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Researchers have developed a simple and cheap method to screen large numbers of sand flies to determine their species and what type of Leishmania parasite — the microorganism that causes leishmaniasis — they might be carrying.

The study was published in the August issue of the American Journal of Tropical Medicine and Hygiene.

Monitoring both host and Leishmania parasite species in endemic regions is important for determining a patient's prognosis and choosing appropriate treatment, as well as for assessing the likelihood of the disease expanding to surrounding areas.

But because relatively few sand flies are infected with the Leishmania parasite — even in endemic areas — a large number of specimens have to be tested to get any informative data.

Conventional methods for determining host and Leishmania parasite species include dissection and observation of physical characteristics — both of which require considerable time and skill.

Lead researcher Hirotomo Kato, from the Japan-based Yamaguchi University, and colleagues have developed a faster method that tests for the presence of a certain genes to determine host and parasite species.

They were able to test 319 sand fly specimens captured from endemic areas of Ecuador, and detect the parasite in five of them in a short space of time.

"To our knowledge, there are not any other methods to analyse such numbers of sand flies individually with minimum effort," Kato told SciDev.Net.

The method costs about US$1 per sample, but they are trying to reduce this, said Kato.

The new technique is currently being used for epidemiological studies in endemic areas of Argentina, Ecuador and Peru.

Hiba Salah-Eldin, a researcher at the Institute of Endemic Diseases at the Sudan-based University of Khartoum said this new technique will help scientists study the host-parasite relationship, and possibly even help to determine why only some species of sand fly are capable of carrying Leishmania.

Determining the capacity of sand flies in an area to carry Leishmania could help predict potential epidemics, she said.

Salah-Eldin said this method could also help prevent the problem of failing to detect parasites — a difficulty many researchers experience.

Link to abstract in the American Journal of Tropical Medicine and Hygiene

Reference: American Journal of Tropical Medicine and Hygiene 77, 324 (2007)

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