Photosensitization by Brachiaria ruziziensis in a sheep herd. (15th October 2020)

• Record Type: Journal Article
• Authors: Diamantino, Gabriella M.L.; Pierezan, Felipe; Ferreira, Maria Izabel C.; Rocha, Wadson Sebastião D.; Veiga, Vânia Maria O.; Martins, Carlos Eugênio; Veiga, Maíra O.; Soto-Blanco, Benito
• Is Part Of: Toxicon. Volume 185(2020)
• Page Start: 1
• Page End: 4
• Publication Date: 2020-10-15
• Subjects: Plant poisoning -- Brachiaria spp. -- Saponins -- Protodioscin -- Sporidesmin -- Pithomyces chartarum; Toxins -- Periodicals; Venom -- Periodicals; 615.9
• DOI: 10.1016/j.toxicon.2020.06.022
• Languages: English
• ISSNs: 0041-0101

Abstract

Abstract: Some species of the genus Brachiaria are cultivated worldwide in tropical and subtropical climate regions as the main feed for ruminants. Several studies report photosensitization by Brachiaria decumbens, Brachiaria brizantha, and Brachiaria humidicola, but the poisoning by Brachiaria ruziziensis have been reported only twice. Cutaneous and hepatic lesions may be caused by the steroidal saponins present in the leaves or by the mycotoxin sporidesmin produced by the saprophyte fungus Pithomyces chartarum . The present report describes the clinical and pathological changes observed in an outbreak of hepatogenic photosensitization in sheep kept in B. ruziziensis pastures. In addition, the present study will provide a better understanding of the etiology of this photosensitization through the evaluation of the saponin protodioscin and the spore count of P. chartarum . Santa Inês and Lacaune mixed-breed sheep showed signs of photosensitization after feeding B. ruziziensis . Clinical signs included jaundice, apathy, dehydration, and photosensitization characterized by facial edema and cutaneous scars, especially in the ears. Pathological examination of the liver revealed diffuse infiltrates of foamy cells, rare multinucleated cells, and mild enlargement of hepatocytes (megalocytosis). The skin showed acute epidermal and dermal necrosis with occlusive thrombi. B. ruziziensis showed low levels of protodioscin (0.020 ± 0.024% in mature leaves and 0.065 ± 0.084% in sprouts) but high P. chartarum spore counts (mean of 479, 844 ± 443, 951 spores/g plant). Thus, sheep grazing B. ruziziensis pastures must be closely monitored because of the risk of photosensitization. Highlights: Several studies report photosensitization by Brachiaria pastures in ruminants. Photosensitization may be caused by the steroidal saponins present in the leaves or by the mycotoxin sporidesmin. An outbreak of hepatogenic photosensitization is described in sheep kept in B. ruziziensis pastures. B. ruziziensis showed low levels of protodioscin but high P. chartarum spore counts.