Molecular, Phylogenetic and Immunohistochemical Detection of Bovine Mycoplasmosis in Clinical and Subclinical Mastitic Cows in Wasit Province, Iraq

Background Bovine mycoplasmosis is a specific emerging infectious disease worldwide that causes clinical and subclinical mastitis, which impacts the global and national economy through reducing milk production and increasing treatment costs. Objective The study detected the molecular prevalence of mycoplasmosis in clinical and subclinical mastitis infected lactating cows, phylogenic analysis of detected strain, immunohistochemical detection of inflammatory TNF‐α and identification of udder histological alterations. Materials and Methods Udders of 263 lactating cows from various regions of Wasit Province, Iraq, were examined clinically, and subsequently milk samples were collected. California mastitis test (CMT) was performed to all clinical and subclinical milk samples, and the positive milk samples were examined molecularly by PCR to detect Mycoplasma bovis ( M. bovis) . The phylogenic tree of positive samples was constructed using MEGA software based on obtained sequences from GenBank NCBI‐database. Furthermore, udder tissues were obtained to identify the immunohistochemical expression of TNF‐α and udder histological changes. Results Clinical examination identified that 6.46% of study cows were infected with mastitis, whereas CMT identified 42.3% of subclinical mastitis cows. Molecular detection of M. bovis expressed positive prevalence rate in clinically and subclinically infected cows by 52.94% and 11.54%, respectively. Phylogenetically, the positive isolates showed sequences identical to the NCBI‐GenBank Egyptian M. bovis isolate with 99%–100% similarity and 0.0001%–0.0018% nucleotide changes. Histologically, the udder tissues exhibited a remarkable interstitial oedema, focal aggregation of inflammatory cells, infiltration of mononuclear cells, vacuolar degeneration, interstitial fibrosis, and destruction and desquamation of acinar epithelium. Immunohistochemically, the TNF‐α was expressed from mild to severe in udder tissues. Conclusion The obtained results represent the unique study in Iraq that highlighted molecular detection of M. bovis in clinical and subclinical mastitic cows that was attributed to the Egyptian strain. However, specific quantitative and qualitative molecular and immunological studies that cover all Iraqi regions are required to identify the disease prevalence and economic losses that are caused by various bacterial pathogens, including M. bovis to provide precise management strategy to eliminate the disease.