Genetic analysis of Plasmodium falciparum infections on the north-western border of Thailand.
Genetic characterization of Plasmodium falciparum infections in north-western Thailand, a region of low transmission intensity (1 infection/person each year), has found a comparable number of parasite genotypes per infected person to regions with hyperendemic malaria. Clone multiplicity and parasite diversity were found to be homogeneous across 129 infected individuals comprising a range of age-groups (1.32 parasite genotypes; n = 98), patients (aged 2-16 years) with recrudescent infections (1.54; n = 13), and pregnant women (1.61; n = 18). Individuals belonging to groups with a high risk of infection, as deduced by clinical epidemiology, did not harbour a higher number of clones per infection, nor greater parasite diversity than low-risk groups. In fact, multiple genotype infections were as common in low-risk groups, suggesting that there is frequent transmission of polyclonal infections from a single inoculum, rather than superinfection. Such a polyclonal transmission system would enable generation of extensive parasite diversity by recombination, despite the low level of transmission. However, co-infection with P. vivax was associated with fewer P. falciparum genotypes per infection.
Paul
R E
RE
Department of Zoology, Oxford University, UK. topotito@pasteur.fr
Brockman
A
A
Price
R N
RN
Luxemburger
C
C
White
N J
NJ
Looareesuwan
S
S
Nosten
F
F
Day
K P
KP
D000293:Adolescent; D000328:Adult; D000818:Animals; D002648:Child; D002675:Child, Preschool; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D016780:Malaria, Vivax / Q000453:epidemiology / Q000469:parasitology; D008297:Male; D010963:Plasmodium falciparum / Q000145:classification / Q000235:genetics*; D010966:Plasmodium vivax / Q000145:classification / Q000235:genetics; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000453:epidemiology / Q000469:parasitology; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology