Comparison of microscopy and PCR for the detection of human Plasmodium species and Plasmodium knowlesi in southern Myanmar

Objectives: To determine the distribution of Plasmodium (P) species including Plas-modium knowlesi and to compare the specificity and sensitivity of microscopy with nested PCR in malaria diagnosis. Methods: The study was conducted in Kawthaung, southern Myanmar. Ninety clinically suspected malaria patients were screened for malaria by Giemsa stained microscopy and confirmed by nested PCR. Results: Among the participants, 57 (63.3％) were positive and 33 (36.7％) were negative by microscopy. Of positive samples, 39 (68.4％) were Plasmodium falciparum, 17 (29.8％) Plasmodium vivax and 1 (1.8％) Plasmodium malariae, whereas 59-amplified by PCR were 40 (67.8％), 18 (30.5％) and 1 (1.7％) respectively. PCR amplified 2 mi-croscopy negative samples. Two samples of P. falciparum detected by microscopy were amplified as P. vivax and vice versa. All samples were negative for Plasmodium ovale, P. knowlesi and mixed infections. Microscopy had a very good measure of agreement (k= 0.95) compared to nested PCR. Sensitivity and specificity of microscopy for diag-nosis of P. falciparum were 92.5％(95％CI:79.6–98.4) and 96.0％(95％CI:86.3–99.5) respectively, whereas for P. vivax were 83.3％(95％CI:58.6–96.4) and 97.2％(95％CI:90.3–99.7). Conclusions: P. knowlesi was not detected by both microscopy and PCR. Giemsa stained microscopy can still be applied as primary method for malaria diagnosis and is considered as gold standard. As to the lower sensitivity of microscopy for vivax malaria, those with previous history of malaria and relapse cases should be diagnosed by RDT or PCR combined with microscopy. Inaccuracy of species diagnosis highlighted the requirement of training and refresher courses for microscopists.

Modified technique of Wolbachia removal from Malaysian Aedes albopictus

Objective: To develop an artificial and modified Wolbachia removal technique using tetracycline from naturally Wolbachia infected Aedes albopictus (Ae. albopictus) so as to be able to produce generations of Wolbachia free offsprings.Methods:In this study, seven different tetracycline treatment methods were conducted to obtain the best removal method. Four methods focused on larvae tetracycline treatment, one method on both larvae and adult tetracycline treatment and the last two methods on adult mosquito sucrose treatment.Results:All larval tetracycline treatments resulted in either high larvae mortality, sterile F0 adult mosquitoes or unsuccessful Wolbachia removal. Treatment of both larvae and adults resulted in reduced larvae mortality, successful Wolbachia removal but slow mosquito fecundity. As for the adult treatment, 1.0 mg/mL as previously published was not able to completely remove Wolbachia in F1 generation whereas 1.25 mg/mL successfully removed Wolbachia from F1 and F2 mosquitoes in 2 weeks. Conclusions: This method is different from the previously published methods as it provides an improved Wolbachia removal technique from Ae. albopictus with high egg hatchability, low larvae mortality, increased fecundity and better Wolbachia removal rate.