细胞因子在猪呼吸道疾病中的作用及存在的问题和研究价值

细胞因子，如干扰素-α(IFN-α)，肿瘤坏死因子-α(TNF-α)，白细胞介素-1、-6和-8(IL-1，-6，-8)，在多数感染的早期都会产生。这些细胞因子的活性已在体外和裸鼠实验中广泛研究，但有关细胞因子在肉用动物感染中的作用的体内实验研究却很少，本文综述细胞因子在猪的呼吸道感染中的作用，并探讨其对呼吸道病毒性感染的相关性。     

支原体在当前肥育猪呼吸道疾病发生中的作用

根据近一年来的报告，肥育猪呼吸疾病的发生率正在升高。     

猪肺炎支原体在猪呼吸道疾病中的作用

猪支原体肺炎在猪的呼吸道疾病综合征中起到核心作用。过去，肺炎支原体的感染被称作地方性肺炎（EP），主要使10周龄左右的猪只发病，由于继发其它的病原，也可使12-16周龄的猪群发生呼吸道疾病。现在猪呼吸道疾病综合征（PRDC）的发生越来越多见，临床症状和肺部出现病变的时间推迟到了16-18周龄，有的甚至到18-20周龄。     

猪呼吸道冠状病毒研究进展

综述了猪呼吸道冠状病毒(PRCV)的病原学意义、分子生物学特性、与传染性胃肠炎病毒TGEV的鉴别诊断、PRCV对TGEV的免疫保护作用等四个方面的研究进展。     

猪呼吸道冠状病毒感染

猪呼吸道冠状病毒(PRCV)于1984年首次分离于利时,是传染性胃肠炎病毒(TGEV)的一个变异株,一种非肠道致病性冠状病毒。Pensaert等1986年首报道,PRCV 感染于1984年出现后,迅速传遍整个欧。在英国,近100%的TGEV抗体阳性,它是由TGEV呼道变异株,即PRCV所引起。自从PRCV出现后,TGE的病率降低。PRCV与TGEV的交叉保护力是主要原因?有人持肯定态度,有人持否定态度。在英国TGEV的新调查表明,1996年1月在East Anglia发生了猪传性胃肠炎(TGE),其典型病例与1980年的相似。该发猪场PRCV血清阳性,似乎是PRCV与TGEV无交叉保力。但…     

猪呼吸道疾病综合征

前　　言在猪的所有各种呼吸道疾患中 ,与猪呼吸道疾病综合征 (ＰＲＤＣ)有关的那些 ,都是猪肺炎的主要病因 ,都可导致猪的生产性能下降以至死亡 ,并且推迟达到上市体重的时间。ＰＲＤＣ是断奶猪、生长猪和肥育猪的一种新型呼吸道疾患 ,它比通常的呼吸道疾患传播更广 ,病情更严重 ,也更难以防制。ＰＲＤＣ的病因常常很复杂 ,是入侵的或正常携带的病原体同环境因素 (比如尘埃或气温波动 )相互作用的结果。这一疾患在多年龄猪场表现为地方流行性 ,是因为猪场中存在着年长的感染猪这一永久的病原微生物藏匿者。这一微生物藏匿者中通常藏匿有多…     

猪呼吸道疾病

猪呼吸道疾病是近年来我国养猪生产中最突出的问题，流行普遍，危害大，猪群不仅发病率高、死亡率高，造成的经济损失大，而且难于控制。引发呼吸道疾病的病因众多，不仅有病原性的，而且还有环境因素以及猪群本身免疫力低下等因素，都可诱发或促进、加重呼吸道疾病的发生，因此又称为猪呼吸道疾病综合征(Porcine rerespiratory disease complex，PRDC)。     

猪呼吸道疾病原因及其防制

猪呼吸道疾病是一类以气喘病（即霉形体肺炎）为主的广泛而又严重的疾病,不但在集约化饲养的商品猪场中较为普遍,而且在种猪场也不同程度地存在。主要侵害猪的上下呼吸道,对肺脏产生不同程度的病理变化。根据欧洲及美国等国的调查表明,在屠宰场中猪酮体肺脏病变率占屠宰量的４０％～８０％。由于呼吸道疾病引起的症状及肺部病变直接影响猪的生长和饲料利用率,损失是巨大的。猪的呼吸道疾病是一种综合症,引起疾病的原因既有主要病原的致病作用,也有其他微生物的混合感染或继发感染;既有饲养中的营养因素,也有饲养环境中的不良条件,…     

大环内酯类抗生素及其在猪呼吸道疾病防控上的潜在作用

呼吸道疾病是养猪业面临的动物健康的最重大挑战之一。在猪的整个保育期和生长/育肥阶段,传染性细菌和病毒与环境应激的联合作用会导致猪暴发猪呼吸道疾病综合征(Porcine RespiratoryDiease Complex,PRDC)。PRDC 对猪健康的影响会导致动物生产性能下降,药物治疗成本和死亡率的上升。     

Effect of ascariasis and respiratory diseases on growth rates in swine.

Growth rates, measures of ascarid burden, and the levels of anteroventral pneumonia and atrophic rhinitis at slaughter were determined for 352 hogs born between March 8 and March 28, 1987 on 15 farms located in Prince Edward Island. Regression analyses were used to determine associations between average daily gain (ADG) and independent variables controlling for sex, farm, and litters nested within farm. The regression model accounted for 75.4% of the variation in ADG. The number of intestinal ascarids at slaughter did not affect ADG. However, the "life-time burden" (a composite measure based on fecal egg counts and duration of infection) was associated with ADG (p less than 0.05) in a quadratic manner. Although heavy ascarid burdens decreased the growth rate of swine, the magnitude of the effect was minimal. The maximum improvement one could expect from reducing the ascarid burden on heavily infected farms would be less than 1%. Severe atrophic rhinitis and the presence of anteroventral pneumonia each had a detrimental effect on ADG (p less than 0.001). The corresponding reductions in mean ADG were 7.7% and 2.8% respectively. There was significant interaction between the effects of atrophic rhinitis and anteroventral pneumonia on ADG (p less than 0.05). Hogs with both anteroventral pneumonia and severe atrophic rhinitis had a 17.6% lower ADG than hogs with neither disease. There is much greater potential for improvement in ADG through control of respiratory diseases than through control of ascariasis.     

Infectious agents associated with respiratory diseases in 125 farrow-to-finish pig herds: a cross-sectional study

A study was carried out in 125 farrow-to-finish pig herds to assess the relationships between pathogens involved in respiratory disorders and to relate these findings to clinical signs of respiratory diseases and pneumonia and pleuritis at slaughter. Clinical examination and sampling were carried out on four different batches in each herd (pigs aged 4, 10, 16 and 22 weeks). Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, swine influenza viruses (SIV), porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) were detected by serological or PCR tests. Pneumonia-like gross lesions and pleuritis were scored at the slaughterhouse. The results indicate that the percentage of pigs PCR-positive for PCV2 at 4, 10 and 16 weeks old was associated with the percentage of pigs PCR-positive for M. hyopneumoniae at these ages. On the other hand, the percentage of pigs with antibodies against PRRSV at 10, 16 and 22 weeks was positively correlated with the percentage of pigs seropositive for M. hyopneumoniae at 22 weeks, with the percentage of pigs with antibodies against SIV H1N1 and SIV H1N2 and the percentage of pigs sero-positive for A. pleuropneumoniae serotype 2. The findings also indicate that, within the five studied pathogens, M. hyopneumoniae, PRRSV and SIV H1N1 are the major pathogens involved in pneumonia-like gross lesions even though PCV2 may play a role. A. pleuropneumoniae serotype 2, in association with PRRSV, is significantly associated with extensive pleuritis. Respiratory diseases could be significantly reduced by implementing measures including appropriate management practices to control these pathogens.     

Differential production of proinflammatory cytokines in the pig lung during different respiratory virus infections: correlations with pathogenicity.

The acute stages of infection with swine influenza virus (SIV), porcine respiratory coronavirus (PRCV) and porcine reproductive-respiratory syndrome virus (PRRSV) were shown to differ in terms of clinical and lung inflammatory effects and proinflammatory cytokine profiles in bronchoalveolar lavage (BAL) fluids. Caesarian-derived colostrum-deprived pigs were inoculated intratracheally with one of the three viruses. SIV infection was followed within 1 day post inoculation (d PI) by characteristic respiratory and general signs, and excessive lung epithelial desquamation and neutrophil infiltration (38 to 56 per cent of BAL cells at 1 d PI vs 0 to 1 per cent in controls). High concentrations of bioactive interferon-alpha (IFN -alpha), tumour necrosis factor-alpha (TNF -alpha) and interleukin-1 (IL -1) coincided with peak symptoms and neutrophil infiltration. PRCV infection was asymptomatic and produced a mild bronchointerstitial pneumonitis and neutrophil infiltration (13 to 22 per cent of BAL cells at 4 d PI). IFN -alpha titres parallelled those found during SIV infection, TNF -alpha was negligible and IL -1 undetectable. PRRSV infection induced anorexia and lethargy between 3 and 5 d PI. There was marked infiltration with mononuclear cells in alveolar septa and BAL fluids between 7 and 10 d PI, while neutrophils remained at less than 11 per cent of BAL cells at any time. IL -1 was produced from three throughout 10 d PI, while IFN -alpha production was minimal and TNF -alpha undetectable. These data strongly suggest that proinflammatory cytokines can be important mediators of viral respiratory disease.     

Lipopolysaccharide induces inflammatory cytokines in the pig amnion

Inflammatory mediators that are induced by gram-negative bacteria in the course of intrauterine infections threaten successful pregnancy. To compare the effect of two different routes of cytokine induction, bacterial lipopolysaccharide (LPS) was administered in vivo either into the cord vein or into the amniotic cavity of pig fetuses in the second half of gestation for 20 h and cytokines were detected in the amnion.Tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) were induced in the amniotic epithelium after intra-amniotic but not after intra-venous administration of LPS. The presence of IL-8 was confirmed by RT-PCR. In contrast, transforming growth factor-beta1 (TGF-beta1) was expressed constitutively and was found in all samples of the amniotic epithelium.Amniotic fluid contained only minute levels of TNF-alpha. IL-8 levels in amniotic fluid increased after the treatment with LPS and the highest IL-8 levels were found in dead LPS-treated fetuses.     

Viral respiratory diseases

An overview of the more commonly encountered viral diseases of the dog and cat is presented. The reader is acquainted with the principles of antiviral therapy and the drugs that have been studied for use in animal viral respiratory diseases. An update on vaccination principles and guidelines is provided.     

Proinflammatory cytokines and viral respiratory disease in pigs

Swine influenza virus (SIV), porcine respiratory coronavirus (PRCV) and porcine reproductive and respiratory syndrome virus (PRRSV) are enzootic viruses causing pulmonary infections in pigs. The first part of this review concentrates on known clinical and pathogenetic features of these infections. SIV is a primary respiratory pathogen; PRCV and PRRSV, on the contrary, tend to cause subclinical infections if uncomplicated but they appear to be important contributors to multifactorial respiratory diseases. The exact mechanisms whereby these viruses cause symptoms and pathology, however, remain unresolved. Classical studies of pathogenesis have revealed different lung cell tropisms and replication kinetics for each of these viruses and they suggest the involvement of different lung inflammatory responses or mediators. The proinflammatory cytokines interferon-alpha (IFN-alpha), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) have been shown to play key roles in several respiratory disease conditions. The biological effects of these cytokines and their involvement in human viral respiratory disease are discussed in the second part of this review. The third part summarises studies that were recently undertaken in the authors' laboratory to investigate the relationship between respiratory disease in pigs and bioactive lung lavage levels of IFN-alpha, TNF-alpha and IL-1 during single and combined infections with the above viruses. In single SIV infections, typical signs of swine "flu" were tightly correlated with an excessive and coordinate production of the 3 cytokines examined. PRCV or PRRSV infections, in contrast, were subclinical and did not induce production of all 3 cytokines. Combined infections with these 2 subclinical respiratory viruses failed to potentiate disease or cytokine production. After combined inoculation with PRCV followed by bacterial lipopolysaccharide, both clinical respiratory disease and TNF-alpha/IL-1 production were markedly more severe than those associated with the respective single inoculations. Taken together, these data are the first to demonstrate that proinflammatory cytokines can be important mediators of viral respiratory diseases in pigs.     

鸡群发生呼吸道疾病的原因

长期以来,鸡群中发生的呼吸道疾病是一类大型的、在经济上占有重要地位的疾病.Jordan把该类疾病描述为"主要出现呼吸道的临床症状和/或大体病变,而不伴有其他器官和组织病变".有效控制该病的先决条件是对其致病因子、流行病学、病理学和诊断学方法的了解.