Down the rabbit hole: Why people think rabbit ears act as a dewormer for dogs Robyn Lowe The Skeptic

There is so much misinformation in the animal health sphere, ranging from the tame to the outright ridiculous – but it all has the potential to impact negatively on animal (and human) health and welfare.

One of the common myths veterinary professionals hear – and we will burst the bubble at this point by clarifying it is indeed a myth – is that rabbit ears, often fed as a treat to dogs, act as a natural dewormer. This is incorrect. You may think this is relatively harmless – the dog gets a nice treat, and no one is hurt. But the issues associated with this practice have quite deep roots.

Firstly, it is an endorsement of the naturalistic fallacy, which makes way for different and more harmful forms of health misinformation, and secondly, many parasitic worms have zoonotic potential. There is also the problem that many of these pet food shops selling and advertising these treats as natural ‘dewormers’ are making medicinal claims – which should be reported to the Veterinary Medicines Directorate.

How does it ‘work’?

Those who believe in the deworming properties of rabbit ears often state that the indigestible hair from the ear scours the gut lining to rid the gastrointestinal tract of worms. However, there is absolutely no evidence that rabbit ears, or any other hair covered body part like a limb, will work as a natural dewormer. 

We know that raw meat can be a vector for parasites, with one review stating the potential hazard of some parasitic infections in pet animals is based upon the ingestion of raw meat. Livestock act as intermediate hosts for some parasites, carrying cysts in their meat or offal and enhancing the chance to make the human an occasional host. When raw meat is ingested, cats and dogs can act as definitive hosts for these endoparasites. Harbouring the adult stage of the parasites which are shed as eggs via the faeces, thus leading to environmental burden. 

If rabbit ears did actually act to deworm dogs, any carcass-eating animals such as foxes would likely have similar protective mechanisms – so, to understand why hair ingestion doesn’t work, we can look at the prevalence of endoparasites in foxes.

The fox data

The most common endoparasites of foxes are worms – a paper published in the journal Parasitology Research found a total of 32 helminth (intestinal worm) species in red foxes — including Alaria, Pearsonema, Taenia, Toxocara, Trichinella larvae and Ucinaria — all of which are considered significant for medical and veterinary health. A similar study found many of the same helminths, with 86% of animals carrying Uncinaria stenocephala (a hookworm), 81% with Toxocara canis (a type of large roundworm well known to infect dogs), and 28% with Angiostrongylus vasorum, and a further study identified 17 helminth species from 136, stating that fox helminth species significantly increased in number in the last 35 years, with Toxascaris leonina, Mesocestoides litteratus, Trichuris vulpis and Angiostrongylus vasorum being four new veterinary-relevant species.

Furthermore, a team of ten biologists from the UK and Germany carried out a study of 588 foxes from across Great Britain to look at disease-causing parasites. The results, were published in Veterinary Parasitology and showed that the most common gut parasites were Uncinaria stenocephala and Toxocara canis, occurring in 41% and 62% of the foxes, respectively.

There are clearly some major downfalls to this data when assessing whether rabbit ears, or any other hairy appendage, will treat worms – mainly the fact that raw meat is a big potential vector to introduce parasites. Even so, as far as we are able to tell, the data suggests that regular eating of hair-covered carcasses – as a fox would be likely to do – does not protect against worms. We can therefore reasonably extrapolate that other hair-covered dog treats making these claims do so without any evidence to substantiate them.

Belief in misinformation proceeds to further beliefs not founded in evidence

When owners start to believe in products because they are ‘natural’, believing them to be perhaps safer for their pets, or less harmful, these beliefs may also lead to further belief in natural or alternative views and practices, that may be even more harmful.

Furthermore, when it comes to the motivation behind raw feeding, a survey on this topic found that 26% of respondents said the main reason they choose to provide raw meat-based diets was ‘to respect the dog’s carnivorous nature’. Pet owners feeding raw animal products also reported lower levels of trust in veterinary advice than pet owners not feeding raw animal products, and they were also less likely to find vaccinations and parasite screening to be of benefit to their pet.

The link between medical mistrust and the naturalistic fallacy has been the subject of research, which found strong correlations between vaccine mistrust and adherence to complementary and alternative medicine and conspiracy ideation. The results of a study by Cuevas et al. suggest that mistrust toward healthcare may unfavourably affect patient-clinician interactions and patients’ health-related outcomes.

So, while we may think that the marketing of rabbit ears as natural ‘de-wormers’ is benign, that it’s just a dog enjoying a nice treat, it can be correlated with, or even potentially open the owner up to, a much deeper mistrust and respect of the depth of veterinary professionals’ knowledge, which ultimately could be of negative consequence to the health and welfare of those pets, or the people interacting with them.

Illegal medicinal claims

A product is medicinal by presentation if it gives the averagely well-informed person the impression that the product treats or prevents disease, or they gain that impression. This regulation includes product labels, leaflets, websites and social media advertisements or oral recommendations, and any other forms of literature relating to the product issued before, during or after the sale. A product which is medicinal by presentation must have a Marketing Authorisation granted by the Secretary of State before it can be placed on the market, unless it is covered by Schedule 6 to the VMR exemptions for small pet animals.

This means that if a person placing the product on the market, or the manufacturer, or a connected third party, expressly indicates or recommends the product for treating or preventing disease, the product is medicinal by presentation. Certain words are considered medicinal as they’re normally associated with authorised medicines. All the shops claiming that their product is a natural ‘de-wormer’ suggest that it can ‘control a disease’ and therefore, in my opinion, are medicinal by presentation.

These products should be reported to the VMD. If the VMD deems the wording is only ‘misleading or false’ but does not imply a medicinal effect, it will not cover any claim made for an unauthorised veterinary medicine. False or misleading advertising claims about a product that is not a veterinary medicinal product are dealt with by local Trading Standards Officers under the Consumer Protection from Unfair Trading Regulations.

Zoonotic risk

Among the parasitic worms of dogs, the species that are generally considered to be of most concern in the UK, because they’re zoonotic (i.e. can be transferred to humans), are Toxocara canis and Echinococcus granulosus.

Some worms are also of concern because of the harm they can do to dogs. In the UK, the worm of greatest concern in this regard is Angiostrongylus vasorum – which does not pose a risk to humans.

The “lungworm” Angiostrongylus vasorum is really a heartworm, but larvae migrating through the lungs can cause coughing and breathing difficulties, hence its common name. Foxes are the natural host for the parasite and appear to tolerate infection very well. Domestic dogs can also be infected without becoming clinically unwell, but a small percentage of infected dogs will develop blood clotting complications, neurological signs or will die suddenly as a result of infection. Infection occurs through the consumption of intermediate hosts such as slugs and snails so dogs that eat these or faeces or grass that contain slugs, are at particular risk of infection.

For these dogs and those living in areas where there are high levels of the parasite, monthly effective licensed deworming treatments are essential. Rabbit ears are not going to cut it! Other lungworms infecting dogs in the UK include Crenosoma vulpis and Eucoleus aerophilus. These lungworms can cause respiratory problems in dogs but are much less common than A.vasorum.

Protection against zoonotic worms needs a multi modal approach

Routine treatment for worms in dogs has traditionally been used in the UK to reduce egg shedding in dog faeces by Toxocara faeces. Eggs in the environment also pose a risk to people, and treating dogs helps to reduce this risk. The argument against this “blanket treatment” is that it leads to over treatment for some dogs and could lead to environmental contamination.

A study in 2016 showed 5% of dogs to be shedding eggs at any one time. This does not sound like a lot but when shedding by dogs is followed over a year, prevalence is much higher. This shedding over time is important because, eggs are long lived and build up in the environment. A recent study found 86% of public parks to be contaminated with eggs. This means that everyone in the UK may be exposed to Toxocara infection from contaminated parks, as well as playing fields, allotments, and homes where pets live.

The potentially severe and debilitating consequences of infection make preventing exposure important, and we all have a responsibility to help reduce this level of contamination. A few simple precautions suggested by Ian Wright, Veterinary Parasitologist, will help to reduce contamination and help keep everyone safe from infection.

1. Regular treatment of dogs for worms

Puppies provide the largest source of potential infection, so treatment for worms should start at two weeks of age for puppies and repeated every two weeks until two weeks after weaning, and then every month until six months old. The mum should also be treated at the same time. Adult dogs should be treated at least every three months to reduce egg shedding. This is because any dog could shed eggs intermittently their whole lives. Pets that hunt, are on raw diets, or that are in contact with young children or immune suppressed adults should be treated monthly, as these dogs represent the greatest risk of infection.

2. Picking up and responsibly disposing of dog faeces

UK county councils take the threat of dog fouling very seriously and have instituted a number of measures to control it, including providing clearly visible convenient disposal bins, imposing fines for dog fouling, banning dogs from children’s playgrounds and sports fields, and DNA testing of faecal samples to identify guilty pets. It is important to pick up your own dog’s faeces, but also to positively encourage others to do the same through schools, vets, and social media.

3. Thorough washing of fruit and vegetables

Fruit and vegetables in allotments and kitchen gardens can become contaminated by faeces from infected dogs, cats and foxes.  These can be made safe for human consumption if first thoroughly washed or cooked.

4. Good hand hygiene

Washing of hands before eating and after prolonged petting of dogs or outdoor activity reduces the risk of many parasites being transferred from hand to mouth.

5. Cooking meat and offal before feeding to dogs

Cooking meat, or ensuring it has been adequately pre-frozen, will help to kill parasites that may be present, before consumption by dogs.

These simple preventative measures, alongside good flea control, will also help to protect against tapeworm. Dogs that have access to fallen livestock carcasses are at particular risk from Echinococcus granulosus, so keeping dogs on lead and sticking to paths around ruminants is also a very sensible precaution. Out of respect for farmers, risk of Echinococcus granulosus or not, we advise that you adhere to on-lead walking around any livestock.

Why not test and treat dogs positive for worms rather than “blanket treat”?

Routine screening dogs for worms, and then treating positive dogs rather than using preventative treatments, is a strategy adopted by some European countries. Routine testing is a valid alternative to routine treatment if carried out at the same frequency as routine treatment would have been applied. This leads to reduced drug use, but has a number of limitations.

Often, routine testing is carried out as a one-off screen, or once per year, and infections may be missed by single tests. Even if tests are carried out more frequently, the shedding of zoonotic eggs in the faeces can occur between tests. If pet owners are going to adopt routine testing instead of routine treatment, then they must understand that this shedding can occur. 

There is huge value though in testing regularly alongside routine deworming to show that treatment is being effective and to look for early signs of drug resistance. Although a single test may miss infection, regular testing will show if treatment is failing.

Ultimately, while your dog might enjoy chewing on a rabbit ear, they are fine to use as a sporadic treat, but they are simply no substitute for proven deworming practices.

The post Down the rabbit hole: Why people think rabbit ears act as a dewormer for dogs appeared first on The Skeptic.

The fashionable trend among pet owners to feed their dogs rabbit ears, in the belief that they can help act as a natural dewormer, is entirely misguided
The post Down the rabbit hole: Why people think rabbit ears act as a dewormer for dogs appeared first on The Skeptic.