This study aimed to describe the first reports of outbreaks of hepatogenous photosensitization in cattle, sheep, and horses caused by spontaneous ingestion of Chamaecrista serpens, as well as to reproduce poisoning in sheep experimentally. Eleven photodermatitis outbreaks of unknown cause occurred in cattle, sheep and horses on nine farms in the semiarid region of Bahia, northeastern Brazil, between July 2017 and July 2020. Cutaneous lesions of photosensitization initiated until one week after the animals were introduced in paddocks invaded by the plant at the beginning of the rainy season. The photosensitive skin lesions were progressive and consisted of hyperemia, edema, ulcerative-crusted lesions with necrosis, especially in non-pigmented skin areas. The lesions in young animals were more severe. The animals avoided the sun and exhibited hyporexia, weight loss, restlessness, irritability, and severe itching. An experimental study was made using seven sheep, and resulted in photodermatitis, similar to that observed in the natural poisoning, seven days after the beginning of plant ingestion. Two sheep were reserved for the control group. Serum biochemistry changes indicated liver injury caused by the plant. Skin biopsies and liver biopsy guided by ultrasound were performed. The one sheep that had more pronounced skin lesions was euthanized and necropsied. At the necropsy, the liver was enlarged, diffusely pale, and firm, with an evident lobular pattern and an empty gallbladder. Histopathology revealed similar skin and liver lesions in samples from biopsies and the necropsy. There was a marked disorganization of the cords of hepatocytes associated with degenerative necrotic changes on the liver. The cutaneous injuries included orthokeratotic hyperkeratosis, hypergranulosis, acanthosis, and extensive areas of epidermic necrosis and ulceration. Three sheep were protected from sunlight and the lesions regressed within 45 days after the plant's consumption ceased. In conclusion, C. serpens causes hepatogenous photosensitization in ruminants and horses, and should be included in the list of differential diagnoses in cases of photosensitive dermatitis.

这项研究旨在描述牛，羊和马自发摄入沙门氏菌引起的肝源性光敏性暴发的首次报道。以及通过实验重现绵羊中毒的方法。在2017年7月至2020年7月之间，巴西东北部巴伊亚州半干旱地区的9个农场的牛，羊和马发生了11起原因不明的光皮炎暴发。对光敏性的皮肤损害始于动物被引入由入侵的围场后的一周雨季开始时的植物。感光性皮肤病变是进行性的，包括充血，水肿，结c性溃疡结皮性病变，尤其是在无色素的皮肤区域。小动物的病变更为严重。这些动物避开阳光，表现出低氧，体重减轻，躁动不安，易怒和严重瘙痒。对七只绵羊进行了实验研究，结果导致了光皮炎，类似于开始摄入植物后7天在自然中毒中观察到的情况。为对照组保留了两只绵羊。血清生化变化表明该植物引起肝损伤。进行超声引导下的皮肤活检和肝活检。对一只皮损更为明显的绵羊实施安乐死并进行尸检。剖检时，肝脏肿大，弥漫性苍白，结实，有明显的小叶型和空胆。组织病理学检查显示，活检和尸检中的皮肤和肝脏病变相似。肝细胞的索明显混乱，与肝脏的变性坏死变化有关。皮肤损伤包括角膜塑形过度角化病，肉芽肿过多，棘皮症，以及广泛的表皮坏死和溃疡区域。在停止食用植物后的45天内，保护了三只绵羊免受日光照射，并且病斑逐渐消退。结论，C. serpens在反刍动物和马中引起肝源性光敏化，在光敏性皮炎的情况下应包括在鉴别诊断中。