Epidemiological and pathological aspects of salmonellosis in cattle in southern Brazil

ABSTRACT: Salmonellosis is a bacterial disease that affects several domestic animal species, and is commonly diagnosed in cattle, horses, and pigs. This study aimed to describe the epidemiological and pathological findings of eleven cases of enteric salmonellosis and two cases of salmonellosis with pulmonary involvement in cattle in Rio Grande do Sul State, Brazil. Clinical signs included fever, yellow diarrhea, sometimes with blood streaks, and dyspnea, with a clinical course ranging from 1 to 30 days. Eight cases occurred as outbreaks, whereas five cases occurred individually. Risk factors included inadequate handling practices, such as overcrowded facilities and comorbidities, including anaplasmosis. The main gross finding of the enteric presentation was fibrinonecrotic enterocolitis, occasionally associated with button ulcers, mesenteric lymphadenomegaly, splenomegaly, cholecystitis and hepatomegaly. In addition, one steer with a chronic clinical progression presented severe segmental thickening of the ileum, associated with intestinal rupture and peritonitis. In the respiratory system, the main findings were reddened, non-collapsed lungs, with multifocal areas of atelectasis. The main microscopic findings were observed in the small and large intestines, and these were characterized by severe necrosis and mucosal ulceration, associated with marked inflammatory infiltrate of neutrophils and fibrin deposition intermixed by rod-shaped bacterial aggregates, and fibrosis, as well as interstitial pneumonia. Seven cases yielded positive bacterial cultures for Salmonella spp. and three serovars, namely Typhimurium, Dublin, and Panama were identified. All cases exhibited immunolabeling for Salmonella spp. using immunohistochemistry.摘要：沙门氏菌病（Salmonellosis）是一种可感染多种家畜的细菌性疾病，在牛、马和猪中较为常见。本研究旨在描述巴西南里奥格兰德州11例牛肠性沙门氏菌病及2例伴肺部受累的牛沙门氏菌病的流行病学与病理特征。临床症状包括发热、黄色腹泻（偶带血痕）及呼吸困难，病程为1至30天不等。其中8例为暴发疫情，5例为散发病例。危险因素包括不当的饲养管理操作（如饲养设施过度拥挤）以及合并症，如无浆体病（Anaplasmosis）。肠性病例的主要大体病理表现为纤维素性坏死性小肠结肠炎，偶可伴发纽扣状溃疡、肠系膜淋巴结肿大、脾脏肿大、胆囊炎及肝脏肿大。此外，1例呈慢性病程的阉牛可见回肠节段性严重增厚，伴随肠破裂及腹膜炎。呼吸系统的主要病理表现为肺脏发红、无萎陷，存在多灶性肺不张区域。镜下主要病理改变见于小肠与大肠，表现为严重坏死及黏膜溃疡，伴随显著中性粒细胞炎性浸润、纤维蛋白沉积，混有杆状细菌聚集体及纤维化，同时可见间质性肺炎。7例病例的沙门氏菌属（Salmonella spp.）细菌培养结果为阳性，共鉴定出3种血清型：鼠伤寒沙门氏菌（Typhimurium）、都柏林沙门氏菌（Dublin）及巴拿马沙门氏菌（Panama）。所有病例均通过免疫组织化学法检测出沙门氏菌属免疫标记阳性。