Detoxification of Molluscicide ICI 24223 by Free Chlorine and by Certain pH Levels

Abstract

The effects of two unrelated water qualities, free chlorine residual and pH, on 24223 (isobutyl-triphenyl-methylamine) when it is used against a Puerto Rican laboratory strain of Australorbis glabratus are considered. To effect 100% mortality after 24 hr exposure, 32 times as much molluscicide was necessary in the presence of 1 ppm free chlorine as without it. The theory is proposed that there may be a molluscicide detoxifying mechanism in snails which is stimulated by chlorine just as there is a fluoride detoxifying agent in fish stimulated by chloride. The toxicity of 24223 is also affected by pH, for four times as much molluscicide may be necessary to cause 100% mortality after 24-hr exposure at pH 4.0 to 5.3 as at pH 8, and eight times as much at pH 10 as at pH 8. In estimates of large-scale control programs, not only should the pH of the water presently occupied by snails be considered, but also the pH of the soil, which might affect the habitats to which snails may remove under stress. Several newly synthesized chemicals give promise of proving effective against the snail vectors of schistosomiasis. Among them two: Bayer 73 (5-chlorosalicylic acid (2-chloro, 4nitro) anilide) and 24223 (isobutyl-triphenyl-methylamine) are so outstanding that their use in large-scale control operations is imminent (Gillet and Bruaux, 1961; Bruaux and Gillet, 1961; Meyling et al., 1962). By previous experiments we have shown that Bayer 73 vs. the Puerto Rican Australorbis glabratus in the laboratory is inactivated by free chlorine in the water solvent (Fox et al., 1963); and that it may also be detoxified by test waters of high acidity or high alkalinity Received for publication 23 April 1963. * This investigation was supported in part by the Puerto Rico Department of Health, by the World Health Organization, by Research Grants E-3821, National Institute of Allergy and Infectious Diseases, and R. G. 7152, Division of General Medical Sciences, U. S. Public Health Service. Medical student summer trainees under Graduate Research Training Grant 2E-15, National Institute of Allergy and Infectious Diseases, also assisted in the work. (Fox, Ritchie, and Frick, 1963). The present experiments had as their objective to find out whether 24223 is similarly rendered less effective by free chlorine or by certain pH levels. MATERIALS AND METHODS The snails used in all experiments were from a basic laboratory stock colony of Australorbis glabratus maintained in the U. S. Army Tropical Research Medical Laboratory and designated TRMLBLS. This strain was reared from specimens originally collected in Puerto Rico and has been under colonization since 1956. 24223 was received through the courtesy of Dr. Frederick F. Ferguson, U. S. Public Health Service, on 26 July 1962. The container was labeled as follows: ICI 24223, Dispersible Powder, 350 grammes, PD/AS, 756059, F 517. Imperial Chemical Industries Limited. Pharmaceutical Division, Wilmslow Cheshire. Accession No. 5510. Date 5/22/61. This was the hydrochloride formulation of 24223 with 94% active ingredient. The desired concentrations of the toxicant were obtained by the two-tube schedule of Fox and Garcia-Moll (196.1) as follows: Tube 1, 1 g of 24223 plus 93 ml methanol; Tube 2, 1 ml of Tube 1 plus 99 ml of distilled water. A free chlorine residual of approximately 1 ppm was obtained by adding sodium hypochlorite (Clorox,