Molecular incidence and clearance of Plasmodium falciparum infection.
BACKGROUND
Although the epidemiology of malaria has been based primarily on microscopy and rapid diagnostic tests, molecular methods are necessary to understand the complexity of natural infection in regions where transmission is intense and simultaneous infection with multiple parasite genotypes is common such as sub-Saharan Africa.


METHODS
To compare microscopic and molecular estimates of the incidence and clearance of Plasmodium falciparum infection, we followed 80 children monthly for 1 year in the village of Bancoumana in Mali.


CONCLUSIONS
Similar seasonal patterns were observed with both methods (rainy season peak, dry season nadir), although molecular methods detected more infections than microscopy (571 vs 331 in 906 specimens), more new infections (311 vs 104 during 829 person-months) and spontaneous clearance events (317 vs 116) and found higher incidence (0.38 vs 0.13 new genotypes/person/month, p < 0.001) and spontaneous clearance rates (0.38 vs 0.14 genotypes cleared/person/month, p < 0.001). These differences were greatest for persistently-infected subjects in whom neither new infections nor the clearance of old infections could be detected by microscopy (0.71 new infections and 0.73 cleared infections per month using molecular methods vs 0.000 by microscopy, p < 0.001).


CONCLUSIONS
Molecular methods provide information about genetic diversity, the intensity of transmission and spontaneous clearance in the absence of drug treatment that cannot be obtained by microscopy. They will be necessary to evaluate the efficacy of vaccines, drugs and other control strategies for diseases such as malaria in which simultaneous infection with more than one organism (genotype) is common.
Center for Infectious Diseases, Tulane University School of Public Health and Tropical Medicine, #8317, J. Bennett Johnston Building, Room 510, 1324 Tulane Avenue, New Orleans, LA, 70112, USA. krogstad@tulane.edu.|Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA. krogstad@tulane.edu.|Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. krogstad@tulane.edu.
Donald J
DJ
Krogstad
Center for Infectious Diseases, Tulane University School of Public Health and Tropical Medicine, #8317, J. Bennett Johnston Building, Room 510, 1324 Tulane Avenue, New Orleans, LA, 70112, USA. okoita@icermali.org.|Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. okoita@icermali.org.
Ousmane A
OA
Koita
Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. mouctard@icermali.org.
Mouctar
M
Diallo
Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA. gerone@tulane.edu.
John L
JL
Gerone
Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. belco_p@yahoo.com.
Belco
B
Poudiougou
Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. mdiakite@icermali.org.
Mahamadou
M
Diakité
Faculty of Medicine, Pharmacy and Odontostomatology, Mali-Tulane Tropical Medicine Research Center, University of Bamako, Bamako, Mali. ytoure76@gmail.com.
Yéya T
YT
Touré
D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D016778:Malaria, Falciparum / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008302:Mali / Q000453:epidemiology; D008853:Microscopy / Q000379:methods*; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D017720:Molecular Epidemiology; D010963:Plasmodium falciparum / Q000235:genetics / Q000302:isolation & purification*; D011446:Prospective Studies