title: Case investigation and reactive case detection for malaria elimination in northern Senegal.
abstract: BACKGROUND
  Given progress in malaria control in recent years, many control programmes in sub-Saharan Africa will soon be required to strengthen systems for surveillance in order to further drive transmission to zero. Yet few practical experiences are available to guide control programmes in designing surveillance system components in low transmission, pre-elimination, and elimination phases.
  
  
  METHODS
  A malaria case investigation programme was piloted for 12 weeks in 2012 in Richard Toll district of northern Senegal. Malaria infections (N = 110) were identified through facility-based passive case detection and investigated within three days. Rapid diagnostic tests (RDT) and a brief questionnaire were administered to 5,520 individuals living within the index case compound or within five neighbouring compounds.
  
  
  RESULTS
  In comparison with family and neighbours, index cases were more likely to be male, age 15-49, and to report travel within the past 15 days that entailed an overnight stay. Twenty-three (0.4%) of family/neighbours were RDT-positive. Potential risk factors for infection among family and neighbours were examined, including: sex, age, occupation, travel history, bed net usage, and residence (index vs neighbouring compound). Adjusting for all factors, relative risk (RR) of infection was associated with residence in the index case household (RR = 3.18, p < 0.05) and recent travel, including travel to Dakar (RR = 19.93, p < 0.001), travel within the region (RR = 9.57, p < 0.01), and to other regions in Senegal (RR = 94.30, p < 0.001). Recent fever among RDT-positive family/neighbours was uncommon (30%). Modifications to testing criteria were examined to optimize the efficiency of secondary case investigations in this population. Limiting blood testing to residents of the index case compound and neighbours with recent travel or fever would have identified 20/23 (87%) of the infections through testing 1,173 individuals. Information on the remaining three infections suggests that additional screening for boarding school attendees may facilitate identification of all cases.
  
  
  CONCLUSIONS
  The primary risk factor for malaria infection in the low transmission district of Richard Toll is travel. Additional intervention and monitoring strategies to target travellers at risk of malaria infection are needed in this region. Optimizing case investigation with specific targeted testing and treatment of at-risk family and neighbours strengthens the systems needed for continued progress towards malaria elimination in northern Senegal.
authors.affiliation: PATH Malaria Control and Evaluation Partnership (MACEPA), Seattle, WA, USA. mlittrell@path.org.
authors.forename: Megan
authors.initials: M
authors.lastname: Littrell
authors.forename: Gnagna Dieng
authors.initials: GD
authors.lastname: Sow
authors.forename: Algaye
authors.initials: A
authors.lastname: Ngom
authors.forename: Mady
authors.initials: M
authors.lastname: Ba
authors.forename: Balla Mbacke
authors.initials: BM
authors.lastname: Mboup
authors.forename: Yakou
authors.initials: Y
authors.lastname: Dieye
authors.forename: Boniface
authors.initials: B
authors.lastname: Mutombo
authors.forename: Duncan
authors.initials: D
authors.lastname: Earle
authors.forename: Richard W
authors.initials: RW
authors.lastname: Steketee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000379:methods; D060740:Disease Eradication; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008288:Malaria / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012307:Risk Factors; D012675:Senegal / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014195:Travel; D055815:Young Adult
references.citation: Travel Med Infect Dis. 2013 Jan-Feb;11(1):15-22
references.pmid: 23478045
references.citation: Cochrane Database Syst Rev. 2009 Jul 08;(3):CD007483
references.pmid: 19588433
references.citation: Malar J. 2011 Oct 21;10:313
references.pmid: 22018266
references.citation: Nat Commun. 2012;3:1237
references.pmid: 23212366
references.citation: Lancet. 2013 Sep 7;382(9895):900-11
references.pmid: 23594387
references.citation: PLoS Med. 2011 Jan 25;8(1):e1000396
references.pmid: 21311583
references.citation: PLoS One. 2012;7(10):e45797
references.pmid: 23049687
references.citation: PLoS Med. 2011 Jan 25;8(1):e1000402
references.pmid: 21311580
references.citation: Am J Trop Med Hyg. 2013 Feb;88(2):289-91
references.pmid: 23249688
references.citation: PLoS Med. 2011 Jan 25;8(1):e1000400
references.pmid: 21311581
references.citation: Lancet. 2010 Nov 6;376(9752):1592-603
references.pmid: 21035841
references.citation: PLoS Med. 2013;10(6):e1001467
references.pmid: 23853551
references.citation: Malar J. 2013 Jan 24;12:33
references.pmid: 23347703
references.citation: PLoS One. 2013 May 20;8(5):e63830
references.pmid: 23700437
references.citation: PLoS One. 2012;7(8):e43162
references.pmid: 22952642