云南地区部分猪场猪呼吸道疾病综合症（PRDC）患病猪群中PRRSV，PCV-2，CSFV，PRV混合感染调查

 针对云南省不同地区不同季节猪呼吸道疾病综合征进行流行病学调查，根据其临床特征，在不同规模养殖场共采集1164份血清样品，利用ELISA和RT-PCR方法检测其猪瘟抗原CSFV，猪繁殖与呼吸综合征抗原PRRSV，猪伪狂犬病PRV gE抗体及猪圆环病毒2型PCV-2特异抗体。结果表明：各季节和不同生长阶段猪群存在一种及两种以上的病毒混合感染，四重感染相对较少。从全年看单独感染占39.10%，PCV-2感染率最高，其次是PRV，PRRSV和CSFV；二重感染占26.13%，以PCV-2+PRV最常见，其次是PCV-2+ PRRSV、PRV+PRRSV；三重感染占8.05%，PCV-2+ PRRSV+PRV最常见；有四重感染出现，仅占1.57%。从季节来看，春季和夏季混合感染最高，分别为76.53%和60.74%，冬季和秋季的混合感染率分别为59.50%和53.55%。从年龄和性别看，育肥猪的混合感染率高于仔猪，分别为68.66%和61.11%，种公猪的感染率高于母猪，分别为70.00%和55.51%。说明4种病毒有单独感染或混合感染，推测其中PCV-2在混合感染中可能充当免疫抑制的角色，混合感染使PRDC症状更明显,死亡率增高。

An Epidemiological Survey on PCV-2, CSFV, PRRSV and PRV that Play as Main Pathogens of PRDC in Some Herds of Swinein Yunnan Areas

1164 whole pig blood and serum samples from different season and growth stage in Yunnan areas were detected for antigen and antibody of classical swine fever virus(CSFV), porcine respiratory disease complex(PRRSV), pseudorabies virus(PRV) and porcine circovirus 2（PCV-2） with ELISA and RT-PCR. The results showed that each season and different growth stages exist in infection mixed with one or more than two viruses. Few cases were caused by 4 viruses. 39.10% infection was caused by singular virus; PCV-2, PRV, PRRSV and CSFV were the most common viruses. 26.13% infection was caused by double infection in which PCV-2+PRV, PRV+PRRSV, and PCV-2+PRRSV were the common combined type. 8.05% infection was caused by triple infection, in which PCV-2+PRRSV+PRV was the common combined type, while 1.57% infections were caused by fourfold infection. PCV-2 infection could play a role of immunosuppression in mixed infection. Co infection of these viruses caused a serious symptom and high mortality of PRDC(porcine respiratory disease complex).