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.