Seasonal changes in the abomasal nematodes of naturally infected ewes in Moulay-Bouazza (Morocco).

The nematode populations of 93 abomasa of ewes from Middle-Atlas (Morocco) were studied over a period of 3 years. The main species present were Ostertagia circumcincta, Marshallagia marshalli, Trichostrongylus axei and T. vitrinus; less frequent species were O. ostertagi and O. trifurcata. Two peaks of infection were recorded, 1 at the end of winter or the beginning of spring (February--March), and another in autumn (September). The first population peak consisted mostly of O. circumcincta and T. axei, and the second population peak, in autumn, had a high prevalence of M. marshalli and T. vitrinus.