Douglas J. Gould

Prevalence of Malaria exhibiting Reduced Sensitivity to Chloroquine in Southern Thailand.

Abstract A study to determine the approximate prevalence of malaria parasites exhibiting reduced sensitivity to 4 mg. of chloroquine base per lb. body weight was undertaken in the Self-Help Land Settlements of Satul, Yala and Narathivas Provinces, Southern Thailand. A further study to determine the approximate prevalence of malaria parasites exhibiting reduced sensitivity to a therapeutic course of 10 mg. per lb. of base was conducted in the Self-Help Land Settlements of Yala and Narathivas Provinces. The data indicate that in approximately 79% of the 307 cases with P. falciparum infections the parasites showed reduced sensitivity to 4 mg. per lb. of the drug, and in approximately 53% of the 111 school children with P. falciparum the parasites exhibited reduced sensitivity to 10 mg. per lb. The 4 cases of simple P. vivax infection appeared to be highly sensitive to chloroquine. The 3 mixed ( P. falciparum and P. vivax ) infections reverted to simple infections with P. falciparum . A recommendation to evaluate the usefulness of chloroquine in all malaria eradication and control programmes is proposed.

Surveys on chloroquine resistant P. Falciparum in Thailand

Abstract Surveys for the prevalence of chloroquine resistant P. falciparum were carried out in north, central and south Thailand. The frequency of unsatisfactory response to 1500 mg. of chloroquine base ranged from a high of 85% to a low of 6% in different areas. In a series of hospital patients 37·5% had a poor clinical response and 25% an inadequate parasitological response.

Colonization of Culex gelidus theobold and some resultant effects on its biology

Abstract Interest in Culex gelidus manifested itself when Japanese encephalitis virus was isolated repeatedly from this species in Malaya. Colonization was initiated by introducing large numbers of wild, blood-engorged females into a cage containing pans of water for egg deposition. The aquatic stages were reared in pans by conventional techniques and the adults were maintained in two types of cages. Blood meals for the females were provided by offering human beings and pigs on alternate days. Temperature of 27–28°C., relative humidity of 80 per cent. and artificial lighting provided satisfactory environmental conditions for the adults. When initial attempts were made to subcolonize the species in the United States all adult material went into a state of diapause. Subsequent lenghtening of the “day” period and installation of an exhaust fan in the insectary eliminated this problem. In retrospect, it is not clear whether the problem of diapause was related to the phenomenon of photoperiodicity or to the level of carbon dioxide in the atmosphere of the insectary. In studies on the effect of colonization upon the biology of the mosquito, only changes in the reproductive biology could be detected. Extensive alteration of reproductive behaviour occurred early in the process of colonization, but a gradual return to the “wild” condition took place over four generations.