Anophelism in the Algerian Sahara and some implications of the construction of a trans-Saharan highway.

The influence on malaria incidence in Algeria of anophelism in the oases and construction of a trans-Saharan highway is discussed. The few remaining cases of malaria in Algeria are of Plasmodium vivax, a parasite absent from tropical West Africa where P. falciparum, now eradicated from the Mediterranean Basin, predominates. Epidemics arising from imported falciparum malaria are considered to be unlikely in Algeria north of the desert, but some oases are at risk. More precise estimates of the probabilities of outbreaks in these oases require analyses of their populations of Anopheles sergentii s.l., a taxon comprising vector and nonvector forms, and also establishment of the northerly limits of the distributions in Niger of A. arabiensis and A. gambiae.

Recent developments of insecticide resistance in some Turkish anophelines.

Susceptibility tests carried out since 1974 in both the field and the laboratory with Anopheles sacharovi, A. hyrcanus and A. maculipennis from Turkey have revealed resistance to organophosphate and carbamate insecticides in all three species, in the first two in the southern Chukurova plain and in the third in the northern area around Osmanjik. Resistance was indicated by significant survivals when exposed to dosages killing presumed susceptible strains of these and other anopheline species. The temperature at which the susceptibility tests were carried out had a marked influence on mortalities. Broad spectra of resistance were shown by all three species, though with interspecific differences, and are attributed to the extensive and intensive use of a wide range of chemicals for agricultural pest control. Of the insecticides readily available for house-spraying for malaria control, malathion would appear to be the one with the greatest potential usefulness.

Some aspects of epidemiology of resurgent malaria in Turkey.

The resurgence of autochthonous Plasmodium vivax malaria in Turkey is a matter of considerable concern. Anopheles sacharovi is the important vector but other species, notably A. superpictus, may play a role in transmission. The epidemiology is discussed in terms of factors related to the mosquito, factors related to the human host and human ecology as it affects dispersal of the parasite. Although the development of insecticide resistance is grave, the present situation is mainly attributable to operational deficiencies stemming from administrative and financial constraints.

Receptivity to malaria in Europe.

Experimental work has confirmed the refractoriness of Anopheles atroparvus to tropical strains of Plasmodium falciparum to which A. labranchiae may also be refractory. This indicates a lower receptivity to malaria in Europe than the existing vector densities and increasing number of parasite carriers would suggest.

Studies on the infectivity of tropical African strains of Plasmodium falciparum to some southern European vectors of malaria.

Preliminary experiments in Garki, Nigeria, with A. atroparvus from Italy have shown a refractoriness to infection with the local strain of P. falciparum. Comparative studies involving A. labranchiae and two strains of A. atroparvus, all from Italy, and one local strain of A. gambiae species B, were carried out at Kismu, Kenya. While oocysts developed in 77% of A. gambiae and, from day 14 onwards, 100% of the oocyst positive mosquitos had sporozoites in the salivary glands, oocysts were seen in only 4% of one of the A. atroparvus strains; the development of these oocysts appeared to be arrested at an early stage. A labranchiae and the other strain of A. atroparvus showed no oocysts. None of the Italian mosquito strains was positive for sporozoites. It is concluded that the importation of falciparum malaria cases from tropical Africa is unlikely to produce epidemics in those southern European areas where A. labranchiae and A. atroparvus used to be malaria vectors.