaluated for pathologic lesions. The IDV + groups seroconverted to IDV by 10 DPI. Clinical scores were higher in IDV + groups than IDV- groups on 2-5 DPI (p = 0.001). After MHA challenge on 5 DPI, clinical scores (6-10 DPI) were slightly lower in IDV+MHA+ group than IDV-MHA+ group (p < 0.05) but not significantly different between MHA+ groups and MHA- groups. The average gross pathology score was higher for IDV-MHA+ group than groups IDV-MHA- and IDV+MHA+; however, no significant differences were identified among groups. Under the conditions of this study, infection with IDV before MHA enhance neither clinical disease nor lung pathology, relative to calves infected with MHA alone.
牛呼吸道疾病（BRD）具有重要的经济意义，流感 D 病毒（IDV）通常在患有 BRD 的牛中被发现。溶血曼海姆菌（MHA）是 BRD 的机会性细菌病原体；监测数据表明，MHA 和 IDV 共同感染发生在牛中。本研究的目的是评估 IDV 和 MHA 共同感染牛的协同发病机制。16 头奶牛犊随机分为四组，每组 4 头。IDV+MHA+组在接种后 0 天（DPI）经鼻腔接种 D/bovine/C00046N/Mississippi/2014（D/46N），并在 5 DPI 经气管内接种 Mannheimia haemolytica D153（MHA D153）。IDV+MHA-组仅在 0 DPI 时接种 D/46N；IDV-MHA+组仅在 5 DPI 时接种 MHA D153；IDV-MHA-组均未接种任何药物。每天两次计算临床评分。在 10 DPI 时，处死 IDV+MHA+、IDV-MHA+和 IDV-MHA-牛，并评估其病理损伤。IDV+组在 10 DPI 时血清转化为 IDV。在 2-5 DPI 时，IDV+组的临床评分高于 IDV-组（p=0.001）。在 5 DPI 时接种 MHA 后，IDV+MHA+组的临床评分（6-10 DPI）略低于 IDV-MHA+组（p<0.05），但 MHA+组与 MHA-组之间无显著差异。IDV-MHA+组的平均大体病理学评分高于 IDV-MHA-组和 IDV+MHA+组；然而，各组之间没有明显差异。在本研究条件下，与单独感染 MHA 的牛相比，感染 IDV 后再感染 MHA 既不会加重临床疾病，也不会加重肺部病理变化。
