Seneciosis in cattle associated with photosensitization

Senecio spp. poisoning is the main cause of cattle mortality in the central region of Rio Grande do Sul. This paper reports an outbreak of seneciosis in cattle with high prevalence of photosensitization, where 83 out of 162 cows (51.3%) presented this clinical sign. The outbreak occurred in September 2013, affecting adult cows that were held in a 205 hectare-pasture from April to October 2013 with abundant Senecio brasiliensis infestation. Main clinical signs were weight loss, excessive lacrimation or mucopurulent ocular discharge, nasal serous discharge, ventral diphteric glossitis, crusts in the nose, teats, dorsum of ears, and vulva. Liver biopsy was performed in all the cows under risk; the histopathological findings in the liver biopsies consisted of fibrosis, megalocytosis, and biliary ductal proliferation and were present in 73.4% of the biopsied animals. Six cows had increased serum activity of gamma glutamyl transferase. Three affected cows were necropsied. The main necropsy findings were a hard liver, distended gall bladder, edema of the mesentery and abomasum. Liver histological changes in the necropsied cows were similar to those of the biopsied livers. Spongiosis was detected in the brain of necropsied cows and is characteristic of hepatic encephalopathy.

Senecio spp. POISONING OF HORSES IN SOUTHERN BRAZIL

Cases of seneciosis in horses occurring in four farms in the state of Santa Catarina and in another in the state of Rio Grande do Sul, southern Brazil, are reported. S. brasiliensis or S. oxyphyllus or both were detected in four of the five properties. Five horses (one on each property) were necropsied, and tissues for histopathological examination were collected from four horses. Neurological signs, such as depression, ataxia, aimeless walking, circling, head pressing, faulty prehension of food, dysphagia and blindness were consistently observed. Other signs included inappetence, loss of weight, colic, subcutaneous edema, icterus and photodermatitis. At necropsy the livers were firmer and darker than normal and had accentuation of lobular pattern. Edema of the mesentery and ascites were observed in one horse. Main histopathological changes consisted of hepatic chiefly periportal fibrosis, hepatomegalocytosis and biliary hyperplasia. Marked cholestasis and morphological evidence of hepatic encephalopathy were seen respectively in the liver and brain of one of the horses.

Sheep production as a Senecio spp. control tool

Since poisoning by Senecio spp. is one of the main causes of cattle death in southern Brazil, control of these plants is a priority for the local livestock production. After the pasture has been mowed, grazing by 16 sheep was efficient for controlling Senecio brasiliensis and Senecio madagascariensis populations in a 5.5-hectare area that had long been severely infested with these species. A total of 28,629 plants among S. brasiliensis (flower-of-souls, 10,122) and S.madagascariensis (fireweed, 18,507) were almost completely eliminated in a two-year period. The number of sheep was kept at 3.0 stock units/ha, but a variable number of cattle were temporarily stocked according to pasture availability. The major sanitary practice applied to the sheep was anthelmintic administration. Liver biopsies taken from sheep and cattle before and after experimental period didn't reveal any change associable with seneciosis. The performance levels of the sheep were comparable to those observed in flocks managed under traditional extensive grazing systems in southern Brazil.

Clinical and pathological aspects of chronic Senecio spp. poisoning in sheep

This paper describes an outbreak of chronic Senecio spp. poisoning in grazing sheep in Rio Grande do Sul, Brazil, causing the death of 10 out of 860 adult sheep. Eight sick ewes were euthanized and necropsied. Cattle from this farm were also affected. Clinical signs included progressive weight loss, apathy and photosensitization. Four out of seven tested sheep had increased gamma-glutamyl transferase serum activity and two of them presented serum elevation of alkaline phosphatase. At necropsy, three out of eight ewes presented slightly irregular toughened livers with multifocal nodules, two out of eight ewes had a whitish liver with thickened fibrotic Glisson's capsule partially adhered to the diaphragm, and three out of eight ewes had smooth and grossly normal livers. Necropsy findings attributed to liver failure included hydropericardium (7/8), ascites (5/8), icterus (2/8), hydrothorax (1/8), and edema of mesentery (1/8). The main hepatic histological findings that allowed the establishment of the diagnosis were megalocytosis, proliferation of bile ducts and fibrosis. Spongy degeneration was observed in the brains of all eight necropsied sheep and was more severe at the cerebellar peduncles, mesencephalon, thalamus, and pons. These are suggested as the portions of election to investigate microscopic lesions of hepatic encephalopathy in sheep with chronic seneciosis. The diagnosis of Senecio spp. poisoning was based on epidemiology, clinical signs, laboratory data, necropsy and histological findings.