Occurrence of the leucine-to-phenylalanine knockdown resistance (kdr) mutation in Anopheles arabiensis populations in Tanzania, detected by a simplified high-throughput SSOP-ELISA method.
BACKGROUND
Molecular markers of insecticide resistance can provide sensitive indicators of resistance development in malaria vector populations. Monitoring of insecticide resistance in vector populations is an important component of current malaria control programmes. Knockdown resistance (kdr) confers resistance to the pyrethroid class of insecticides with cross-resistance to DDT through single nucleotide polymorphisms (SNPs) in the voltage-gated sodium channel gene.


METHODS
To enable detection of kdr mutations at low frequency a method was developed that uses polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA)-based technology, allowing rapid, reliable and cost-effective testing of large numbers of individual mosquitoes. This was used to assay mosquitoes from sites in lower Moshi, Tanzania.


RESULTS
Sequence-specific oligonucleotide probes (SSOP) were used for simultaneous detection of both East and West African kdr mutations with high specificity and sensitivity. Application of the SSOP-ELISA method to 1,620 field-collected Anopheles arabiensis from Tanzania identified the West African leucine-phenylalanine kdr mutation in two heterozygous individuals, indicating the potential for resistance development that requires close monitoring.


CONCLUSIONS
The presence of the West African kdr mutation at low frequency in this East African population of An. arabiensis has implications for the spread of the kdr gene across the African continent.
Kulkarni
Manisha A
MA
Department of Natural Resource Sciences, McGill University, Macdonald Campus, Ste Anne de Bellevue, Quebec H9X 3V9, Canada. manisha.kulkarni@elf.mcgill.ca
Rowland
Mark
M
Alifrangis
Michael
M
Mosha
Frank W
FW
Matowo
Johnson
J
Malima
Robert
R
Peter
Justin
J
Kweka
Eliningaya
E
Lyimo
Issa
I
Magesa
Stephen
S
Salanti
Ali
A
Rau
Manfred E
ME
Drakeley
Chris
C
D000818:Animals; D000852:Anopheles / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D007305:Insecticide Resistance / Q000235:genetics*; D007930:Leucine / Q000235:genetics; D009154:Mutation; D015345:Oligonucleotide Probes / Q000235:genetics; D010649:Phenylalanine / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D011722:Pyrethrins / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D013636:Tanzania
D015345:Oligonucleotide Probes; D011722:Pyrethrins; D010649:Phenylalanine; D007930:Leucine