4. Co-Infection of Mycoplasma hyopneumoniae with others

Apart from co-infection of Mhp with viruses or bacteria, there are many pathogens which comes from the pig farms diet (Michiels et al., 2018). The presence of mycotoxin in foods and feeds have become a serious global challenge for animals and humans health not only in the developing as well as the developed countries(Stoev, 2013). Fumonisin mycotoxin is a metabolite produced mainly by Fusarium moniliforme Sheld , which can be subdivided into several subtypes, such as Fumonisin B1 (FB1), Fumonisin B2(FB2) and Fumonisin B3(FB3). The FB1 is considered to be the main pathogen for inducing porcine pulmonary edema(Harrison, Colvin, Greene, Newman, & Cole, 1990) and pulmonary fibrosis that develops in cases of chronic exposure (Zomborszky-Kovács et al., 2002). Several groups have studied the interaction between Mhp-infection and FB1-fed pig, their results revealed a strong oedematous changes in the interstitium of lung in addition to deteriorated and extended bronchointerstitial pneumonic process and severe illness requiring euthanasia observed in one pig and evidence of progressive pathology in two pigs between study days 44 and 58 by using computed tomography (CT) and histopathologic review (Posa et al., 2013b; Posa et al., 2016). Therefore, FB1 aggravated the progression of infection. On the contrast, Michiels and co-workers indicated that the pigs which received feed contaminated with the mycotoxin deoxynivalenol (DON) did not show more severe disease and lesions under experimental pre-Mhp infection compared to the pigs which were fed with non-contaminated feed(Michiels et al., 2018). Furthermore, the opportunistic fungal pathogen Pneumocystis can also be co-infectied with Mhp, related interstitial pneumonia in both the Pneumocystis positive lungs and lungs with a mild Mhp infection (Kureljusic, Weissenbacher-Lang, Nedorost, Stixenberger, & Weissenbock, 2016). Consequently, the health level of pigs to some extent can be determine by the kind of feed administered.
Parasitism can also play an important role to negatively impact the pig’s ability to respond to respiratory pathogens (Tjornehoj, Eriksen, Aalbaek, & Nansen, 1992). Some adult lungworms that are localized within the terminal bronchioles do elicit bronchitis, bronchoalveolitis, alveolar emphysema and atelectasis(Opriessnig, Gimenez-Lirola, et al., 2011). Furthermore, the pattern of gene expression in the lungs and draining lymph nodes indicated a local Th2-skewed response induced byAscaris suum , infection with A. suum significantly compromised the effect of Mhp vaccination (Steenhard et al., 2009), which indicated that it is necessary to control parasite to provide a better environment for pig in farms.