Influence of climate on pasture infectivity of ovine trichostrongyles in dry pastures.

The pattern of pasture contamination and the influence of some climatic factors on the development of ovine Trichostrongyles have been studied in dry pastures of Castilla-La Mancha (central Spain) during a 3-year period (1986-1988). The main identified genera were Ostertagia and Trichostrongylus, followed by Haemonchus, Cooperia and Nematodirus. Two peaks of pasture contamination were detected: from mid-winter to early-spring and from mid-autumn to early-winter. No significant differences in this pattern were observed during the 3 years except Haemonchus (1986-1988, P < 0.05; 1987-1988, P < 0.001). Seasons differed significantly (spring-autumn, P < 0.05; summer-the rest of the year, P < 0.001). The temperature was negatively correlated with the level of pasture infectivity (except for Trichostrongylus); however, the rainfall was positively correlated with pasture infectivity.