Chloroquine/sulphadoxine-pyrimethamine for gambian children with malaria: transmission to mosquitoes of multidrug-resistant Plasmodium falciparum.
OBJECTIVE
In the Gambia, chloroquine (CQ) plus sulphadoxine-pyrimethamine (SP) is the first-line antimalarial treatment. Plasmodium falciparum parasites carrying mutations associated with resistance to each of these drugs were present in 2001 but did not cause a significant loss of therapeutic efficacy among children receiving the combination CQ/SP. We measured their effect on parasite transmission to Anopheles gambiae mosquitoes.


METHODS
We conducted a single-blind, randomised, controlled trial with follow-up over 28 d. Mosquito feeding experiments were carried out 7, 10, or 14 d after treatment.


METHODS
The study took place in the town of Farafenni and surrounding villages in the Gambia.


METHODS
Participants were 500 children aged 6 mo to 10 y with uncomplicated P. falciparum malaria.


METHODS
Children were randomised to receive CQ, SP, or CQ/SP.


METHODS
Outcomes related to transmission were determined, including posttreatment gametocyte prevalence and density. Infectiousness was assessed by membrane-feeding A. gambiae mosquitoes with blood from 70 gametocyte-positive patients. Mutations at seven loci in four genes associated with drug resistance were measured pre- and posttreatment and in the midguts of infected mosquitoes.


RESULTS
After SP treatment, the infectiousness of gametocytes was delayed, compared to the other two treatment groups, despite comparable gametocyte densities. Among bloodmeal gametocytes and the midguts of infected mosquitoes, the presence of the four-locus multidrug-resistant haplotype TYRG (consisting of mutations pfcrt-76T, pfmdr1-86Y, pfdhfr-59R, and pfdhps-437G) was associated with significantly higher oocyst burdens after treatment with the combination CQ/SP.


CONCLUSIONS
Parasites with a multidrug-resistant genotype had a substantial transmission advantage after CQ/SP treatment but did not have a significant impact on in vivo efficacy of this drug combination. Protocols that include measuring transmission endpoints as well as therapeutic outcomes may be a useful strategy when monitoring the evolution of drug resistance in malaria parasites in vivo.
Hallett
Rachel L
RL
Immunology Unit and Infectious Diseases Epidemiology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Dunyo
Samuel
S
Ord
Rosalynn
R
Jawara
Musa
M
Pinder
Margaret
M
Randall
Anna
A
Alloueche
Ali
A
Walraven
Gijs
G
Targett
Geoffrey A T
GA
Alexander
Neal
N
Sutherland
Colin J
CJ