title: High prevalence of asymptomatic malaria infections: a cross-sectional study in rural areas in six departments in Haiti.
abstract: BACKGROUND
  Public health measures are poised for transition from malaria control to malaria elimination on the island of Hispaniola. Assessment of the reservoir of asymptomatic infections from which acute malaria cases may derive is critical to plan and evaluate elimination efforts. Current field technology is ill suited for detecting sub-microscopic infections, thus highly sensitive survey methods capable of detecting virtually all infections are needed. In this study the prevalence of infection with Plasmodium falciparum was determined in patients seeking medical care primarily for non-febrile conditions in six departments in Haiti using a newly designed qRT-PCR-based assay.
  
  
  METHODS
  Three different methods of parasite detection were compared to assess their utility in approximating the prevalence of P. falciparum infections in the population: malaria rapid diagnostic test (RDT) designed to detect histidine-rich protein 2 (HRP2), thick smear microscopy, and a quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay based upon the small sub-unit ribosomal RNA. The limit of detection of the qRT-PCR assay utilized was 0.0003 parasite/µL of blood. Venous blood was obtained from a total of 563 subjects from six departments in Haiti, all of whom were seeking medical attention without complaints consistent with malaria. Each subject was questioned for knowledge and behaviour using demographic and epidemiological survey to identify risk factors for disease transmission.
  
  
  RESULTS
  Among the 563 samples tested, ten and 16 were found positive for malaria by RDT and microscopy, respectively. Using the qRT-PCR test to assess the infection status of these subjects, an additional 92 were identified for a total of 108. Based upon the qRT-PCR assay results, a wide variation in prevalence of infection in asymptomatic subjects was seen between geographic locations ranging from 4-41%. The prevalence of infection was highest in the Grand Anse, Nord and Sud-Est Departments, and demographic data from questionnaires provide evidence for focal disease transmission.
  
  
  CONCLUSIONS
  The qRT-PCR assay is sufficiently sensitive to identify an unexpectedly large number of asymptomatic, submicroscopic infections. Identifying and clearing these infections presents a significant challenge to both control and elimination efforts, but the qRT-PCR assay offers a reliable method to identify them.
authors.affiliation: Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, USA. elbadrym@ufl.edu.|Emerging Pathogen Institute, University of Florida, Gainesville, FL, USA. elbadrym@ufl.edu.
authors.forename: Maha A
authors.initials: MA
authors.lastname: Elbadry
authors.affiliation: Interdisciplinary Center for Biotechnology Research (ICBR), University of Florida, Gainesville, USA. balkhedery@ufl.edu.
authors.forename: Basima
authors.initials: B
authors.lastname: Al-Khedery
authors.affiliation: Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, USA. mstagliamonte@ufl.edu.
authors.forename: Massimiliano S
authors.initials: MS
authors.lastname: Tagliamonte
authors.affiliation: Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, USA. yowellca@ufl.edu.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Yowell
authors.affiliation: Laboratoire National de Santé Publique (LNSP), Ministère de la Santé Publique et de la Population (MSPP), Port-au-Prince, Haiti. raccurt@yahoo.fr.
authors.forename: Christian P
authors.initials: CP
authors.lastname: Raccurt
authors.affiliation: Laboratoire National de Santé Publique (LNSP), Ministère de la Santé Publique et de la Population (MSPP), Port-au-Prince, Haiti. alexandre.existe@gmail.com.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Existe
authors.affiliation: Laboratoire National de Santé Publique (LNSP), Ministère de la Santé Publique et de la Population (MSPP), Port-au-Prince, Haiti. jboncy2001@yahoo.fr.
authors.forename: Jacques
authors.initials: J
authors.lastname: Boncy
authors.affiliation: Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, USA. riptos@epi.ufl.edu.|Emerging Pathogen Institute, University of Florida, Gainesville, FL, USA. riptos@epi.ufl.edu.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Weppelmann
authors.affiliation: Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, USA. madsenbeau@phhp.ufl.edu.|Emerging Pathogen Institute, University of Florida, Gainesville, FL, USA. madsenbeau@phhp.ufl.edu.|Department of Health Services Research, Management and Policy, College of Public Health and Health Professions, University of Florida, Gainesville, USA. madsenbeau@phhp.ufl.edu.
authors.forename: Valery E M
authors.initials: VE
authors.lastname: Beau De Rochars
authors.affiliation: Programme National de Contrôle de la Malaria, Port-au-Prince, Haiti. jflemoine@mspp.gouv.ht.
authors.forename: Jean F
authors.initials: JF
authors.lastname: Lemoine
authors.affiliation: Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, USA. bokech@ufl.edu.|Emerging Pathogen Institute, University of Florida, Gainesville, FL, USA. bokech@ufl.edu.
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Okech
authors.affiliation: Emerging Pathogen Institute, University of Florida, Gainesville, FL, USA. damej@ufl.edu.|Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, USA. damej@ufl.edu.
authors.forename: John B
authors.initials: JB
authors.lastname: Dame
mesh_terms: D000328:Adult; D058345:Asymptomatic Infections / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D006205:Haiti / Q000453:epidemiology; D006801:Humans; D007118:Immunoassay; D016778:Malaria, Falciparum / Q000175:diagnosis* / Q000453:epidemiology*; D008853:Microscopy; D010963:Plasmodium falciparum / Q000302:isolation & purification*; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012424:Rural Population; D055815:Young Adult