Chulalongkorn Medical Journal


Background: Besides well-perceived species of Plasmodium infecting humans, at least four simian malaria species including P. knowlesi, P. cynomolgi, P. inui and P. fieldi have been incriminated in human infections in Thailand. The vectors of simian malaria in this country have been recently identified to be Anopheles latens and An. introlatus.

Objectives: To address whether mosquitoes in Barbirostris complex in Narathiwat Province could vector simian malaria and to analyze species distribution of Anopheles in this complex from the sampled population.

Methods: A total of 115 mosquitoes from Sukhirin and Waeng Districts in Narathiwat Province morphologically assigned to Barbirostris complex were included for analysis. DNA was extracted from salivary gland samples of individual mosquitoes. Molecular identification of mosquito members of Barbirostris complex was performed by PCR amplification of the internal transcribed spacer 2 (ITS2) region and its partial flanking sequences of Anopheles RNA cistron, followed by sequencing. Analysis of individual salivary gland samples was done by species-specific nested PCR targeting mitochondrial cytochrome oxidase I of four human Plasmodium species, P. knowlesi, P. cynomolgi, P. inui and P. fieldi.

Results: Two amplicon lengths comprising ~1.9 and ~1 kb fragments were observed in 72 and 43 mosquitoes, respectively. Sequence analysis of the 5’ portion of ITS2 from 20 randomly selected mosquitoes has shown two distinct phylogenetic clades. All 12 mosquitoes bearing 1.9-kb amplicons displayed perfect sequence identity across samples and were placed in a clade related to but distinct from An. saeungae. Nine specimens with 1-kb amplicons were clustered within An. barbirostris species A3. All salivary gland samples gave negative results for malarial DNA.

Conclusion: Two genetically distinct lineages have been identified in Barbirostris complex inNarathiwatProvince. None of these carried malarial DNA in their salivary glands, suggesting that they might not vector simian malaria.





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