Spread and evolution of Plasmodium falciparum drug resistance

The frequency of asymptomatic malaria parasitaemia was investigated in rural and urban school-children aged six to 12 years in southwestern Nigeria between January 1987 and October 1988. Asymptomat...

Malaria in Nigeria: a revisit.

For a growing number of citizens, the upheavals caused by rapid urban development completely transform malaria epidemiology in tropical Africa. This paper is the first of a series on this phenomenon in Brazzaville, capital of the Congo Republic, where a third of the country's population is already concentrated. After describing the main human and physical geographical aspects of the town, the most significant results of the previous studies of this town and the surrounding rural area are reviewed. They show the existence, until the beginning of the 1950s of a stable, holoendemic situation characterized by a malaria prevalence approaching 90% in children in both urban and rural areas. Since then the intensive development of anti-malaria campaigns in urban areas over about ten years led temporarily to a considerable decrease in the level of endemicity, while in rural areas it remained unchanged. In the 1960s, the vector control and systematic chemoprophylactic measures gradually stopped, permitting the study of a new malaria dynamic related only to the evolving particularities of a changing urban ecosystem.

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_5/b_fdi_18-19/26255.pdf

Malaria and urbanization in central Africa: the example of Brazzaville. Part I: Description of the town and review of previous surveys.

Malaria is a protozoan disease transmitted by the bite of the Anopheles mosquito. Among five species that can infect humans, Plasmodium falciparum is responsible for the most severe human malaria. Resistance of P. falciparum to chloroquine and pyrimethamine/sulfadoxine, conventionally used antimalarial drugs, is already widely distributed in many endemic areas. As a result, artemisinin-based combination therapies have been rapidly and widely adopted as first-line antimalarial treatments since the mid-2000s. Recent population and evolutionary genetic analyses have proven that the geographic origins of parasite lineages resistant to the conventional drugs are considerably limited. Almost all resistance emerged from either Southeast Asia or South America. The Greater Mekong subregion in Southeast Asia is probably the most alarming source of resistance, from which P. falciparum resistant to chloroquine and pyrimethamine/sulfadoxine dispersed to Africa. The emergence of artemisinin resistance has also recently been confirmed in the Greater Mekong. The WHO Global Malaria Programme has recently launched a "Global Plan for Artemisinin Resistance Containment," which aims to prevent the spread of artemisinin resistance while also stopping the emergence of novel resistance. However, an inadequate understanding of a mechanism of artemisinin resistance and the lack of reliable genetic markers to monitor artemisinin resistance make it difficult to survey the spread of resistance. Elucidation of such markers would substantially contribute to the design of an effective policy for the containment of artemisinin resistance.

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Evolution of Plasmodium falciparum drug resistance: implications for the development and containment of artemisinin resistance.

The current incidence of pernicious attacks and of mortality due to malaria were studied in Brazzaville. The results of this study, which concerned all the medical units of the town, were analysed in terms of previous studies on the epidemiology of malaria transmission in the various districts of the town. It was estimated that the annual incidence of pernicious attacks in children in Brazzaville is 1.15 per thousand between 0 and 4 years, 0.25 per thousand between 5 and 9 years and 0.05 per thousand between 10 and 14 years. The annual mortality due to malaria was estimated at 0.43 per thousand between 0 and 4 years and 0.08 per thousand between 5 and 9 years. These values are about 30 times lower than those expected from the results of previous studies of the mortality due to malaria in intertropical Africa. Whereas considerable differences in intensity of malaria transmission exist in the different districts of Brazzaville, the incidence of pernicious attacks and the resulting mortality are remarkably unvarying whatever the level of transmission. In particular, similar results were observed for the sector Mfilou-Ngamaba-Ngangouoni, where malaria is holoendemic with over 100 infective bites per person per year and a parasite rate of 80.95% in schoolchildren, and the central sector of Poto-Poto-Ouenze-Moungali, where malaria is hypoendemic with less than one infective bite per person every three years and a parasite rate of less than 4% in schoolchildren. These results are discussed in terms of previous observations in urban and surrounding rural areas.(ABSTRACT TRUNCATED AT 250 WORDS)

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_5/b_fdi_18-19/26258.pdf

Malaria and urbanization in Central Africa: the example of Brazzaville: Part V: Pernicious attacks and mortality

Chloroquine-resistant falciparum malaria in Benin.

Chloroquine-resistant falciparum malaria in the Congo.

Chloroquine-resistant Plasmodium falciparum malaria from Ivory Coast.

24 cases of Plasmodium falciparum malaria in a group of 73 non-immune subjects coming mostly from central Africa have been tested in vitro for chloroquine sensitivity: 5 are sensitive, 19 are resistant among whom one is also quinine-resistant. The comparison of the major clinical and biological features in the two groups by methods of statistical calculation shows that the parasitological diagnosis is retarded and that hemolysis is more frequent in the strains of Plasmodium falciparum resistant to chloroquine. Thrombopenia is more frequent with chemosensitives strains. In any case, the delay between the first symptoms and the parasitological diagnosis is increased with an average of 17 days in comparison to what was observed in the 1970's. Under the influence of several complex factors including human ones, the clinical aspects are changed in comparison to forms usually observed. In this context of an extension of the emergence of the chemoresistance and in the aim of efficiency, only the quinine I.V., with an average dose of 16.5 mg/kg per day of quinine-base, has been chosen as a curative treatment during 5 days allowing a rapid recovery without after-effects for all the cases.

[Current aspects of imported drug-resistant Plasmodium falciparum].

La sensibilite a la chloroquine et au cycloguanil a ete etudiee sur des isolats de Plasmodium falciparum, preleves chez des patients en provenance d'Afrique tropicale n'ayant pas recu de medicament par un test isotopique in vitro ou par la mise en evidence de la mutation 5108N de la dihydrofolate reductase (DHFR). Une chimioresistance a la chloroquine ou au cycloguanil est constatee pour pres de la moitie des isolats. Les taux les plus eleves de chimioresistance sont observes dans les pays d'Afrique ou la transmission du paludisme est permanente. La frequence globale de la resistance conjointe a la chloroquine et aux antifoliniques se situe a 28 % en 1995-97. Un ajustement des recommandations chimioprophylactiques pour les pays d'Afrique francophone est propose.

R. Roue

Papers

Chloroquine-resistant falciparum malaria in Benin.

Chloroquine-resistant falciparum malaria in the Congo.

Chloroquine-resistant Plasmodium falciparum malaria from Ivory Coast.

[Current aspects of imported drug-resistant Plasmodium falciparum].

Resistance to chloroquine and cycloguanil of Plasmodium falciparum in patients arriving in France after travel in Africa without chemoprophylaxis