Background
Malaria remains an important public health problem in Latin America, and the development of insecticide resistance in malaria vectors poses a major threat to malaria elimination efforts. Monitoring of insecticide susceptibility and the determination of the mechanisms involved in insecticide resistance are needed to effectively guide the deployment of appropriate vector control measures. Here, molecular assays have been developed to screen for mutations associated with insecticide resistance on the voltage-gated sodium channel (
VGSC
) and acetylcholinesterase-1 (
Ace
-
1
) genes in four malaria vectors from Latin America.
Methods
Degenerate primers were designed to amplify a partial fragment on the
VGSC
and
Ace
-
1
genes. Wild-caught individuals for
Anopheles albimanus
(also historical samples and individuals from a laboratory strain),
Anopheles darlingi
,
Anopheles vestitipennis
and
Anopheles pseudopunctipennis
were used to optimize the PCR assays. All samples were sequenced to validate the PCR results and DNA alignments were constructed for each gene using the unique haplotypes observed.
Results
Primers designed successfully amplified the
VGSC
gene in
An. albimanus
,
An. darlingi, An. vestitipennis
and
An. pseudopunctipennis
, and the
Ace
-
1
gene in both
An. albimanus
and
An. darlingi
. DNA sequencing revealed that compared with
Anopheles gambiae
, there were a total of 29, 28, 21 and 24 single nucleotide polymorphisms (SNPs) on the
VGSC
gene for
An. albimanus
(308 bp),
An. darlingi
(311 bp),
An. pseudopunctipennis
(263 bp) and
An. vestitipennis
(254 bp), respectively. On the 459 bp fragment of the
Ace
-
1
gene, a total of 70 SNPs were detected in
An. darlingi
and 59 SNPs were detected in
An. albimanus
compared with
An. gambiae
. The SNPs detected on the
VGSC
gene were all synonymous. On the
Ace
-
1
gene, non-synonymous substitutions were identified on three different codons. All species showed the homozygous wild-type
kdr
allele (coding for leucine) at codon 995 (formerly reported as codon 1014) on the
VGSC
gene, but one s...