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Genetic diversity of Plasmodium falciparum in human malaria cases in Mali.

Nabet C, Doumbo S, Jeddi F, Konaté S, Manciulli T, Fofana B, L'Ollivier C, Camara A, Moore S, Ranque S, Théra MA, Doumbo OK, Piarroux R - Malar. J. (2016)

Bottom Line: The lack of linkage disequilibrium further revealed an absence of local clonal expansion, which was corroborated by the genotype relationship results.Indeed, results suggest that parasite populations are polymorphic enough to adapt to their host and to counteract interventions, such as anti-malarial vaccination.Additionally, the panmictic parasite population structure imply that resistance traits may disseminate freely from one area to another, making control measures performed at a local level ineffective.

View Article: PubMed Central - PubMed

Affiliation: UMR MD3 IP-TPT, Parasitology Laboratory, Timone Hospital, Aix-Marseilles University, Marseilles, France. cecile.nabet@ap-hm.fr.

ABSTRACT

Background: In Mali, Plasmodium falciparum malaria is highly endemic and remains stable despite the implementation of various malaria control measures. Understanding P. falciparum population structure variations across the country could provide new insights to guide malaria control programmes. In this study, P. falciparum genetic diversity and population structure in regions of varying patterns of malaria transmission in Mali were analysed.

Methods: A total of 648 blood isolates adsorbed onto filter papers during population surveillance surveys (December 2012-March 2013, October 2013) in four distinct sites of Mali were screened for the presence of P. falciparum via quantitative PCR (qPCR). Multiple loci variable number of tandem repeats analysis (MLVA) using eight microsatellite markers was then performed on positive qPCR samples. Complete genotypes were then analysed for genetic diversity, genetic differentiation and linkage disequilibrium.

Results: Of 156 qPCR-positive samples, complete genotyping of 112 samples was achieved. The parasite populations displayed high genetic diversity (mean He = 0.77), which was consistent with a high level of malaria transmission in Mali. Genetic differentiation was low (FST < 0.02), even between sites located approximately 900 km apart, thereby illustrating marked gene flux amongst parasite populations. The lack of linkage disequilibrium further revealed an absence of local clonal expansion, which was corroborated by the genotype relationship results. In contrast to the stable genetic diversity level observed throughout the country, mean multiplicity of infection increased from north to south (from 1.4 to 2.06) and paralleled malaria transmission levels observed locally.

Conclusions: In Mali, the high level of genetic diversity and the pronounced gene flux amongst P. falciparum populations may represent an obstacle to control malaria. Indeed, results suggest that parasite populations are polymorphic enough to adapt to their host and to counteract interventions, such as anti-malarial vaccination. Additionally, the panmictic parasite population structure imply that resistance traits may disseminate freely from one area to another, making control measures performed at a local level ineffective.

No MeSH data available.


Related in: MedlinePlus

Maps of Mali showing four study sites and four malaria epidemiological patterns [6, 24]. Annual isohyets (mm) separate each climatic zone. The climatic zones from north to south are as follows: Saharian zone (malaria transmission is sporadic to epidemic), Sahelian and Sudano-Sahelian zones (hyper-endemic for malaria, short transmission season of 3–4 months), Sudano-Guinean zone (hyper-endemic for malaria, long transmission season of 4–6 months). In the urban area of Bamako, conditions are not favourable for malaria transmission (hypo-endemic malaria)
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Fig1: Maps of Mali showing four study sites and four malaria epidemiological patterns [6, 24]. Annual isohyets (mm) separate each climatic zone. The climatic zones from north to south are as follows: Saharian zone (malaria transmission is sporadic to epidemic), Sahelian and Sudano-Sahelian zones (hyper-endemic for malaria, short transmission season of 3–4 months), Sudano-Guinean zone (hyper-endemic for malaria, long transmission season of 4–6 months). In the urban area of Bamako, conditions are not favourable for malaria transmission (hypo-endemic malaria)

Mentions: Blood samples were collected in Rharous (Timbuktu District), Bamako (Bamako District), Doneguebougou (Kati District), and Bougoula Hameau (Sikasso District) (Fig. 1). Each of the study sites represents a different pattern of malaria transmission as defined by previous Malian epidemiological reports [6, 24, 25]. According to these reports, malaria is hypo-endemic in the urban zone of Bamako, whereas the disease is sporadic with occasional epidemics in Rharous, which is located in the Sahara Desert. Malaria is hyper-endemic in Doneguebougou [a site located in the Sudano-Sahelian zone, where malaria is characterized by a short transmission season (3–4 months)] and Bougoula [which is located in the Sudano-Guinean zone, where the transmission season is longer (4–6 months)].Fig. 1


Genetic diversity of Plasmodium falciparum in human malaria cases in Mali.

Nabet C, Doumbo S, Jeddi F, Konaté S, Manciulli T, Fofana B, L'Ollivier C, Camara A, Moore S, Ranque S, Théra MA, Doumbo OK, Piarroux R - Malar. J. (2016)

Maps of Mali showing four study sites and four malaria epidemiological patterns [6, 24]. Annual isohyets (mm) separate each climatic zone. The climatic zones from north to south are as follows: Saharian zone (malaria transmission is sporadic to epidemic), Sahelian and Sudano-Sahelian zones (hyper-endemic for malaria, short transmission season of 3–4 months), Sudano-Guinean zone (hyper-endemic for malaria, long transmission season of 4–6 months). In the urban area of Bamako, conditions are not favourable for malaria transmission (hypo-endemic malaria)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940954&req=5

Fig1: Maps of Mali showing four study sites and four malaria epidemiological patterns [6, 24]. Annual isohyets (mm) separate each climatic zone. The climatic zones from north to south are as follows: Saharian zone (malaria transmission is sporadic to epidemic), Sahelian and Sudano-Sahelian zones (hyper-endemic for malaria, short transmission season of 3–4 months), Sudano-Guinean zone (hyper-endemic for malaria, long transmission season of 4–6 months). In the urban area of Bamako, conditions are not favourable for malaria transmission (hypo-endemic malaria)
Mentions: Blood samples were collected in Rharous (Timbuktu District), Bamako (Bamako District), Doneguebougou (Kati District), and Bougoula Hameau (Sikasso District) (Fig. 1). Each of the study sites represents a different pattern of malaria transmission as defined by previous Malian epidemiological reports [6, 24, 25]. According to these reports, malaria is hypo-endemic in the urban zone of Bamako, whereas the disease is sporadic with occasional epidemics in Rharous, which is located in the Sahara Desert. Malaria is hyper-endemic in Doneguebougou [a site located in the Sudano-Sahelian zone, where malaria is characterized by a short transmission season (3–4 months)] and Bougoula [which is located in the Sudano-Guinean zone, where the transmission season is longer (4–6 months)].Fig. 1

Bottom Line: The lack of linkage disequilibrium further revealed an absence of local clonal expansion, which was corroborated by the genotype relationship results.Indeed, results suggest that parasite populations are polymorphic enough to adapt to their host and to counteract interventions, such as anti-malarial vaccination.Additionally, the panmictic parasite population structure imply that resistance traits may disseminate freely from one area to another, making control measures performed at a local level ineffective.

View Article: PubMed Central - PubMed

Affiliation: UMR MD3 IP-TPT, Parasitology Laboratory, Timone Hospital, Aix-Marseilles University, Marseilles, France. cecile.nabet@ap-hm.fr.

ABSTRACT

Background: In Mali, Plasmodium falciparum malaria is highly endemic and remains stable despite the implementation of various malaria control measures. Understanding P. falciparum population structure variations across the country could provide new insights to guide malaria control programmes. In this study, P. falciparum genetic diversity and population structure in regions of varying patterns of malaria transmission in Mali were analysed.

Methods: A total of 648 blood isolates adsorbed onto filter papers during population surveillance surveys (December 2012-March 2013, October 2013) in four distinct sites of Mali were screened for the presence of P. falciparum via quantitative PCR (qPCR). Multiple loci variable number of tandem repeats analysis (MLVA) using eight microsatellite markers was then performed on positive qPCR samples. Complete genotypes were then analysed for genetic diversity, genetic differentiation and linkage disequilibrium.

Results: Of 156 qPCR-positive samples, complete genotyping of 112 samples was achieved. The parasite populations displayed high genetic diversity (mean He = 0.77), which was consistent with a high level of malaria transmission in Mali. Genetic differentiation was low (FST < 0.02), even between sites located approximately 900 km apart, thereby illustrating marked gene flux amongst parasite populations. The lack of linkage disequilibrium further revealed an absence of local clonal expansion, which was corroborated by the genotype relationship results. In contrast to the stable genetic diversity level observed throughout the country, mean multiplicity of infection increased from north to south (from 1.4 to 2.06) and paralleled malaria transmission levels observed locally.

Conclusions: In Mali, the high level of genetic diversity and the pronounced gene flux amongst P. falciparum populations may represent an obstacle to control malaria. Indeed, results suggest that parasite populations are polymorphic enough to adapt to their host and to counteract interventions, such as anti-malarial vaccination. Additionally, the panmictic parasite population structure imply that resistance traits may disseminate freely from one area to another, making control measures performed at a local level ineffective.

No MeSH data available.


Related in: MedlinePlus