Background: Feline pulmonary Langerhans cells histiocytosis (PLCH) is a rare disorder that results in progressive respiratory failure secondary to pulmonary parenchymal infiltration with Langerhans cells (LCs). A diagnosis of PLCH is proposed based on the clinical features and pathological findings and confirmed based on the infiltrating histiocytic cells. There are few documented cases of feline PLCH, and this case report of PLCH in an African Lion could present new information and aspects of this feline histiocytic disease. Case presentation: An African lion at Hohhot Zoo showing severe hyporexia and dyspnea with subsequent mental depression and emaciation died of exhaustion after a 35-day course of illness. Empirical treatment did not have a significant effect. An autopsy revealed that the lungs were enlarged and hardened due to infiltrative lesions, with many yellowish-white foci in all the lobes and sections. Furthermore, the kidneys were atrophied and had scattered grayish-white lesions on the surface. At the same time, congestion was widely distributed in various locations, including the liver, subcutaneous loose connective tissues, serosal surface and other tissues and organs. Histologically, proliferative histiocytic cells (PHCs) were scattered in the alveolar cavities, bronchioles and submucosa of bronchioles, with evident cellular and nuclear pleomorphism, and thus the alveolar septa were obliterated. The histopathological changes in other organs included chronic sclerosing glomerulonephritis, proliferated Kupffer cells in the liver, adrenal edema and interstitial connective tissue hyperplasia, as well as atrophy of the small intestines and spleen. Furthermore, immunohistochemical analysis results were strongly positive for CD1a, vimentin, S100 and E-cadherin in the membrane or cytoplasm of PHCs, supporting an LC phenotype. Conclusions: Here, we present a rare pulmonary Langerhans cell histiocytosis case in an African lion.

Clostridium perfringens is a major livestock pathogen responsible for histotoxic diseases and intestinal infections, posing serious threats to public health and the poultry and breeding industry. Overreliance on antibiotics has driven the emergence of drug-resistant strains and disruption of gut microbiota homeostasis, underscoring the urgent need for alternative control strategies. In this study, a lytic phage designated vB_CppII_Hohhot was isolated from wastewater samples collected from large-scale dairy farms in Inner Mongolia. The optimal multiplicity of infection was determined to be 0.1. pH stability was assessed. The phage was found to remain stable across pH 3 to 11, but no viable phage was detected at pH 12 (detection limit: <1 PFU/mL). Temperature adaptability was also assessed. Peak titers were achieved between 37°C and 40°C, and the titer was observed to fall below the detection limit at temperatures above 45°C. At a constant temperature of 37 °C, the phage rapidly reached the plateau phase within 40 min, with bacterial counts significantly reduced by 14 h. Whole-genome sequencing revealed that the phage genome consisted of 76 open reading frames, with no detectable antibiotic resistance or virulence genes; an endolysin gene potentially responsible for its lytic activity was also identified. In a prophylactic mouse model, phage administration significantly reduced pathological damage. Collectively, these findings provide a newly isolated candidate agent and a theoretical basis for the prophylactic application of phages against C. perfringens-associated infections.