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New research reveals over a third of dogs with Angiostrongylus vasorum could be symptomless

New research reveals over a third of dogs with Angiostrongylus vasorum could be symptomless

New Research Reveals Over A Third Of Dogs With Angiostrongylus Vasorum Could Be Symptomless

2 months ago

10th June, 2022 09h01


Hook, June 2022: A new study which assessed the clinical pictures of dogs naturally infected by Angiostronglyus vasorum, reported that over a third (36.1%) were clinically asymptomatic and apparently healthy.1 This new data suggests that infection could be more common among seemingly healthy dogs than vets or owners realise, challenging perceptions of what has historically been thought of as a largely clinical disease. This is the first time such high levels of asymptomatic infection in dogs has been documented.

An important challenge for veterinarians when dealing with asymptomatic A. vasorum infections is the hidden risk of perioperative bleeding. Bleeding can be traumatic or spontaneous. A. vasorum infection has long been associated with coagulopathies 3 but the causal mechanisms of haemorrhage in angiostrongylosis remain poorly understood.

Hidden environmental risk increases challenge

Evidence has also emerged suggesting that there may be more of a hidden environmental risk for dogs than previously thought. A separate study, by Robbins et al, showed L3 larvae of both 

A. vasorum and Crenosoma vulpis arising from the gastropod intermediate host to be immediately infective to dogs and remain so for up to eight weeks meaning that dogs may only need to lick the molluscs’ slime to be at risk of infection.2 This is the first study to shed light on the high infectivity of these larvae. A further study has shown the increased prevalence of A. vasorum risk in areas of high public dog walking.4

Robbins et al also showed that co-infections of A. vasorum and C. vulpis are possible and can be transmitted together thus potentially increasing the number of dogs at risk.2

Although presentation of clinical case varies considerably, given these new data, a high level of suspicion for lungworm should be adopted adding A.vasorum to many differential diagnosis lists. Pre-operative testing could also be a wise consideration. 

Need for owner education

Owners’ lack of awareness of lungworm and how it can affect dogs, adds to this hidden hazard. A recent study revealed that that almost half of dog owners (42%) don’t know what lungworm is and how their pets can be affected by it and over three quarters (79%) are not up to date with monthly lungworm treatments.5

Jenny Helm, BVMS Cert SAM Dip-ECVIM CA FHEA MRCVS, European Specialist in Small Animal Internal Medicine, has an active research interest in canine lungworm. She said: “Owners need to be aware that healthy dogs could be silently carrying and spreading the disease and that asymptomatic carriers could develop clinical signs at any time. They need to be aware that dogs don’t necessarily have to eat slugs and snails to become infected, as recent evidence suggest that other routes of transmission are possible.”

Lungworm is on the rise

Lungworm cases are increasing6,7, and whilst it used to be confined to certain areas, it has now spread throughout much of the UK, and new cases are being reported in many different areas of the country. Despite the increase in risk for dogs, data on prevalence remains patchy. To address this knowledge gap and to help veterinarians keep updated about A. vasorum in their area, Elanco has developed a version of the lungworm map specifically for veterinarians. You can help bridge the knowledge gap by uploading your all cases (including asymptomatic positive cases), to the map

For those veterinarians keen to run lungworm awareness campaigns in their area, Elanco has support available (How to Guide, posters and artwork to download) at

A final word from Jenny Helm: “The dual hidden aspects of A. vasorum mean that it’s now more important than ever to educate owners about the risks of lungworm infection keep their pets safe, both at home and on the operating table. Please make sure that you and your clients are up to date with the lungworm risks in your area. Also, I would strongly encourage all practices to upload your cases to the lungworm map to enable the profession to understand more about current risks regarding angiostrongylosis in the UK.”


  1. Colombo, M., Traversa, D., Grillotti, E., Pezzuto, C., De Tommaso, C., Pampurini, F., Schaper, R., Drake, J., Crisi, P.E., Russi, I. and Ripamonti, M., 2021. Highly Variable Clinical Pictures in Dogs Naturally Infected with Angiostrongylus vasorum. Pathogens, 10(11), p.1372.
  2. Robbins, W., et al. (2021) ‘Infectivity of gastropod-shed third-stage larvae of Angiostrongylus vasorum and Crenosoma vulpis to dogs.’ Parasites Vectors 14:307)
  3. ESCCAP (2021). Worm Control in Dogs and Cats [ESCCAP Guideline 01 Sixth Edition]. Available  (last accessed 18th May).
  4. Tolhurst, B. A., et al. (2021)‘Co-Occurrence of Domestic Dogs and Gastropod Molluscs in Public Dog-Walking Spaces and Implications for Infection with Angiostrongylus vasorum: A Preliminary Study.’ Animals. 11(9):2577.
  5. YouGov Research Survey of 535 GB 18+ dog owners 2021
  6. Morgan, E. R. et al. (2009) Canine pulmonary angiostrongylosis: The influence of climate on parasite distribution. Parasitology International 58 (2009) 406–410
  7. Taylor, C. S. et al. (2015) ‘Increased prevalence and geographic spread of the cardiopulmonary nematode   Angiostrongylus vasorum in fox populations in Great Britain.’ Parasitology. 142(9). 1190-1195.

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