title: 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 falciparum-positive blood slides prepared from children with axillary temperature 37.5 degrees 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.
authors.affiliation: Centro de Salud International, Institut d'Investigacions Biomedicas August Pi i Sunyer (IDIBAPS), Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain. dmschellenberg@aol.com
authors.forename: D M
authors.initials: DM
authors.lastname: Schellenberg
authors.forename: J J
authors.initials: JJ
authors.lastname: Aponte
authors.forename: E A
authors.initials: EA
authors.lastname: Kahigwa
authors.forename: H
authors.initials: H
authors.lastname: Mshinda
authors.forename: M
authors.initials: M
authors.lastname: Tanner
authors.forename: C
authors.initials: C
authors.lastname: Menendez
authors.forename: P L
authors.initials: PL
authors.lastname: Alonso
mesh_terms: D000740:Anemia / Q000453:epidemiology / Q000209:etiology; D000818:Animals; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D016778:Malaria, Falciparum / Q000097:blood / Q000453:epidemiology* / Q000635:transmission; D008297:Male; D018512:Parasitemia / Q000097:blood / Q000453:epidemiology; D012307:Risk Factors; D013636:Tanzania / Q000453:epidemiology