猪“红眼病”的实验室诊断及药物控制

Laboratory Diagnosis and Drug Control of Pinkeye Disease in Pigs

滇南某养猪场在引进数头后备母猪后,在育肥猪集中暴发一种快速传播的“红眼病”,该病以结膜充血、增生直至失明为特征,虽不致死,却延迟出栏时间并影响销售外观,其病原必需尽快明确,以便有效控制。采集患病仔猪抗凝血样和结膜增生组织,取白细胞做聚合酶链反应(PCR)和逆转录(RT)-PCR扩增分别检测伪狂犬病病毒和猪瘟病毒,对血样和结膜组织样品做PCR扩增检测衣原体,随后对扩增产物进行琼脂糖凝胶电泳检查,回收扩增条带进行TA克隆及测序分析;先后在每千克饲料分别拌入红霉素2~2.4 g或恩诺沙星1 g或强力霉素0.25 g~0.30 g,分别投喂,每日2次,观察药物控制效果。结果表明,血样检查伪狂犬病病毒和猪瘟病毒核酸均呈阴性,使用衣原体属特异性引物和猪衣原体(Chlamydia suis)种特异性引物扩增分别获得符合预期大小(1 025 bp和750 bp)的单一条带,核酸序列比对显示与猪衣原体日本分离菌株的同源性最高(99%);恩诺沙星和红霉素只有短暂控制效果,强力霉素能有效消除红眼症状。说明该猪场发生的“红眼病”本质上是由猪衣原体引起的传染性结膜炎,可使用四环素类药物加以控制。

Shortly after the introduction of gilts into a pig farm in southern Yunnan,a transmissible pinkeye disease characterized by conjunctival hyperemia,hyperplasia and blindness occurred.Although it was non-lethal,the finish time of pigs delayed and their sale-related appearance were impaired so much so that its pathogen needed to be determined for effective control.Anticoagulated blood samples and conjunctival hyperplasia tissues were collected from ill piglets.Polymerase chain reaction(PCR)and reverse transcription(RT)-PCR amplification were used to test the presence of pseudorabies virus and classical swine fever virus in the white blood cells,respectively.The blood samples and conjunctiva tissue was subjected to PCR for determination of the presence of particular Chlamydia species.Amplification products were then examined by agarose gel electrophoresis,followed by TA cloning and sequencing of the corresponding bands.Erythromycin,10%enrofloxacin or doxycycline were separately added by 2 g-2.4 g,1 g and 0.25 g-0.30 g to per kg feed for 3-4 weeks,twice a day,and the drug control effect was observed.The nucleic acids of pseudorabies virus and classical swine fever virus were negative in the blood samples.Single bands(1025 bp and 750 bp)were obtained using specific primers for amplification of the Chlamydia genus and C.suis species,respectively.BLAST revealed the highest sequence identity(99%)to a Japanese strain of C.suis.Enrofloxacin and erythromycin appeared only temporary control effect,and doxycycline can effectively eliminate the symptoms of pinkeye.The pinkeye disease in this pig farm proved to be an infectious conjunctivitis caused by C.suis and could be control using tetracyclines.