The small intestine of rats was divided into twenty sections in a reproducible manner in order to study the distribution of Nippostrongylus brasiliensis by stretching it under a tension of 5g in adrenaline saline.A small but significant difference between the distribution of parasites in male and female rats was observed.As larvae had virtually ceased to reach the intestine by the fifth day all changes in distribution after that day were due to movements of the established adult population.Up to the twelfth day of a primary infestation the majority of the worms were found between the third and tenth sections, the population mode being in the fifth or sixth section. After the thirteenth day the number of worms in this region fell sharply.The female worms had not ceased from egg-laying by the time most of the worms were being rejected.The posterior half of the small intestine, i.e. the eleventh to twentieth sections, was not heavily parasitized, many of the worms seen being in passage to the anus.The first section was not parasitized until the seventh day, but thereafter remained parasitized until long after worms had disappeared from the more posterior sections.The relative number of male worms present increased as the infestation aged.Throughout the experiment the relative number of male worms present at the anterior end of the smaller intestine was higher than that at the posterior.Fourth-stage larvae were found chiefly in the sections that were later most heavily parasitized by adult worms.

No abstract

1. A spring-rise in faecal strongyloid egg count is described in sheep housed under conditions designed to prevent reinfestation. Large rises were observed in the majority of 3-year-old breeding ewes and primiparous ewe-hoggs, and occasional small rises occurred in nulliparous ewe-hoggs and wether-hoggs.2. Falls were observed in the packed red-cell volumes of ewes during the period of spring-rise and a close inverse correlation was found between packed-cell volumes and transformed worm egg counts. No evidence was obtained to attribute the falls in packed-cell volume to factors other than worm burden.3. The fall in packed-cell volume was partially alleviated by feeding of one type of perennial rye-grass, but no direct effect of feeding on the worm-egg output was found.4. Theories of spring-rise are discussed and the conclusion reached that latent overwintering larvae must play a major part generally in the phenomenon.

No abstract

No abstract