You may have heard about canine lungworm in the news. It is a disease that was rarely seen in the UK until relatively recently, but cases are now on the increase and it can be fatal. Could your dog be at risk? Is there anything you can do to stop it? Find out more below.
Lungworm is an uncommon parasite of dogs, although it is a bit of a misnomer. Although it is a type of worm, it doesn’t actually live in the lungs! However, it does pass through them as part of its lifecycle and can cause a cough, hence the name. The scientific name of the worm is Angiostrongylus vasorum. There are other species of lungworm in the UK, but these are rare and less often fatal.
The adult lungworms actually live in the large vessels near the heart. They attach here and feed, and produce eggs. These eggs quickly hatch and the juvenile larvae migrate through the lung tissue before being coughed up, and then swallowed. They pass in the faeces where they spend some time maturing in slugs and snails. If a dog then eats the slug, licks infected slime, or even eats another animal that has eaten the slug, they swallow the larvae. These larvae burrow through the gut wall and migrate back to the heart as they turn into adults. This process takes just over 4 weeks to complete.
Traditionally, lungworm was rare in the UK and cases were restricted to the wetter and warmer South, and usually in more built-up areas. However warmer summers and greater movement of animals mean that cases are on the rise and have been seen as far north as Scotland. Particular hot spots for cases occur in west Wales, London, the South East, and the Midlands.
Dogs that are at a higher risk of lungworm are young dogs (usually those that are less than two years old), although any dog that regularly (even accidently) eats slugs and snails is at risk. Dogs that spend a lot of time outside alone may be more prone to accidently eating slugs as they chew on toys or other objects left outdoors.
Unfortunately one of the difficult things about lungworm is that it can be hard to diagnose. There is no one symptom that makes lungworm a likely diagnosis, and all of the symptoms are non-specific and even vague. Coughing, shortness of breath, increased effort to breathe, increased tendency to bleed, and blood that doesn’t effectively clot are all signs. More extreme signs include fluid in the abdomen, seizures, collapse and death. At first, symptoms may only appear in dogs exercising, but as the infestation progresses symptoms will appear even in dogs at rest.
Lungworm testing used to be difficult, with faecal samples, x-rays, and visualisation of the airways using a scope all playing a part. Faecal samples were the most reliable way to detect the disease, but repeated samples were needed in order to avoid a falsely negative result. Recently a new blood test has been developed that will identify over 98% of lungworm-positive dogs correctly. It uses a very small sample of blood and- if vets have the test in their lab- can be run in as little as 15 minutes. Unfortunately the test only detects the most common and dangerous lungworm species, so further diagnostics may be suggested even with a negative result. In areas where the disease is very common, vets may even suggest using the test routinely before surgery in order to rule out any infection that could cause problems during an operation.
Lungworm can be treated with prescription worming treatments, although in severe infestations other medications may also be prescribed. For those dogs so severely affected that their breathing is compromised, oxygen therapy, antibiotics and steroids may be required, and some dogs with bleeding disorders may require blood transfusions. Either way, a hospital stay of several days is likely to be required.
Luckily, lungworm can be prevented using simple, common prescription medications. There are two ingredients currently licensed to prevent lungworm in the UK. Milbemycin (a common ingredient in prescription wormers) and Moxidectin (a prescription wormer usually used in spot-on solutions) are both known to be effective at preventing lungworm from becoming a problem in your dog. Moxidectin is slightly more effective than milbemycin, as it kills 100% of adult worms (milbemycin only kills 85% of adult worms). Although the products are readily available, in order to prevent lungworm the drugs both need to be given every four weeks for them to be effective, so usual worming protocols are unlikely to be sufficient.
As well as preventative medical treatment, there are a few things you can do to keep lungworm risk lower in your area. Removing faeces regularly means any larvae do not have a chance to get into the environment and the slugs, thereby breaking the lifecycle. Some people have tried using slug pellets and poisons, but this has been shown to be ineffective at stopping lungworm as well as potentially dangerous to your dog. Bringing your dog’s toys inside at night and regularly cleaning outdoor water bowls is worthwhile doing to reduce the number of slugs your dog has contact with.
So could your dog be at risk for lungworm? If you think the answer is yes, have a chat with your vet or nurse. It might be the case that a simple switch of worming product is all that is needed to protect your beloved pet.