Parasiticides in dogs and cats: a risk-based approach

There are emerging concerns that parasiticide use in small animal veterinary medicine is contributing to environmental contamination with pesticide compounds

Over the last few years, there have been emerging concerns that parasiticide use in small animal veterinary medicine is contributing to environmental contamination with pesticide compounds. The most studied of these compounds are fipronil and imidacloprid, agents which are highly toxic to invertebrates and found in topical spot-on flea treatments for our pets (Kindemba, 2009; Perkins et al, 2021) and which also show toxicity to non-target taxa (Gibbons et al, 2014). The concern is that as these products build up in our rivers and waterways, the direct and indirect impacts on invertebrates, as well as other non-target species, including humans, could be devastating and irreversible.

More and more evidence is accumulating around the effects of medicines and drugs in our environment – so these products are by no means the only cause for concern. Prozac metabolites in the environment contaminated by human sewage may alter starling physiology and behaviour (Bean et al, 2014) and illicit drugs such as cocaine may be affecting aquatic organisms such as eels (Capaldo et al, 2018) and shrimps (Miller et al, 2019). The effects of drugs and their metabolites in the environment are not yet fully understood but could include lethal and sub-lethal effects in many non-target species, including changes to behaviour and reproduction. Pesticides such as neonicotinoids are compounds of particular concern globally, due to their high toxicity to invertebrates and implication in declines in insect populations, leading to many bans and restrictions of their use in agriculture. For example, the EU banned outdoor use of neonicotinoids in 2018 to protect pollinators such as bees. However, with an increasing pet population, contamination from parasiticide products must also be carefully considered.