The development of single infections of Nematodirus battus in lambs

Abstract

The course of single infections of Nematodirus battus was studied and the developmental phases of the fourth larval stage described. The third moult occurred between days 2 and 4 after infection and the fifth between days 8 and 10. The period of maximum larval penetration of the intestinal mucosa occurred around day 4 and most of the larvae had returned to the mucosal surface by day 6, during the middle of the fourth-stage. Some larvae remained deep in the mucosa and moulted to the fifth-stage in this site.The relationship between growth and morphological development was not constant and was different in worm populations from different sites. Some larvae grew very rapidly during the early fourth-stage and then entered a period of lethargus while continuing to develop sexually, while others grew and developed throughout the larval stage.The worms recovered from the second 30% of the small intestine were consistently smaller and less advanced morphologically than those from the first 30%. The worms in the posterior region of the small intestine were preferentially lost from the mucosa in the third- and fourth-stages between days 2 and 4 and from the mucosal surface as adults between days 12 and 16.