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 Plasmodium 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 microscopy 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 (κ = 0.95) compared to nested PCR. Sensitivity and specificity of microscopy for diagnosis 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.

Humoral immune response to falciparum malaria during pregnany

Humoral immune respone against Plasmodium Falciparum was studied ontwo hundred and thirty seven pregnant and non pregnant women in Tha-hton township during premonsoon season of 1998. Slide positivity rate among pregnant women was 7.3

(10/137), fifty percent of which were primigravide. Eighty percent of infection occured druing second trimester. Antimalarial antibiodies were determined by both Indirect Fluorescent Antibody Test (IFAT) and Enzyme Linked Immunosorbent Assay (ELISA). IFAT seropositivity rate was 63.33

(n=33) in primigravidae and 83.63

(n=11) in non pregnant healthy women. In the convalescent sera, the rates were 77.14

(n=7) and 87.33

(n=15) respectively. These IFAT results were also comparable with those of ELISA. Lower seropositivity rate and mean antibodytitre were observed in pregnant women compared with non-pregnants. These findings inply that there is suppression of antimalarial immunity druing pregnancy

The drug sensitivity patterns of Plasmodium falciparum in Myanmar (1990)

During 1990, sensitivity of P. falciparum to antimalarials was conducted in Mawlamyaing, Lashio and Seik Phyu townships. There were 40 successful in vitro test in Mawlamyaing, 39 in Lashio, 26 in Seik Phyu township. Chloroquine was found to be highly resistant (95 to 100 Percent) in Mawlamyaing and Lashio areas but 31 Percent sensitivity was detected in Seik Phyu township. Amodiaquine was found to be much more sensitive (38 to 67 Percent) than chloroquine. Effective concentration (EC99) for chloroquine varies from 7.4 to 8.4 U mol/L and EC99 for amodiaquine varies from 0.58 to 1.6 U mol/L. In all the areas studied sulfadoxine/pyrimethamine sensitivity was seen in 65 to 80 Percent. All the isolates from the three areas were 100 Percent sensitive to mefloquine and were also highly sensitive (93 to 100 Percent) to quinine. EC99 of quinine varies from 1.35 to 2.7 U mol/L and EC99 of mefloquine varies from 1.5 to 2.2 U mol/L in the areas.

Plasmodium falciparum; merozoite invasion rate in erythrocytes with b-thalassaemia trait and glucose-6-phosphate dehydrogenase deficient genes

The malaria parasite invasion-erythrocyte membrane protein variation hypothesis was tested on red cells collected from subjects with G-6-PD deficiency and -thalassaemia trait genes. A series of in vitro competition assays were carried out by using serial dilution technique and the FITC-labelling method (1). The results showed that the invasion rates of P. falciparum merozoites into two G-6-PD hemizygotes deficient cell were Gd- 100 Percent of normal and Gd-Myanmar 95 Percent of normal. But in erythrocytes from two patients with double gene defects viz. G-6-PD mild deficient gene GdB-with -thalassaemia trait gene was 25 Percent and G-6-PD severely deficient gene Gd-Myanmar with -thalassaemia trait gene was 20 Percent susceptible to merozoite invasion. The invasion rate of malaria merozoites in these cells could be inhibited by the partial loss of vital attachement of the red cell membrane required for the process of invasion.

A rapid diagnosis of malaria parasites by acridine orange staining method

The study was designed to find out the diagnostic value of Acridine orange staining method in detection of malaria parasite (Plasmodium falciparum) in comparison with the conventional thick and thin blood films. Thirty two P. falciparum and two P. vivax malaria cases were included in thestudy and the thick blood film and acridine orange staining methods were found to be more sensitive in detecting asexual and sexual parasites (gametocytes) than the thin film. It needs 2-4 weeks time to train a technician to beable to detect the parasites in thick and thin film methods, but acridine orange staining method can be transferred within an hour. Another advantage of acridine orange staining method is the shortest examination time, lasting only 45 seconds whereas the thick and thin blood films need 5 to 10 minutes. Hence, it is concluded that the acridine orange staining method is useful for quick diagnosis of malaria although accessary eauipment is required.

The changing incidence of plasmodium vivax infection in subjects with malaria (Short report)

Malaria is still the most important parasitic disease in the tropics. Malaria is caused by a protozoan parasite of the genus Plasmodium, of which three species are commonly known to infect people living in Union of Myanmar. They are P. falciparum, P. vivax and P. malariae. Although vivax and malariae infections are not generally life threatening , they can cause a sometime severe acute illness. Vivax forms of malaria are characterized by relapses i.e. reappearance of symptoms of parasitaemia following a "latent" or symptomless period of up to five years. Chronic or repeated vivax malaria infection often causes impaired growth in activity in adults. Therefore our findings will suggest closer supervision and effective measures against increasing incidence of vivax malaria in some areas of Myanmar Naing-Ngan.

In vitro and in vivo antimalaial activities of artesunate

Artesunate, a derivative of Quinghaosu (Artemisinine) was test for antimalarial activities against four isolates of Plasmodium falciparum in vitro and Plasmodium berghei- mouse model in vivo. The minimum inhibitory concentration of Artesunate in vitro was 6.0 p Mol per well whereas in vivo ED 90 was 1.4 mg/kg day.

Inhibition of Plasmodium falciparum merozoites invasion by immune sera from malaria infected subjects

The study was conducted on sera samples of 92 subjects from malaria endemic areas. All 92 subjects have experienced either previous or present infection with different parasitaemia levels of Plasmodium falciparum. The relationship between frequency of malaria infection, parasite densities and immunofluorescence malaria antibody titres of P. falciparum were studied. There was no significant correlation between IFA titres and parasitaemia levels or frequency of malarial infection. The serum inhibition to invasion of P. falciparum merozoites in vitro was found to vary according to the sera obtained from subjects with various malarial immune status. Parasite inhibitory antibody was not evident in sera from acutely infected subjects but was significantly observed in sera from convalescent subjects with an inhibition of P.falciparum merozoite invasion up to 85 per cent.