RELATIONSHIP BETWEEN THE EXCRETION OF PROTOSTRONGYLID LARVAE IN SHEEPIN NORTH-WEST SPAIN AND CLIMATIC CONDITIONS

The relationship between different climatic factors (temperature, rela tive humidity and rainfall) and the pattern of lungworm larval excreti on was studied in sheep under a continuous grazing pattern in North-we st Spain, where the climate is intermediate between sub-humid Mediterr eanean with an Atlantic tendency and European Atlantic. Over a period of one year, 44 animals were sampled once a month at random from a flo ck of 80 Galician breed sheep, all over 4 years old. Faeces were taken directly from the rectum and the number of first stage larvae per gra m of faeces was determined for each animal, and the species of Prostos trongylidae (Nematoda) identified. Larval excretion was irregular duri ng the study. The prevalence and intensity of infection were greater i n the colder months (40.9%; x=12.3 +/- 40.4) and less in the warmer mo nths (21.9%; xBAR= 0.7 +/- 2.7). The species of Protostrongylidae iden tified identified and prevalences (%) were Neostrongylus linearis (71. 5), Muellerius capillaris (18.8) and Cystocaulus ocreatus (9.7). Betwe en November and March, with low temperatures, the prevalence and inten sity of parasitism with N. linearis and M. capillaris were greater tha n in the months with high temperatures (May to September). Multiple li near regression analysis showed statistical correlation between temper ature, relative humidity and rainfall considered together and the numb er of N. linearis larvae per gram of faeces. Linear regression showed a correlation between the temperature and the percentage of sheep that passed M. capillaris. In general, the prevalence and intensity of inf ection of the sheep with N. linearis, M. capillaris and C. ocreatus la rvae decrease when the temperature increases and increase when the rel ative humidity and rainfall increases.