title: The effect of dexamethasone on resistance of older lambs to infection with Nematodirus battus.
abstract: Old lambs (8 months of age) infected with 50,000 L3 of Nematodirus battus had larvae developing normally in their tissues on day 4 post-infection (P.I.), but by day 8 P.I. there were only 4105 +/- 1044 worms left in the alimentary tract. Some of these worms contained crystals in their intestine. Eight-month-old lambs treated with dexamethasone and infected with 50,000 L3 of N. battus contained a mean worm burden of 7878 +/- 1262 on 18 days P.I. Untreated 8-month-old lambs similarly infected were virtually worm free by day 18 P.I. Peripheral eosinophilia became elevated in the untreated lambs over the course of infection and, at post-mortem, the tissue mast cell and eosinophil counts were much higher than in the dexamethasone treated group. Although the phenomenon of age resistance is thought to have a strong immunological component, there may also be other physiological factors, resulting in fewer nematodes and lower fecundity of the worms.
authors.affiliation: Department of Biology, University of Leeds, UK.
authors.forename: M D
authors.initials: MD
authors.lastname: Winter
authors.forename: C
authors.initials: C
authors.lastname: Wright
authors.forename: D L
authors.initials: DL
authors.lastname: Lee
mesh_terms: D000375:Aging / Q000276:immunology*; D000818:Animals; D000909:Antibodies, Helminth / Q000096:biosynthesis; D002452:Cell Count; D003907:Dexamethasone / Q000494:pharmacology*; D004804:Eosinophils / Q000276:immunology; D005938:Glucocorticoids / Q000494:pharmacology*; D007411:Intestinal Diseases, Parasitic / Q000276:immunology / Q000469:parasitology; D008407:Mast Cells / Q000276:immunology; D009348:Nematoda / Q000502:physiology; D009349:Nematode Infections / Q000276:immunology*; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000469:parasitology*; D013997:Time Factors
chemical_list: D000909:Antibodies, Helminth; D005938:Glucocorticoids; D003907:Dexamethasone