title: Longitudinal survey of malaria morbidity over 10 years in Saharevo (Madagascar): further lessons for strengthening malaria control.
abstract: BACKGROUND
  Madagascar has been known for having bio-geo-ecological diversity which is reflected by a complex malaria epidemiology ranging from hyperendemic to malaria-free areas. Malaria-related attacks and infection are frequently recorded both in children and adults living in areas of low malaria transmission. To integrate this variability in the national malaria control policy, extensive epidemiological studies are required to up-date previous records and adjust strategies.
  
  
  METHODS
  A longitudinal malaria survey was conducted from July 1996 to June 2005 among an average cohort of 214 villagers in Saharevo, located at 900 m above the sea. Saharevo is a typical eastern foothill site at the junction between a costal wet tropical area (equatorial malaria pattern) and a drier high-altitude area (low malaria transmission).
  
  
  RESULTS
  Passive and active malaria detection revealed that malaria transmission in Saharevo follows an abrupt seasonal variation. Interestingly, malaria was confirmed in 45% (1,271/2,794) of malaria-presumed fevers seen at the health centre. All four Plasmodia that infect humans were also found: Plasmodium falciparum; Plasmodium vivax, Plasmodium malariae and Plasmodium ovale. Half of the malaria-presumed fevers could be confirmed over the season with the highest malaria transmission level, although less than a quarter in lower transmission time, highlighting the importance of diagnosis prior to treatment intake. P. falciparum malaria has been predominant (98%). The high prevalence of P. falciparum malaria affects more particularly under 10 years old children in both symptomatic and asymptomatic contexts. Children between two and four years of age experienced an average of 2.6 malaria attacks with P. falciparum per annum. Moreover, estimated incidence of P. falciparum malaria tends to show that half of the attacks (15 attacks) risk to occur during the first 10 years of life for a 60-year-old adult who would have experienced 32 malaria attacks.
  
  
  CONCLUSIONS
  The incidence of malaria decreased slightly with age but remained important among children and adults in Saharevo. These results support that a premunition against malaria is slowly acquired until adolescence. However, this claims for a weak premunition among villagers in Saharevo and by extension in the whole eastern foothill area of Madagascar. While the Malagasy government turns towards malaria elimination plans nowadays, choices and expectations to up-date and adapt malaria control strategies in the foothill areas are discussed in this paper.
authors: Institut Pasteur de Madagascar, BP 1274 Antananarivo (101), Madagascar. milijaon@pasteur.mg
authors: Léon P
authors: LP
authors: Rabarijaona
authors: Milijaona
authors: M
authors: Randrianarivelojosia
authors: Lucie A
authors: LA
authors: Raharimalala
authors: Arsène
authors: A
authors: Ratsimbasoa
authors: Arthur
authors: A
authors: Randriamanantena
authors: Laurence
authors: L
authors: Randrianasolo
authors: Lanto A
authors: LA
authors: Ranarivelo
authors: Fanja
authors: F
authors: Rakotomanana
authors: Rindra
authors: R
authors: Randremanana
authors: Jocelyn
authors: J
authors: Ratovonjato
authors: Marie-Ange
authors: MA
authors: Rason
authors: Jean-Bernard
authors: JB
authors: Duchemin
authors: Adama
authors: A
authors: Tall
authors: Vincent
authors: V
authors: Robert
authors: Ronan
authors: R
authors: Jambou
authors: Frédéric
authors: F
authors: Ariey
authors: Olivier
authors: O
authors: Domarle
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008270:Madagascar / Q000453:epidemiology; D008288:Malaria / Q000453:epidemiology* / Q000401:mortality* / Q000469:parasitology; D008297:Male; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000302:isolation & purification; D010965:Plasmodium malariae / Q000302:isolation & purification; D041122:Plasmodium ovale / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000302:isolation & purification; D012424:Rural Population; D012621:Seasons; D055815:Young Adult