Isolamento e caracterização de espécies de Pythium de ambientes aquáticos no Estado do Rio Grande do Sul e avaliação da patogenicidade em modelo experimental

RESUMO: Foram coletadas 186 amostras de água de ambientes pantanosos em 13 municípios das regiões Sul, Central e Oeste do Rio Grande do Sul, Brasil, com o objetivo de isolar e caracterizar espécies de Pythium e avaliar a sua patogenicidade empregando coelhos como modelo experimental. Em 11,8% (n=22) das águas coletadas foram isoladas diferentes espécies de Pythium incluindo: P. insidiosum (n=1), P. catenulatum (n=3), P. pachycaule voucher (n=1), P. rhizo-oryzae (n=3), P. torulosum (n=4) e Pythium spp. (n=10). Zoósporos desses micro-organismos foram produzidos in vitro e inoculados por via subcutânea em coelhos, os quais foram avaliados durante 45 dias. Dentre os oomicetos testados, apenas P. insidiosum evidenciou patogenicidade, causando pitiose no modelo experimental, evidenciando que, em nossas condições, apenas esta espécie de Pythium é patógena para mamíferos.

Experimental intoxication by the mushroom Ramaria flavo-brunnescens in sheep

Ramaria flavo-brunnescens collected in autumn from 1990 to 1994 was orally administered to 11 sheep. These animals were dosed with 100-430 g/kg bw administered over 3-13 d. Six sheep showed clinical signs and 4 of them died. The mininum toxic dose was of 150 g/kg bw. Clinical signs were anorexia, hyperthermia, dyspnea, polyuria, ataxy, muscle tremors and seizures. The eyes had hyperemia of the sclera and, in some cases, hemorrhages of the anterior chamber or corneal opacity. Sheep dosed with higher doses had ulcerations of the tongue and necrotic lesions in the hooves. The main histologic lesions of the feet and tongue were miopachynsis and endotelial degeneration followed by degeneration, necrosis and ulceration of the epithelium. Hemorrhages of the anterior chamber, and severe congestion and hemorrhages of the iris, ciliary body and process were observed in the eyes. Congestion and perivascular hemorrhages occurred in the central nervous system. The similarity of clinical signs and pathologic lesions induced by R flavo-brunnescens and those caused by ergotism in cattle and sheep suggests the presence ofa vasoactive constrictive substance in the mushroom. Fresh R flavo-brunnescens dosed in autumn 1993 was not toxic at doses of 200-400 g/kg demonstrating variations in the toxicity of the mushroom from year to year.