Characteristics of Plasmodium falciparum parasites that survive the lengthy dry season in eastern Sudan where malaria transmission is markedly seasonal.

1998 ◽  
Vol 59 (4) ◽  
pp. 582-590 ◽  
Author(s):  
H A Babiker ◽  
A M Abdel-Muhsin ◽  
D Walliker ◽  
L C Ranford-Cartwright ◽  
G Satti
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Dry Season ◽  
Eastern Sudan

Population dynamics of Plasmodium falciparum in an unstable malaria area of eastern Sudan

Parasitology ◽  
2000 ◽  
Vol 120 (2) ◽  
pp. 105-111 ◽  
Author(s):  
H. A. BABIKER ◽  
A. A. ABDEL-MUHSIN ◽  
A. HAMAD ◽  
M. J. MACKINNON ◽  
W. G. HILL ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Population Dynamics ◽  
Malaria Transmission ◽  
Dry Season ◽  
Allele Frequencies ◽  
Wet Season ◽  
Transmission Season ◽  
Large Repertoire ◽  
Eastern Sudan

The Plasmodium falciparum population in Asar village, eastern Sudan, where malaria transmission is markedly seasonal, was monitored monthly over a period of 15 months. A cohort of infected patients was treated and then followed monthly throughout the dry season until the next transmission season. Parasitaemia detected by microscopy among the cohort reduced dramatically following treatment, but remained sporadic during the dry season, and reappeared following the onset of the next wet season. However between 40 and 50% of the cohort retained a persisting parasitaemia detectable by PCR throughout the dry season. These parasites were genetically complex, consisting of multiple clones with a large repertoire of alleles of the studied genes. While the number of clones per host dropped significantly following treatment of acute cases during the transmission season, drug treated people nevertheless maintained an average of one clone throughout the dry season. Allele frequencies of MSP-1, MSP-2 and GLURP showed slight, statistically insignificant, fluctuations between the dry and wet seasons. A higher frequency of inbreeding was estimated among the parasites that survived the dry season compared to the wet season.

Overlapping antigenic repertoires of variant antigens expressed on the surface of erythrocytes infected by Plasmodium falciparum

Parasitology ◽  
1999 ◽  
Vol 119 (1) ◽  
pp. 7-17 ◽  
Author(s):  
H. A. GIHA ◽  
T. STAALSOE ◽  
D. DODOO ◽  
I. M. ELHASSAN ◽  
C. ROPER ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Plasmodium Falciparum ◽  
Membrane Protein ◽  
Malaria Transmission ◽  
Erythrocyte Membrane ◽  
Clonal Variation ◽  
Single Infection ◽  
Erythrocyte Membrane Protein ◽  
Degree Of Overlap ◽  
Eastern Sudan

Antibodies against variable antigens expressed on the surface of Plasmodium falciparum-infected erythrocytes are believed to be important for protection against malaria. A target for these antibodies is the P. falciparum erythrocyte membrane protein 1, PfEMP1, which is encoded by around 50 var genes and undergoes clonal variation. Using agglutination and mixed agglutination tests and flow cytometry to analyse the recognition of variant antigens on parasitized erythrocytes by plasma antibodies from individuals living in Daraweesh in eastern Sudan, an area of seasonal and unstable malaria transmission, we show that these antibodies recognize different variant antigens expressed by parasites of different genotype. Comparing the levels and acquisition of antibody to variant antigens in pairs of parasite isolates expressing different variant types, there is a correlation between the acquisition of antibodies to some combinations of variant antigens but not to others. These results indicate that (1) a single infection will induce the production of antibodies recognizing several variants of surface-expressed antigens, (2) the repertoire of variable antigens expressed by different parasites is overlapping and the degree of overlap differs between isolates, and (3) the expression of at least some variant antigens is genetically linked.

scholarly journals Impact of an Irrigation Dam on the Transmission and Diversity of Plasmodium falciparum in a Seasonal Malaria Transmission Area of Northern Ghana

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Eric Kyei-Baafour ◽  
Bernard Tornyigah ◽  
Benjamin Buade ◽  
Langbong Bimi ◽  
Abraham R. Oduro ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Parasite Density ◽  
Parasite Prevalence ◽  
Dry Season ◽  
Water Bodies ◽  
Northern Ghana ◽  
Wet Season ◽  
Transmission Area ◽  
Dam Site

Water bodies such as dams are known to alter the local transmission patterns of a number of infectious diseases, especially those transmitted by insects and other arthropod vectors. The impact of an irrigation dam on submicroscopic asexual parasite carriage in individuals living in a seasonal malaria transmission area of northern Ghana was investigated. A total of 288 archived DNA samples from two cross-sectional surveys in two communities in the Bongo District of Northern Ghana were analysed. Parasite density was determined by light microscopy and PCR, and parasite diversity was assessed by genotyping of the polymorphic Plasmodium falciparum msp2 block-3 region. Submicroscopic parasitaemia was estimated as the proportional difference between positive samples identified by PCR and microscopy. Dry season submicroscopic parasite prevalence was significantly higher (71.0%, p=0.013) at the dam site compared with the nondam site (49.2%). Similarly, wet season submicroscopic parasite prevalence was significantly higher at the dam site (54.5%, p=0.008) compared with the nondam site (33.0%). There was no difference in parasite density between sites in the dry season (p=0.90) and in the wet season (p=0.85). Multiplicity of infection (MOI) based on PCR data was significantly higher at the dam site compared with the nondam site during the dry season (p<0.0001) but similar between sites during the wet season. MOI at the nondam site was significantly higher in the wet season than in the dry season (2.49, 1.26, p<0.0001) but similar between seasons at the dam site. Multivariate analysis showed higher odds of carrying submicroscopic parasites at the dam site in both dry season (OR = 7.46, 95% CI = 3.07–18.15) and in wet season (OR = 1.73, 95% CI = 1.04–2.86). The study findings suggest that large water bodies impact year-round carriage of submicroscopic parasites and sustain Plasmodium transmission.

scholarly journals Plasmodium falciparum increases its investment in gametocytes in the wet season in asymptomatic individuals

2020 ◽  
Author(s):  
Colins O. Oduma ◽  
Sidney Ogolla ◽  
Harrysone Atieli ◽  
Bartholomew N. Ondigo ◽  
Ming-Chieh Lee ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Parasite Prevalence ◽  
Dry Season ◽  
Wet Season ◽  
Western Kenya ◽  
Gametocyte Carriage ◽  
Vector Abundance ◽  
Asymptomatic Individuals

AbstractIn many regions, malaria transmission is seasonal, but it is not well understood whether P. falciparum modulates its investment in transmission in response to seasonal vector abundance. In two sites in western Kenya (Chulaimbo and Homa Bay), we sampled 1116 asymptomatic individuals in the wet season, when vectors are abundant, and 1743 in the dry season. We screened for P. falciparum by qPCR, and gametocytes by pfs25 RT-qPCR. Parasite prevalence in Chulaimbo and Homa Bay was 27.1% and 9.4% in the dry season, and 48.2% and 7.8% in the wet season respectively. Mean parasite densities did not differ between seasons (P=0.562). A contrasting pattern of gametocyte carriage was observed. In the wet season, fewer infections harbored gametocytes (22.3% vs. 33.8%, P=0.009), but densities were 3-fold higher (P<0.001). Thus, in the wet season, among gametocyte positive individuals, higher proportion of all parasites were gametocytes, reflecting an increased investment in transmission.

scholarly journals PO 8418 NEW MALARIA EPIDEMIOLOGY IN COASTAL LAGOON OF BENIN: PLASMODIUM INFECTION IN ANOPHELES MELAS

2019 ◽  
Vol 4 (Suppl 3) ◽  
pp. A35.1-A35
Author(s):  
Claudiane Adigbonon ◽  
Benoît S Assogba ◽  
Luc S Djogbenou
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Malaria Transmission ◽  
Coastal Lagoon ◽  
Plasmodium Malariae ◽  
Dry Season ◽  
Anopheles Coluzzii ◽  
Plasmodium Ovale ◽  
Malaria Epidemiology ◽  
Tropical Areas

IntroductionMalaria is a worldwide disease affecting many people particularly in the tropical and sub-tropical areas. It is caused by Plasmodium parasites and essentially transmitted by female mosquitoes belonging to the Anopheles genus. Our understanding of the infectivity of these vectors to Plasmodium is necessary to design sustainable strategies for their control. This aspect remains unknown in the coastal and lagoon area of Benin where Anopheles melas and Anopheles coluzzii are sympatric. This study aims to investigate the infectivity of these two vectors to Plasmodium to understand their role in malaria transmission in southern Benin.MethodsInsecticide spray catch technique was used to collect females in 80 houses randomly selected in our study site. Three hundred and twenty (320) females were identified using PCR–species technique, Plasmodium infection was determined by the TaqMan method during the dry season. This assay detects all four malaria-causing species and discriminates Plasmodium falciparum from Plasmodium ovale, Plasmodium vivax and Plasmodium malariae (OVM).ResultsDuring the dry season, the sporozoïte rates were 0.2% and 0.3% for Anopheles melas and Anopheles coluzzii, respectively. However, we observed that positivity to the OVM (one of Plasmodium ovale, Plasmodium vivax and Plasmodium malariae species) was significantly higher in Anopheles melas (95%) than in Anopheles coluzzii (33.33%) (Chi-sq=15 857, df=1, p<0.001). These results indicated that Anopheles melas is more infected by one of the species Plasmodium ovale, Plamodium vivax and Plasmodium malariae than by Plasmodium falciparum, contrarily to Anopheles coluzzii.ConclusionThese findings reinforce the debate on the role of Anopheles melas in malaria transmission in coastal lagoon areas of Benin.

scholarly journals Chronic Plasmodium falciparum infections in an area of low intensity malaria transmission in the Sudan

Parasitology ◽  
2000 ◽  
Vol 120 (5) ◽  
pp. 447-456 ◽  
Author(s):  
A. A. HAMAD ◽  
I. M. EL HASSAN ◽  
A. A. EL KHALIFA ◽  
G. I. AHMED ◽  
S. A. ABDELRAHIM ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Marker Gene ◽  
Allelic Polymorphism ◽  
Chain Reaction ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Polymerase Chain ◽  
The Village ◽  
Eastern Sudan

Chronic Plasmodium falciparum malaria infections in a Sudanese village, in an area of seasonal and unstable malaria transmission, were monitored and genetically characterized to study the influence of persistent infection on the immunology and epidemiology of low endemicity malaria. During the October–December malaria season of 1996, 51 individuals out of a population of 420 had confirmed and treated P. falciparum malaria in the village of Daraweesh in eastern Sudan. In a cross-sectional survey carried out in December 1996, an additional 6 individuals were found to harbour a microscopically negative but polymerase chain reaction (PCR)-positive P. falciparum infection. On 1 January 1997, a cohort of 43 individuals aged from 9 to 53, recruited from this group of recently malaria-infected individuals agreed to donate fortnightly blood samples for the next 9 months, the first 6 of which constitute the long Sudanese dry season when transmission falls to undetectable levels. Each blood sample was tested for the presence of persistent malaria infection by microscopy and PCR. Parasite-positive samples were genotyped using PCR assays that detect allelic polymorphism at the MSP-1, MSP-2 and GLURP marker gene loci. Of 43 individuals 16 were found to maintain chronic P. falciparum infections which were continuously genetically characterized.

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