As a responsible owner, you probably follow the general advice and worm your dog regularly. But what if someone told you that this might be unnecessary for your dog, and may even be damaging our wildlife?
A new faecal antigen test for gut worms in dogs has recently been developed by Idexx (a well reputed veterinary laboratory). With a small sample of your dog’s poo, they can detect the presence of worms more accurately than ever before. This means vets and owners will have the knowledge to target their worming very specifically i.e. treating dogs only when they need to be treated. The theory is great, but in reality, will this test be useful? Let’s explore.
Targeted treatment – pros and cons
There’s good logic in faecal testing. Infected dogs can be identified and treated, rather than blanket treating every dog, meaning fewer unnecessary drugs in your dog’s body, and better for the environment. But testing comes with its downsides too – time, cost and vet visits – and regular preventative worming gives us peace of mind that our pets are completely protected.
The big question is this – are the risks of a parasitic infection in your dog greater than the risks of unnecessary treatment? There’s a lot to consider and no simple answer, but vet Martin Whitehead suggests it’s important to open the discussion and get thinking about this.
Note: The focus here is on internal parasites (endoparasites) i.e. those which get inside your dog’s body. External parasites such as
What internal parasites are a concern?
The main parasites of concern in the UK are:
- Roundworms
- Hookworms
- Whipworms
- Tapeworms
- Lungworm (Angiostrongylus vasorum in particular. This is confusingly sometimes classed as a heartworm because it travels through the heart, but in the UK it is widely referred to as ‘lungworm’).
The European Scientific Counsel Companion Animal Parasites (ESCCAP) provides a more comprehensive list of all internal worms found in Europe here, but remember not all of these are found in the UK.
Why do we de-worm our dogs?
Parasite control is a consideration for all dog owners, and rightly so – they are unpleasant for your dog, unpleasant for you, and can cause some nasty diseases too.
We de-worm dogs for several reasons:
- Worms have the ‘ick’ factor
Let’s be honest, parasites are not pleasant. Just the thought of them might kick off an involuntary squirm! Dogs also lack the social etiquette to deal with wormy troubles discretely so you may be honoured with bottom dragging across your cream carpet, revolting bum chewing, and messy diarrhoea. Worming our dogs gives us peace of mind that we won’t need to deal with these consequences.
- Illness in your dog
Itchy bums aside, worms can also cause more serious symptoms in your dog such as:
- Diarrhoea, sometimes with blood
- Pot belly appearance
- Weight loss
- Vomiting
- Tummy cramps
- Anaemia
- Death in severe cases
Worm-related illness in adult dogs is actually quite rare, but young dogs can become very ill so it is undisputed that worming puppies is an essential part of their healthcare. As they get older, dogs suffer much less with illness from worms. There is one important exception to this – lungworm.
Lungworm
Angiostrongylus vasorum, or lungworm, is a unique worm which affects dogs and foxes. It is spread when they eat infected slugs, snails or their slime trails (e.g. that on a discarded sandwich or a ball left in the garden). They travel into the gut, then move through the body to the lungs where they can cause respiratory problems. It also has a serious effect on blood clotting and can cause unexpected, sometimes fatal, bleeding.
The prevalence of lungworm is increasing in the UK. It used to be quite localised to the south-west in the 1980s but is now much more widespread across the UK and into Europe too.
How do I know if my dog has it?
Worryingly, you may not. Lungworm can be present in your dog without showing any signs for several weeks or months. When signs develop, they can be vague and mild (e.g. lethargy and coughing) or sudden and life-threatening (serious bleeding or neurological signs). Vets nowadays will often request that your dog is tested or treated for lungworm before any surgery, as sometimes the first sign is an uncontrollable bleed from what should be a routine operation.
How can it be treated?
If your dog is diagnosed with lungworm because they are very ill with the symptoms, it may prove fatal. If an infection is picked up on a blood test before signs of illness develop, there are a small number of prescription-only products that can treat it. Regular monthly prevention is often recommended with a licensed product because it can be so serious.
- Zoonoses (diseases passed onto humans)
Some internal parasites can carry disease which can be passed onto humans, but in reality, these diseases are very rare. Children and those with a weakened immune system are most at risk.
Roundworms
These can be passed onto humans through eating worm eggs in the soil, causing a disease called toxocariasis. This is very rare, but children are at greatest risk as they tend to play in the soil and are more inclined to put dirty fingers in their mouths. The worms can spread within the body and cause serious problems with your eyes or internal organs. Dogs, cats and foxes can spread toxocara eggs into the soil, so worming your dog only goes someway in preventing infection if you have cats or foxes visiting your garden and local parks.
Tapeworms
There are several types of tapeworms with different levels of risk. Picking up a tapeworm infection from dog faeces is rare; we are more likely to get an infection from eating undercooked meat or infected soil. The flea tapeworm (Dipylidium) is passed on to dogs by eating
Why do we want to limit use of antiparasitic medications?
Environmental concerns
We are becoming more educated in the environmental impacts of over-using antiparasitic drugs. Recent studies have found some drugs commonly used to treat or prevent parasites in dogs (fipronil and imidocloprid) are present at dangerous levels in many UK rivers and have been linked to the death of songbird chicks. Historically, these drugs were used in agriculture as pest control products, but with mounting environmental concerns, the outdoor use of imidocloprid and fipronil were banned in 2018 and 2017 respectively. It is now suspected that these drugs are coming from household drains after spot-on products are washed off our pets. Once in our waterways, they can be toxic to invertebrates and may be having a devastating effect on our ecosystems.
To date, no research has been done on any other anti-parasitic products, but suspicion of their environmental impact is present and their potential impacts are concerning.
Unnecessary for our pets
Preventatively treating our pets regardless of whether they have these parasites means we are exposing them to unnecessary drugs. Although antiparasitic drugs are generally safe, all drugs have the potential for side-effects, so every time we give them, we run the risk of an adverse effect. Some breeds are more sensitive to certain drugs, so giving them only necessary medication seems sensible.
Cost to the owner
Simply put, if you give your dog medication it doesn’t need, you are putting money (as well as the medication!) down the drain.
A targeted approach to worming your dog
There are some very important parasites to prevent, but with the negative impacts of wormers in mind, we should perhaps be taking a more bespoke approach; creating a unique worming plan for each dog based on their own individual risk rather than simply treating every dog, every month. A 3 month old puppy would have a very different plan to that of a 13 year old dog who doesn’t go out much, and different again for a farm dog who scavenges carcasses regularly.
The main risk groups are:
- Puppies and young dogs are at high risk of all worms.
- Dogs sharing a house with young children or someone with a weakened immune system need roundworm cover ideally (although risk still exists from the wild reservoir of infection in cats and foxes).
- Farm dogs / dogs on a raw food diet are at increased risk of tapeworm infection from eating raw meat. Legally, dogs that travel must also be treated for tapeworm before they return to the UK.
- Dogs in a high risk area or with a high risk lifestyle need prevention for lungworm.
How do we identify what worms are present?
Easy – by testing your dog’s poo for the presence of worm eggs. However, this sometimes gives us a negative result even if the worms are present in the gut (called a false negative) for several reasons.
- Eggs are not necessarily shed in every poo, so can be missed.
- In very early infections, eggs may not have been produced yet.
- Eggs are the result of worm mating, so a single sex infection (i.e. if the worms are all male or all female) would also give a negative result.
Back to the Idexx faecal antigen test……….
Idexx have developed a new test which looks for the worm protein antigen i.e. the presence of the worm itself, not just the eggs. This has a 5 times higher rate of detection than traditional faecal egg tests – if there are parasites present, there will be antigen.
It tests for hookworm, roundworm, whipworm, Cystoisospora, and flea tapeworm.
The practicalities of faecal testing
- Collecting the sample
This might be off-putting for some people.
- Time
It takes time to collect the sample, send it off and wait for the results.
- Cost
The test costs money, and unfortunately, significantly more than the cost of a worming tablet.
- What do we do with the results?
Ideally, if we get a positive result for one worm, we treat for that worm specifically. However, the treatment for roundworm, hookworm and whipworm is the same so if you get a positive result for roundworm, you will also inadvertently treat for hookworm and whipworm. Many combination products also exist which cover multiple parasites (fleas, ticks, lice and mites as well as worms), appealing to our 21st Century desire for convenience. However, this will also make targeted treatment more difficult. The exception is tapeworm, which can be targeted specifically with a drug called Praziquantel that only kills tapeworms.
- The lungworm dilemma
It is widely agreed that for most dogs, monthly lungworm prevention is advised. The products licensed for this purpose will also kill roundworm, hookworm and whipworm, so if you give regular lungworm prevention, you will also be blanket treating for these other parasites.
Conclusion
There’s a lot to consider here. While it is advisable to worm our dogs only when they need it in theory, the cost and practicalities of this make it hard to achieve in reality. Many practices nowadays have monthly health care plans for their clients, which include all parasite prevention, vaccinations and other benefits for a set monthly fee. The intention is good – prevention is better than cure – but maybe the inclusion of faecal testing should be considered as part of the plans, to minimise over-treatment, but keep the cost down for the client.
As we learn more, we should be open to change and improvement. Consideration, if not action, should be given to the concept of blanket treatment and 100% preventative strategies, and we should be open to making changes as our knowledge grows.
Discussion