Parasite control in pets - Veterinary Practice
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Parasite control in pets

Should we reconsider our parasite control strategies as they are harmful to the environment?

Most of us are worried about the environment. In fact a recent BVA survey found that 89 percent of UK vets wanted to play a more active role in sustainability (BVA, 2019), but I suspect many of us struggle to see how we as individuals can take enough action to have a major impact on global CO2 levels, rising temperatures, melting ice caps, plastic pollution and ecological collapse.

Well, here’s one area where we do have a huge opportunity to make a significant difference.

Let me explain. Many non-domesticated species appear to be undergoing population collapse all around us. Put bluntly, the flies and bugs don’t get squashed on your windscreen these days, largely because they aren’t there any more. Remember that 2017 article by Hallmann looking at insect populations in Germany? “More than 75 percent decline in total flying insect biomass over 27 years in protected areas” (Hallman et al., 2017).

Or how about the one in Nature in 2019 by Powney: “Widespread losses of pollinating insects in Britain” (Powney, 2019) or the Sussex Wildlife Trust’s “Insect declines and why they matter” (Goulson, 2019)?

Sanchez-Bayo and Wyckhuys (2019) stated that over 40 percent of insect species are threatened with extinction, with Lepidoptera, Hymenoptera and dung beetles (Coleoptera) being most affected. Four aquatic taxa are imperilled and have already lost a large proportion of species, and “habitat loss by conversion to intensive agriculture is the main driver of the declines. Agrochemical pollutants, invasive species and climate change are additional causes”.

Imidacloprid, to members of the genus Apis (the honey bees), is one of the most toxic chemicals ever created as an insecticide, either killing them outright, changing the way they communicate and navigate or affecting their appetite. The Buglife report on neonicotinoid insecticide in British freshwaters (Buglife, 2017) states that “veterinary pour-ons and flea collars are implicated as the most likely source of pollution”. The article goes on to state that imidacloprid applied to pets can be washed off by rain, bathing or washing of bedding, which may result in the pollution of sewage, storm drains and water courses or direct pollution of a river, lake or pond if the animal is allowed to swim. In addition, some imidacloprid is likely to be excreted by the animals in urine and faeces after absorption through the skin.

Avermectins, also used as topical parasiticides, have similarly catastrophic effects on invertebrates and therefore everything else further up the food chain. As a consequence, insectivorous bird numbers have also taken a huge hit. UK populations of the grey partridge have declined 92 percent since 1967, nightingales by 93 percent, cuckoos by 77 percent and spotted flycatchers by 93 percent (Goulson, 2019).

According to NOAH, the UK veterinary medicines market is worth £725 million, of which half is now for pets. Parasite treatments account for 39.5 percent of the total (NOAH, 2019). So maybe as much as £140 million worth of parasite medication is being used in or on pets each year, with very little testing, but “the prophylactic use of broad‐spectrum pesticides goes against the long‐established principles of integrated pest management” (Goulson, 2013).

The conclusion is that “A serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends” (Sanchez-Bayo and Wyckhuys, 2019). Section 6.1 of our Code of Professional Conduct states that “Veterinary surgeons must seek to ensure the protection of public health and animal health and welfare, and must consider the impact of their actions on the environment.”

And by happy coincidence, a recent RCVS survey found that vets are among the UK’s most trusted professionals (Loeb, 2020), ranking above doctors and dentists (although we lost out to opticians and pharmacists. Ouch). So, when we, as possibly the only working scientists that many of our clients have ever actually met, talk to them about the environment, there’s a very good chance that they’ll be listening to what we have to say.

This, then, is a call to action for us as veterinary surgeons:

  1. Stop blanket parasite treatments for pets, especially for parasites that either aren’t there or don’t cause a problem if they are. Just this week there are adverts in the veterinary press for a product that “covers 22 parasites across cats and dogs”, but how many cases of Eucoleus boehmi have you seen in your career? And did you know that a single large dog dose of that product contains the LD50 of imidacloprid for 50 million bees? Indiscriminate treatment has consequences
  2. Start risk assessing our patients – fairly straightforward for most UK parasites once you look at the numbers
  3. Get into the habit of testing before treatment. If American clients all bring in faecal samples at their pet’s annual health check, why don’t the Brits? Because we don’t ask them to
  4. Start doing regular faecal exams in our practice laboratories or pressure our commercial labs to do them for us more cheaply than such services are currently available direct to the public
  5. Be well informed on the environmental profile of all the products we stock and ask the sales reps and technical advisors probing questions about their safety for our patients, the environment and the people who handle them, which includes us
  6. Ask yourself “Would I willingly apply pesticides and other toxic chemicals to my children on a monthly basis?”

Steve Garland, entomologist and Chair of the Wildlife Trusts’ policy setting body for England said: “I really believe that the catastrophic decline of insects can be reversed by drastically reducing the use of chemicals in the environment and creating strong Nature Recovery Networks to give them space to live and thrive in safety.” (Goulson, 2019).

Maybe it’s time we don’t just listen to the scientists, but started acting like the ones we’re meant to be.


British Veterinary Association


BVA news – BVA joins leading veterinary figures in green initiative.

Hallmann, C., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D. and de Kroon, H.


More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLOS ONE, 12, p.e0185809

Powney, G., Carvell, C., Edwards, M., Morris, R., Roy, H., Woodcock, B. and Isaac, N.


Widespread losses of pollinating insects in Britain. Nature Communications, 10.

Goulson, D.


Insect declines and why they matter. Somerset: The Wildlife Trusts

Sánchez-Bayo, F. and Wyckhuys, K.


Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8-27

Shardlow, M.


Neonicotinoid Insecticides in British Freshwaters: 2016 Water Framework Directive Watch List Monitoring Results and Recommendations. Buglife – the Invertebrate Conservation Trust, Peterborough, UK

National Office for Animal Health


Industry Facts & Figures

Goulson, D.


REVIEW: An overview of the environmental risks posed by neonicotinoid insecticides. Journal of Applied Ecology, 50, 977-987


RCVS Code of Professional Conduct, section 6.1

Loeb, J.


Vets are among UK’s most trusted professionals. Veterinary Record, 186, 4

Andrew Prentis

Andrew Prentis, BVSc, MRCVS, is a veterinary surgeon and a member of Vet Sustain’s Greener Veterinary Practice working group . Having retired from clinical practice, he campaigns for environmental protection, biodiversity and sustainability both in and around the veterinary profession.

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