STUDIES ON SPRING RISE PHENOMENON IN OVINE HELMINTHIASIS .I. SPRING RISE IN STABLED SHEEP

Abstract

Serial ova count studies were conducted to determine some of the characteristics of the spring rise in fecal shedding of nematode ova by parasitized sheep in flocks in the Montreal area. Substantial spring rises occurred in most ewes following their lambing but that great variation existed in the magnitude, duration, and pattern of the rises. Although rams did not display Increased ova counts, a slight but well-defined rise developed in 1 unbred ewe. Larval studies in ewes parasitized by a variety of nematode species, revealed that Haemonchus contortus was the major contributor to the spring rise in fecal ova output. Preparturient treatment of ewes with thiabendazole, at the rate of 100 mg./kg. of body weight, suppressed spring rise but failed to arrest completely the fecal shedding of nematode ova.