TY - JOUR

T1 - Detection of very low level Plasmodium falciparum infections using the nested polymerase chain reaction and a reassessment of the epidemiology of unstable malaria in Sudan

AU - Roper, C

AU - Elhassan, I M

AU - Hviid, L

AU - Giha, H

AU - Richardson, W

AU - Babiker, H

AU - Satti, G M

AU - Theander, T G

AU - Arnot, D E

N1 - Keywords: Adolescent; Adult; Age Distribution; Animals; Blood Preservation; Child; Cohort Studies; Cross-Sectional Studies; Cryopreservation; DNA, Protozoan; DNA, Ribosomal; Humans; Incidence; Malaria, Falciparum; Morbidity; Plasmodium falciparum; Polymerase Chain Reaction; Prevalence; Seasons; Sensitivity and Specificity; Sudan

PY - 1996

Y1 - 1996

N2 - We have used the nested polymerase chain reaction (PCR) to assay for low level Plasmodium falciparum infections that were below the threshold of detection of blood film examination. This revealed a substantial group of asymptomatic, submicroscopically patent infections within the population of a Sudanese village present throughout the year although clinical malaria episodes were almost entirely confined to the transmission season. In our September, January, April, and June surveys, the PCR-detected prevalences were 13%, 19%, 24%, and 19%, respectively. These figures reveal a much higher prevalence of dry season infection than previous microscopic surveys have indicated. Furthermore, 20% of a cohort of 79 individuals were healthy throughout the September to November transmission season but were PCR-positive for P. falciparum in a least one of a series of samples taken in the ensuing months. Levels of exposure to P. falciparum infection were therefore higher than was previously believed in this region, highlighting the fact that many individuals were infected but healthy for most of the year. The reservoir parasite population was thus larger and more stable than previously thought, a finding that is consistent with the high levels of genetic variation at polymorphic loci reported from analysis of P. falciparum parasites in this area.

AB - We have used the nested polymerase chain reaction (PCR) to assay for low level Plasmodium falciparum infections that were below the threshold of detection of blood film examination. This revealed a substantial group of asymptomatic, submicroscopically patent infections within the population of a Sudanese village present throughout the year although clinical malaria episodes were almost entirely confined to the transmission season. In our September, January, April, and June surveys, the PCR-detected prevalences were 13%, 19%, 24%, and 19%, respectively. These figures reveal a much higher prevalence of dry season infection than previous microscopic surveys have indicated. Furthermore, 20% of a cohort of 79 individuals were healthy throughout the September to November transmission season but were PCR-positive for P. falciparum in a least one of a series of samples taken in the ensuing months. Levels of exposure to P. falciparum infection were therefore higher than was previously believed in this region, highlighting the fact that many individuals were infected but healthy for most of the year. The reservoir parasite population was thus larger and more stable than previously thought, a finding that is consistent with the high levels of genetic variation at polymorphic loci reported from analysis of P. falciparum parasites in this area.

M3 - Journal article

C2 - 8615441

VL - 54

SP - 325

EP - 331

JO - Journal. National Malaria Society

JF - Journal. National Malaria Society

SN - 0002-9637

IS - 4

ER -