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Dehydrochlorination of DDT by Asian Blood-Sucking Leeches^*

Takuji Kimura, Hugh L. Keegan AND Thomas Haberkorn

The toxicity of DDT for Southeast Asian buffalo leeches, Hirudinaria manillensis, was tested with a modification of the standard WHO procedures for determining susceptibility-resistance of mosquito larvae to insecticides. Specimens of H. manillensis from Bangkok, Thailand, and Kuala Lumpur, Malaysia, showed a high degree of tolerance. LC₅₀ values after 120 hours' continuous exposure were 100 ppm for leeches from Kuala Lumpur and 60 ppm for specimens from Bangkok.

The absorption of DDT by specimens of Hirudo nipponia from Japan and of H. manillensis from Malaysia was determined by radioactive assessment of chloroform extracts of leeches that had been exposed for 24 hours in aqueous solution containing 7.1 ppm of ringlabeled C¹⁴ DDT. Results showed that 16% of exposed DDT was recovered from H. nipponia, and 17.4% from H. manillensis.

After assessment of absorption of DDT by the leeches, the chloroform extracts were evaporated to dryness, taken up in acetone, and chromatographed. The chromatogram of H. nipponia extract showed that 49% of the absorbed DDT had been converted to the nontoxic DDE. Chromatograms of extracts by H. manillensis showed neither production of DDE nor other metabolites of DDT analogues. This, as far as could be determined, was the first demonstration of dehydrochlorination of DDT by an annelid.

^* This study was supported financially by the United States Army Medical Research and Development Command, Office of The Surgeon General, Washington, D.C. The views of the authors do not purport to reflect the position of the Department of the Army.

Present address: Department of Preventive Medicine, Medical Field Service School, Brooke Army Medical Center, Fort Sam Houston, Texas.