Longworm in Dogs

What is longworm?

Longworms are worms that live in the lungs or in the blood vessels around the lungs and cause symptoms there. There are two different longworms that are important for dogs:

• The true lungworm, Oslerus osleri
• The French heartworm, Angiostrongylus vasorum

The true lungworm, Oslerus osleri

The true lungworm is a worm that forms nodules in the larger airways of dogs. These nodules cause the symptoms. Signs that dogs may show include:

• Harsh, dry cough
• Coughing during exercise
• Coughing when temperature changes occur
• Shortness of breath, weight loss and poor appetite in young dogs

The French heartworm, Angiostrongylus vasorum

This worm lives in the smaller blood vessels of the lungs and therefore causes different symptoms compared to the true lungworm. It mainly affects your dog’s condition and stamina:

• Lethargy
• Poor appetite and weight loss
• Coughing
• Shortness of breath
• Bleeding in the lungs
• Heart failure

Heart failure can occur in severe infections. If many blood vessels in the lungs become blocked, the heart can no longer pump blood through the lungs properly.

Both types of longworm are being seen more often, which means there is certainly a chance that your dog could become infected.

How can my dog become infected with longworm?

Your dog can become infected with the true lungworm by eating the faeces of infected dogs. A female dog can also pass this worm to her puppies through the uterus. Your dog can become infected with the French heartworm by eating slugs or snails. Frogs, mice and birds also eat slugs and snails. Your dog can therefore also become infected if it eats these animals. Dogs especially tend to eat frogs from time to time.

Are slugs poisonous to dogs?

Slugs are not poisonous to dogs themselves, but they can pose a serious risk because they can carry longworm larvae (Angiostrongylus vasorum). Slugs in particular may carry these larvae after ingesting infected slug slime or fox faeces. Slugs act as the so-called intermediate host of longworms. When a dog eats a slug, licks one, or even just eats grass that contains slug slime, it can become infected.

The larvae hatch in the intestines. They then travel via the liver and heart to the lungs, where they mature and cause symptoms. The adult worms lay eggs. These are coughed up by the dog and swallowed again, ending up back in the intestines. They are then excreted in the faeces, which contaminates the environment. That is why it is important to prevent your dog from ingesting slugs or slug trails, especially in spring and autumn when longworm infections occur more frequently.

How do I know if my dog is infected with longworm?

If your dog shows symptoms that fit with longworm, imaging can often provide an indication of infection. In the case of the true lungworm, the nodules can be seen when the airways are examined with a camera. With the French heartworm, abnormalities can often be seen on X-rays of the lungs.

A definite diagnosis can usually be made quite easily through a faecal examination. Eggs and larvae can be found in the stool. However, it may take several months (1 to 5 months) before larvae appear in the faeces. If the stool test is negative but the symptoms still suggest longworm, a lung lavage can also be performed. The French heartworm can also be detected with a blood test.

How can longworm be treated in dogs?

Milbemax is a tablet that is registered for the treatment of French heartworm. It is also effective against the true lungworm. The treatment consists of giving Milbemax once a week for four weeks. Panacur can also be used. The treatment duration may vary between 7 and 21 days.

By having your dog’s stool examined 7 to 10 days after treatment, you can determine whether your dog has recovered.

Can my dog recover from longworm?

If an infection is detected early, your dog can often recover well from longworm. However, treatment may take some time and may require additional supportive care for your dog. If the lungs and blood vessels have been severely affected by the infection, your dog may continue to have symptoms. In severe infections, dogs can even die from the disease.

Can I prevent longworm in my dog?

The best way to prevent your dog from becoming infected with longworm is to ensure that it does not eat slugs, frogs or the faeces of other dogs. Ideally, everyone would clean up their dog’s faeces.

You can also prevent longworm infections by treating your dog regularly with a product such as Milbemax. In that case, treatment should be given every month.

You can also choose a spot-on product to prevent infection. For example, Advocate can be used. This product also works against fleas and can therefore also be used for flea prevention. These pipettes are available from your veterinarian.

You can also read our article “How often should you deworm a dog?” to learn more about how frequently your dog should be treated for worms. Our Worm Guide can also help you with this.

Do you still have questions about longworm or deworming your dog? Please contact us via veterinarian@vetsend.co.uk.