Navigation Links
A genetic identity card for Plasmodium populations to improve control strategies
Date:11/8/2007

WHO figures show that malaria currently affects between 300 and 600 million people in various parts of the world. Several malaria-hit regions are experiencing an advance of the disease owing to the parasites increasing resistance to most antimalarial drugs. Any increase in efficacy of medical treatments, with optimal limitation of resistance, requires that scientists unravel the evolutionary strategies of the enemy they are fighting. One of the research leads involves prior determination of the population genetic structure of Plasmodium falciparum.

This work was recently accomplished by a joint team of researchers from the IRD and the CNRS (2). Dissections were conducted on over 10 000 mosquitoes of the species Anopheles gambiae and Anopheles funestus, two of the principal malaria vectors in Sub-Saharan Africa. The work was done simultaneously on two sites in Cameroon and one Kenyan site, all three strongly infected by malaria. This large-scale investigation resulted in the isolation of 746 Plasmodium falciparum oocysts from the gut of 183 infected mosquitoes.

Two years previously, a preliminary study carried out in Kenya by the same team solely on A. gambiae, had yielded 600 oocysts from 145 infected mosquitoes caught in 11 different localities. The oocyst of the parasite provided the researchers with a means of access to the diploid phase of the microorganism, containing all its genetic information. Up to then, nearly all studies aiming to determine the genetic structure of Plasmodium populations were elaborated with parasite samples taken from humans. However, that kind of genetic analysis results in several points of bias. With samples collected from humans, scientists can work only on the haploid phase of the parasite cycle during which only one example of each chromosome is present. Therefore they cannot measure the rate of association and organization between genes within populations.

Moreover, in the zones where malaria is endemic, infected individuals are bitten regularly by mosquito vectors. Consequently, there is a high frequency of infection of one subject by several Plasmodium falciparum with different genotypes. Monoinfected patients, the only ones that can be selected for a pertinent genetic analysis, are therefore too rare to enable scientists to obtain representative results.

Assays on short sequences of DNA located on the 14 chromosome pairs of the parasite genome enabled the IRD and CNRS team to draw up quite a detailed genetic identity card of the different populations studied. They revealed an extremely high rate of genetic diversity but also a considerable overall rate of inbreeding, approaching 50%. This high level of inbreeding can be explained by the existence of a process of self-fertilization, selfing (3), combined with a non-random genotypic distribution of parasite oocysts in the mosquito vector guts. The set of data corroborated those acquired in Kenya in 2005. They confirmed the persistence of a strong population genetic structure of Plasmodium between mosquito vectors, associated with a reproduction regime combining genetic mixing and selfing.

A genetic identity card of Plasmodium falciparum populations could help improve malaria control strategies. The use of mathematical models that take into account genetic information about parasite infection foci could then feasibly predict the changes occurring in genes involved in drug resistance. Therapies could then be targeted according to the evolution dynamics of Plasmodium populations with the aim of controlling parasite populations while minimizing resistance development. This study also proved that the parasites overall reproduction strategy is the same in the two vector species investigated. One of the approaches envisaged by the international scientific community for limiting morbidity from malaria would entail the progressive eradication of its principal vector Anopheles gambiae.

To achieve this some research teams envisage the introduction into the wild of mosquitoes modified genetically to render them incapable of transmitting the parasite to humans. However, seeing that Plasmodium can use a number of different vectors, neutralizing just one, albeit one of the most dangerous, runs the risk of weakening only slightly the efficiency of the parasites reproduction strategy which could then merely switch to the other available vectors.


'/>"/>

Contact: Gregory Flechet
fichesactu@paris.ird.fr
33-014-803-7607
Institut de Recherche Pour le Dveloppement
Source:Eurekalert

Related biology news :

1. Does the desire to consume alcohol and tobacco come from our genetic makeup?
2. Diverse genetic abnormalities lead to NF-κB activation in multiple myeloma
3. Many parents at-risk for cancer disclose genetic test results to children
4. Genetics determine optimal drug dose of common anticoagulant
5. Claims of sex-related differences in genetic association studies often not properly validated
6. American College of Medical Genetics responds to new FDA labeling decision for warfarin
7. UNC study questions FDA genetic-screening guidelines for cancer drug
8. Genome study shines light on genetic link to height
9. Selexis Announces Advanced Approach to Maximize Power of Genetic Elements for Rapid Development of High Performance Cell Lines
10. Genes, Environment and Health Initiative invests in genetic studies, environmental monitoring
11. Rutgers Genetics receives $7.8 million for autism research
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/29/2017)... 29, 2017  higi, the health IT company that ... North America , today announced a Series B ... of EveryMove. The new investment and acquisition accelerates higi,s ... to transform population health activities through the collection and ... higi collects and secures data today on behalf ...
(Date:3/27/2017)... N.Y. , March 27, 2017  Catholic ... Information and Management Systems Society (HIMSS) Analytics for ... EMR Adoption Model sm . In addition, CHS ... of U.S. hospitals using an electronic medical record ... for its high level of EMR usage in ...
(Date:3/24/2017)... Research and Markets has announced the addition ... Trends - Industry Forecast to 2025" report to their offering. ... The Global Biometric ... of around 15.1% over the next decade to reach approximately $1,580 ... market estimates and forecasts for all the given segments on global ...
Breaking Biology News(10 mins):
(Date:10/10/2017)... ... October 10, 2017 , ... For the ... won a US2020 STEM Mentoring Award. Representatives of the FirstHand program travelled to ... Experience from US2020. , US2020’s mission is to change the trajectory of STEM ...
(Date:10/10/2017)... PA (PRWEB) , ... October 10, 2017 , ... ... year’s recipients of 13 prestigious awards honoring scientists who have ... presented in a scheduled symposium during Pittcon 2018, the world’s leading conference and ...
(Date:10/9/2017)... ... October 09, 2017 , ... ... medical journal, Epilepsia, Brain Sentinel’s SPEAC® System which uses the surface electromyography ... generalized tonic-clonic seizures (GTCS) using surface electromyography (sEMG). The prospective multicenter phase ...
(Date:10/6/2017)... (PRWEB) , ... October 06, 2017 , ... ... host a lunch discussion and webinar on INSIGhT, the first-ever adaptive clinical trial ... Investigator, Dana-Farber Cancer Institute. The event is free and open to the public, ...
Breaking Biology Technology: