Pomorska-Mól Małgorzata, Dors Arkadiusz, Kwit Krzysztof, Czyżewska-Dors Ewelina, Pejsak Zygmunt
Department of Swine Diseases, National Veterinary Research Institute, Partyzantów 57, 24-100, Pulawy, Poland.
BMC Vet Res. 2017 Dec 4;13(1):376. doi: 10.1186/s12917-017-1298-7.
Respiratory co-infections are important factor affecting the profitability of pigs production. Swine influenza virus (SIV) may predispose to secondary infection. Haemophilus parasuis (Hps) can be a primary pathogen or be associated with other pathogens such as SIV. To date, little is known about the effect of coinfection with SIV and Hps on the disease severity and inflammatory response and the role of Hps in the induction of pneumonia in the absence of other respiratory pathogens. In the study we investigated the influence of SIV and Hps coinfection on clinical course, inflammatory response, pathogens shedding and load at various time points following intranasal inoculation. The correlation between local concentration of cytokines and severity of disease as well as serum acute phase proteins (APP) concentration has been also studied.
All co-infected pigs had fever, while in single inoculated pigs fever was observed only in part of animals. Necropsy revealed lesions in the lungs all SIV-inoculated and co-inoculated pigs, while in Hps-single inoculated animals only 1 out of 11 pigs revealed gross lung lesions. The SIV shedding was the highest in co-inoculated pigs. There were no differences between Hps-single inoculated and co-inoculated groups with regard to Hps shedding. The significant increase in Hps titre in the lung has been found only in co-inoculated group. All APP increased after co-infection. In single-inoculated animals various kinetics of APP response has been observed. The lung concentrations of cytokines were induced mostly in SIV + Hps pigs in the apical and middle lobe. These results correlated well with localization of gross lung lesions.
The results revealed that SIV increased the severity of lung lesions and facilitated Hps (PIWetHps192/2015) replication in the porcine lung. Furthermore, Hps influenced the SIV nasal shedding. Enhanced Hps and SIV replication, together with stronger systemic and local inflammatory response contributed to a more severe clinical signs and stronger, earlier immune response in co-inoculated animals. We confirmed the previous evidence that single-Hps infection does not produce significant pneumonic lesions but it should be in mind that other strains of Hps may produce lesions different from that reported in the present study.
呼吸道混合感染是影响养猪业盈利能力的重要因素。猪流感病毒（SIV）可能易引发继发感染。副猪嗜血杆菌（Hps）可以是主要病原体，也可与其他病原体如SIV相关联。迄今为止，关于SIV和Hps混合感染对疾病严重程度和炎症反应的影响以及在无其他呼吸道病原体情况下Hps在诱发肺炎中的作用知之甚少。在本研究中，我们调查了SIV和Hps混合感染对鼻内接种后不同时间点临床病程、炎症反应、病原体排出及载量的影响。还研究了细胞因子局部浓度与疾病严重程度以及血清急性期蛋白（APP）浓度之间的相关性。
所有混合感染的猪均出现发热，而单接种猪中仅部分动物出现发热。尸检发现所有接种SIV及混合接种的猪肺部有病变，而单接种Hps的11头猪中只有1头出现明显肺部病变。混合接种的猪中SIV排出量最高。单接种Hps组和混合接种组在Hps排出方面无差异。仅在混合接种组中发现肺内Hps滴度显著升高。混合感染后所有APP均升高。在单接种动物中观察到APP反应的不同动力学。细胞因子的肺内浓度主要在SIV+Hps猪的尖叶和中叶诱导产生。这些结果与明显肺部病变的定位密切相关。
结果表明，SIV增加了肺部病变的严重程度，并促进了Hps（PIWetHps192/2015）在猪肺中的复制。此外，Hps影响SIV的鼻腔排出。Hps和SIV复制增强，以及更强的全身和局部炎症反应导致混合接种动物出现更严重的临床症状和更强、更早的免疫反应。我们证实了之前的证据，即单一Hps感染不会产生明显的肺部病变，但应记住，其他Hps菌株可能产生与本研究报道不同的病变。
