The evolution of malaria in Brazil, its morbidity, the malaria control programs, and the new challenges for these programs in the light of the emergence of asymptomatic infection in the Amazon region of Brazil were reviewed. Rondônia and, in our group, in If a mean of 25% is taken for the asymptomatic infection caused by Plasmodium sp. in the Amazon region of Brazil, malaria control will be difficult to achieve in that region with the measures currently utilized for such control.
At least six Brazilian research groups have demonstrated that asymptomatic infection by Plasmodium is an important impediment to malaria control, among mineral prospectors in Mato Grosso and riverside communities in
Key words: malaria -asymptomatic infection -control -Brazilian AmazonMalaria is the most widespread and most serious parasitic disease in the world. Forty percent of the world's population (2.4 billion people) is exposed to the infection, especially people who live in tropical and subtropical countries. In these regions, between 300 and 500 million cases are diagnosed every year, causing 1.5 to 2.7 million deaths per year, mostly among African children (WHO 2002). In 2001, according to a review by Hay et al. (2004), the overall incidence of malaria in the areas at risk in the world was 396 million cases, of which more than 80% were on the African continent, leading to the death of 1,123,000 cases, mostly children (Hay et al. 2004).In the Americas and in the Caribbean, 38% of the population (308 million people), in 21 countries, live in areas with malaria transmission, with a mean of 1.3 million cases per year. Thirty-six percent of these are in Brazil (OPS 1997, 1998, WHO 2002.Since 1970, when just over 52,000 cases were recorded in Brazil, malaria has gradually been increasing in this country. In the 1990s, the number of cases surpassed 500,000. In 1999, there were 610,000 notified cases of malaria in Brazil, and 99% of them were in the Amazon region (Ministério da Saúde 2003). Taking into account possible underreporting and cases of asymptomatic infection , Alves et al. 2002, Suárez-Mutis et al. 2004, Ladeia-Andrade 2005, it may be considered that more than 600,000 cases are occurring in Brazil every year (personal estimation). The number of cases of malaria re- show the areas at risk (Fig. 1) and the number of malaria cases notified in Brazil from 1970 to 2005 (Fig. 2).The course followed by malaria usually takes the form of a feverish acute systemic disease. The severity of the disease varies according to the parasite species (Plasmodium falciparum, P. vivax, P. malariae, and P. ovale; the last of these is not found in Brazil), the inoculum, the strain of the parasite, and the degree of previous immunity. Since the time of Hippocrates (460-377 BC), cases of infection of greater or lesser severity have been known. In 1900, Robert Koch first recognized cases of asymptomatic Plasmodium infection among patients in Papua New Guinea (Harrison 1978). This characteristic of malaria has been of concern for some time, particula...
