Contagious caprine pleuropneumonia (CCPP) is a fatal disease of goats, caused by Mycoplasma capricolum subsp. capripneumoniae (Mccp), characterized by high morbidity and mortality. CCPP is listed by WOAH as one of the most severe diseases that affect goats and cause significant economic losses. Despite its serious implications, limited information is available so far about Mccp tissue tropism in the natural host. In this study, novel endemic Mccp strains (n=04) were isolated from local goats and were characterized using conventional and molecular tools. The tissue tropism of local Mccp strains in the natural host was elucidated by a novel caprine infection model (CCPP model). The pathogenesis and tissue tropism of Mccp were comprehensively studied employing hematology, gross and histopathology, immunohistochemistry (IHC), and PCR techniques. Hematological analyses exhibited significant decreases in RBCs count and PCV (P<0.05), with a significant increase in MCV, TLC, and DLC. Postmortem examination revealed moderate-to-severe gross lesions in the respiratory passages and lungs that include tracheal hemorrhages, bronchio-alveolar exudation, fibrinous pleurisy, and pulmonary red-hepatization. Histopathology revealed leukocytic infiltration in the bronchiolar mucosa and alveoli, fibrosis of bronchiolar and interalveolar septa, exfoliation of bronchiolar epithelium, and emphysema. Interestingly, IHC revealed reactivity of Mccp (antigens) in bronchiolar epithelium, while tracheal epithelium was non-reactive to anti-Mccp antisera. These outcomes advocate that the bronchiolar epithelium is the primary niche for Mccp in goats during infections, providing significant insights into CCPP pathogenesis in goats and updates for future diagnostic and therapeutic strategies.

To Cite This Article: Saeed M, Anwar S, Faiq M, Khan H, Khan R, Naveedullah, Khan MA, Ahmad I and Khan FA, 2025. Bronchiolar epithelium revealed as a primary tropism site of mycoplasma capricolum subsp. Capripneumoniae in a novel caprine ccpp model. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.301