Lungworms of dogs & cats

What family are the relevant lungworms in? What are their characteristics?

Metastrongyles

• Lungs or related blood vessels

• Normally L1 in faeces

  • Have kinky tails typically

• Normally indirect life cycle with mollusc host

• Lympho-tracheal migration

What are the relevant lungworm species in dogs and cats?

Dogs:

• Angiostrongylus vasorum (Heartworm of dogs)

• Oslerus osleri

• Crenosoma vulpis

• Filaroides hirthi

Cats:

• Aelurostrongylus abstrusus

Where are adult angiostrongylus vasorum found?

Pulmonary artery and right ventricle

What is the morphology of angiostrongylus vasorum?

• 2cm long (a lot smaller than dirofilaria immitis)

• Barber pole appearance in females

What are the hosts of angiostrongylus vasorum?

• Intermediate host —> slugs and snails

• Paratenic hosts (not required for life cycle) —> frogs

• Found in foxes and dogs

Explain the lifecycle of angiostrongylus vasorum

• L1 in faeces, ingested by slug, development to L3 temp dependent

• Slugs ingested by dog, L3 cross intestinal wall and mature to L4 and L5 within abdominal LN

• Migration continues via liver and caudal vena cava to right side of heart and pulmonary arteries

• Worms reach maturity and lay eggs (females are ovovivparous) which are released into bloodstream

• Reach capillary beds and hatch into L1 (Ovoviviparous)

• Move across into alveolus and transported up airway to larynx and swallowed

• Passed in faeces

What would you expect in a positive angiostrogylus vasorum faecal smear?

Low numbers because intermediate shedders

What is the PPP of angiostrongylus vasorum?

5-8 weeks

What are the clinical signs of angiostrongylus vasorum?

• Often asymptomatic but can cause sudden death

• Respiratory

  • Coughing

  • Dyspnoea

  • Weight loss

  • Pulmonary hypertension

• Coagulopathies (parasite produces proteins causing this)

  • Fluctuating haematoma/bleeding disorders

• Neurological (due to above bleeding near nerves)

How is angiostrongylus vasorum diagnosed?

• Antigen SNAP test

• Radiography

  • Enlarge heart & pulmonary artery

  • Patchy alveolar and interstitial pattern

  • Able to differentiate from other lungworms

• L1 in faeces

• Trans-tracheal wash or bronchoalveolar lavage

• Baermann apparatus to detect L1

  • Low sensitivity

  • Repeat samples

What morphological features would you use to distinguish L1 angiostrongylus vasorum from other worms?

• Dorsal notch on tail of L1

• 300-400µm

How is angiostrongylus vasorum treated?

Typically MLs/BZs

• Moxidectin

• Milbemycin oxime

• Fenbendazole

How is angiostrongylus vasorum controlled?

• Corticosteroids for damage

• Cage rest indicated during treatment (2-3 days)

• Prophylaxis = monthly treatment with MLs

• Prevent dogs from ingesting snails or slugs

Where is angiostrongylus found in the world?

• Prevalent throughout Europe incl. UK

• Fox as reservoir host

• Increase in slug & snail population due to climate change

• Contact more likely in natural grasslands, open areas

• Risk of infection greatest in open grassy areas and wooland/scrub

Describe the life cycle of Aelurostrongylus abstrusus

• True lungworm both adults and larvae found in lungs of cats

• Adults in lung parenchyma —> very small 10mm

• L1 in faeces

• Snail intermediate host (Develop to L3) then ingested by cat or paratenic host which is then ingested by cat

• Paratenic hosts —> small mammal, frog, lizard

• Larvae penetrate across intestinal wall into LN and blood system to make its way to lung

What is the diagnostic features of aelurostrongylus abstrusus?

S shaped tail of L1 = 350-400µm

What is the PPP of aelurostrongylus abstrusus?

5-6 weeks

How does aelurostronguylus abstrusus present clinically?

• Normally asymptomatic because so small

• Coughing/ resp disease

• Can lead to hyperplasia of bronchioles, alveolar ducts & pulmonary arteries if high burdens

  

How is aelurostronguylus abstrusus diagnosed?

• L1 in faeces —> Baermann technique

  • Fresh faecal samples in 3-7 day period

• L1 in transtracheal wash or bronchoalveolar lavage

• No antigen test

How is Aelurostrongylus abstrusus treated?

Bz and MLs

• Fenbendazole —> for at least 3 days, up to 7 days.

• Moxidectin, Emodepside

What are the features of the oslerus osleri life cycle?

• Not typical metastrongyle

• Direct lifecycle

Describe the life cycle of oslerus osleri

• Adults in nodules in trachea of dogs

• Direct lifecycle

• Females are ovoviviparous

• Larvated eggs/L1 are passed by the female.

• L1 are released into the tracheal lumen, move up to the pharynx, swallowed & passed in faeces.

• Then L1 is ingested passed through intestine via blood and lymphatic system to lungs

What is the infective stage of Oslerus osleri?

L1 larvae

What is the PPP Oslerus osleri?

10-18 weeks

How does autoinfection occur with O. osleri?

• Infective L1 penetrate into the intestinal wall without leaving the host

• Migrate to the trachea, and develop into adult parasites

How does transmission of oselrus osleri from bitch to pup occur?

• L1 in sputum

• Transmission mainly by the bitch grooming/licking its pup

• Upon ingestion/introduction into the mouth of the pup, L1 cross the intestinal wall, travel via the lymphatics and blood system to the lungs and trachea.

How does oslerus osleri present clinically?

• Tracheo-bronchitis

• Coughing

How do you diagnose oslerus osleri?

• Young dogs, 1-2 years old (PPP = 10-18 weeks)

• Bronchoscopy to identify nodules

• Larvae in faeces (low sensitivity)

• Transtracheal wash or bronchoalveolar lavage cytology or tracheal swabs may reveal larvae or eggs

How is oslerus osleri treated?

Fenbendazole

What are the features of Crenasoma vulpis?

• Adults found in lungs (specifically in mucus) of dogs and foxes

• 1.5 cm in size

• Adult worm showing anterior cuticular rings

• L1 has a straight pointed tail

What are the features of Eucoleus aerophilus?

• Typically found in wildlife —> foxes

• Faeco-oral route, infects resp tract

• Not metastrongyle so eggs passed in faeces

• Occasional infections of cats and dogs

• Diagnosis of ‘lemon’ shaped eggs