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Biomedical subjects

A R Zahar

Publications and source records attributed to A R Zahar.

4 recordsLinked to original sources
PubMed1984

Vector control operations in the African context.

In order to define the scope of vector control as a component of malaria control in the WHO African Region, examples of recent experiences with different vector control methods in this region are reviewed. Residual house spraying applied alone or in combination with mass drug administration has failed to interrupt malaria transmission in savanna areas for several technical and administrative reasons. Nevertheless, there is evidence that residual house spraying has led to an improvement in general health. However, the existence of DDT and dieldrin/HCH and lately malathion resistance in the Sudan in Anopheles gambiae s.l. would militate against the use of residual house spraying as a main tool for long-term malaria control. It should therefore be used only to reduce malaria prevalence to an acceptable level until integrated control methods can be developed and become operational.Experience with larval control, space spraying, and biological control of vectors is also reviewed, and the value of self-help methods of reducing man-vector contact under African conditions is examined. All these methods need to be more thoroughly assessed. Several proposals are made for applied field research.

Africa↗
PubMed1974

Review of the ecology of malaria vectors in the WHO Eastern Mediterranean Region.

On the basis of published records and unpublished reports to WHO, the author reviews the information available on the ecology of 15 anopheline malaria vectors occurring in areas of the WHO Eastern Mediterranean Region where attack measures are being applied. The information, which is still incomplete, relates chiefly to the period since 1956, the year when the malaria eradication programme in the Region was launched. An attempt is made to evaluate the control measures undertaken so far, and to provide data on the sensitivity to insecticides, behaviour, and mortality of vector populations.

Africa, Eastern↗
PubMed1973

The practical implications of resistance of malaria vectors to insecticides.

Insecticide resistance is an inherent characteristic dependent on relatively simple genetic mechanisms. This seems to be especially true of dieldrin resistance in anopheline mosquitos, though less obvious in DDT resistance among these species; little is known as yet about the inheritance of organophosphate and carbamate resistance as it occurs in Anopheles albimanus. The speed of selection of resistance depends on the original frequency of the gene or genes involved, the nature of the resistance imparted, and the selection pressure of the insecticide. This in turn depends on the inherent toxicity of the chemical, the efficiency with which it is applied, the proportion of the mosquito population coming under its influence, and the behaviour of the mosquito. In the past, too much reliance has been placed on the determination of the LD(50) in assessing the presence or absence of insecticide resistance. Quite high incidences of resistant individuals can result in such small changes in the LD(50) that resistance may be overlooked. The use of single discriminating dosages is advocated, based on concentrations of insecticides that normally kill all susceptible individuals. The authors discuss such dosages in respect of dieldrin and DDT, and put forward newly-established tentative discriminating dosages for organophosphorus and carbamate insecticides, which await field confirmation.From a practical standpoint, an insecticide should not be abandoned or replaced by another as soon as resistance is confirmed. This may not be necessary where the degree of resistance is not high and the vector is not highly efficient. Certain procedures are proposed in order to assess the epidemiological and entomological implications of resistance before the insecticide concerned is abandoned.

Animals↗