A new paper in Environmental Toxicology and Chemistry, published by Oxford University Press, finds that common medications used for flea and tick control in dogs and cats may pose a significant environmental risk for insects in the wild.
Isoxazoline antiparasitic drugs are a new type of medication used by veterinarians globally to treat companion animals for flea and tick control. First launched in 2013 they became popular because they were the first orally-administered drugs that worked against both fleas and ticks for a month or more. Dogs and cats eliminate the drugs through defecation.
The European Medicines Agency has highlighted the risk of these substances contaminating ecosystems, though there is limited data on their environmental release. The particular concern is about the potential environmental contamination and impact of veterinary parasiticides on non-target species. Isoxazoline antiparasitic drugs exist to kill fleas and ticks on pets; they may also kill other insects when pets excrete the active chemicals in the medications. Recent studies suggest pets transfer parasiticides to the environment via feces, urine, or shedding their hair. The particular concern is that dung-feeding insects, including flies, dung beetles, and some butterflies—which are important to nutrient cycling, soil health, and pest control—may harmed by consuming the feces of dogs and cats treated with these drugs.
French researchers here studied 20 dogs and 20 cats owned by veterinary students and treated with isoxazoline antiparasitic drugs over a three-month period. The investigators collected feces samples from the pets to determine the potential exposure dung-feeding insects may have to the toxic chemicals.
This study examined isoxazoline fecal elimination in dogs and cats. The researchers detected two of the four active substances in isoxazoline antiparasitic drugs in pet feces after the end of the recommended treatment period. The environmental risk assessment indicated that dung-feeding insects could be highly exposed to isoxazoline parasiticides due to pet medication, with potentially disastrous consequences for environmental lifecycles.
The paper, “Prolonged fecal elimination of isoxazoline antiparasitic drugs in dogs and cats: is there a risk for non-target species?” is available (at midnight on January 14 th ) at https://doi.org/10.1093/etojnl/vgaf285 .
Direct correspondence to:
Philippe J. Berny
Vetagro Sup, Campus Vétérinaire
Cell-Environment Interaction Department
One av Bourgelat F-69280
Marcy l’étoile, FRANCE
philippe.berny@vetagro-sup.fr
To request a copy of the study, please contact:
Daniel Luzer
daniel.luzer@oup.com
Environmental Toxicology and Chemistry
Experimental study
Animals
Prolonged fecal elimination of isoxazoline antiparasitic drugs in dogs and cats: is there a risk for non-target species?
14-Jan-2026
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