SAC Parasites - Ruminants

Ruminant Gastrointestinal Parasites

Course Overview

  • Discussion on ruminant gastrointestinal (GI) parasites.
  • Specific focus on parasites affecting cattle and pigs.
  • Importance of the material due to upcoming exam on Tuesday.

Introduction to Ruminants

  • Ruminants possess a unique four-chambered stomach which allows them to digest high cellulose materials.
    • Components of the ruminant stomach:
    • Rumen: The largest chamber where fermentation occurs.
    • Omasum: Acts as a filter.
    • Abomasum: The true or glandular stomach, similar to monogastric mammals.
    • Reticulum: Works closely with other chambers during digestion.
  • Importance of the abomasum in harboring economically significant parasites.

Case Study: Personal Experience in Veterinary Medicine

  • Story of being kicked by a cow during a physical exam in a food animal barn as a fourth-year veterinary student.
    • Incident occurred during a physical exam on a cow with visible cervical injury.
    • Attempted to perform an exam similar to small animal practices, leading to a knee injury.
Transition to Abomasal Worms
  • Introduction of abomasal worms as a primary focus.

Key Parasites of Ruminants

Haemonchus spp. (Barber Pole Worm)

  • Classification: Trichostrongyle category.

  • Unique anatomy described as the barber pole due to its spiraled structure.

  • Feeding Mechanism: Attaches to the abomasum and consumes blood, analogous to hookworms in dogs and cats.

  • Impact on Blood Components:

    • Chronic blood loss leads to anemia and significant protein loss, specifically albumin.

    • Albumin’s role in hydrostatic and oncotic pressures in blood vessels explained.

    • Loss of albumin results in edema, particularly under the jaw ("bottle jaw") due to loss of oncotic pull.

  • Other health implications include ulcers, diarrhea, and unthriftiness in affected cattle.

  • The FAMACHA scoring system is introduced for field assessment of parasite burden via conjunctival color evaluation.

Ostertagia ostertagi (Brown Stomach Worm)
  • Commonly known as the brown stomach worm, significant in North America.
  • Distinction between the modes of damage:
    • It invades gastric glands damaging acid-producing parietal cells which results in elevated pH (from ~2 to ~6), impairing digestion.
  • Types of Disease:
    • Type I Ostertagiasis: Younger calves (7-15 months), easier to treat, lower complications.
    • Type II Ostertagiasis: Older animals (12-20 months), resistant to dewormers, difficult to diagnose due to lack of egg burden, seasonal/geographical dependency.
  • Critical management practice includes pasture rotation to limit nematode survival in the environment over seasons.

Other Parasitic Worms

Trichostrongylus spp. (Black Scours Worm)
  • Common parasite in sheep with potential zoonotic transmission.
Bunostomum phlebotomum (Cow Hookworm)
  • Infection can be through ingestion or skin penetration.
  • Causes anemia, as well as irritation leading to behavioral symptoms in cattle.
Nematodirus spp.
  • Simple pathology unless under heavy infestation conditions.
Moniezia spp. (Tapeworms of Cattle)
  • Life cycle similar to that found in equines, potentially economic implications when affecting liver and bile ducts during slaughter.

Pathogenesis & Diagnosis of Intestinal Worms

Esophagostomum spp.
  • Leaves abscesses in distal ileum, cecum, and colon, leading to necropsy findings.
Trichuris spp. (Whipworm)
  • Similar egg appearance to that in dogs; affects large bowel, may cause diarrhea from heavy burdens.
Chabertia ovina (Large Mouth Bowel Worm)
  • Characterized by increases in mucus and blood in stool, primarily impacting young animals.

Parasite Control Measures

  • Emerging Resistances: Recognized as a significant issue in veterinary medicine, especially concerning dewormers.

    • Emphasis on weighing animals for appropriate dosing (rarely practical).
    • Utilization of classes of dewormers, including:
    • Benzimidazole (Albendazole, Fenbendazole): Commonly used but resistance is developing.
    • Membrane Depolarizing (Levamisole, Pyrantel): Also shows resistance but very effective. Potential toxicity concerns in overdosing.
    • Macrocyclic Lactones (Ivermectin): Known for broad-spectrum effects.

  • Importance of deworming timing and strategies alongside pasture management to combat reinfection and resistance.

Final Thoughts on Veterinary Practices

  • Reflection on the one health philosophy showing interconnection between human, animal, and environmental health.
  • Importance of responsible usage of antiparasitics to ensure efficacy remains over time, emphasizing awareness regarding emerging resistance and the need for empirically validated treatment plans.
  • Discussion on the implications of resistance in both antibiotics and antiparasitics, stressing the necessity of strategic approaches in treatment protocols.