Niskanen Rauni, Lindberg A, Tråvén M
Department of Ruminant Medicine and Veterinary Epidemiology, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.
Vet J. 2002 May;163(3):251-9. doi: 10.1053/tvjl.2001.0657.
Previous reports on the spread of bovine virus diarrhoea virus (BVDV) from animals primarily infected with the agent are contradictory. In this study, the possibility of transmission of BVDV from calves simultaneously subjected to acute BVDV and bovine coronavirus (BCV) infection was investigated. Ten calves were inoculated intranasally with BVDV Type 1. Each of the 10 calves was then randomly allocated to one of two groups. In each group there were four additional calves, resulting in five infected and four susceptible calves per group. Virulent BCV was actively introduced in one of the groups by means of a transmitter calf. Two calves, susceptible to both BVDV and BCV, were kept in a separate group, as controls. All ten calves actively inoculated with BVDV became infected as shown by seroconversions, and six of them also shed the virus in nasal secretions. However, none of the other eight calves in the two groups (four in each) seroconverted to this agent. In contrast, it proved impossible to prevent the spread of BCV infection between the experimental groups and consequently all 20 study calves became infected with the virus. Following infection, BCV was detected in nasal secretions and in faeces of the calves and, after three weeks in the study, all had seroconverted to this virus. All calves, including the controls, showed at least one of the following clinical signs during days 3-15 after the trial started: fever (> or =40 degrees C), depressed general condition, diarrhoea, and cough. The study showed that BVDV primarily infected cattle, even when co-infected with an enteric and respiratory pathogen, are inefficient transmitters of BVDV. This finding supports the principle of the Scandinavian BVDV control programmes that elimination of BVDV infection from cattle populations can be achieved by identifying and removing persistently infected (PI) animals, i.e. that long-term circulation of the virus without the presence of PI animals is highly unlikely.
先前关于主要感染牛病毒性腹泻病毒（BVDV）的动物传播该病毒的报道相互矛盾。在本研究中，对同时感染急性BVDV和牛冠状病毒（BCV）的犊牛传播BVDV的可能性进行了调查。10头犊牛经鼻接种1型BVDV。然后将这10头犊牛随机分为两组。每组再额外增加4头犊牛，使每组有5头感染犊牛和4头易感犊牛。通过一头感染病毒的犊牛向其中一组主动接种强毒株BCV。将两头对BVDV和BCV均易感的犊牛单独饲养作为对照组。如血清转化所示，所有10头主动接种BVDV的犊牛均被感染，其中6头还通过鼻分泌物排出病毒。然而，两组中的另外8头犊牛（每组4头）均未出现针对该病原体的血清转化。相反，事实证明无法防止BCV感染在实验组之间传播，因此所有20头研究犊牛均感染了该病毒。感染后，在犊牛的鼻分泌物和粪便中检测到了BCV，在研究进行三周后，所有犊牛均出现针对该病毒的血清转化。所有犊牛，包括对照组，在试验开始后的第3至15天均至少出现以下临床症状之一：发热（≥40℃）、全身状况不佳、腹泻和咳嗽。该研究表明，即使与肠道和呼吸道病原体共同感染，主要感染BVDV的牛传播BVDV的效率也很低。这一发现支持了斯堪的纳维亚BVDV控制计划的原则，即通过识别和清除持续感染（PI）动物，可以实现牛群中BVDV感染的消除，也就是说，在没有PI动物的情况下，病毒长期循环的可能性极小。
