Partner study description

Researchers at the Tanzanian National Institute for Medical Research contributed samples from individuals in eight villages in the Muheza district in northeastern Tanzania.

Four of these villages are located in lowland and four in highland areas. Malaria is more common in lowland areas, where people are bitten up to 15 times more frequently by infected mosquitoes than in highland areas (EIR range 30-400 ib/p/year). The area has two rainy seasons, a short one (November-December) and a long one (March-July). Malaria transmission is highest in both highland and lowland areas during and following the long rainy season.

The 769 paired DNA and plasma samples contributed to Consortial Project 2 (CP2) come from a cross-sectional survey conducted in July 2004, at the end of the long rainy season.

Study population

The study population comprises 39 different ethnic groups, of which the Wasambaa (42%) and Wadigo (26%) are the major tribes. These two groups are almost mutually exclusive within the study villages.

Children (0-15 years) make up for two thirds of the study population and slightly less than a quarter of these were under 5 years old.

Morbidity and infection density

Infection with malaria parasites (P. falciparum, P. malariae and P. ovale) was determined by inspection of blood smears on slides. Asexual (blood stage) forms of the parasites and gametocytes were counted and parasite density recorded relative to the number of white blood cells in the same sample.

Clinical Information

A special feature of this data set is the extensive clinical information on morbidity and drug treatment history that was recorded for all individuals in this survey. Of the recorded parameters, temperature, history of fever, haemoglobin levels, and spleen enlargement are the most relevant of in establishing whether a malaria episode is symptomatic or asymptomatic, mild or severe. Of the 278 infected individuals, 55 (20%) were symptomatic.

Study summary

Cross-sectional survey

769 samples

Age range: 0-47
< 5 years: 118 (15%)
5-15 years: 428 (56%)
> 15 years: 223 (29%)

Female: 411 (53%)

Infected: 278 (36%)

Publications

• A global network for investigating the genomic epidemiology of malaria
  Malaria Genomic Epidemiology Network
  Nature, 2008; 456(7223) 732-7
  10.1038/nature07632