SURVIVAL OF 1ST-STAGE NEOSTRONGYLUS-LINEARIS LARVAE IN OVINE FECES UNDER ENVIRONMENTAL-CONDITIONS IN GALICIA (NORTH-WEST SPAIN)

A study was made on the survival of first larval stage of Neostrongylu s linearis, from November 1990 to October 1991, under natural conditio ns in an inland locality in Galicia (North-West Spain). The faeces wer e obtained from a sheep naturally infected with this nematode. Once a month, faeces were placed on a 0.5 x 0.5 m plot, in natural conditions , until we had 12 deposits. Samplings were done weekly until there was no more faecal matter in the plots. Larval survival was determined us ing the Baermann migration technique, and we calculated the number of larvae per gram after the transformation of the weight of the faecal s ample, in order to discard weight variations owing to climatic conditi ons. Over the whole Period of this study, the percentages of larval su rvival in the faeces of the 12 deposits changed from the first week on wards. In those samples that were left in the pasture more than three weeks, survival was less than 50 %. After the seventh week only very s mall numbers of active N. linearis larvae were obtained. We observed a positive influence of relative humidity on survival during the first week's presence of the faeces in the pasture. In the same way, a stati stically significant negative correlation was proved between larval su rvival in faeces and temperatures during the first three weeks post-de posit.