Anti-tick effects of Stylosanthes humilis and Stylosanthes hamata on plots experimentally infested with Boophilus microplus larvae in Morelos, Mexico.

The anti-tick effects of the tropical pasture legumes Stylosanthes humilis and Stylosanthes hamata were evaluated and compared with two common grasses, Cenchurus ciliaris and Andropogon gayanus, in the state of Morelos, Mexico, on plots experimentally infested with larvae of the tick Boophilus microplus. The effect was evaluated by recovery of larvae from the experimental plots by flagging during a 4 week period. The anti-tick effect due to Stylosanthes was significantly higher for S. humilis and S. hamata (p < 0.05) and slightly better for S. humilis (3% survival) than for S. hamata (12% survival). Further studies are required to determine the potential role of Stylosanthes plants for tick control in Mexico.

Development and recovery of Haemonchus contortus first larval stages on experimental plots in Mexico.

The objective of this study was to determine the influence of relative humidity, environmental temperature and precipitation on the development of Haemonchus contortus from egg to infective larvae on experimental plots in a subtropical subhumid climate of Mexico. The study was of 1 year duration, with the highest rates of recovery of first-stage (L1) and second-stage larvae (L2) obtained at the end of the rainy season, and of third-stage larvae (L3) in the post-rainy season during the autumn. The lowest rate of recovery of L1 was in winter, whereas that of L2 and L3 mainly occurred in the dry season. The shortest development period for L1 was 12 h, for L2 18 h, and for L3 36 h. The longest development period for L1 was 66 h, for L2 156 h and L3 216 h. Statistical analysis of the data obtained showed significant differences in the time of development from eggs to infective larvae with respect to the season of the year.