Angiostrongylus vasorum: how to prevent it in dogs
5-month-old Cocker Spaniel in Asturias, with a garden, who eats snails and slugs and plays with his toys on the lawn. Several cases of Angiostrongylus vasorum have been diagnosed in the area.
Which preventive regimen is most appropriate?
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A. A macrocyclic lactone effective against A. vasorum (milbemycin oxime or moxidectin) every month, and reduce access to snails and slugs
Correct. Monthly administration kills larvae before they mature (the prepatent period is about 6–7 weeks). Bringing toys and bowls in from the garden reduces contact with gastropods.
B. Internal deworming with pyrantel and praziquantel every three months
Neither pyrantel nor praziquantel is effective against A. vasorum, and a three-monthly regimen leaves time for larvae to mature and cause disease.
C. Antigen test every six months and treat only if positive
Waiting for a positive result allows the dog to develop coagulopathy or severe lung lesions. In at-risk dogs, monthly prevention is preferable to screening alone.
D. A deltamethrin collar, which prevents insect-borne transmission
A. vasorum is not insect-borne; it is acquired by eating snails, slugs or paratenic hosts (such as frogs) carrying L3 larvae.
lightbulb Key takeaway
The fox is the main wild reservoir. In Spain cases concentrate in humid northern areas, but they are diagnosed in other regions too. Young dogs and those that eat gastropods are at highest risk.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.