Resistance of Hookworm Larvae Part 1 Resistance of Hookworm Larvae to Alkylphosphate Insecticides

In vitro studies were made on resistance of the larvae of Anchylostoma caninum against alkylphosphate insecticides, Parathion, Diazinon, Chlorthion and ACC 4124 (Sumicide). The results were as follows. 1) In the emulsions of Parathion, Diazinon, Chlorthion and sumicide, having the concentration over 10-5 %, 10-3%, 10-3% and 10-2% respectively, most of the larvae died within four days. This indicated that these alkylphosphates were in some degree possible to prevent hookworm diseases due to the toxity to the larvae, when sprayed in the field. 2) Hookworm larvae in contact with alkylphsphates, nerve toxin, were lead to death after showing abnormal movement. The stages to death may be divided into stage of incubation, convulsion, ataxia, palsy and death. 3) Microscopically the bodies of dead larvae were observed to be of minute or moderate granular degeneration, and consequently internal components were not discernible. 4) In the alkylphosphate emulsions, the larvae moulted quite rapidly. 5) With the lapse of time both lethality and the rate of ecdysis increased in parallel correlation, while the count of the head movement of larvae per minute was in inverse proportion to them.