A theoretical model of the dynamics of an Anopheles gambiae population under challenge with eggs giving rise to sterile males.

An explanation is given of the probable effects of seeding a breeding place of Anopheles gambiae with hybrid eggs that produce almost exclusively sterile males. For the calculations, the dynamics of an A. gambiae population in a single breeding place have been simulated in a computer programme.General considerations and implications are discussed with reference to practical applications, and the conclusion is reached that it will be feasible to eradicate the species from any breeding place only if the number of factory-produced eggs distributed daily bears a known, optimal relationship to the numbers deposited daily on the site.The period of treatment, if the first-day ratio of normal: factory-produced eggs is 1: 1, was estimated to be in the region of 9 weeks. Several runs of the computer have been condensed in a graph which might be used in the early evaluation of progress in the field.

The critical level of interference in species eradication of mosquitos.

The problem of species eradication of insects of the subfamily Anophelini is reviewed in the light of new information produced by analytical means. The concept of the critical level of interference, beyond which eradication would occur, is explained in simple terms. The dynamics of anopheline populations challenged with residual insecticide spraying or sterile adult releases are discussed in an attempt to define the minimal requirements of successful trials.

The dynamics of malaria.

Previous studies on dynamic systems of transmission of malaria, and of eradication of infection following the interruption of transmission, have now been adapted for advanced techniques using the facilities offered by computers.The computer programmes have been designed for a deterministic model suitable for a large community and also for a stochastic model relevant to small populations in which infections reach very low finite numbers. In this model, new infections and recoveries are assessed by the daily inoculation rate and are subject to laws of chance. Such a representation is closer than previous models to natural happenings in the process of malaria eradication. Further refinements of the new approach include the seasonal transmission and simulation of mass chemotherapy aimed at a cure of P. falciparum infections.These programmes present models on which the actual or expected results of changes due to various factors can be studied by the analysis of specific malaria situations recorded in the field. The value of control methods can also be tested by the study of such hypothetical epidemiological models and by trying out various procedures.Two specific malaria situations (in a pilot project in Northern Nigeria and in an outbreak in Syria) were studied by this method and provided some interesting results of operational value. The attack measures in the pilot project in Northern Nigeria were carried out according to the theoretical model derived from the basic data obtained in the field.