Merck + Co., Inc.

Wesley L Shoop

Richard L Monaghan

Prakash S Masurekar

Dan A Ostlind

John R Egerton

Michael A Wallace

Bruce F Michael

The present invention provides a method for the treatment of helminthiasis which comprises administering to an infected host an effective amount of nodulisporic acid or a analog thereof.

Anthelmintic use of nodulisporic acid and analogs thereof

An active avermectin analogue which can be produced by directed biosynthesis is described. The compound, named 26-R-Avermectin B.sub.1 a, is active in the Haemonchus egg to L3 assay and has the following structure: ##STR1##

Active avermectin analogue

A novel strain of Trichostrongylus colubriformis has the unique characteristics of being significantly resistant to the effect of antihelmintic drugs, in particular the antihelmintic drugs ivermectin and thiabendazole. The novel strain of T. colubriformis was prepared by the serial passage of the helminth through sheep. Twenty passages of the helminth through sheep were adequate to impart resistance to oral therapy of 20 times that normally expected with ivermectin. The highly resistant parasite is useful to screen for antihelmintic agents with different modes of action than that of ivermectin or thiabendazole which represent two of the three major classes of modern, broad spectrum anthelmintics.

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Somerville, NJ, United States of America

Wesley L Shoop