TY - JOUR
T1 - High gametocyte complexity and mosquito infectivity of Plasmodium falciparum in the Gambia
AU - Nwakanma, Davis
AU - Kheir, Amani
AU - Sowa, Mercy
AU - Dunyo, Sam
AU - Jawara, Musa
AU - Pinder, Margaret
AU - Milligan, Paul
AU - Walliker, David
AU - Babiker, Hamza A.
N1 - Funding Information:
The authors dedicate this paper to the memory of Professor David Walliker of Edinburgh University, who died on 22 May 2007. David has enriched the field of genetics of malaria parasites through 40 years of consistent research at Edinburgh University (1966–2005). This paper represents his last engagement with the subject. The work described here would not have been possible without the co-operation of the villagers of Yallal, Alkali Kunda, Jariari, Daru and Dai Mandika and the staff of the Medical Research Laboratories, the Gambia. We thank Dr. Margaret Mackinnon and Prof. Andrew Read for their help with analysis and comments on the manuscript. Financial support was received from the Medical Research Council, UK. Amani Khier is supported by the Gordon Memorial College Trust Fund, UK.
PY - 2008/2
Y1 - 2008/2
N2 - The purpose of this work was to determine the infectivity to mosquitoes of genetically diverse Plasmodium falciparum clones seen in natural infections in the Gambia. Two principal questions were addressed: (i) how infectious are gametocytes of sub-patent infections, particularly at the end of the dry season; and (ii) are all clones in multiclonal infections equally capable of infecting mosquitoes? The work was carried out with two cohorts of infected individuals. Firstly, a group of 31 P. falciparum-infected people were recruited in the middle of the dry season (May, 2003), then examined for P. falciparum at the beginning (August 2003) and middle (October, 2003) of the transmission season. On each occasion, we examined the genotypes of asexual forms and gametocytes by PCR and RT-PCR, as well as their infectivity to Anopheles gambiae using membrane feeds. One individual gave rise to infected mosquitoes in May, and two in August. Different gametocyte genotypes co-existed in the same infection and fluctuated over time. The mean multiplicity of infection was 1.4, 1.7 and 1.5 clones in May, August and October, respectively. Second, a group of patients undergoing drug-treatment during August 2003 was tested for asexual and gametocyte genotypes and their infectivity to mosquitoes. Forty-three out of 100 feeds produced infections. The genetic complexity of the parasites in mosquitoes was sometimes greater than that detectable in the blood on which the mosquitoes had fed. This suggested that gametocytes of clones existing in the blood below PCR detection limits at the time of the feed were at least as infectious to the mosquitoes as the more abundant clones. These findings emphasise the crucial role of gametocyte complexity and infectivity in generating the remarkable diversity of P. falciparum genotypes seen in infected people, even in an area of seasonal transmission.
AB - The purpose of this work was to determine the infectivity to mosquitoes of genetically diverse Plasmodium falciparum clones seen in natural infections in the Gambia. Two principal questions were addressed: (i) how infectious are gametocytes of sub-patent infections, particularly at the end of the dry season; and (ii) are all clones in multiclonal infections equally capable of infecting mosquitoes? The work was carried out with two cohorts of infected individuals. Firstly, a group of 31 P. falciparum-infected people were recruited in the middle of the dry season (May, 2003), then examined for P. falciparum at the beginning (August 2003) and middle (October, 2003) of the transmission season. On each occasion, we examined the genotypes of asexual forms and gametocytes by PCR and RT-PCR, as well as their infectivity to Anopheles gambiae using membrane feeds. One individual gave rise to infected mosquitoes in May, and two in August. Different gametocyte genotypes co-existed in the same infection and fluctuated over time. The mean multiplicity of infection was 1.4, 1.7 and 1.5 clones in May, August and October, respectively. Second, a group of patients undergoing drug-treatment during August 2003 was tested for asexual and gametocyte genotypes and their infectivity to mosquitoes. Forty-three out of 100 feeds produced infections. The genetic complexity of the parasites in mosquitoes was sometimes greater than that detectable in the blood on which the mosquitoes had fed. This suggested that gametocytes of clones existing in the blood below PCR detection limits at the time of the feed were at least as infectious to the mosquitoes as the more abundant clones. These findings emphasise the crucial role of gametocyte complexity and infectivity in generating the remarkable diversity of P. falciparum genotypes seen in infected people, even in an area of seasonal transmission.
KW - Anopheles mosquito infectivity
KW - Gametocytes
KW - Plasmodium falciparum
KW - RT-PCR
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U2 - 10.1016/j.ijpara.2007.07.003
DO - 10.1016/j.ijpara.2007.07.003
M3 - Article
C2 - 17709108
AN - SCOPUS:37249045656
SN - 0020-7519
VL - 38
SP - 219
EP - 227
JO - International Journal for Parasitology
JF - International Journal for Parasitology
IS - 2
ER -