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Abstract. Plasmodium falciparum malaria was the cause of death of Emperor Charles V. This confirmation was achieved by microscopy analysis of the Emperor's remnants.

Dealing with malaria in the last 60 years is seen by the author in the perspective of his own experience. His malaria work, which began in 1941, covered the study of the habits of the mosquitoes dwelling in the savanna country of Eastern Colombia and the effect on malaria transmission of the newly introduced DDT residual spraying. The success of the campaign he later directed in Sarawak and Brunei contributed to the launching by WHO of its global malaria eradication campaign. Further successful work in Uganda showed the possibility of effective control and even eradication in highland country but left unsolved the problem of how to interrupt transmission of holoendemic malaria in Africa. The author's work with WHO in the Middle East showed to what extent social and economic conditions could influence the course of a malaria campaign. This was also the experience in America, both in Colombia in the author's early work and later in Mexico during an evaluation of the national malaria programme. Development of insecticide resistance was also encountered in his career and the refractoriness of the European vectors was also observed in his work as a malariologist.

The success of the campaigns against malaria in Europe, the USA and other countries in the temperate zone, prompted WHO to launch its global eradication campaign in 1955. It failed to achieve eradication in tropical countries due to climatic, social and economic conditions different from those prevailing in the temperate zone, where eradication had been achieved using control measures.

The finding of two imported cases of malaria in Spain is reported. Although their origin, their age and their clinical history were different, they both showed parasites of atypical morphology. One was diagnosed as P. vivax and the other as P. ovale, but the morphology observed in both cases does not correspond to what is considered as normal in the two species. In the first case forms similar to those of P. ovale were observed and in the second case P. vivax-like forms. The findings reported confirm the overlapping morphological variability of the two species.

Human malaria originated in tropical areas of the Old World but the Pleistocene glaciations delayed its spread in the Northern Hemisphere. The last glaciation produced temperatures 9 degrees C lower than those prevailing today in Southern Europe, making the transmission of malaria there virtually impossible. When temperatures approximately equal to those of today were reached 10,000 years ago, the disease and some of its most effective vectors, Anopheles labranchiae and A. sacharovi, spread to the North although the refractoriness of the European vectors to Pasmodium falciparum probably delayed the spread of the malignant tertian parasites. Malaria may have spread earlier in the Levant and parts of Asia, due to a less marked drop of temperature during the last glaciation but we have witnessed in contemporary times the spread of A. stephensi, one of the most effective vectors in the area. The first noticeable decline of malaria was seen in Europe during the nineteenth century due to new agricultural practices and changed social conditions. The final disappearance of the disease in Europe and North America was due more to those changed conditions than to the use of DDT and other residual insecticides which were going to fall in so-called eradication campaigns in the Third World.

The campaign against malaria in Sardinia carried out by the Ente Regionale per la Lotta Anti-Anofelica in Sardegna (ERLAAS), appears today as one of the greatest efforts against malaria since the discovery of its aetiology and mode of transmission. The disease was eradicated without achieving the eradication of the vector, Anopheles labranchiae, the main objective of the campaign. This species eradication failure had been at first attributed to the indigenous character of A. labranchiae and its long standing in the island. A more recent analysis, based on paleoclimatological information, makes virtually impossible the presence of A. labranchiae during the last (Würm) glacial period and indicates a comparatively recent introduction of the species in the island. It was the absence of A. atroparvus, with which it has usually to compete in Southern Europe, what permitted the wide distribution of A. labrianchiae in the island. Four decades after the events the concept of species eradication as an anti-malaria weapon appears as basically wrong, the results of Sardinia as well as those obtained in the Italian mainland having demonstrated that the eradication of the vector was not required for the successful eradication of the disease.

Field and laboratory studies were carried out on populations of Anopheles sicaulti and An. labranchiae from the Moroccan province of Tetouan, in order to evaluate the hypothesis of a specific rank for the former taxon, recently suggested by White (1978). The egg morphology, and particularly the exochorion pattern and the number of float ribs, showed a complete range of variation, from typical sicaulti to typical labranchiae. Females laying "intermediate" eggs are those prevailing in the study area (60.5% of the eggs collected in the Tetouan province were of this type); in some localities (Ben Karriche and Restinga) only such females were observed. The latter finding would indicate a polygenic control of the egg pattern, as the two supposed parental forms do not seem to segregate from the "intermediate" one. No pure labranchiae populations were observed in the study area, while a pure sicaulti sample was found at Kantara. More widespread appears to be the coexistence of the "intermediate" form either with sicaulti (at Mdiq and Beni Yder, in both cases with a ratio of about 1.7:1), or with both sicaulti and labranchiae (at Souk Khemis and Tatoufet, with a ratio of about 2:1:1 in the two cases). These data seem to indicate that in the considered area sicaulti interbreeds freely with labranchiae. Crossing experiments failed to evidence post-mating barriers between the two taxa; fertile hybrids were obtained in the expected numbers. The polytene chromosome studies showed no differences of diagnostic value between sicaulti and labranchiae, that have the same banding pattern. Also the genetic structure, analyzed by means of starch-gel electrophoresis on the basis of 16 gene-enzyme systems appears to be quite similar in the two forms: allele frequencies at the polymorphic loci do not show significant differences. The average Nei's genetic distance found between sicaulti and labranchiae is exceedingly low (D = 0.014); values of the same magnitude were observed between conspecific populations both in An. labranchiae and An. atroparvus (average D = 0.016 in the two cases). The polymorphic loci in the Tatoufet population, that includes the three forms: sicaulti, "intermediate" and labranchiae, are in Hardy-Weinberg equilibrium, indicating that it represents a panmictic unit. The overall picture does not favour a specific rank for sicaulti, that seems rather a local variant of An. labranchiae. The need is stressed for further investigations involving populations living in the Rabat area, from where sicaulti was originally described.

Climatic changes must have greatly affected the distribution of malaria in prehistoric times. Paleobotanical evidence, snowline depression studies and information obtained from deep sea sediment cores, indicate that southern Europe must have suffered a drop of summer temperatures of approximately 9 degrees C during the last glacial maximum, 18,000 years ago. Such a drop would have been decisive as regards the distribution of malaria and its vectors. If present at all, the disease would have been confined to the southernmost parts of the continent but P. falciparum and today's most effective vectors--A. labranchiae and A. sacharovi--would have been excluded from Europe. In western Asia, summer temperatures 6 degrees C lower than those of today would have had less effect on the malaria situation. The introduction of falciparum malaria in southern Europe is placed in Hellenistic and Early Imperial Roman times, based on paleoclimatological evidence and historical and medical data. In America P. falciparum is also considered a late entrant but vivax and quartan malaria may have been introduced in pre-Columbian times. In the Pacific, the disease is known to have been spread by man since the Age of Discovery until contemporary times.