The incidence of clinical malaria detected by active case detection in children in Ifakara, southern Tanzania

Abstract

Between July 2000 and June 2001, we used weekly active case detection (ACD) of clinical malaria episodes in 618 children aged <5 years to describe the epidemiology of malaria in Ifakara, southern Tanzania. Plasmodium falciparnm-positive blood slides prepared from children with axillary temperature ~>37.5°C were used to define clinical malaria and a rolling cross-sectional survey documented the prevalences of parasitaemia and anaemia. A random subsample of children was visited daily for 1 month at the end of the study to assess the effect of more frequent visits on estimated incidence rates. Only 50 (8%) children had 1 or more episodes of clinical malaria during the year, an overall incidence of 0.275 episodes/100 child-weeks-at-risk, with no age dependence. The maximum parasite prevalence of 25% was reached in children aged 4 years. The incidence of illness was significantly lower in children visited daily than in those visited weekly, suggesting a marked effect of frequent visits on estimated incidence rates. We conclude that the age pattern of malaria detected through ACD is a more robust epidemiological indicator than absolute incidence rate estimates and that, in contrast to the surrounding area, Ifakara town is subject to only moderate perennial malaria transmission.

Estimates of the changing age-burden of Plasmodium falciparum malaria disease in sub-Saharan Africa

“…A variety of definitions of clinical malaria were reported, falling into two groups: malaria symptoms (fever and sometimes other symptoms) plus any parasitaemia2425262728293031; or malaria symptoms plus parasite density above a certain threshold. The threshold was either fixed32; dependent on transmission intensity, increasing at higher transmission33; or dependent on age, with the thresholds decreasing with age, except possibly in the first year of life34353637.…”

“…Other studies rely on passive case detection (PCD) via local health clinics. It is generally acknowledged that the former gives a more accurate picture of the true burden of disease, although with frequent intervention and treatment, ACD may also modify transmission patterns6.…”

Studies on mosquito biting risk among migratory rice farmers in rural south-eastern Tanzania and development of a portable mosquito-proof hut

“…The climate is hot and humid, with an annual rainfall between 1200 and 1800 mm and mean annual temperature of 20–32 °C [19]. All the villages have moderate perennial malaria transmission [20], as climatic conditions and rice farming (both irrigated and non-irrigated) create ideal conditions for high densities of mosquitoes [21]. Most community members are subsistence farmers, cultivating mostly rice, but also maize and other crops such as sweet potatoes and beans.…”

Evaluation of prevalence's of pfdhfr and pfdhps mutations in Angola

“…In other African countries, SP - ITP has been also introduced in children as a control measure to reduce malaria morbidity and mortality in this most vulnerable population [12] and has been evaluated in a number of clinical trials in these countries, with success [12-17]. Thus, Angolan NMCP intends in the near future to introduce this control measure in Angola.…”