Chronic infections with Trichostrongylus colubriformis in lambs: influence of anthelmintic treatment on intestinal morphology and mucosal cell populations.
Intestinal mucosal morphology, topography and populations of crypt intraepithelial globule leucocytes (IGLs), goblet cells and mucosal mast cells were compared in 4 groups of 3-month-old lambs which had been reared worm-free from birth. Groups 1 and 2 were infected daily on 5 days per week with 2500 Trichostrongylus colubriformis larvae for 18 weeks. Group 2 lambs were treated with fenbendazole (5 mg per kg) at week 10 and week 15. Group 3 lambs were infected as above with T. colubriformis for 10 weeks, dosed with fenbendazole and given no further larvae. A fourth group of 4 lambs (Group 4) was maintained worm-free throughout the experiment as controls. All lambs were killed at week 20. Worm populations (range 410 to 30460) and mucosal damage varied considerably between individuals in the untreated Group 1 lambs, but damage was severe, with total villous atrophy, in lambs with large worm burdens. In 3 lambs with moderate worm burdens, worms were seen only in circumscribed flat "finger-print" lesions in the jejunal mucosa. There was no correlation between IGL numbers, mast cell numbers and final worm burdens in Group 1 lambs, though there was a trend towards an association between high worm populations and low IGL numbers. Only trivial pathological changes were detected in the re-infected Group 2 lambs. Low worm egg counts were found in this group 4 weeks after the first anthelmintic treatment, and virtually no eggs were present after the second treatment. Mucosal morphology in Group 3 lambs, which were not re-infected, resembled the controls at the end of the experiment. IGL numbers were greater in both treated groups than in controls, and numbers in the re-infected Group 2 lambs were greater than those in Group 3 lambs. Mucosal mast cell numbers did not differ significantly between groups, but crypt goblet cell numbers were increased in all 3 infected groups, compared with controls.
D000818:Animals; D001562:Benzimidazoles / Q000627:therapeutic use*; D002908:Chronic Disease; D005260:Female; D005273:Fenbendazole / Q000627:therapeutic use*; D007411:Intestinal Diseases, Parasitic / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D007413:Intestinal Mucosa / Q000473:pathology; D007421:Intestine, Small / Q000473:pathology*; D008297:Male; D012008:Recurrence; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000473:pathology*; D014252:Trichostrongyloidiasis / Q000662:veterinary*; D014253:Trichostrongylosis / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*
D001562:Benzimidazoles; D005273:Fenbendazole