title: Teladorsagia circumcincta egg output at the onset of natural and induced lactation in ewes.
abstract: Nineteen ewes maintained under 'worm-free' conditions received anthelmintic and 1 week later were dosed on 5 days each week with 500 Teladorsagia circumcincta larvae for between 10 and 12.5 weeks. Faecal egg counts were determined twice weekly. There were three groups: pregnant (P) ewes (n = 6) which each reared twin lambs, hormone-treated (H) ewes (n = 7) which were not pregnant and were given exogenous hormones (dexamethasone, oestradiol-17 beta, progesterone) for 37 days to induce udder development and milk production, and untreated barren (B) ewes (n = 6). The plasma concentrations of oestradiol-17 beta, prolactin and progesterone were measured. Starting 10-15 days before birth in Group P, there was a biphasic periparturient rise in egg count and the onset of the first peak in egg count preceded the parturient peak in plasma prolactin concentration by several days. Most Group H (5/7) and all Group B ewes remained highly resistant to Teladorsagia infection throughout, despite an induced rise in prolactin concentrations in Group H ewes. It was concluded that factors other than prolactin initiate the periparturient rise but that prolactin is one factor which maintains the response once lactation commences.
authors.affiliation: Moredun Research Institute, Edinburgh, U.K.
authors.forename: R L
authors.initials: RL
authors.lastname: Coop
authors.forename: D J
authors.initials: DJ
authors.lastname: Mellor
authors.forename: E
authors.initials: E
authors.lastname: Jackson
authors.forename: F
authors.initials: F
authors.lastname: Jackson
authors.forename: D J
authors.initials: DJ
authors.lastname: Flint
authors.forename: R G
authors.initials: RG
authors.lastname: Vernon
mesh_terms: D000818:Animals; D004958:Estradiol / Q000097:blood; D005243:Feces / Q000469:parasitology; D005260:Female; D007774:Lactation; D010028:Ostertagia / Q000502:physiology*; D010029:Ostertagiasis / Q000469:parasitology / Q000662:veterinary*; D010270:Parasite Egg Count / Q000662:veterinary; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000469:parasitology / Q000662:veterinary*; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood; D012756:Sheep; D012757:Sheep Diseases / Q000469:parasitology*; D014252:Trichostrongyloidiasis / Q000662:veterinary*
chemical_list: D011374:Progesterone; D004958:Estradiol; D011388:Prolactin