Species which are pathogenic to dogs include:
- Angiostrongylus vasorum
- Angiostrongylus cantonensis (rat lungworm)
The life cycle of this parasite is similar to Aelurostrongylus abstrusus, involving a gastropod (mollusc) intermediate host. Encysted infective larvae are ingested by dogs that eat paratenic hosts such as snails. Following ingestion, the larvae migrate to visceral lymph nodes where they molt to adult worms before making their way into the lungs and pulmonary arteries.
A. cantonensis shows obligate neurotropism, i.e. larvae must migrate through the central nervous system (CNS) before taking up residence in the pulmonary arteries. These larvae of A. cantonensis can be seen in the CNS within hours to days following ingestion. Autochthonous A. vasorum infections have also been reported, but only in Canada.
These lungworms were first reported in foxes, which are the natural definitive host but have since been diagnosed in dogs.
Angiostrongylosis is considered to be a disease of primarily young animals.
Clinical signs associated with A. vasorum are related to right-sided heart failure and include malaise, coughing, dyspnea, anemia, pulmonary hypertension and pneumonia. Death may ensue with severe infestations, primarily due to a DIC-related systemic coagulopathy and consequential acute respiratory distress syndrome.
Hemoperitoneum, hemothorax and intracranial hemorrhage have also been reported due to visceral migration, with secondary meningitis and encephalomyelopathy due to intracranial migration. Immune-mediated thrombocytopenia has also been observed.
A separate, characteristic, syndrome has been described with A. cantonensis consisting of hind limb paresis, lumbar hyperaesthesia and urinary incontinence. Some dogs develop additional signs such as hemoptysis, scleral hemorrhage, forelimb paresis, cranial nerve palsies, altered mentation, coma and seizures.
Diagnosis is based on presenting clinical signs, evidence of tracheobronchial fluid or fecal larvae (using Baermann technique) and ELISA serology. PCR assays can be used to speciate the particular parasite involved.
A differential diagnosis would include other cardiopulmonary parasites such as Aelurostrongylus abstrusus, Eucoleus aerophilus, Crenosoma vulpis and Dirofilaria immitis. Signs of progressive meningo-encephalomyelopathy are seen with a number of other diseases, including distemper, neosporosis, toxoplasmosis, cryptococcosis and other fungal diseases such as Blastomyces spp.
Treatment of active angiostrongyliasis can be difficult. The use of anthelmintics may worsen the clinical symptoms due to exacerbated release of metazoan antigens from dying worms. However, concurrent use of corticosteroids (e.g. prednisolone) or other immune modulators (e.g. cyclosporin) may ameliorate this complicating issue.
Recommended drugs are fenbendazole (50 mg/kg PO q 24 hours for 5-35 days) or ivermectin in incrementally increasing daily doses for 4 - 6 weeks. The prognosis of angiostrongyliasis should be considered guarded when complicated by haemostatic dysfunction and even more so when the condition gives rise to severe neurological deficits.
Acquired immunity appears to be short lived or incapable of preventing re-infection.
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