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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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Enterolobium contortisiliquum (Leg. Mimosoidae) is reported as a poisonous plant related to photosensitization and photodermatitis, digestive disturbs and abortion. To date, the clinical and pathological features of photosensitization has not been reproduced or only reproduced associated with very mild presentations. The objective of this study was to reproduce in cattle the clinicopathological features of photosensitization associated with the ingestion of the pods of E. contortisiliquum. The pods were harvested from a property with a history of an ongoing outbreak of photosensitization and abortion in cattle. Six 24-month-old steers were cannulated and used in the experiment, two of them served as negative controls. E. contortisiliquum pods were administered to four steers through ruminal cannula. In the first phase of the experiment, daily doses of 30 g/kg/body weight (bw) and 20 g/kg/bw were administered to Bovines 1 and 2 respectively, for three consecutive days. In the second phase, starting four days after the last daily feeding of the pods, these two bovines were challenged with the same doses of the pods for three consecutive days and another two steers (Bovines 3 and 4) were fed 15 g/kg/bw each for three consecutive days. In the two phases, the steers developed signs compatible with ruminal acidosis which were more severe during the second phase. Three and five days after the administration of the pods, two steers presented photodermatitis characterized by hyperemia and edema on the skin of the dorsum of the neck, of the shaved skin around the cannula, of muzzle and ear. Lesions evolved to dermal necrosis with sloughing and subsequent scar retraction and dermal thickening. Ulceration of mucosae exposed to sunlight was also observed. All the steers which received the pods had significant elevations in the serum activities of gamma-glutamyl transferase (GGT) and aspartate aminotransferase (AST). The levels of GGT and AST remained elevated for up to 12 days after the administration of the pods was discontinued. Histopathological hepatic changes detected by liver biopsies were hepatocellular swelling and randomly scattered individual hepatocellular necrosis. The current study presents solid experimental evidence that the ingestion of E. contortisiliquum definitely induces the classical lesions of hepatogenous photosensitization in cattle., (Copyright © 2017 Elsevier Ltd. All rights reserved.)