Crystal-associated cholangiopathy in sheep grazing Brachiaria decumbens containing the saponin protodioscin

Abstract

An outbreak of hepatogenous photosensitization is reported in a flock of 28 sheep grazing Brachiaria decumbens in Mato Grosso do Sul State, Central-Western Brazil. Seven lambs and an adult sheep were affected and 6 of them died. Two surviving affected lambs and one lamb without clinical signs had increased serum values of gamma glutamyltransferase, bilirubin, and cholesterol. In two adult unaffected sheep those parameters were within normal values. An adult sheep submitted to necropsy presented moderate body condition, unilateral corneal opacity, drying of the muzzle, moderate jaundice, increased lobular pattern of the liver, and a distended gallbladder. Histological lesions were epithelial degeneration, necrosis, and hyperplasia of small bile ducts. Mild amounts of foamy macrophages were observed, mainly in the centroacinar zone. Diffuse swelling and vacuolation were observed in hepatocytes. Crystal negative images were found within bile ducts, foamy macrophages, and the lumen of some renal tubules. The heart showed multifocal areas of degeneration and necrosis of the muscle fibers. Pasture samples (Brachiaria decumbens) contained 2.36% of protodioscin. No Pithomyces chartarum spores were found in the pasture. Samples from a similar neighboring B. decumbens pasture grazed by cattle without photosensitization contained 1.63% of protodioscin isomers. Outbreaks of photosensitization caused by Brachiaria spp. are common in cattle in the Brazilian Cerrado (savanna) with about 51 million hectares of Brachiaria spp pastures. Sheep farming has been recently developed in this region, and the number of sheep is increasing significantly. Because sheep are more susceptible than cattle to lithogenic saponins, poisoning by Brachiaria should be an important limiting factor for the sheep industry.

Spontaneous poisoning by Brachiaria decumbens in goats

“…The diagnosis of poisoning by Brachiaria decumbens was based on epidemiological and clinical-pathologic findings, which were very similar to those described in spontaneous and experimental cases of this poisoning in ruminants in Brazil and other parts of the world (Abas-Mazni et al 1985, Opasina 1985, Lemos et al 1998, Brum et al 2007, Mustafa et al 2012, Oliveira et al 2012.…”

Identification of lamb flocks susceptible and resistant against Brachiaria poisoning

“…poisoning (Brum et al 2007, Castro et al 2007, Saturnino et al 2010, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014.…”

“…Affected animals show apathy, anorexia, icterus, skin pruritus, photophobia, serous ocular discharge, subcutaneous edema in the face and ears; in the skin of poorly pigmented areas there are lesions characterized by erythema, hair loss, and crusts. These areas evolve to necrosis and sloughing of patchy areas of affected skin, associated in many cases to deformity of the ears due to scarring of these lesions (Brum et al 2007, Saturnino et al 2010, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014.…”

“…Main necropsy findings include icterus, enlarged yellow to orange discolored liver with marked lobular pattern, and distended gall bladder (Brum et al 2007, Castro et al 2007, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014.…”

“…In the portal triads there is periportal fibrosis, acicular birefringent crystals within bile ducts, bile duct proliferation and lymphoplasmacytic inflammatory infiltrate (Brum et al 2007, Castro et al 2007, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014. Skin lesions are characterized by hyperkeratosis and parakeratosis, epidermal coagulative necrosis, necrotic debris, bacterial clumps, neutrophilic inflammatory infiltrate and necrosis of the dermal vessels (Lemos et al 1996, Faccin et al 2014.…”