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Will livestock drug cause dung crisis?

Will livestock drug cause dung crisis?

Dung beetles and earthworms don'ttend to get a lot of respect--except when they're not around. Ecologically, these invertebrates provide a valuable housekeeping service. Not only do they break down and carry away dung, but in the process they also aerate soil and enhance the ability of water to percolate into the ground. For these reasons, growing veterinary use of the drug ivermectin in livestock to control parasites--such as roundworms--could have unintended environmental repercussions. A new British study shows that the drug, excreted in the feces, can exert a dramatic insecticidal effect on dung fauna.

While feces of nontreated calves wereimmediately colonized by dung beetles in the field--sometimes by hundreds per "pat'--and later by earthworms, the dung of ivermectin-treated animals remained largely devoid of such invertebrates, according to a report in the June 4 NATURE by zoologists Richard Wall and Les Strong of Bristol University in England. Within 100 days, the researchers say, the control pats had "largely disappeared,' whereas the drug-containing dung samples "were still largely intact.' This situation could spell a serious, impending problem, especially to livestock farmers, Wall believes, because "for every pat [of dung] you have, you reduce available pasture land; cows won't graze up to the edge of their cow pat.'

Bill Hill, a spokesperson for theRahway, N.J.-based MSD-AGVET (a division of Merck & Co.), the drug's maker, says there have been no anecdotal reports from ivermectin users of problems with dung degradation. Moreover, he says, because the drug is registered only for infrequent administration by injection or as a paste, its effects on dung beetles would be limited to feces passed in the few days after each treatment. But Wall says while that may be true today, it would not be true if the drug were administered from a controlled-release implanted pellet, which he says is now under development--an application that would shed the drug into the feces daily for months.
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Title Annotation:environmental repercussions of use of ivermectin in livestock
Author:Raloff, Janet
Publication:Science News
Date:Jun 6, 1987
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