VET 350 Sections 6.3.4-6.3.5 PowerPoint-1

Ancyclostomatoidea and Metastrongyloidea

Hookworms (Ancyclostomatoidea)

  • Head is bent dorsally, leading to the name "hookworm"

  • Habitat: Small intestine

  • Blood-suckers which can cause anemia

  • Enter host via ingestion or skin penetration

  • Associated conditions:

    • Cutaneous larva migrans

    • Hookworm dermatitis in abnormal hosts

  • Zoonotic potential: Ancylostoma braziliense

Important Hookworms

  • Ancylostoma caninum: Can cause severe anemia, particularly in puppies.

  • Uncinaria stenocephala: Found in temperate or arctic regions.

Ancylostoma

  • Characteristics: Three teeth on both sides of the mouth.

  • Pre-patent period (PPP): 2-3 weeks.

  • Larvae can be transmitted via nursing (transmammary transmission) to pups.

Uncinaria

  • Features cutting plates instead of teeth.

  • Can cause protein-losing enteropathy, resulting in poor growth and diarrhea.

  • Main route of infection: Ingestion. L3 stage can cause hypersensitivity reactions.

  • No direct vertical transmission observed.

Lungworms (Metastrongyloidea)

  • Bursate nematodes that inhabit respiratory tracts or associated blood vessels.

Aelurostrongylus Abstrusus Life Cycle

  • Hosts: Final (cats) and intermediate (birds, rodents, slugs/snails).

  • Larvae can be in the environment or within paratenic hosts.

Identification Techniques

  • Baermann technique: Can recover larvae.

  • Most first stage larvae (L1) exhibit a dorsal indentation on the tail.

Important Lungworms

  • Pathogenic potential varies based on location in the respiratory tract:

    • Aelurostrongylus and Muellerius: Located in terminal alveolar ducts, easily walled off.

    • Dictyocaulus and Metastrongylus: Found in the lumen of the upper respiratory tract.

    • Protostrongylus: Can cause mild issues.

    • Filaroides osleri: Embedded in airway walls.

    • Angiostrongylus: Affects blood vessels.

Angiostrongylus

  • A. vasorum: Lives in the pulmonary artery and right heart side.

  • Notable appearance: Barber’s pole.

  • Adult worms secrete anticoagulants, increasing bruising and hemorrhage risk.

  • L1 larvae entering alveoli can cause dyspnea and exercise intolerance.

Filaroides (Oslerus)

  • Most common species: Filaroides osleri.

  • Found in nodules at the distal trachea or upper bronchi,

  • Visualization possible via endoscopy.

  • L1 infective, transmitted to pups during maternal grooming.

Dictyocaulus

  • Habitat: Trachea and larger bronchi.

  • Disease: Bovine parasitic bronchitis.

  • Symptoms: Reduced weight gain, coughing, respiratory distress.

  • Commercial vaccine available.

Life Cycle of Dictyocaulus Viviparus

  • Cycle begins: Adult worms lay eggs in lungs, which are coughed up and swallowed.

  • L1 larvae passed in feces mature while grazing, triggering respiratory symptoms.

  • Infective L3 larvae can migrate from feces back onto pasture via environmental factors.

Epidemiology

  • Disease prevalence peaks in summer and fall.

  • L3 larvae can endure winter on pasture.

  • Immunity development enables lower larval buildup.

  • Asymptomatic older animals may harbor infections; newly introduced hosts at risk.

  • Pilobolus: Fungi that propel larvae up to 9 feet.

Pathogenesis

  • Lung tissue may collapse or consolidate.

  • Migrating larvae lead to mucus production, blocking alveoli, causing coughing.

  • Components (eggs, larvae, dead adults) can cause parasitic pneumonia.

  • Reinfection syndrome occurs when immune cattle are exposed to high larval counts.

  • Many larvae become trapped in grey-green granulomatous reactions.

Dictyocaulus Arnfieldi

  • Prefers donkeys over horses.

  • In horses, larvae tend to die in lungs, leading to chronic cough.

  • Can cause alveolar overinflation due to epithelial changes.

Metastrongylus

  • Habitat: Larger bronchioles and smaller bronchi.

  • Can induce severe lung damage.

  • Intermediate host: Earthworms; primarily affects outdoor pigs.