[目的] 探讨PRRSV-GXA毒株对断奶仔猪的致病性.[方法] 将12头PRRSV/PCV2抗体和抗原阴性的健康仔猪随机分为感染组(9头)和对照组(3头),感染组通过口服和肌肉注射方式接种PRRSV-GXA株细胞毒(4 ml/头),对照组接种无病毒的细胞培养液(4 ml/头).感染后第11、14和21天分别剖杀感染组3头和对照组1头,根据临床症状、病理学变化、特异性抗体水平以及病毒核酸等判断其致病性.[结果] 仔猪感染PRRSV后第6～10天体温稍微升高,随后逐渐恢复至正常.早期出现短暂的精神沉郁,轻度厌食但没有出现典型临床症状.剖检的病理变化仅见于感染后第21天,有2头感染仔猪肺膈叶前缘出现小的局灶性间质性肺炎,镜检肺泡壁间质增宽,有多量单核细胞和淋巴细胞浸润.在感染后第9天检测到PRRSV特异性抗体,并随着时间呈上升趋势,感染后第21天达到较高值.在4头感染仔猪的肺脏及肺门淋巴结检测到病毒核酸,其中1头仔猪扁桃体也检测到病毒核酸.[结论] PRRSV-GXA毒株对仔猪的毒力较弱,但能刺激机体产生较高水平特异性抗体.%[ Objective ] To investigate the pathgenicity of piglets infected with PRRSV GXA strain. [ Method ] A total of 12 4-week-old healthy piglets which were negative of antibody and antigen of PRRSV/PCV2 were randomly divided into challenge group(9 piglets) and control group (3 piglets). GXA strain of PRRSV(4 ml/head) was inoculated intranasally and intranscularly simultaneously and cell culture medium of non RRRSV(4 ml/head) was inoculated in conteol group. Three piglets( in challenge group ) and one piglet( in control group) were killed individually in 11,14 and 21 d after starting experiment. Pathogenicity was evaluated by temperature detection, clinical symptom, pathological,specific antibody and viral nucleic acid. [ Results] Rectal temperature increased lightly at 6 d post-infection and then to regain normal. GXA strain of PRRSV caused no obviously clinical signs. Pathological change was only observed in two infected piglets at 21 d post-infection, which characterized as small focal interstitial pneumonia in lung. The histological lesions of PRRSV infected piglets were characterized by infiltration of macrophages and lymphocytes in alveolar septum. Challenge group produced a higher level of special-antibody titres and PEESV DNA had been detected. [ Conclusion ] The pathological lesions were milder in piglets infected PRRSV GXA strain.
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