Advice on worming cats and dogs depends on who’s giving it
Advice on worming cats and dogs depends on who’s giving it
How do cat and dog owners in the UK know to worm their pets?
Wormers can be bought without professional advice from general stores, with professional advice from certain pet stores or pharmacies, from veterinary practices (including prescription-only products) and increasingly via online subscription and box schemes. As a dog owner I’ve found the advice from suppliers varies:
I’ve been reassured that as long as my dog is healthy, there is no need to worm;
I’ve been advised that worms can cause upset stomachs, agitation and digestive problems; elsewhere that some worms can be deadly; or that continuous treatment is vital to protect my pet and my family.
Some veterinary practices offer products tailored for my pet, others offer comprehensive monthly worming; many offer a regular supply of wormers via a pet healthcare scheme.
Veterinary practices warn about the risk of lungworm in dogs while non-prescription product suppliers generally do not.
Confusing and conflicting terms are used: some practice websites say they offer ‘premium’ or ‘vet strength’ or only the newest products, while some of the non-prescription websites offer ‘vet recommended’ products. All in all, it’s confusing.
Unlike ectoparasite infestations, worm infections are usually covert and the most common do not normally adversely affect the health of pets beyond kitten- and puppy-hood. For many years, there has been public health advice to worm pets regularly to prevent Toxocara infection in humans (Al Jabr et al 1997; NHS 2022). More recently, since the availability of wormers licensed to prevent disease due to the lungworm Angiostrongylus vasorum (also known as French heartworm) in dogs, there have been pharmaceutical company-run campaigns to increase awareness of this parasite among vets and dogs owners.
Rational use of wormers is as important as for flea and tick treatments
There are many good reasons to be careful not to overuse wormers, including the possibility that they have a detrimental effect on the environment, the risk of drug resistance in worms, adverse effects in treated pets and in humans who handle the products, financial cost to pet owners, and environmental factors associated with product consumption (packaging waste, emissions generated through manufacturing, transport of product etc). It is the policy of British veterinary professional organisations that vets should only use parasiticides according to a risk assessment (BVA 2021). However, there is no precise answer to the question of which pets need worming and how often, because of knowledge gaps about the risk of infection and burden of disease in animals and humans.
ESCCAP (European Scientific Counsel Companion Animal Parasites), an organisation of veterinary parasitologists, publishes guidelines for veterinary professionals and pet owners on worming cats and dogs (ESCCAP 2021). They identify the worms of main concern in the UK as Toxocara roundworms because of the possibility of human infection; Taenia tapeworms, which can infect livestock if deposited by pets in the countryside; Dipylidium tapeworms, which can infect humans, but are manageable through flea control, Echinococcus granulosus tapeworm (a potentially life-threatening disease if contracted by humans) that can infect dogs that eat raw meat or offal or have access to carcasses; and A. vasorum, which is carried by slugs and snails and can cause fatal disease in dogs. The guidelines give advice on worming frequency according to lifestyle factors (summarised below). They state that regular faecal examination for lower risk groups is a good alternative to standard deworming advice, and include this option in every risk category. The guidelines seem sensible, but lack a description of the methodology by which they were developed (e.g. whether based on a systematic review of the evidence, or if there was input from disciplines other than parasitology) and include no references to support recommendations.
ESCCAP recommendations for worming dogs and cats
If wormers are used, there is a huge choice: both non-prescription and prescription wormers are suitable for controlling roundworms and tapeworms (some non-prescription products are unsuitable for E. granulosus tapeworm), but prevention of lungworm is only provided by products available on a vet’s prescription.
In an attempt to find out how closely pet owners follow the ESCCAP recommendations, a pharmaceutical company-sponsored study surveyed 1000 UK cat and dog owners (Pennelegion et al 2020). The results suggested that 97% of dogs and 68% of cats were in the risk category that requires monthly worming, but that on average pets were dewormed only three times a year. However, to assess Toxocara risk, the survey asked if the pet “interacts with children/elderly”, a definition of risk that is very much wider than in the guidelines (does the pet share a home with children aged under 5 years and people who are immunocompromised), which the report’s authors admit may have led to an overestimate of the proportion of pets in the high-risk category. This research has been used by at least one pharmaceutical company as a basis for CPD aimed at SQPs and by another to promote a product to vets.
Pet owners should receive consistent and clear evidence-based advice
Worming advice aimed at pet owners is confusing and closely related to product sales. Pet owners need clear advice about parasite risk connected with pet ownership, and not just about the parasites for which drug prevention is available. Advice should include information about general hygiene measures, and there should be consistent advice from different providers. Pet owners should be informed about the possibility of test and treat* (Clarification: I am not suggesting that test and treat is a wholesale alternative to preventive treatment. There is a need for independent information about the different tests and their limitations so that veterinary professionals can give accurate advice on which to base parasite management decisions). There is a need for guidelines that have a clear relationship with the evidence and that define the uncertainties. Companies should not use misleading information about risk to promote increased use of parasiticides.
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Written by Andrea Tarr, Founder and Director, Veterinary Prescriber.
You might also be interested to read:
Parasite protection - who’s advising pet owners?
Towards more rational use of parasiticides - but how?
How to make sure you have access to independent information on veterinary medicines
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