Novel Plasmodium falciparum clones and rising clone multiplicities are associated with the increase in malaria morbidity in Ghanaian children during the transition into the high transmission season

A.  OFOSU-OKYERE  a1, M. J.  MACKINNON  a2, M. P. K.  SOWA  a2, K. A.  KORAM  a1, F.  NKRUMAH  a1, Y. D.  OSEI  a3, W. G.  HILL  a2, M. D.  WILSON  a1 and D. E.  ARNOT  a2 c1
a1 Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
a2 Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK
a3 Department of Biochemistry, University of Ghana, Legon, Ghana


A survey of Plasmodium falciparum infection and clone multiplicity in Ghanaian children was carried out to study the effect of the onset of the malaria transmission season on disease incidence. Fortnightly blood samples were collected from 40 children living in the rural town of Dodowa, between February and August 1998. P. falciparum parasite densities were calculated and PCR genotyping was carried out using the polymorphic MSP-1 and MSP-2 genes as target loci for the estimation of the number of parasite clones in each sample. The average clone number was estimated using maximum likelihood techniques and the minimum number of clones per patient was analysed for the effects of age, sex, season, minimum number of clones per child, level of parasitaemia and parasite genotype. The statistical analysis indicated that the more clones a child carried, the more likely they were to have a clinical malaria episode. This was true after adjusting for age and season effects and for the measured circulating parasitaemia. The probability of clinical disease also increased if the MSP-1 MAD 20 and the MSP-2 FC 27 alleles were present. This longitudinal analysis thus indicates that the probability of a Ghanaian child having a symptomatic malaria episode is positively associated with both increasing numbers and novel types of P. falciparum clones.

(Received June 29 2000)
(Revised February 5 2001)
(Accepted February 14 2001)

Key Words: malaria; Plasmodium falciparum; clone multiplicity; virulence; seasonal transmission; Ghana.

c1 Corresponding author: Institute of Cell, Animal and Population Biology, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK. Tel and Fax: +0131 650 8655. E-mail: