LAUSR

Studies of the survival, recovery and migration of cyathostomin infective larvae in a Bermuda grass (Cynodon dactylon) pasture were carried out in the Baixada Fluminense county, Rio de Janeiro state. Fresh feces (± 1 kg) from naturally infected horses were deposited monthly on Bermuda grass. Samples of feces and surround - ing grass were collected every seven days, from March 2005 to March 2007, and larva were counted. In the feces, cyathostomin L survived for up to 15 weeks, with higher recovery rates during the rainy period (46 228/kg dried herbage - dh), and on the grass for up to 12 weeks. The recovery of L 3 was greater during the dry period in the grass base (1 868/kg dh) compared to the apex (809/kg dh). The migration of L 3 from feces to grass varied during the period. Climatic factors, such as temperature and rain, influenced the development and migratory behavior of cyathostomin L. With regard to the grass base, significant differences were observed at the different collec - tion times. The results demonstrate that under local conditions animals are at permanent risk since the infective larvae are always present on pasture.