Canis ISSN: 2398-2942

Angiostrongylus vasorum

Synonym(s): A vasorum

Contributor(s): Stephen Barr, Rory Bell

Introduction

Classification

Taxonomy

  • Superfamily: Metastrongyloidea.
  • Genus: Angiostrongylus.

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Clinical Effects

Epidemiology

Habitat

  • Adults in pulmonary artery Angiostrongylus vasorum pathology and occasionally right ventricle of dogs, foxes and other Canidae. Foxes probably act as a reservoir of infection in Great Britain.
  • Rarely, adults in anterior chamber of eye.
  • L3 in wide variety of molluscs (terrestrial and freshwater snails and probably slugs).
  • L1 can be carried to lodge in organs (brain, kidneys, etc).

Lifecycle

  • Various canine species act as definitive host for A. vasorum, with dogs and foxes being the main species of interest in this instance Lifecycle Angiostrongylus vasorum - diagram. Intermediate hosts are required for maturation of L1 larvae that have been excreted in feces by the definitive host. Canines become infected following ingestion of L3 larvae, most commonly by eating the intermediate host species, namely slugs and snails. Some frog species may act as paratenic and/or intermediate hosts and direct ingestion of L3 larvae secreted by intermediate hosts may be possible (Barcante et al, 2003).
  • Following ingestion, L3 larvae cross the host's intestinal wall and enter the abdominal lymph nodes where they develop to the L5 larval stage. The L5 larvae migrate towards the right side of the heart through the hepatic portal vein, caudal vena cava and liver.
  • On reaching the right side of the heart and pulmonary vasculature the larvae mature to adults and reproduction begins. Eggs intermittently released by female worms are transported through the pulmonary vasculature to lodge in the capillaries where they hatch. The L1 larvae cross the capillary and alveolar walls to enter the alveoli and are subsequently coughed up, swallowed and excreted in feces. the prepatent period is approximately 38-57 days (Bolt et al, 1994).
  • Adult.
  • First stage larva (L1).
  • Third stage larva (L3).

Transmission

  • To dog by ingestion of L3 in mollusc.
  • To mollusc by ingestion of L1 in dog feces.

Pathological effects

  • Pulmonary artery obstruction, endoarteritis and thrombosis occur, as well as parenchymal damage to various organs due to larval migration.
  • Fibrosis and induration of lungs and occlusion of the pulmonary arteries can cause pulmonary hypertension and right-sided cardiac failure, resulting in hydrothorax, hydropericardium, liver congestion and ascites.
  • Disseminated intravacular coagulation can occur Disseminated intravascular coagulation. Immune-mediated thrombocytopenia Immune-mediated thrombocytopenia , and/or factor deficiency are less commonly decribed following infection, all of which result in a predisposition to, or spontaneously occurring, hemorrhage.
  • Embolic larvae to other organs, especially kidney and brain resulting in granulomatous hemorrhagic or infarcted foci.

Control

Control via animal

  • Anthelmintic treatment.
  • Remove from access to molluscs.
  • Place on concrete to reduce contamination for mollusc and remove feces immediately when passed.
  • Consider all dogs living in the same environment potentially infected.

Control via chemotherapies

  • Aims of treatment are to eliminate the parasitic infection and control clinical signs.
  • The most commonly used treatments are:
  • One study compared fenbendazole with moxidectin-imidacloprid in mild to moderately affected dogs and found the treatments to be similarly efficacious. Imidacloprid formulations provide a convenient treatment option in the form of a single spot-on solution as compared to daily oral dosing with fenbendazole.
  • Aspirin Acetyl salicylic acid or corticosteroids have been suggested as concurrent therapy. Aspirin or any non-steroidal anti-inflammatory should not be administered if there is a concern about a coagulopathy.
  • Corticosteroids are often prescribed initially to prevent the rare occurrence of anaphylaxis Anaphylaxis, urticaria and angioedema following rapid worm kill. However, thery are probably more useful to reduce pulmonary inflammation as a result of larval migration.
  • Bronchodilators/mucolytic expectorants may be helpful if there is evidence of respiratory disease.
  • Diurectics (frusemide Furosemide ) if right-sided heart failure present and edema.
  • Desmopressin Desmopressin (DDAVP) 4 microg/kg diluted in saline IV over 10 mins if decreased von- Willebrands factor Von Willebrand's factor is identified.
  • Supportive therapy may be required depending on clinical presentation. In the case of coagulopathy, blood products may be required to stop bleeding or correct severe anemia. Whole blood administration may be most appropriate if there is a combined anemia and coagulopathy.
  • Oxygen therapy is indicated in dogs with marked respiratory signs.
  • In dogs with neurological signs, supportive therapy is needed especially if there is recumbency or immobility.

Control via environment

  • Control of snails is impractical as there is a broad range of snails that can serve as intermediate hosts and they are ubiquitous.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Morgan E R, Tomlinson A, Hunter S, Nichols T, Roberts E, Fox M T & Taylor M A (2008) Angiostrongylus vasorum and Eucoleus aerophilus in foxes (Vulpes vulpes) in Great Britain. Vet Parasitol 154, 48-57 PubMed.
  • Chapman P S, Boag A K, Guitian J & Boswood A (2004) Angiostrongylus vasorum infection in 23 dogs (1999-2002). JSAP 45, 435-440 PubMed.
  • Barcante T A, Barcante J M, Dias S R & Lima Wdos S (2003) Angiostrongylus vasorum (Baillet, 1896) Kamensky, 1905: emergence of third stage larvae from infected Biomphalaria glabrata snails. Parasitol Res 91, 471-475 PubMed.
  • Bolt G, Monrad J, Koch J & Jensen A L (1994) Canine angiostrongylosis: a review. Vet Rec 135, 447-452 PubMed.
  • Bourque A, Conboy G, Miller L, Whitnew H & Ralhan S (2002) Angiostrongylus vasorum infection in 2 dogs from Newfoundland. Can Vet J 43(11),876-879 PubMed.
  • Gould S M & McInnes E L (1999) Immune-mediated thrombocytopenia associated with Angiostrongylus vasorum infection in a dog. JSAP 40, 227-232.
  • Bolt G, Monrad J, Koch J & Jensen A L (1994) Canine angiostrongylosis. Vet Rec 135, 447-452.

Other sources of information

  • Brennan S (2008) Canine angiostrongylus vasorum infection. Veterinary Review September, pp 25-26.

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