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Asymptomatic Plasmodium vivax infections among Duffy-negative population in Kedougou, Senegal.

ABSTRACT: Background:In the southeastern Senegal, the report of Plasmodium vivax infections among febrile patients in Kedougou constitutes a new emerging health problem. Methods:Samples from 48 asymptomatic schoolchildren sampled twice a year over 2?years were used to explore the reservoir of P. vivax parasite infections in this region. Both Duffy genotyping and Plasmodium species diagnostic assays were performed. Results:PCR assays detected Plasmodium genomic DNA in 38.5% (74/192) of samples. Pure P. falciparum and P. vivax infections were identified in 79.7% (59/74) and 20.3% (15/74) of samples, respectively. All schoolchildren were classified as Duffy-negative by genotyping. P. vivax infections were detected in five children: in two children during both years, in one child in 2010 and on May 2011, and only in 2010 for the remaining two children. Conclusions:This unexpectedly high proportion of P. vivax infections in asymptomatic Duffy-negative children highlights to consider vivax malaria as an emerging problem in Senegal.

SUBMITTER: Niang M

PROVIDER: S-EPMC6311047 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Asymptomatic <i>Plasmodium vivax</i> infections among Duffy-negative population in Kedougou, Senegal.

Niang Makhtar M Sane Rokhaya R Sow Abdourahmane A Sadio Bacary D BD Chy Sophy S Legrand Eric E Faye Ousmane O Diallo Mawlouth M Sall Amadou A AA Menard Didier D Toure-Balde Aissatou A

Tropical medicine and health 20181229

<h4>Background</h4>In the southeastern Senegal, the report of <i>Plasmodium vivax</i> infections among febrile patients in Kedougou constitutes a new emerging health problem.<h4>Methods</h4>Samples from 48 asymptomatic schoolchildren sampled twice a year over 2 years were used to explore the reservoir of <i>P. vivax</i> parasite infections in this region. Both Duffy genotyping and <i>Plasmodium</i> species diagnostic assays were performed.<h4>Results</h4>PCR assays detected <i>Plasmodium</i> gen ...[more]

PMID: 30618490

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Project description:BackgroundControl efforts towards malaria due to Plasmodium falciparum significantly decreased the incidence of the disease in many endemic countries including Senegal. Surprisingly, in Kedougou (southeastern Senegal) P. falciparum malaria remains highly prevalent and the relative contribution of other Plasmodium species to the global malaria burden is very poorly documented, partly due to the low sensitivity of routine diagnostic tools. Molecular methods offer better estimate of circulating Plasmodium species in a given area. A molecular survey was carried out to document circulating malaria parasites in Kedougou region.MethodsA total of 263 long-term stored sera obtained from patients presenting with acute febrile illness in Kedougou between July 2009 and July 2013 were used for malaria parasite determination. Sera were withdrawn from a collection established as part of a surveillance programme of arboviruses infections in the region. Plasmodium species were characterized by a nested PCR-based approach targeting the 18S small sub-unit ribosomal RNA genes of Plasmodium spp.ResultsOf the 263 sera screened in this study, Plasmodium genomic DNA was amplifiable by nested PCR from 62.35% (164/263) of samples. P. falciparum accounted for the majority of infections either as single in 85.97% (141/164) of Plasmodium-positive samples or mixed with Plasmodium ovale (11.58%, 19/164) or Plasmodium vivax (1.21%, 2/164). All 19 (11.58%) P. ovale-infected patients were mixed with P. falciparum, while no Plasmodium malariae was detected in this survey. Four patients (2.43%) were found to be infected by P. vivax, two of whom were mixed with P. falciparum. P. vivax infections originated from Bandafassi and Ninefesha villages and concerned patients aged 4, 9, 10, and 15 years old, respectively. DNA sequences alignment and phylogenetic analysis demonstrated that sequences from Kedougou corresponded to P. vivax, therefore confirming the presence of P. vivax infections in Senegal.ConclusionThe results confirm the high prevalence of P. falciparum in Kedougou and provide the first molecular evidence of P. vivax infections in Senegal. These findings pave the ways for further investigations of P. vivax infections in Senegal and its contribution to the global burden of malaria disease before targeted strategies can be deployed.

Project description:Expanded malaria control efforts in Sénégal have resulted in increased use of rapid diagnostic tests (RDT) to identify the primary disease-causing Plasmodium species, Plasmodium falciparum. However, the type of RDT utilized in Sénégal does not detect other malaria-causing species such as Plasmodium ovale spp., Plasmodium malariae, or Plasmodium vivax. Consequently, there is a lack of information about the frequency and types of malaria infections occurring in Sénégal. This study set out to better determine whether species other than P. falciparum were evident among patients evaluated for possible malaria infection in Kédougou, Sénégal.Real-time polymerase chain reaction speciation assays for P. vivax, P. ovale spp., and P. malariae were developed and validated by sequencing and DNA extracted from 475 Plasmodium falciparum-specific HRP2-based RDT collected between 2013 and 2014 from a facility-based sample of symptomatic patients from two health clinics in Kédougou, a hyper-endemic region in southeastern Sénégal, were analysed.Plasmodium malariae (n = 3) and P. ovale wallikeri (n = 2) were observed as co-infections with P. falciparum among patients with positive RDT results (n = 187), including one patient positive for all three species. Among 288 negative RDT samples, samples positive for P. falciparum (n = 24), P. ovale curtisi (n = 3), P. ovale wallikeri (n = 1), and P. malariae (n = 3) were identified, corresponding to a non-falciparum positivity rate of 2.5%.These findings emphasize the limitations of the RDT used for malaria diagnosis and demonstrate that non-P. falciparum malaria infections occur in Sénégal. Current RDT used for routine clinical diagnosis do not necessarily provide an accurate reflection of malaria transmission in Kédougou, Sénégal, and more sensitive and specific methods are required for diagnosis and patient care, as well as surveillance and elimination activities. These findings have implications for other malaria endemic settings where species besides P. falciparum may be transmitted and overlooked by control or elimination activities.

Dataset Information

Asymptomatic Plasmodium vivax infections among Duffy-negative population in Kedougou, Senegal.

Publications

Asymptomatic <i>Plasmodium vivax</i> infections among Duffy-negative population in Kedougou, Senegal.

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