Respiratory Tract

Question 1

Dictyocaulus viviparous (Trichostrongyle)

BOVINE LUNGWORM

Answer 1

• White, thread-like worm (<8cm long- large)
• Trachea & larger bronchi
• Causes parasitic bronchitis (Bovine dictyocaulosis/ husk/ hoose)
• welfare imp:

Calves: ↓LWG (light infections)–> death

• Adult cows: ↓ milk yields
  Important disease of farmed deer

Question 2

Dictyocaulus viviparous (Trichostrongyle)

LC

Answer 2

• Inside Host: Adult parasites reside in trachea & larger bronchii, ♀ release eggs which are coughed up by the host & swallowed –>pass through the s.intestine & hatch. First stage larvae (L1) in faeces (NOT eggs). eggs hatch in rumen
• In Environment: L1 develops to the infective L3 stage
• Inside Host: larvae consumed, penetrate the SI –>lacteals–> local lymph–> venous system–> lungs
• PPP= 3.5 weeks (L3 larvae ingestion first appearance of L1 in faeces)

Question 3

Metastrongylus spp.

(PORCINE LUNGWORM)

Answer 3

Metastrongylus spp (metastrongyle)

• Bronchioles (and smaller bronchi)
• 3 spp. (very similar)
• Comparison with D. viviparus (cattle)- similar gross appearance and pathology
• Very pathogenic: ↓ growth rate (light infections) severe lung damage

Life cycle

• *Indirect life cycle:**
• Earthworm intermediate host (unlike other metastrongyles) - Outdoor pigs only
• L3 larvae–> mesenteric lymph nodes –>lungs
• Adults–> embryonated eggs (wavy outline) –>faeces (NOT L1)

Epidemiology

• Immunity develops quickly
• ↑ free-range pigs–> parasite more common

Question 4

Dictyocaulus filaria (trichostrongyle)

OVINE LUNGWORM

Answer 4

• Most important lungworm of sheep + goats –> Chronic cough + unthriftiness (poor weight gain)
• In temperate areas outbreaks are sporadic, whereas in warmer climates they’re fairly regular

Life Cycle

• Direct (similar to Dictyocaulus viviparus in cattle)
• PPP= 5 weeks

Epidemiology

Similar to Dictyocaulus viviparus in cattle

Muellerius, Protostongylus spp. (metastrongyles)

• V. common but are not very pathogenic ∴ little economic importance

Life Cycle

• Indirect (mollusc intermediate hosts)
• Adult worms in alveoli / parenchyma (Muellerius) or small bronchioles (Protostrongylus)
• PPP= 6-10 weeks (Muellerius), 5-6 weeks (Protostrongylus)

Epidemiology

• Common due to: wide range of intermediate hosts, prolonged survival of larvae in faeces & long periods (>2 years) of patency (duration that adult parasite survives & passes L1 in faeces) –> ↑prevalence
• Poor host immunity

Question 5

Dog Lungworm

Filaroides (Oslerus) spp. (Atypical metastrongyle)​

Answer 5

Life Cycle

• Atypical Features: Direct life cycle, Adult worms live in tracheal nodules,
• Transmission= primarily bitch puppies during grooming
• Adult worms (1cm long) found in fibrous nodules (<2cm) near tracheal bifurcation
• Small numbers of L1 in sputum (saliva) –> vertical transmission from bitch puppies during grooming
• Horizontal transmission (ingestion of L1 from faeces) rarely, if ever happens- usually= ‘dead end’

Clinical Significance

• Asymptomatic (usually) chronic dry debilitating cough
• Associated with breeding kennels and racing greyhounds

Question 6

Aelurostrongylus abstrusus (metastrongyle)

FELINE LUNGWORM

Answer 6

Uncommon

Adult worms (1cm long) live in lung parenchyma + small bronchioles

L1 larvae passed in faeces (kinky tail)

Life Cycle

Indirect life cycle: Mollusc intermediate hosts (slugs, snails)

Cat infected by eating: infected mollusc or a paratenic host (e.g. frogs)

Clinical significance

Asymptomatic –>serious respiratory problems (must be distinguished from feline TB)