The pathophysiology and development of immunity during long-term subclinical infection with Trichostrongylus colubriformis of sheep receiving different nutritional treatments.
The objective of this study was to investigate the relationship between protein nutrition, the pathophysiology, and acquisition and expression of immunity in long-term subclinical intestinal parasitism in sheep. Growing sheep were either uninfected controls or parasitised for 27 weeks with a daily dose of 2500 larvae of Trichostrongylus colubriformis, whilst they were given access to: (1) a low protein food, (2) a high protein food, or (3) a choice between the two foods, where they were allowed to select their diet. Blood samples were taken weekly for determination of serum albumin, total protein, Ca, P, urea and fructosamine concentrations. At the end of the study all sheep received a single (secondary) challenge infection (30,000 T. colubriformis L3) after treatment with anthelmintic to assess their immune status. The concentrations of sheep-mast cell proteinases (SMCP) in intestinal tissue, the number of circulating eosinophils and the total worm numbers recovered from the intestinal tract were used to investigate the effects of previous nutrition on the acquisition and expression of immunity. From the biochemical variables measured over 27 weeks, only serum fructosamine was affected by the interaction between feeding treatment and parasitism: fructosamine concentrations declined only in the parasitised animals on the low protein food during Weeks 6-15 of infection. This casts doubt on the usefulness of plasma fructosamine levels as an indicator of gastrointestinal parasitism, due to its being influenced by the nutritional environment. Total protein, albumin, calcium and phosphorus concentrations in the serum were affected by parasitism, but independently of feeding treatment. During the period of secondary challenge eosinophil numbers and SMCP concentrations were higher in the parasitised animals, reflecting the animals immune responsiveness. The numbers of worms recovered from the intestine of previously parasitised sheep were low; all three indicators of the development of acquired immunity were unaffected by previous nutritional treatment of the sheep. The results do not support the view that the pathophysiology of long term subclinical intestinal parasitism and the expression of acquired immunity induced by a trickle infection could be affected by the feeding treatment of the sheep (protein nutrition).
Genetics and Behavioural Sciences Department, Scottish Agricultural College, Edinburgh, UK.
I
I
Kyriazakis
D H
DH
Anderson
R L
RL
Coop
F
F
Jackson
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D001562:Benzimidazoles / Q000627:therapeutic use; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins; D005243:Feces / Q000469:parasitology; D005260:Female; D005518:Food Preferences; D019270:Fructosamine / Q000097:blood; D007958:Leukocyte Count; D007978:Levamisole / Q000627:therapeutic use; D010270:Parasite Egg Count; D010758:Phosphorus / Q000097:blood; D012016:Reference Values; D012709:Serum Albumin / Q000378:metabolism; D012756:Sheep; D012757:Sheep Diseases; D014253:Trichostrongylosis / Q000276:immunology / Q000503:physiopathology / Q000662:veterinary*
D000871:Anthelmintics; D001562:Benzimidazoles; D004044:Dietary Proteins; D012709:Serum Albumin; D010758:Phosphorus; D007978:Levamisole; D019270:Fructosamine; C011030:oxfendazole