Lungworm in Dogs: Understanding, Impact, and Diagnosis
Lungworm, known scientifically as Angiostrongylus vasorum, is a parasitic nematode that can have serious health consequences for dogs. Over recent decades, this parasite has become a growing concern for veterinarians and pet owners in many parts of the world, including the UK, Europe, and increasingly in other regions. Recognising the threat posed by lungworm, understanding its effects, and knowing how to identify and test for infection are essential for anyone responsible for canine health.
Lungworm is a common name for several species of parasitic worms that reside in the lungs and associated blood vessels of various animals. In dogs, the primary culprit is Angiostrongylus vasorum, sometimes referred to as the “French heartworm”. Another species, Crenosoma vulpis, can also infect dogs but is less commonly encountered.
Lungworm completes its life cycle between two hosts: molluscs (such as slugs and snails) serve as intermediate hosts, while dogs and certain wild animals (like foxes) are definitive hosts. The adult worms typically take up residence in the pulmonary arteries and right side of the heart, while their larvae migrate through the dog’s body, causing diverse clinical signs.
- Intermediate Hosts: Slugs and Snails
- Slugs and snails become infected by ingesting lungworm larvae found in dog faeces. The larvae continue to develop inside the mollusc.
- Definitive Hosts: Dogs
- Dogs become infected by accidentally or intentionally eating infected slugs or snails, or sometimes by ingesting contaminated grass, toys, or water bowls.
- Larval Migration and Maturation
- Once ingested, the larvae migrate from the gut to the heart and lungs, where they mature into adults and begin producing new larvae, perpetuating the cycle.
The effects of lungworm infection in dogs can range from mild and nonspecific to severe and life-threatening. Symptoms often depend on factors such as the number of worms, the dog’s age and immune status, and how long the infection has been present.
- Respiratory Issues: Coughing, difficulty breathing, rapid breathing, and exercise intolerance.
- Bleeding Disorders: Disrupted blood clotting, leading to unexplained bruising, nosebleeds, or prolonged bleeding from minor wounds.
- General Illness: Lethargy, decreased appetite, weight loss, and general malaise.
- Gastrointestinal Problems: Vomiting, diarrhoea, and abdominal pain.
- Neurological Signs: In rare cases, fits, behavioural changes, or other neurological symptoms due to bleeding in the brain.
Many signs are non-specific and may be mistaken for other illnesses. Some infected dogs may show no signs at all, making diagnosis based on symptoms alone challenging.
Young dogs, due to their inquisitive nature, are particularly vulnerable as they are more likely to eat slugs or snails accidentally. However, all dogs, regardless of age or lifestyle, can be at risk, especially in areas where lungworm is known to be present.
Early detection of lungworm is essential for effective treatment and limiting long-term damage. Several diagnostic methods are available to veterinarians:
- Faecal Examination (Baermann Test):
- The traditional method for detecting lungworm larvae. A sample of the dog’s faeces is placed in water, encouraging any larvae present to migrate out, so they can be identified under a microscope. Collecting faeces over three consecutive days increases detection chances.
- Blood Tests:
- Some laboratories offer blood tests that detect either antibodies (the dog’s immune response to infection) or antigens (components of the parasite itself). Useful when larvae are not yet being shed or if clinical signs suggest infection despite a negative faecal result. Blood tests are specific to certain lungworm species.
- Imaging (X-rays/Ultrasound):
- Thoracic x-rays or ultrasound scans may reveal changes in the heart and lungs consistent with lungworm infection, such as lung patterns or enlargement of the heart. However, these findings are not specific and cannot confirm lungworm on their own.
- Other Diagnostic Aids:
- Occasionally, bronchoscopy or airway washes may be performed to look for larvae directly in the lung tissue or fluid.
If you suspect your dog may have lungworm or is at risk, consult your vet as soon as possible. Do not attempt to diagnose or treat lungworm at home veterinary assessment and prescription medication are essential. If lungworm is confirmed, treatment typically involves prescription antiparasitic drugs, and prognosis is good if caught early.
- Regular worming with products effective against lungworm (ask your vet for recommendations)
- Promptly picking up and disposing of your dog’s faeces to reduce environmental contamination
- Discouraging dogs from eating slugs, snails, or drinking from puddles or outdoor bowls
- Regularly cleaning toys, bowls, and outdoor areas
Lungworm is a serious and potentially life-threatening parasite that can affect dogs of all ages and backgrounds. By being aware of the risk, recognising the symptoms, and understanding how to test for and prevent lungworm, owners can play a vital role in protecting their canine companions. If you have any concerns, always speak to your veterinary professional promptly—early action can save lives.
