Malaria Transmission Studies in Mali
Condition: Malaria, Falciparum
MeSH terms: Malaria; Malaria, Falciparum
Study type: Observational

Summary: 
      Background:

      - Malaria is an illness caused by a parasite spread by mosquitoes. When a mosquito bites a
      person who is infected with a kind of parasite called a gametocyte, it is able to spread the
      infection to another person. Not everyone infected with parasites have gametocytes in their
      blood. As a result, not everyone can spread malaria to others. Researchers are interested in
      learning more about why some healthy people have gametocytes in their blood and others do
      not. Identifying the people who have gametocytes in their blood can help target treatment and
      reduce the spread of malaria. This study will focus on the people of the village of Kenieroba
      in Mali, where malaria is common.

      Objectives:

      - To study the relationship between gametocytes and malaria transmission in Mali.

      Eligibility:

      - Individuals between 6 months and 65 years of age who live in Kenieroba, Mali, and will stay
      in the area for 1 year.

      Design:

        -  For 1 year, participants will have study visits once every 2 weeks (twice a month, for a
           total of 24 visits). The visits will last 30 minutes each.

        -  At each visit, participants will provide a small blood sample. They will report any
           symptoms of malaria such as fever, headache, and body aches. Participants will be
           encouraged to seek medical treatment if they experience malaria symptoms between visits.

        -  Participants who have malaria symptoms will have a blood test for malaria parasites.
           Those who have parasites in the blood will receive antimalarial treatment.

        -  Three times over 1 year, a larger blood sample will be collected. These blood samples
           will be taken once in the dry season, once in the wet season, and once in the next dry
           season.

        -  Women between 14 and 45 years of age will also provide urine samples to test for
           pregnancy. Pregnant women will not be asked to give blood samples.
    

Detailed description: 
      Plasmodium falciparum malaria continues to evade control efforts in part through the
      complexity of its life cycle, which involves both humans and mosquitoes. While it is known
      that the gametocyte form of the parasite transmits disease, it is unclear which individuals
      constitute the primary gametocyte reservoir in a given human population. It is also unclear
      how an individual s asexual parasite density, acquired immune responses, and red blood cell
      (RBC) polymorphisms affect the presence and transmission of gametocytes. Investigating these
      effects has been limited in part because gametocytes are often present in peripheral blood at
      densities below the limit of microscopic detection. Recent technical advances in the
      molecular detection of gametocytes have set the stage for a better understanding of
      gametocyte epidemiology and biology in humans. In a setting of highly seasonal transmission,
      we are conducting an epidemiological study to estimate gametocyte prevalence over 1 year in
      the village of Kenieroba, Mali. In a cohort of 500 individuals that represents the
      age-distribution of the entire village population, we will explore how age, asexual parasite
      prevalence, season, and RBC polymorphisms affect variation in gametocyte prevalence (detected
      by a sensitive molecular method). From these same individuals, we will purify plasma IgG and
      compare its transmission-blocking activity by age group and season. These assessments will
      provide a foundation for future studies of gametocytemia dynamics within individuals as well
      as the impact of host immunity on gametocyte infectivity in our study population. Such
      information will enable us to identify those individuals that are primarily responsible for
      malaria transmission in Kenieroba. Incorporation of such findings into new or existing
      computer-based models of parasite infection and transmission may improve our evaluation of
      existing malaria control strategies.
    

Time perspective: Prospective
Keywords: Asymptomatic Parasitemia; RBC Polymorphism; Acquired Immunity