The age on which pigs get infected by Classical Swine Fever (CSF) plays a role with regard to the level to which the virus can be persistent in pigs.
猪感染经典猪瘟（CSF）的年龄与病毒能否长期存在于仔猪体内有关。
That was one of the outcomes of recent research at the Catalan research institute IRTA-CReSA, Spain. The study was published recently in the journal Transboundary and Emerging Diseases.
这是西班牙加泰罗尼亚研究所IRTA-CReSA近期的研究成果之一。这项研究最近发表在Transboundary and Emerging Diseases杂志上。
CSFv may persist when pregnant sows get infected
妊娠母猪感染经典猪瘟病毒后，病毒可能会持续
The study draws on a few earlier publications. Since the late 70s, it has already been documented that CSFv may persist when pregnant sows become infected during the 2nd or 3rd pregnancy. Piglets born from these sows are infected with high virus loads, but are unable to generate an immune response.
这项研究借鉴了一些早期的出版物。自上世纪70年代末以来，已有文献表明，妊娠母猪在第2次或第3次妊娠期间受到经典猪瘟病毒感染时，病毒可能会持续存在。这些母猪生出的仔猪感染了高病毒载量，但不能产生免疫反应。
Piglets from CSF infected sows can have high virus loads but not show any immune response. Photo: Bert Jansen
感染经典猪瘟的母猪，其仔猪病毒载量高，但没有任何免疫反应。图：Bert Jansen
In the current research article, that phenomenon is described as follows: “These animals may appear clinically healthy or show unspecific clinical signs despite the permanent viraemia and high viral shedding, in absence of immune response to the virus.”
在目前的研究文章中，这种现象被描述为：“尽管在缺乏病毒免疫反应的情况下，这些猪有长期病毒血症和高病毒脱落，但临床上却可能是健康的或表现出非特异性的临床症状。”
Something like that would make it difficult to detect the virus through the diagnostic techniques traditionally used for the epidemiological monitoring of the disease. Consequently, those animals go unnoticed on farms, spread the virus and neutralise efforts made to eradicate the disease.
诸如此类的事情使得通过传统上用于疾病流行病学监测的诊断技术来检测病毒变得困难。因此，这些猪被忽视，继续传播病毒，抵消了为根除这种疾病而做出的努力。
Generating viral persistence in newborn piglets
在新生仔猪中产生病毒持久性
In a more recent study, it was reported that CSFv is also capable of generating viral persistence after infecting newborn piglets with low and moderate virulence strains, such as the Catalonia 2001 strain (Cat01) that caused an outbreak in 2001 in different farms in northern Spain. Those newborn pigs can go clinically unnoticed or show symptoms not associated with the African Swine Fever because an immune response is not generated. So far it was not known if this phenomenon can occur only in newborn pigs or also in older animals.
在最近的一项研究中，有报道称，猪瘟病毒还能够在用低毒和中等毒力菌株感染新生仔猪后产生病毒持久性，例如2001年在西班牙北部不同农场引起暴发的加泰罗尼亚2001菌株（Cat01）。由于没有产生免疫反应，这些新生仔猪可能没有在临床上引起注意，或者表现出与非洲猪瘟无关的症状。到目前为止，尚不清楚这种现象是否只发生在新生仔猪身上，成年猪是否也有该现象也未可知。
In the most recent study, which was published recently in Transboundary and Emerging Diseases, the Spanish researchers showed that piglets born from a sow without pestivirus which were infected with the Cat01 strain at 21 days of age can also develop persistent infection with CSFv. This age of infection is important, since 21 days after birth the animals are weaned and together with piglets from other litters in some farms, where they could spread the disease.
在最近发表于Transboundary and Emerging Diseases杂志上的一项研究中，西班牙研究人员发现，出生时没有携带病毒的母猪在21天大的时候感染了Cat01株，其产下的仔猪也会发展为持续性的猪瘟感染。这个感染年龄很重要，因为出生后21天，这些猪就会断奶，它们会和其他窝仔猪一起断奶，从而传播疾病。
In total 9 pigs were infected with Classical Swine Fever virus and sampled weekly during 6 weeks and viral, clinical, pathological and immunological tests were carried out.
共9头猪感染经典猪瘟病毒，6周内每周取样，进行病毒、临床、病理和免疫学检测。
Age plays a role
年龄是一个因素
Interestingly, the proportion of animals that presented this form of the disease (44.4%) was lower than previously reported in studies with newborn piglets, less than 21 days old, where about 60% of the animals were persistently infected. This result suggests that the age at which animals become infected plays a role in establishing persistent infection with CSFv, with older animals being less susceptible to developing persistent infection with CSFv.
有趣的是，出现这种类型疾病的动物比例（44.4%）低于此前对新生仔猪的研究报告，新生仔猪出生不到21天，其中约60%的动物持续感染。这一结果表明，动物受感染的年龄对猪瘟病毒的持续感染有一定的影响，年龄较大的猪不易发生猪瘟病毒的持续感染。
In addition, in this study the researchers found that animals persistently infected with CSFv have alterations in some of the immune system cell populations. Those alterations have been described in other species as signs of ‘immune depletion’, a phenomenon that can negatively affect the response of the immune system, not only against CSFv, but also against other infections. The researchers wrote that future studies will help clarify the importance that these findings may have, both for the control of the CSF, and for animal health in general.
此外，在这项研究中，研究人员发现，持续感染猪瘟病毒的生猪的某些免疫系统细胞群发生了变化。在其他物种中，这些变化被称为“免疫衰竭”的迹象，这种现象不仅会对猪瘟病毒产生负面影响，还会对其他感染产生负面影响。研究人员写道，未来的研究将有助于阐明这些发现对猪瘟控制及动物健康的重要性。
Important disease for animal health worldwide
影响全球生猪健康的疾病
As a background to the research, the scientists wrote that CSF continues to be one of the most important diseases for animal health worldwide, generating high economic losses due to the costs derived from the death of the animals, as well as the eradication efforts.
作为研究的背景，科学家们写道，经典猪瘟仍然是世界范围内对生猪健康影响最大的疾病之一，由于生猪死亡的成本以及根除病毒付出的代价，经典猪瘟带来了很高的经济损失。
The research article was authored by José Alejandro Bohórquez, Miaomiao Wang, Marta Pérez-Simó, Enric Vidal, Rosa Rosell and Llilianne Ganges, all attached to IRTA-CReSA, Spain. Rosa Rosell also is attached to the Generalitat de Catalunya, Spain.
该论文作者为José Alejandro Bohórquez、Miaomiao Wang、Marta Pérez-Simó、Enric Vidal、Rosa Rosell 及Llilianne Ganges，他们都来自西班牙IRTA-CReSA。Rosa Rosell同时也隶属于西班牙加泰罗尼亚政府。
文章来源：Pig Progress
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（文/爱猪网记者刘坤颖编译，爱猪网原创，转载请注明出处）
