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Research in veterinary science1975; 18(1); 82-93;

The pathogenesis of single experimental infections with Strongylus vulgaris in foals.

Abstract: The clinical signs, pathology and clinical pathology associated with single experimental infections of Strongylus vulgaris in worm-free pony foals are described. The major clinical signs which became apparent in the infected foals during the first three weeks were pyrexia, anorexia, dullness and abdominal pain. Within the first two weeks of infection lesions were confined to the intestine and terminal branches of the intestinal arteries and consisted of mucosal, submucosal and serosal haemorrhage together with arteritis of submucosal and serosal arteries and also a marked inflammatory reaction. The main lesion seen three weeks after infection was gross thrombosis of the anterior mesenteric artery or one of its major branches. On section these affected arteries showed marked intimal thickening with infiltration of plasma cells, lymphocytes, macrophages and neutrophils. Between one and four months after infection the gross lesions were predominantly in the arteries and consisted of fibrous thickening of the arterial wall and thrombosis associated with the presence of developing fourth stage larvae. Four months after infection the arterial lesions were still prominent and microscopically there was fibrosis of the wall of the affected artery with wide-spread disruption of the intima. In the adventitia organised thrombi were apparent in the vasa vasorum and resulted in the obliteration of their lumina. The typical lesion associated with the return of fifth stage larvae to the intestine was nodule formation in close proximity to thrombosed terminal intestinal arteries and sections of parasites were seen in the intestinal wall surrounded by neutrophils and necrotic debris. By nine months after infection the arterial lesion had healed, but histologically there was fibrosis of the intima and macrophages containing haemosiderin were seen in the arterial wall. The most significant haematological findings during the experimental period were a marked polymorphonuclear leucocytosis and an increase in the number of circulating eosinophils in the infected animals. Also marked was an increase in the serum globulin levels of the infected foals.
Publication Date: 1975-01-01 PubMed ID: 1118668
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  • Journal Article

Summary

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This study examines the development and impact of single experimental infections caused by Strongylus vulgaris, a prominent internal parasite in horses, focusing on worm-free foals. The primary clinical signs in infected foals include fever, loss of appetite, dullness, and abdominal pain within the first three weeks of infection. The results show an increase in certain white blood cell counts and high serum globulin levels, indicating an immune response. Post-infection, the disease manifests through lesions, inflammation, and arterial thrombosis. Although arterial lesions appeared to have healed nine months post-infection, the arterial wall still showed signs of fibrosis and the presence of haemosiderin.

Understanding the infection process

  • The article focuses on how the parasitic nematode, Strongylus vulgaris, causes infections in pony foals, highlighting the progression of infection and the related pathology.
  • Once the foals are infected, the first clinical signs—fever, loss of appetite, dullness, and abdominal pain—become apparent within the first three weeks.
  • During the initial two weeks, the infection leads to lesions primarily confined to the intestine and the final branches of the intestinal arteries, accompanied by arteritis and a noticeable inflammatory reaction.

Impact on the intestinal arteries

  • Three weeks post-infection, a major symptom is the significant thrombosis of the anterior mesenteric artery or one of its large branches. These affected arteries demonstrated significant intimal thickening and infiltration of various immune cells, indicating an immune response to the infection.
  • The lesions seen between one and four months post-infection primarily consisted of fibrous thickening of the arterial wall and thrombosis. This appearance is correlated with the presence of developing fourth-stage larvae of the nematode.

Long-term effects and healing

  • Even four months after infection, the arterial lesions remained prominent and microscopically, there was fibrosis (formation of excess fibrous connective tissue) of the affected arterial wall along with widespread disruption of the intima (the innermost layer of the artery).
  • No signs of the disease were seen nine months after infection, but microscopic examination revealed fibrosis of the intima, indicating that the damage caused by the infection was permanent.

Clinical pathology findings

  • The blood examination of the infected foals showed increased numbers of polymorphonuclear leukocytes and eosinophils, indices of an immune response.
  • The levels of serum globulin, a group of proteins involved in the immune response, were also increased in the infected foals, forming an integral part of the body’s defense mechanism against the parasite.

Cite This Article

APA
Duncan JL, Pirie HM. (1975). The pathogenesis of single experimental infections with Strongylus vulgaris in foals. Res Vet Sci, 18(1), 82-93.

Publication

ISSN: 0034-5288
NlmUniqueID: 0401300
Country: England
Language: English
Volume: 18
Issue: 1
Pages: 82-93

Researcher Affiliations

Duncan, J L
    Pirie, H M

      MeSH Terms

      • Animals
      • Arteries / pathology
      • Arteritis / veterinary
      • Blood Proteins / analysis
      • Body Temperature
      • Cecum / pathology
      • Erythrocyte Count
      • Hematocrit
      • Hemoglobins
      • Horses
      • Ileum / pathology
      • Intestines / blood supply
      • Leukocyte Count
      • Mesenteric Arteries / pathology
      • Mesenteric Vascular Occlusion / veterinary
      • Rectum
      • Strongyle Infections, Equine / blood
      • Strongyle Infections, Equine / pathology
      • Thrombosis / veterinary

      Citations

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