[Development, survival and distribution of infective larvae of ruminants gastrointestinal nematodes, in the dry season of the "Fluminense lowland", State of Rio de Janeiro, Brazil].

With the objective of studying the development, survival and the distribution of the infective larvae of gastrointestinal nematodes of domestic ruminant, in the period characterized as dry for the area of the Fluminense lowland, RJ, the artificial contamination of the pasture was accomplished with fecal samples of bovine, caprine and ovine, naturally infected. One week after, began the sampling of the faecal masses and of the grass around the same ones, with biweekly repetitions. Larvae of the genus Haemonchus and Trichostrongylus were recovered in the grass contaminated with bovine faeces still 21 weeks after deposit; in the contaminated samples with caprine faeces, the same genus were recovered still 15 weeks after contamination. In the ovine samples, the maximum survival was also of 15 weeks, when the genus Trichostrongylus was recovered. In the bovine, caprine and ovine faecal masses were still recovered larvae in the 21. 15 and 7 weeks after deposit, respectively. For evaluation of the distribution of the larvae in the pasture were studied their vertical and horizontal displacements. It was observed that the larvae migrated vertically, and that 90.6; 93.2 and 88.5% of the larvae of nematodes parasites of bovine, caprine and ovine respectively, were located in the superior half of the grass. It was observed that the horizontal displacement also happened, however, most of the infective larvae did not stand back more than 15 cm of the feces. The results indicate that even in conditions of low rainfalls, characteristic of the period, the environmental conditions made possible the development and the migration of the infective larvae.