Part VI. Unstable highland malaria—analysis of data and possibilities for eradication of malaria

Abstract
In the present era of “Malaria Eradication” it is possible to make a mathematical analysis of malaria epidemiology in any locality and forecast the potential for eradication of this disease. The clinical and entomological picture of unstable highland malaria in New Guinea presented in this paper enables us to forecast that eradication by the residual spraying of DDT once or twice a year is a practical possibility. The major local vector at Minj (5,000 feet) is Anopheles farauti Laveran which is a long-lived species having a sporozoite rate up to about 2 per cent. The seasonal variations in its population density and possibly also in its natural longevity result in seasonal epidemics of malaria in the indigenous community whose level of premunity is generally very low. Parasite rates of the community rise from a dry season level of 5 per cent. to 25 per cent. or more and, in other localities at the same altitude, up to over 70 per cent. Gametocyte rates rise from 1 per cent. to 5 per cent. and above. The dominant species at all times is P. vivax, but there are seasonal changes in the parasite ratio. Both P. falciparum and P. malariae are present. Anophelism sans malaria which is present in certain valleys at the same altitude as Minj requires further study. The optimum time for a residual spray campaign is during the first month of heavy rain following the dry season, i.e. November. It would be difficult to achieve this over a wide area without co-ordination of the work, possibly by volunteers on a village self-help basis.