Paper on the evolution of malaria
As we have previously discussed malaria here (see tag "Malaria"), I thought it would be of interest to take a look at the following paper:
Mideo N, Day T. On the evolution of reproductive restraint in malaria. Proc Biol Sci. 2008 Feb 26 (Epub ahead of print, http://dx.doi.org/10.1098/rspb.2007.1545 , requires subscription).
Abstract:
Malaria is one of the leading causes of death among infectious diseases in the world, claiming over one million lives every year. By these standards, this highly complex parasite is extremely successful at generating new infections. Somewhat surprisingly, however, many malaria species seem to invest relatively little in gametocytes, converting only a small percentage of circulating asexual parasite forms into this transmissible form. In this article, we use mathematical models to explore three of the hypotheses that have been proposed to explain this apparent ‘reproductive restraint’ and develop a novel, fourth hypothesis. We find that only one of the previous three hypotheses we explore can explain such low gametocyte conversion rates, and this hypothesis involves a very specific form of density-dependent transmission-blocking immunity. Our fourth hypothesis also provides a potential explanation and is based on the occurrence of multiple infections and the resultant within-host competition between malaria strains that this entails. Further experimental work is needed to determine which of these two hypotheses provides the most likely explanation.
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Dear sir;
By Abdul Waheed KandhroDear sir;
The Impact of Malaria, a Leading Cause of Death Worldwide
Malaria is one of the most severe public health problems worldwide. It is a leading cause of death and disease in many developing countries, where young children and pregnant women are the groups most affected. It is considered a Leading Causes of Death in Children under Five Years of Age,
Geography
Malaria occurs mostly in poor, tropical and subtropical areas of the world . The area most affected is Africa south of the Sahara, where an estimated 90% of the deaths due to malaria occur. This is due to a combination of factors:
• A very efficient mosquito vector (Anopheles cambia) assures high transmission
• The predominant parasite species is Plasmodium falciparum, which causes the most severe form of malaria
• Local weather conditions often allow transmission to occur year round
• Scarce resources and socio-economic instability hinder efficient malaria control activities.
In other areas of the world malaria is a less prominent cause of deaths, but can cause substantial disease and incapacitation, especially in rural areas of some countries in South America and Southeast Asia.
How Malaria Affects People's Health
Malaria can affect a person's health in various ways. People who have developed protective immunity (through past infections, as is the case with most adults in high transmission areas) may be infected but not made ill by the parasites they carry In most cases, malaria causes fever, chills, headache, muscle ache, vomiting, malaise and other flu-like symptoms, which can be very incapacitating Some persons infected with Plasmodium falciparum can develop complications such as brain disease (cerebral malaria), severe anemia, and kidney failure. These severe forms occur more frequently in people with little protective immunity, and can result in death or life-long neurologic impairment