Carbamoyl Alkyl Phosphorodithioates as Chemotherapeutic Agents: Effects of Dimethoate against Grubs in Cattle1

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Abstract
In 21 cattle, single oral doses of from 2.5 to 40 mg./kg. and intramuscular doses of 5 and 10 mg./kg. of dimethoate (Am. Cyanamid 12,880): O,O-dimethyl-S-(N-mehtylcarbamoylmethyl) phosphorodithioate killed 86% to 100% of second instar Hypoderma larvae in the backs of cattle within 1 week after treatment. The lowest dose tested with H. bovis was 5 mg./kg. Ten mg./kg. was the lowest dose uniformly highly effective against third instar larvae. Single oral or intramuscular doses of 10 and 20 mg./kg. of dimethoate killed 50% or more of the first instar larvae of H. lineatum (De Vill.) in the gullets of five calves in total within 14 to 25 day after treatment. A similar effect was obtained in one calf treated with 5 mg./kg. orally and sacrificed 25 days later, but not in two calves treated with 5 mg./kg. intramuscularly. In calves weighing 118 to 427 kg., single oral doses of 40 mg./kg. and above, of dimethoate produced severe toxic symptoms, and 80 or 1000 mg./kg. were lethal in 2 days or less; 15 and 20 mg./kg. produced mild toxic symptoms, and doses lower than 15 mg./kg. were essentially asymptomatic. Data on toxicity in sheep and other animals are presented. No differences were observed between the toxicity of 99% and 94% material, and two different drench formulations in ruminants gave comparable results. Comparisons are given with other types of compounds that are active chemotherapeutically against cattle grubs.