Larvas Infectantes de nematóides (Strongyloidea), parasitos de bovinos, em pastagens no estado do Rio de Janeiro: comportamento e disponibilidade x vegetação e condições meteorológicas

Abstract

Samples of cattle stool with known OPG (eggs gram of faeces) and larvae culture, were used in the preparation of fecal mass, applied during experimental contamination of native pasture of "Baixada Fluminense", Rio de Janeiro State. Recovery of nematodes larvae was accomplished nightly and dayly in the anterior and posterior halves of the grass, intending to correlate the obtained data with those regarding to metheorological conditions of the meso and micro climates. The study was developed during a one year period, with montly infections in squares of native Brachiaria mutica (Forskal) Stapf, 1919 and Digitaria decumbens Stent, 1930. The behavior of infective L 3 larvae of Strongyloidea was observed in the genera: Cooperia Ranson, 1907, Haemonchus Cobb, 1898, Trichostrongylus Looss, 1905, Bunostomum Railliet, 1902 and Oesophagostomum Molim, 1861. It was observed that the density of vegetal covering, rain precipitation, temperature and relative microclimate humidity were able to induce the disponibility of L3 larvae, xxxiii as well as that in microhabitat with biotic and abiotic favorable conditions, the nocturnal behavior of L3 was the same as the diurnal one. It was also confirmed that moon phases had no influence in disponibility of L3 on the grass, and that the migration dynamics of infective larvae is aleatory. The genus Cooperia showed the best adaptation on the region, followed by Oesophagostomum and Haemonchus; L 3 of these genera were present all time on the grass; the genus Cooperia showed to have the best activity followed by Haemonchus and Oesophagostomum.