Mycoplasma gallisepticum HS strain (MG-HS) is a pathogen that causes chronic respiratory disease (CRD) in chicken, which is characterized by host respiratory inflammatory damage, brings huge economic losses to the poultry industry.  Recently, emerging Chinese herbal medicines (CHM) have been used to treat CRD.  This study was aimed to investigate the preventive and therapeutic effects and their potential mechanisms of Chinese herbal medicinal formulae (CHMF), which consisted of 10 kinds of Chinese herbal medicine including Scutellaria, Houttuynia cordate and licorice, on MG-induced CRD in chickens.  With respect to the preventive effect, the results showed that CHMF could effectively recover the MG-induced decrease on body weight and feed conversion ratio.  Histopathological analysis showed that both prevention and treatment of CHMF could significantly alleviate the severe respiratory inflammation induced by MG infection.  Moreover, compared with the MG infection group, both the prevention groups and the treatment groups of CHMF could effectively reduce the expression of MG adhesion protein (pMGA1.2) to inhibit the proliferation of MG, and thus effectively inhibit the expression of MG-induced inflammatory factors interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α).  In summary, these findings confirm that CHMF can protect chickens from various tissue damage caused by MG infection and has no adverse effects on the performance of chickens in the short term.  And its efficacy against MG is equal to or better than that of tiamulin.

Mycoplasma gallisepticum (MG) is a common avian pathogen that mainly infects poultry, causing significant reductions in body weight gain and egg production, along with damage to immune organs and immunosuppression. MG is susceptible to co-infections with other pathogens, leading to increased mortality rates and significant economic losses in the global poultry industry. While antibiotics have been extensively applied worldwide to treat MG infections in poultry production, concerns regarding antibiotic resistance and residue remain prevalent. Traditional Chinese medicine (TCM), renowned for its natural, safe, and non-toxic properties, has shown significant anti-inflammatory and immune-enhancing effects. This study aimed to investigate the protective effect of TCM on production performance and its impact on MG-induced immunosuppression through the MAPK/ERK/JNK signaling pathway in chickens. Our results showed that TCM alleviated the negative effects of MG infection on production performance, as evidenced by improvements in body weight gain, feed conversion rate, survival rate, and immune organ index. TCM exhibited direct inhibition of the MG proliferation in vitro and in vivo. Furthermore, TCM treatment promoted the normalization of trachea and lung tissue structure in MG-infected chickens, leading to a significant reduction in inflammatory damage. Moreover, following the treatment with the TCM, the production of pro-inflammatory cytokines Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) decreased significantly, accompanied by the downregulation of pro-apoptotic genes caspase3, caspase9, and BAX, both in vitro and in vivo. A mechanism-based study showed that in vitro and in vivo treatment with the TCM significantly reduced the expression of key proteins, including early growth response gene1 (EGR1), p-ERK, p-JNK, and p-JUN. Altogether, TCM improved body weight gain, inhibited pro-inflammation responses, and alleviated tissue damage by inhibiting the MAPK/ERK/JNK signaling pathway to protect the performance and immune system of MG-infected chickens.