Photosensitization in horses caused by Chamaecrista serpens

Chamaecrista serpens is a plant found in pastures in Florida and may be present in other southern states. A low growing legume with yellow flowers it has been referred to as sensitive or slender pea.
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Hepatogenous photosensitization in ruminants and horses caused by the ingestion of Chamaecrista serpens in Brazil

Authors
Múcio F F Mendonça 1 , Luciano A Pimentel 2 , Paula V Leal 3 , José C Oliveira Filho 4 , Lais G Caymmi 5 , Antonio W O Silva 6 , Rubens S Jesus 7 , Tiago C Peixoto 8
Affiliations

1 Postgraduate Program in Animal Science in the Tropics, Federal University of Bahia (UFBA), Av. Adhemar de Barros 500, Salvador, BA 40170-110, Brazil. Electronic address: mucinhoferraro@hotmail.com.
2 Veterinary Pathology Sector, Federal University of Recôncavo of Bahia (UFRB), Rua Rui Barbosa 710, Cruz das Almas, BA 44380-000, Brazil. Electronic address: lucianoanp@yahoo.com.br.
3 Veterinary Pathology Laboratory, UFBA, Av. Adhemar de Barros 500, Salvador, BA 40170-110, Brazil. Electronic address: paulavleal15@gmail.com.
4 Veterinary Pathology Sector, Federal University of Recôncavo of Bahia (UFRB), Rua Rui Barbosa 710, Cruz das Almas, BA 44380-000, Brazil. Electronic address: jcoliveirafilho@ufrb.edu.br.
5 Postgraduate Program in Animal Science in the Tropics, Federal University of Bahia (UFBA), Av. Adhemar de Barros 500, Salvador, BA 40170-110, Brazil. Electronic address: lais_caymmi@hotmail.com.
6 Postgraduate Program in Animal Science in the Tropics, Federal University of Bahia (UFBA), Av. Adhemar de Barros 500, Salvador, BA 40170-110, Brazil. Electronic address: antoniowesley_vet@hotmail.com.
7 Veterinary Pathology Sector, Federal University of Recôncavo of Bahia (UFRB), Rua Rui Barbosa 710, Cruz das Almas, BA 44380-000, Brazil. Electronic address: rubenssilva.agro@gmail.com.
8 Veterinary Pathology Laboratory, UFBA, Av. Adhemar de Barros 500, Salvador, BA 40170-110, Brazil. Electronic address: tcpeixoto@ufba.br.

PMID: 33516858
DOI: 10.1016/j.toxicon.2021.01.013

Abstract

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.

Keywords: Chamaecrista serpens; Hepatogenous photosensitization; Hepatotoxic plants; Photodermatitis.