RESUMO
Background: Thailand has a national goal to eliminate malaria from 80 percent of the country by 2020. An accurate detection and prevalence are critical to effective management of malaria. Rapid diagnostic tests (RDTs) detecting parasite lactate dehydrogenase (pLDH) antigen are used to identify individuals with Plasmodium falciparum infection even in low transmission settings seeking to achieve elimination. Aims: The aim of this study was to evaluate the exact prevalence of malaria in the Thai border area where malaria is endemic by RDT compared with PCR. Methodology: One thousand one hundred thirty blood samples were obtained from study subjects who live along the Myanmar Thailand Border. RTD was performed with the parasite lactate dehydrogenase (pLDH) antigen-based lateral flow test and the primer set used for PCR was designed on the species-specific nucleotide sequence of 18S rRNA plasmodium gene. Results: Malaria infection was demonstrated in 70 (6.2%) subjects and 97 (8.6%) subjects by RDT and PCR respectively. PCR detected a significantly higher number of malaria infection than RDT (P<0.05). Comparison of RDT negative and PCR positive samples suggested that RDT negatives resulted from low parasitaemia. Moreover, PCR was able to identify the species of Plasmodium parasite. Three species, Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae were detected. No Plasmodium ovalae was detected from any of the study location. P. falciparum was predominant along border with a percentage of 31.9 of positive suspected patients. Mixed infections with two or three malaria species were detected in 54 specimens (55.7%). Conclusion: The result demonstrates that PCR should be undertaken to assess the prevalence of malaria in border areas to progress towards malaria elimination in Thailand.
RESUMO
The early detection of scrub typhus in Thailand by nested polymerase chain reaction (PCR) is presented. The diagnosis of scrub typhus, from clinical samples obtained from hospitals in the northern part of Thailand, by nested PCR was compared to immunofluorescence (IF) and Weil-Felix (WF) tests. The primer pairs used for the nested PCR were designed on the basis of the nucleotide sequence of the gene that encodes the 56-kDa antigen, and RFLP analysis was used for identification. Clotted blood from 80 patients suspected of scrub typhus infection were tested. With the IF test, antibodies for Orientia tsutsugamushi were observed in 38 patients checking IgM and IgG titers. Only 21 patients showed positive seroconversion while 17 patients were negative. For the WF test, only 13 patients gave a positive seroconversion. In the early stage of infection, 19, 13 and 3 patients were detected with a sensitivity of 90.47% (19/21), 61.90% (13/21) and 14.28% (3/21) by the nested PCR, IF and WF test respectively. Two patients who were negative for seroconvesion by IF and WF were positive by nested PCR. Therefore, this suggests that nested PCR is applicable for specific rapid diagnosis at an early stage of scrub typhus in endemic regions.