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There are many different worming treatments available for cats. And it can be hard to know what to choose for your beloved feline. Tablet or spot-on? Which worms should you be targeting? Monthly application or quarterly? It’s a confusing world out there, and now there is a rather more complicated question that many pet owners are adding into the mix; which worming treatments are most planet-friendly? Climate change and environmental degradation are huge, complex and important topics. Finding a balance between protecting our cats and keeping our environment safe can be difficult.
Should I be worming my cat?
Cats in the UK, especially those with outdoor access, are exposed to a variety of parasites. Worms can cause health problems in cats, but can also infect humans. The most common intestinal worms in cats are tapeworms and roundworms. These can exist in your cat without causing symptoms, but a high burden can cause vomiting, diarrhoea and weight loss. Worms are commonly a factor in kittens which fail to thrive. In humans, worms may again be an asymptomatic problem. But in some cases can cause serious disease, especially in children and immunocompromised adults.
The European Scientific Counsel Companion Animal Parasites (ESC-CAP) guidelines recommended worming cats between 1 – 12 times yearly, depending on risk (ESCCAP 2018). A study in 2020 looked at the risk to companion animals, and found that all surveyed cats met the risk requirement to be de-wormed at least four times a year, and most (68%) fell into the highest risk category, with a recommendation for more regular treatment (Pennelegion et al., 2020). Many vets, reasonably, therefore recommend regular treatment with a suitable product.
How do wormers get into the environment?
Since you are giving these medications directly to your cat, it is reasonable to expect that they stay in, or on, your cat, right? However, there are various ways in which these chemicals may escape out into the environment, albeit in small quantities.
Spot-on treatments can be washed off the pet owners’ hands after applying the treatment, or after petting a cat with a recent treatment applied. They can also be washed off the pet directly, or from bedding. This leads to the active ingredients being taken into the wastewater system. Tablet wormers may pass through your cat and into their urine and faeces and out into the environment through that route.
It is likely that only very small amounts of these products will find their way into our water systems and soils, but with an estimated 11 million cats in the UK (PDSA, 2020), even tiny amounts add up. The choice of parasiticide could be making a large impact.
Why are wormers bad for the environment?
It has come to more prominence in recent years that some of these parasiticides are being leached into the environment. Cats are often outdoor creatures, and the ingredients found in worming treatments can be found in their skin and hair, and therefore shed into the outside world. Research funded by the Veterinary Medicines Directorate (VMD) has found that imidacloprid and fipronil (two common ingredients in anti-parasite treatments in pets) have been found in 65.9% and 98.6% of English rivers sampled, far higher than would be expected (Perkins et al., 2021).
The actual effect of these chemicals entering the environment is not yet proven. Some compounds used in worming treatments are known to be toxic to fish and other aquatic organisms. Moxidectin, for example, reduced hatching success in zebrafish and altered other biochemical parameters (Muniz et al., 2021). Some compounds appear safe for vertebrate animals but their effect on invertebrates may be problematic. There is a considerable lack of studies around this area, and so although the presence of active ingredients in the environment is concerning, there is little concrete evidence of their ill effects – at least, not yet. That said, the recent decline in insect and other invertebrate species is being caused by something and wormers are unlikely to be completely harmless.
Which worming treatment is best for the environment?
There are currently no studies to show which worming products are most harmful to the environment, and therefore no guidance on which products to use. However, there are some practical steps that we can take to try and reduce the impact of using these products.
- Use appropriate worming products for your cats, given at intervals based on their individual risk. Indoor cats are of lower risk for parasites, prolific hunters are at higher risk.
- Dispose of packaging correctly, and apply products so that none is wasted or washed away.
- Consider using tablet wormers where possible, as spot-on products are more likely to contaminate water supplies.
- Dispose of your cat’s urine and faeces correctly (don’t flush down the toilet!) and hygienically.
Can I use a natural wormer?
There are various ‘chemical-free’ ‘natural wormers’ available and marketed as an alternative to more medicinal products. It can be tempting to turn to these if you are concerned about the compounds found in veterinary parasiticides, however these natural products are unlikely to have any efficacy against worms. Using appropriate worming treatment is important for both our cats’ health and our own, and can still be done alongside environmental responsibility and respect.
- ESCCAP (2018): Control of Ectoparasites in Dogs and Cats
- Wells C, Collins CMT (2022) A rapid evidence assessment of the potential risk to the environment presented by active ingredients in the UK’s most commonly sold companion animal parasiticides Environmental Science and Pollution Research 29:45070–45088
- Muniz MS, Halbach K, Alves Araruna IC, Martins RX, Seiwert B, Lechtenfeld O, Reemtsma T, Farias D.Environ Pollut. (2021) Moxidectin toxicity to zebrafish embryos: Bioaccumulation and biomarker responses. Aug 15;283:117096. doi: 10.1016/j.envpol.2021.117096. Epub 2021 Apr 8.PMID: 33866217
- Perkins R, Whitehead M, Civil W, Goulson D (2021) Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Sci Total Environ 755:143560. https://doi.org/10.1016/j.scitotenv.2020.143560
- PDSA (2020): PAW PDSA Animal Welfare Report 2020. https://www.pdsa.org.uk/media/10540/pdsa-paw-report-2020.pdf
- Pennelegion C, Drake J, Wiseman S, Wright I (2020) Survey of UK pet owners quantifying internal parasite infection risk and deworm- ing recommendation implications. Parasit Vectors 13:218. https://doi.org/10.1186/s13071-020-04086-2