Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Malaria: Plasmodium togetherness a strategy for breeding success

20.02.2004


Malaria, which infects 600 million people in the world and leads annually to 2 million deaths, is the most widespread of infectious diseases. The pathological agent is a microscopic parasite of the Plasmodium genus which develops inside the host’s erythrocytes.

Plasmodia go through a series of asexual reproduction cycles before a transition takes place from asexual stages to production of sexual cells, the gametocytes or pre-gametes, in the host blood. The females of Anopheles, the mosquito vector, ingest blood and gametocytes during a nocturnal feed on human skin. The meal reaches the mosquito’s stomach where Plasmodium sexual reproduction takes place. An encounter and subsequent binding between a male and a female gametocyte produces a zygote which will give rise to infectious forms. These migrate up to the mosquito salivary glands. From there they are transmitted to humans during a second blood meal.

Experimental gametocyte counts in the blood ingested by mosquitoes that had bitten volunteers naturally infected with Plasmodium falciparum showed that these sexual forms are overdispersed, in other words they have a heterogeneous distribution in the mosquito stomach. Their numbers vary between the different blood meals taken on the same volunteer, a feature previously observed in the case of large parasites (macroparasites), such as microfilariae (250 microns).


The IRD team is researching Plasmodium biology and the modes of transmission from the vector to humans and from humans to the vector. They used a computerized simulation model (the individual based model) of gametocyte behaviour in human blood circulation and at the moment of ingestion by the mosquitoes, aiming to find an explanation for this heterogeneity and its role in the parasite’s reproduction.

In the microfilariae, nematode agents of filariases, heterogeneity in the number of parasites ingested by the mosquitoes results from queues of varying lengths they form in the capillaries. Thus a similar aggregation event might occur in Plasmodium gametocytes, even if their very small size (10 microns) theoretically predestine them for a homogeneous distribution in the mosquito stomach. Simulations tested this hypothesis, each assuming different quantities of circulating gametocytes. They showed that the heterogeneous distribution of gametocytes ingested by the mosquito is no chance feature but is density-dependent, increasing with the gametocyte density. This heterogeneity could result from gametocyte togetherness, or aggregation, in the blood capillaries, the clusters so formed persisting in the mosquito stomach where sexual reproduction takes place. Field experiments conducted in Senegal, then others in Cameroon, on blood ingested by mosquitoes from naturally infected volunteers have confirmed these results, thus validating the model the research team adopted.

Comparison of the behaviour of free and clustered gametocytes has illuminated an essential life-cycle characteristic of Plasmodium, the most extensively studied malaria parasite. Aggregation is a means of optimizing the zygote (fertilized ova) production, which results from the encounter and binding between two gametocytes of opposite sex, and therefore of enhancing the production of infectious forms and the parasite’s reproduction rate. Bound in the human host’s peripheral capillaries, male and female gametocytes ingested by a mosquito increase the likelihood of their meeting inside the propitious breeding ground the fly’s stomach provides. The gametocytes differentiate into gametes that possess no particular means of attraction, so this lover’s ritual of clustering is a sophisticated parasite reproduction strategy which compensates for its gametes’ lack of attraction mechanism. Further research is planned, with three main objectives: refining the gametocyte behaviour model; finding out the triggering mechanism behind the cell binding events, well known in the asexual forms which cause cerebral malaria; and identifying the factors that influence the cluster formation.

Marie Guillaume – DIC
Translation : Nicholas Flay

Marie Guillaume | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2004/fiche194.htm

More articles from Health and Medicine:

nachricht Researchers release the brakes on the immune system
18.10.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht Norovirus evades immune system by hiding out in rare gut cells
12.10.2017 | University of Pennsylvania School of Medicine

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>