Overesch Gudrun, Kuhnert Peter
Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Länggasstrasse 122, 3012 Bern, Switzerland.
Prev Vet Med. 2017 Sep 15;145:67-72. doi: 10.1016/j.prevetmed.2017.06.007. Epub 2017 Jun 26.
Enzootic pneumonia (EP) in pigs caused by Mycoplasma (M.) hyopneumoniae has successfully been combatted in Switzerland. A control program was fully implemented in 2004 which is based on total depopulation strategies of affected fattening farms as well as partial depopulation on breeding farms. Thereby, the number of cases has dropped drastically from more than 200 in 2003 to two cases in 2013. Currently monitoring is done based on clinical observation and subsequent diagnostic of coughing pigs. Moreover, in case of more than 10% gross pathological lesions per slaughter batch laboratory confirmation for EP is compulsory. Despite these strict measures it was not possible to eliminate M. hyopneumoniae from Swiss pig production. In fact, during the last few years the number of EP cases has slightly increased. Therefore, genotyping of the involved M. hyopneumoniae strains was conducted in order to elucidate possible sources and routes of infection. All available and typeable samples from totally 22 cases during the period 2014-2016 were investigated by extended multilocus sequence typing (MLST). A total of 16 cases, including eight from 2014, five from 2015 and three from 2016 could thereby be included in the study. MLST revealed that the majority of cases in 2014/2015 were due to two major spread scenarios, i.e. two M. hyopneumoniae sequence types, each scenario involving six individual production farms in five to six different Cantons (states), respectively. Moreover, by comparison of archived sequences some sequence types were observed over ten years demonstrating their persistence over a long time and the possible partial failure of elimination measures in Switzerland. Insufficient sanitation on affected farms and subsequent animal transport of symptomless infected pigs could lead to recurrent cases. Wild boar harbor identical strains found with EP but solid data are missing to assign a role as reservoir to this wild animal. Implementing a monitoring scheme for M. hyopneumoniae in wild boar in combination with genotyping of all available samples from domestic pigs could direct responsible authorities to possible gaps and deficiencies of control measures taken for combating enzootic pneumonia. With the newly installed PubMLST database sequence types for M. hyopneumoniae are now available and allow tracing back strains on the international level.
瑞士成功抗击了由猪肺炎支原体引起的猪地方流行性肺炎（EP）。2004年全面实施了一项防控计划，该计划基于受影响育肥猪场的全群扑杀策略以及种猪场的部分扑杀策略。由此，病例数从2003年的200多例急剧下降到2013年的2例。目前，监测是基于临床观察以及对咳嗽猪的后续诊断进行的。此外，如果每个屠宰批次的大体病理病变超过10%，则必须对EP进行实验室确诊。尽管采取了这些严格措施，但仍无法从瑞士的生猪生产中根除猪肺炎支原体。事实上，在过去几年中，EP病例数略有增加。因此，对相关猪肺炎支原体菌株进行了基因分型，以阐明可能的感染源和感染途径。通过扩展多位点序列分型（MLST）对2014年至2016年期间总共22例病例的所有可用且可分型的样本进行了调查。总共16例病例，包括2014年的8例、2015年的5例和2016年的3例，从而被纳入该研究。MLST显示，2014/2015年的大多数病例归因于两种主要传播情况，即两种猪肺炎支原体序列类型，每种情况分别涉及五到六个不同州的六个个体生产农场。此外，通过比较存档序列，一些序列类型在十年间都有发现，表明它们长期存在，以及瑞士的根除措施可能部分失效。受影响猪场的卫生条件不足以及随后无症状感染猪的运输可能导致病例复发。野猪携带与EP中发现的相同菌株，但缺乏确凿数据来确定这种野生动物作为储存宿主的作用。对野猪中的猪肺炎支原体实施监测计划，并结合对家猪所有可用样本的基因分型，可能会引导相关当局发现抗击地方流行性肺炎所采取控制措施中可能存在的漏洞和不足。随着新安装的PubMLST数据库，现在可以获得猪肺炎支原体的序列类型，并允许在国际层面追踪菌株。
