title: Distribution of Plasmodium falciparum gametocytes and malaria-attributable fraction of fever episodes along an altitudinal transect in Western Cameroon.
abstract: BACKGROUND
  Highland areas are hypoendemic zones of malaria and are therefore prone to epidemics, due to lack of protective immunity. So far, Cameroon has not succeeded in implementing a convenient and effective method to detect, prevent and forecast malaria epidemic in these peculiar zones. This monitoring and evaluation study aims to assess the operational feasibility of using the human malaria infectious reservoir (HMIR) and the malaria-attributable fraction of fever episodes (MAFE) as indicators, in designing a malaria epidemic early warning system (MEWS).
  
  
  METHODS
  Longitudinal parasitological surveys were conducted in sentinel health centres installed in three localities, located along an altitudinal transect in Western Cameroon: Santchou (750 m), Dschang (1,400 m) and Djuttitsa (1,965 m). The syndromes of outpatients with malaria-like complaints were recorded and their blood samples examined. The HMIR and the MAFE were estimated and their spatial-temporal variations described.
  
  
  RESULTS
  The prevalence of asexual Plasmodium infection in outpatients decreased with increasing altitude; meanwhile the HMIR remained fairly constant, indicating that scarcity of malaria disease in highlands is likely due to absence of vectors and not parasites. In lowland, children carried the heaviest malaria burden in the form of febrile episodes, and asexual parasites decreased with age, after an initial peak in the 0-5 year's age group; however, they were similar for all age groups in highland. The HMIR did not show any variation with age in the plain; but some discrepancies were observed in the highland with extreme age groups, and migration of populations between lowland and highland was suspected to be the cause. Plasmodium infection was perennial in the lowland and seasonal uphill, with malaria disease occurring here mostly during the short dry season. The MAFE was high and did not change with altitude.
  
  
  CONCLUSIONS
  It is obvious that a malaria outbreak will cause the sudden rise of HMIR and MAFE in highland, prior to the malaria season; the discrepancy with lowland would then help detecting an incipient malaria epidemic. It is recommended that in designing the MEWS, the National Malaria Control Programme should include these parameters and put special emphasis on: altitude, age groups and seasons.
authors.affiliation: Malaria Research Unit of the Laboratory of Applied Biology and Ecology (MRU-LABEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P. O. Box 067, Dschang, Cameroon. timtchuinkam@yahoo.fr.|Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), BP 288, Yaoundé, Cameroun. timtchuinkam@yahoo.fr.
authors.forename: Timoléon
authors.initials: T
authors.lastname: Tchuinkam
authors.affiliation: Malaria Research Unit of the Laboratory of Applied Biology and Ecology (MRU-LABEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P. O. Box 067, Dschang, Cameroon. bnyih@yahoo.com.
authors.forename: Bridget
authors.initials: B
authors.lastname: Nyih-Kong
authors.affiliation: Malaria Research Unit of the Laboratory of Applied Biology and Ecology (MRU-LABEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P. O. Box 067, Dschang, Cameroon. fofrancois@yahoo.fr.|Hôpital Saint Vincent De Paul, Mission Catholique Sacré Cœur, BP 011, Dschang, Cameroon. fofrancois@yahoo.fr.
authors.forename: François
authors.initials: F
authors.lastname: Fopa
authors.affiliation: Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), BP 288, Yaoundé, Cameroun. simard@ird.fr.|MIVEGEC, UMR IRD224-CNRS5290-UM, Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP 64501, Montpellier, France. simard@ird.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Simard
authors.affiliation: Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), BP 288, Yaoundé, Cameroun. antonio_nk@yahoo.fr.
authors.forename: Christophe
authors.initials: C
authors.lastname: Antonio-Nkondjio
authors.affiliation: Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), BP 288, Yaoundé, Cameroun. hpaawono@yahoo.fr.
authors.forename: Herman-Parfait
authors.initials: HP
authors.lastname: Awono-Ambene
authors.affiliation: Hôpital Saint Vincent De Paul, Mission Catholique Sacré Cœur, BP 011, Dschang, Cameroon. hopitalstvincentdepaul@yahoo.fr.
authors.forename: Laura
authors.initials: L
authors.lastname: Guidone
authors.affiliation: Malaria Research Unit of the Laboratory of Applied Biology and Ecology (MRU-LABEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P. O. Box 067, Dschang, Cameroon. mpoambida@yahoo.fr.
authors.forename: Mbida
authors.initials: M
authors.lastname: Mpoame
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002163:Cameroon / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004197:Disease Reservoirs / Q000469:parasitology*; D062665:Epidemiological Monitoring; D005334:Fever / Q000453:epidemiology* / Q000469:parasitology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000469:parasitology*; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000302:isolation & purification*; D015995:Prevalence; D018571:Sentinel Surveillance; D055815:Young Adult