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CDC/Richard Weber

DNA 'barcoding' offers rapid and low cost ways to monitor human disease vectors and biodiversity in developing countries, scientists told a conference this week.

The comments came during the Second International Barcode of Life Conference in Taipei, Taiwan (18–20 September).

The technique identifies known species and records new ones by sequencing a specific, short area of mitochondrial DNA, previously identified and agreed by scientists.

This "barcode region" of mitochondrial DNA mutates at a rate fast enough to create differences between species, but slow enough to leave members of the same species with nearly identical barcodes. Species that divided recently or are still interbreeding can be difficult to separate using this method.

Comparing the sequence to all others in a database produces a picture of how similar the specimens are. The process takes a few hours and costs as little as US$2.

Yvonne-Marie Linton of the UK's Natural History Museum, and leader of the Mosquito Barcoding Initiative, told SciDev.Net that barcoding should help control mosquitoes carrying diseases like malaria, West Nile disease and dengue fever.

"Often only one or two mosquito species are capable of transmitting disease," she says.

"It is important to know exactly which these are and then we can tie this information in with the ecology of these species, work out where they breed and use larvicidal techniques to control the mosquitoes, not 'blanketly' spray all of them."

And Eldredge Bermingham, acting director of the Smithsonian Tropical Research Institute in Panama, says DNA barcoding helps to identify and protect tropical biodiversity. The Institute has collected many samples that are as yet unclassified and DNA barcoding lets non-experts help classify these cheaply.

"Barcoding efforts based in labs in Mexico, Brazil, Argentina and Panama are discovering new species, and providing geo-referenced data for informed conservation decisions," Bermingham told SciDev.Net.

But David Schindel, executive secretary of the Consortium for the Barcode of Life, based in Washington DC, United States, explains that barcoding's low cost reflects only the sequencing.

Building a reference library of barcode sequences is more expensive.

"Borrowing a book from a public library is free, but someone had to pay for writing and printing and buying the books in the library," he points out.