Lambert G, Fernelius A L
Can J Comp Med. 1968 Apr;32(2):440-6.
This study was initiated to determine the etiologic and pathogenic significance of an American strain of bovine viral diarrhea (BVD) virus (strain NADL-MD) in enteritis of neonatal calves (calf scours). Three colostrum-fed calves from dams exposed intravenously to BVD virus at 6, 16 and 25 days prepartum, respectively, had moderate diarrhea persisting until the eighth day of life. The BVD virus was isolated from all 3 calves and persisted up to 93 days in 1 calf, indicating either that BVD was transmitted in utero or via the dam's milk. Three specific pathogen free (SPF) calves permitted dams' colostrum for the first 4 feedings and then given milk replacer were exposed orally on the day of birth to BVD virus. One calf died of neonatal enteritis 28 hours post-exposure and at necropsy the BVD virus was isolated from several of its organs. The remaining 2 calves had a mild diarrhea persisting to the eighth day of age. Two calves permitted dams' colostrum ad lib. for 72 hours, and then weaned, were exposed orally to BVD virus. Both calves had a mild persistent diarrhea and BVD virus was isolated from their blood for 56 days post-exposure.Of 13 SPF, colostrum-deprived calves exposed orally or intranasally at birth to the BVD virus, 4 had severe diarrhea and died of neonatal enteritis from 38 hours to 13 days postexposure. Isolations of BVD virus were made from several of the organs of the calves at necropsy. All of the 9 surviving calves had a moderate to severe diarrhea frequently persisting for 7 to 10 days, and BVD virus was isolated from the survivors up to 103 days postexposure. Several strains of Escherichia coli were isolated from calves after the second day of life, but were neither pathogenic for mice, nor serologically related to strains of E. coli usually associated with outbreaks of calf scours. Four colostrum-deprived SPF calves were exposed orally at birth to a strain of E. coli isolated from the intestine of the calf with the most acute symptoms and fatal neonatal enteritis. None of the four calves receiving the E. coli had diarrhea. One calf, however, had respiratory distress and died on day 5. Two SPF colostrum-deprived control calves had neither diarrhea nor respiratory distress. The above findings support the conclusion that BVD virus should not be overlooked as a primary cause of the neonatal calf enteritis complex.
本研究旨在确定一株美国牛病毒性腹泻（BVD）病毒（NADL-MD株）在新生犊牛肠炎（犊牛腹泻）中的病因学和致病意义。分别在产前6天、16天和25天经静脉暴露于BVD病毒的3头初乳喂养犊牛，出现中度腹泻，持续至出生后第8天。从所有3头犊牛中分离出BVD病毒，其中1头犊牛中该病毒持续存在达93天，这表明BVD要么是在子宫内传播，要么是通过母乳传播。3头无特定病原体（SPF）犊牛在出生后第1次喂食时喂以母畜初乳，随后4次喂食喂以代乳品，在出生当天经口暴露于BVD病毒。1头犊牛在暴露后28小时死于新生犊牛肠炎，尸检时从其多个器官中分离出BVD病毒。其余2头犊牛出现轻度腹泻，持续至出生后第8天。2头犊牛随意采食母畜初乳72小时，然后断奶，经口暴露于BVD病毒。两头犊牛均出现轻度持续性腹泻，暴露后56天从它们的血液中分离出BVD病毒。13头出生时经口或鼻内暴露于BVD病毒的无初乳SPF犊牛中，4头出现严重腹泻，在暴露后38小时至13天死于新生犊牛肠炎。尸检时从这些犊牛的多个器官中分离出BVD病毒。所有9头存活犊牛均出现中度至重度腹泻，常持续7至10天，暴露后103天仍能从存活犊牛中分离出BVD病毒。出生后第2天起从犊牛中分离出几株大肠杆菌，但这些菌株对小鼠无致病性，血清学上也与通常与犊牛腹泻暴发相关的大肠杆菌菌株无关。4头出生时经口暴露于从症状最严重且死于新生犊牛肠炎的犊牛肠道中分离出的一株大肠杆菌的无初乳SPF犊牛，均未出现腹泻。然而，1头犊牛出现呼吸窘迫，于第5天死亡。2头无初乳SPF对照犊牛既未出现腹泻也未出现呼吸窘迫。上述研究结果支持以下结论：BVD病毒作为新生犊牛肠炎综合征的主要病因不应被忽视。
