PCR detection of malaria parasites in desiccated Anopheles mosquitoes is uninhibited by storage time and temperature
Reliable methods to preserve mosquito vectors for malaria studies are necessary for detectingPlasmodium parasites. In field settings, however, maintaining a cold chain of storage fromthe time of collection until laboratory processing, or accessing other reliable means of samplepreservation is often logistically impractical or cost prohibitive.
As the Plasmodium infectionrate of Anopheles mosquitoes is a central component of the entomological inoculation rateand other indicators of transmission intensity, storage conditions that affect pathogendetection may bias malaria surveillance indicators. This study investigated the effect ofstorage time and temperature on the ability to detect Plasmodium parasites in desiccatedAnopheles mosquitoes by real-time polymerase chain reaction (PCR).
Laboratory-infected Anopheles stephensi mosquitoes were chloroform-killed and stored overdesiccant for 0, 1, 3, and 6months while being held at four different temperatures: 28, 37, -20and -80degreesC.
The detection of Plasmodium DNA was evaluated by real-time PCR amplificationof a 111 base pair region of block 4 of the merozoite surface protein.
Varying the storage time and temperature of desiccated mosquitoes did not impact thesensitivity of parasite detection. A two-way factorial analysis of variance suggested thatstorage time and temperature were not associated with a loss in the ability to detect parasites.Storage of samples at 28degreesC resulted in a significant increase in the ability to detect parasiteDNA, though no other positive associations were observed between the experimental storagetreatments and PCR amplification.
Cold chain maintenance of desiccated mosquito samples is not necessary for real-time PCRdetection of parasite DNA.
Though field-collected mosquitoes may be subjected to variableconditions prior to molecular processing, the storage of samples over an inexpensive andlogistically accessible desiccant will likely ensure accurate assessment of malaria parasitepresence without diminishing PCR-detection of parasites in mosquitoes stored for at least sixmonths.
Author: Mark A RiderBrian D ByrdJoseph KeatingDawn M WessonKevin A Caillouët Credits/Source: Malaria Journal 2012, 11:193
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