Comparative Study of the Effectiveness of the PCR-based Assay and the Dissection Technique in Detecting Filarial Worms in Wild-caught Mosquitoes

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Kobkan Kanjanopas
Suwich Thammapalo
Sumas Loymak



APCR-based assay was developed in the laboratory by using DNAzol reagent to extract Brugia malayi and Wuchereria bancrofti DNA, and the primers HhaI and SspI for their specific amplifications respectively, which was also applied to detect a single L3 larva in pools of 10, 20, 40, 60, 75 and 100 uninfected mosquitoes. The satisfied PCR was compared with the standard dissection technique in a field situation, with mosquitoes collected from Narathiwat, Tak and Ranong provinces every month from December 2000 to August 2001. The study showed that the PCR assay could detect a single L3 in the largest pool of up to 100 uninfected mosquitoes. The precision rates of detecting one L3 in 20 and 100 uninfected mosquitoes were 96.3 and 85.7%, respectively. The accuracy and the specificity between B. malayi and B. pahangi were 100%. The PCR assay was also 2 times more effective in detecting filarial worms in wild-caught mosquitoes than the dissection technique. Only the data for negative or positive wild-caught mosquitoes infected with B. malayi or W. bancrofti are enough to assess the efficiency of mass drug treatment in transmission areas. Therefore, the policy on entomological surveillance of the Lymphatic Filariasis Elimination Programme in Thailand (2001-2006), by the Vector-Borne Disease Office, Disease Control Department, is to use the PCR technique to detect filarial worms in mosquitoes collected from index areas and to confirm the species of parasites by the dissection technique.

Keywords : PCR, dissection technique, B. malayi, W. bancrofti, mosquitoes, Lymphatic Filariasis Elimination Programme in Thailand

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