Pathogenicity for chickens of a reovirus isolated from turkeys

A viral agent that was isolated from livers of commercial turkey poults that died at approximately two weeks of age was characterized as a reovirus. Experimental infection of day-old chickens with this reovirus isolate resulted in the development of tenosynovitis, hepatitis, and myocarditis. In vitro neutralization of the turkey reovirus isolate by antiserum against chicken reovirus correlated with in vivo protection of maternally immune chickens from day-old oral challenge with the turkey reovirus isolate.     

Pathogenicity of Beauveria bassiana in mice.

The potential pathogenicity of Beauveria bassiana was examined by intramuscular injection of high (2 x 10(8)) or low (2 x 10(5)) concentrations of conidia spores, into the left or right quadriceps muscles of CD-1 mice, respectively. The injection sites were monitored over a period of 28 days by both microbiological and histopathological methods. Focal muscle necrosis, edema and inflammation occurred rapidly (within 12 hours) at the high dose application (2 x 10(8)) site, but such lesions were far less severe with the low dose spore application (2 x 10(5)). Fungal spores in the high dose site persisted in normal shape for 2 weeks, after which time they began to degenerate. Almost all spores were cleared from the injection site within the 28-day observation period. Spread to other organs of the body was not observed, except by macrophage transport to regional lymph nodes. At the low dose rate, most spores were cleared within 12 h to 2 d, leaving only mild focal edema and inflammation. Viable fungal colonies could be recovered up to 3 d after injection from the high dose site, but only up to 12 h from the low dose site. It was concluded that B. bassiana does not cause infection, nor multiply, nor survive for more than 3 days when injected intramuscularly into healthy mice.     

猪圆环病毒2型SD/2008株对仔猪的致病性

为了明确PCV2-SD/2008株对猪的致病性,将12头5周龄健康断奶仔猪随机分为PCV2组和对照组,每组6头.PCV2组经口鼻途径接种PCV2 SD/2008株第3代细胞毒(105.61 TCID50/0.1 mL),3 mL/头,对照组经相同途径接种3 mL细胞维持液.PCV2组中的1头猪从感染后14 d开始出现间断腹泻,一直到持续到试验结束.感染后第4、5周,感染组的周平均增重显著低于对照组(P＜0.05).病理组织学检查可见PCV2感染猪的淋巴结和脾脏内淋巴细胞缺失、单核/巨噬细胞和嗜酸性粒细胞浸润;间质性肺炎、坏死性肝炎和肾炎、小血管炎症等变化,并且感染后35 d比感染后14 d的病理变化更加严重.应用免疫组化方法在感染猪的肺、肝、脾、肾、淋巴结、小肠等多种组织中检测到了PCV2抗原,其中颌下淋巴结、肺、小肠中的阳性信号数与检出率最高.结果表明,PCV2 SD/2008株对仔猪具有明显的致病性.     

猪圆环病毒和猪繁殖与呼吸综合征病毒混合感染对仔猪致病性的评估

本研究通过猪圆环病毒2型(Porcine circovirus type 2,PCV2)和猪繁殖与呼吸综合征(Porcine reproductive and respiratory syndrome virus,PRRSV)强毒共感染3周龄健康仔猪来评价其致病性。试验动物随机分为3组,空白对照组(n=3头),PRRSV单独感染组(n=3头),PCV2和PRRSV共感染组(n=6头),从而比较相互之间的差异。通过临床症状、病理学变化、病原学和血清学检查,对二者混合感染仔猪的致病性进行了研究。结果表明PCV2和PRRSV共同感染能引起仔猪断奶后多系统消耗性综合征,表现为淋巴组织肿大、出血,肉芽肿性炎症,坏死性肝炎,仔猪消瘦、生长缓慢等特征性病变;混合感染能加重PRRSV对仔猪引起的间质性肺炎的严重程度。混合感染可以出现支气管肺炎和明显的肝病变,淋巴结多呈界限明显的块状出血等典型病变。     

Pathogenicity of a recently isolated strain of Tritrichomonas foetus in mice

The pathogenicity of a recently isolated strain of T. foetus in mice was studied. The parasite produced local abscesses 3 days post subcutaneous inoculation (p.i.) in albino mice. The abscesses in mice, inoculated with large numbers (4 × 10⁶) of organisms, continued increasing in size until the 14th day. Some absceses ruptured between day 11 to 14 p.i., while others formed a point. Secondary abscesses were also found in some mice. the abscesses in mice, inoculated with small numbers (1 × 10⁶) of organisms reached their maximum on the 5th day and decreased thereafter. All the abscesses had motile trichomonads with no bacterial contamination. The trichomonads, inoculated intraperitoneally in mice, persisted in that cavity till day 5 or 6 p.i., but did not multiply. Subcutaneous inoculations appear to be more reliable than the intraperitoneal ones for studies on pathogenicity. The comparison of present observations with those using a similar model and T. foetus or other trichomonads, suggests that the strain of T. foetus employed was of low pathogenicity.     

Recovery of reovirus type 2 from an immature dog with respiratory tract disease.

Two similar cytopathic agents were recovered from the throat and rectal swab specimens of an immature dog with upper respiratory tract disease. The reference isolate, 14-72R, was shown to be a member of the reovirus group by its physicochemical properties, cytopathic effects in cell cultures, and appearance when examined in the electron microscope. Both isolates hemagglutinated human type O erythrocytes and antigenically were closely related to reovirus type 2. The affected pup had an increase in antibody titer to reovirus types 2 and 3. The latter findings provide evidence for possible heterotypic antibody responses in dogs to reovirus infection.     

Replication and transmission of porcine circovirus type 2 in mice

Little information is known about infection, replication and transmission of porcine circovirus type 2 (PCV2) in species other than swine. Two sets of animal experiments were carried out to investigate the susceptibility of mice to PCV2 and to study their possible role in maintaining and transmitting the virus. In the first experiment 14 mice were inoculated with PCV2 by the intraperitoneal route with 5 x 10(2) TCID50 of the PCV2-ROM strain (Cadar et al., 2007). In a second experiment 24 mice were divided into two groups (A and B); mice in Group A (n = 18) were inoculated orally with 1 x 10(5) TCID50 PCV2-ROM and mice in Group B (n = 6) were left uninoculated until day 12 post inoculation (p.i.), when they were mixed with Group A. The animals were sacrificed at intervals for postmortem investigation and virus genome detection by polymerase chain reaction (PCR). The PCR results indicated that PCV2 could replicate in mice infected intraperitoneally or by the oral route, and that the virus can be transmitted directly from mouse to mouse.     

In vitro and in vivo characterization of avian reoviruses. I. Pathogenicity and antigenic relatedness of several avian reovirus isolates

Pathogenicity, pathogenesis, and antigenic relatedness of four avian reovirus isolates obtained from commercially reared broilers were investigated. Chickens of various ages were inoculated both orally and intratracheally with reovirus. Based on disease signs, mortality, weight depression, tissue lesions, invasiveness, and viral persistence in chickens inoculated at 1 day of age, the isolates were classified as being of low, intermediate, or high pathogenicity. The low-pathogenicity isolate (2177) did not cause mortality, weight depression, or clinical disease. The isolate of intermediate pathogenicity (2035) produced low mortality rates (8%), some weight reduction by 7 weeks postinoculation, and microscopic lesions in the intestine and gastrocnemius tendons. The pathogenic isolates, 2408 and 1733, caused severe clinical disease characterized by stunting, feathering abnormalities, mortality as high as 84%, and microscopic lesions in the liver, intestine, pancreas, and/or gastrocnemius tendon. Highly pathogenic isolates also persisted longer in tissues of infected birds and elicited a more prompt and prolonged antibody response. Birds inoculated at 1 day or 1 week of age were more susceptible to reovirus-induced disease than birds inoculated at 2 weeks, suggesting an age-associated resistance. All isolates produced mortality with equal frequency in embryos. The isolates characterized were found to be antigenically similar based on cross-neutralization and cross-protection studies.     

6株牛支原体分离株对鸡胚和小鼠的致病性研究

为通过复制不同牛支原体(Mycoplasma bovis)感染模型,筛选出毒力较强的M.bovis分离株,本研究采用等浓度的6株M.bovis分离株(W70、1738、677、Q1、Q3、JX02)感染7日龄健康鸡胚和6周龄～8周龄SPF级BALB/c小鼠,观察并比较各组受试动物死亡情况及病理剖检变化,取死亡鸡胚尿囊液或卵黄液,以及小鼠肺组织进行病原学分离培养和PCR鉴定.实验结果表明:各感染组BALB/c小鼠虽然出现一定程度的体重增长抑制,但小鼠并无任何临床呼吸道症状和病理剖检变化,并且病原学分离培养及PCR鉴定结果也均为阴性.在鸡胚感染试验中,6株M.bovis分离株对鸡胚表现出较好的感染性和致死性.感染组鸡胚致死率与对照组比较差异极显著(p＜0.01),而6个分离株间鸡胚致死率也表现出显著差异(p＜0.01).其中,以W70株感染后鸡胚死亡率最高,达63.3％;677株感染后死亡率最低,仅为20％,鸡胚死亡情况大多发生在感染后一周内,而后期仅有零星死亡.综合上述实验结果,初步筛选出W70株、1738株、Q1株、Q3株为毒力相对较强的分离株;与此同时,BALB/c小鼠的建模还需进一步研究.     

H5N1亚型禽流感病毒低剂量感染小鼠发病模型的建立

为模拟哺乳动物感染H5亚型高致病性禽流感病毒(HPAIV)的发病进程,本研究采用对哺乳动物高度致病的H5N1亚型HPAIV株A/bar-headed goose/Qinghai/3/05 (BHG/3/05),以低剂量鼻腔接种小鼠,观察发病、存活、病毒复制及组织病理损伤情况.结果显示,100.4 EID50即能够100％感染小鼠,但发病表现缓慢,死亡延迟至8d以后,存活达60％;体内病毒复制可持续10 d以上,感染后前3d病毒的增殖限于呼吸道,随后扩散至脑、脾、肾等其他器官;组织病理学观察肺脏早期表现出渗出性炎症,第10d发展为典型的间质性肺炎.本研究结果为探讨人禽流感的病理发生机制提供了具有价值的模型.     

Pathogenicity for chickens of a paramyxovirus type 1, isolated from racing pigeons in Sweden

Strains of paramyxovirus type 1 (PMV-1) have been isolated from diseased racing pigeons in Sweden. One of these isolates was selected for studies of the pathogenicity and contagiousness in chickens.The same isolate was previously found to have a high intravenous pathogenicity index (IVPI) in 6 weeks old chickens.In three experiments it was found that the PMV-1 isolate was very pathogenic for 1 week old chickens but not pathogenic for 120 day old pullets inoculated intranasally and ocularly.Symptoms in the young chickens were similar to those seen in the neurotropic form of Newcastle disease. The mortality was high and the incubation period 5–11 days.The disease easily spread to young chickens kept in contact with diseased birds.The microscopic examination revealed an interstitial nonpurulent pneumonia and a nonpurulent encephalitis in the young chickens. In the pullets the only finding was a mild encephalitis.PMV-1 was recovered from all young chickens but not from the pullets.Both the chickens and the inoculated pullets developed antibodies to PMV-1.