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Biomedical subjects

G DAVIDSON

Publications and source records attributed to G DAVIDSON.

At least 19 recordsLinked to original sources
PubMed1965

THE DEVELOPMENT AND TREND OF INSECTICIDE-RESISTANCE IN ANOPHELES ACONITUS DOENITZ AND ANOPHELES SUNDAICUS RODENWALDT.

The spread of insecticide-resistance in the two main vectors of malaria in Java, Anopheles aconitus Dönitz and A. sundaicus Rodenwaldt, has been of concern to workers in the Indonesian malaria eradication programme since DDT-resistance was first detected, in A. sundaicus, in 1954. The history of development of resistance in these two vectors has been summarized in this paper by assembling the available records in chronological order, thus facilitating reference.The picture which emerges is that of somewhat erratic occurrence of DDT-resistance in A. sundaicus and more stable, expanding areas of DDT-resistant A. aconitus. Dieldrin-resistance is more widespread than DDT-resistance in both species and preceded the onset of DDT-resistance in A. aconitus but not in A. sundaicus. These features should not be regarded as species characteristics, however, since selection pressures on the two species have been far from uniform.Malathion appears to be a promising alternative to DDT and dieldrin for the control of the two vectors in the circumstances described.

Animals↗
PubMed1964

ANOPHELES GAMBIAE, A COMPLEX OF SPECIES.

The author reports on some 200 laboratory crossings of 36 strains of Anopheles gambiae from many different parts of Africa which show the existence of five mating-types in what was until recently considered a single species. Three of these mating-types are freshwater forms and have been provisionally called A, B and C. Two are saltwater forms: A. melas, confined to West Africa, and the East African A. merus. Hybrid male sterility is universal when any two of these five forms are crossed, and from some of the crosses grossly abnormal sex-ratios result. From an evolutionary standpoint these five mating-types are probably species or semi-species in view of the fact that they can be found to co-exist sympatrically and still retain their identities. From a practical point of view it may be necessary for the field worker to be able to identify the exact species with which he is dealing before the most efficient means of controlling it can be found.

Africa↗
PubMed1963

DDT-RESISTANCE AND DIELDRIN-RESISTANCE IN ANOPHELES QUADRIMACULATUS.

The nature and mode of inheritance of both DDT-resistance and dieldrin-resistance in Anopheles quadrimaculatus from the United States of America have been studied. Dieldrin-resistance is shown to be dependent on a single, semi-dominant, genetic factor, and DDT-resistance on a single, recessive one, though the expression of this latter factor is to some extent dependent on the genetic background. Both resistances can occur in the same mosquito but can be separated, thus indicating the independent nature of the two genetic factors involved.

Animals↗
PubMed1961

DDT-resistance in Anopheles stephensi.

In view of the increasing number of reports from different parts of the world indicating resistance to DDT in both adults and larvae of Anopheles stephensi, an important malaria vector, a series of laboratory studies has been carried out on the degree, the pattern and the mode of inheritance of resistance in this species. A DDT-resistant strain from Iraq and a susceptible strain from India were used.In four sets of observations made in the course of tests on both adults and larvae a monofactorial type of inheritance was indicated, and the factor involved was shown to be dependent for its expression on the genetic background.DDT-resistance in A. stephensi appears to be similar in most respects to that in A. sundaicus.

Animals↗
PubMed1958

Studies on insecticide resistance in anopheline mosquitos.

This paper describes observations made both on laboratory colonies in London and on wild-caught material in the field of insecticide-susceptible and -resistant strains of A. gambiae, A. sundaicus and A. stephensi. The techniques used in assessing the susceptibilities of both larvae and adults are described and the effects of species, rearing, age, sex, feeding and ovarian development on susceptibility are discussed. The effect of continued selection by DDT in the laboratory of a presumably homogeneous susceptible strain of A. stephensi is then outlined and the phenomenon of "vigour tolerance" demonstrated.Specific, monofactorially-inherited resistance is then described as witnessed with A. gambiae and A. sundaicus. A. gambiae shows a high degree of resistance to dieldrin and cross-resistance to the related cyclodiene compounds and gamma-BHC, but remains susceptible to DDT. Resistance is due to a single gene, partially dominant, the hybrid showing a moderate degree of resistance. A. sundaicus shows a moderate degree of resistance to DDT and cross-resistance to DDT analogues, but remains susceptible to dieldrin and gamma-BHC. Resistance is again due to a single gene but here it is virtually recessive and the hybrid is to all intents and purposes susceptible. The discriminating dosage technique for distinguishing the phenotypes in these species is described.Resistance in other anophelines and in houseflies is discussed and suggestions made as to methods of detecting anopheline resistance in the field.

Animals↗