Livestock meds are harming dung beetles in the Mediterranean

SAN VICENTE DEL RASPEIG, Spain, Nov. 6 (UPI) -- Cattle ranchers and livestock farmers all over the world use ivermectin, a preventative anti-parasitic drug, to keep their animals healthy.

Scientists in Spain say insects like the dung beetle may be paying a steep price for the medicine's popularity. Dung beetle populations are declining in Mediterranean ecosystems where ivermectin use is most concentrated.

Contrary to the findings of veterinarian-authored drug studies on ivermectin, the medicine's molecules can survive the digestive tract of an animal and exit intact. Drug residues can remain active for a month in livestock dung, harming not just the parasites it's designed to target, but also arthropod populations.

A team of researchers from France and Spain found that dung beetles exposed to ivermectin in the lab exhibited sensory and musculoskeletal decline. Their mobility, orientation and reproductive capabilities were all negatively affected.

These findings were supported by observations in the field. Rates of dung decomposition were up to 30 percent lower in areas of concentrated ivermectin use. Scientists say the discrepancy can be explained by the decline of dung beetle populations in those areas.

"The difference between land with beetles and land without is the difference between roughly 350 kilograms of dung per hectare per year that is not being buried in areas affected by ivermectin," researchers wrote in their new paper on the subject, published this week in Scientific Reports.

Ivermectin has been tremendously effective since its discovery in the 1980s. But scientists say there are now more negative side effects to consider when deciding when, where and how much to administer to animals.

Extra dung accumulation, colonization of highly nitrophilous plants and a reduction of biodiversity are all drawbacks for both livestock and the ecosystem.