Molecular characterization of G6PD mutations reveals the high frequency of G6PD Aures in the Lao Theung population.

BACKGROUND: The prevalence and genotypes of G6PD deficiency vary worldwide, with higher prevalence in malaria endemic areas. The first-time assessment of G6PD deficiency prevalence and molecular characterization of G6PD mutations in the Lao Theung population were performed in this study. METHODS: A total of 252 unrelated Lao Theung participants residing in the Lao People's Democratic Republic (PDR) were recruited. All participant samples were tested for G6PD enzyme activity and G6PD gene mutations. The amplification refractory mutation system (ARMS)-PCR for detecting G6PD Aures was developed. RESULTS: The G6PD mutations were detected in 11.51% (29/252) of the participants. Eight G6PD mutations were detected. The G6PD Aures was the most common mutation identified in this cohort, which represented 58.62% (17/29) of all mutation. The mutation pattern was homogenous, predominantly involving the G6PD Aures mutation (6.75%), followed by 1.19% G6PD Union and 0.79% each G6PD Jammu, G6PD Mahidol and G6PD Kaiping. One subject (0.4%) each carried G6PD Viangchan and G6PD Canton. Interestingly, one case of coinheritance of G6PD Aures and Quing Yan was detected in this cohort. Based on levels of G6PD enzyme activity, the prevalence of G6PD deficiency in the Lao Theung population was 9.13% (23/252). The prevalence of G6PD deficient males and females (activity < 30%) in the Lao Theung population was 6.41% (5/78) and 1.72% (3/174), respectively, and the prevalence of G6PD intermediate (activity 30-70%) was 5.95% (15/252). CONCLUSIONS: The G6PD Aures mutation is highly prevalent in the Lao Theung ethnic group. The common G6PD variants in continental Southeast Asian populations, G6PD Viangchan, Canton, Kaiping, Union and Mahidol, were not prevalent in this ethnic group. The technical simplicity of the developed ARMS-PCR will facilitate the final diagnosis of the G6PD Aures.

Genetic analysis of the merozoite surface protein-1 block 2 allelic types in Plasmodium falciparum clinical isolates from Lao PDR.

BACKGROUND: MSP-1 is one of the potential malarial vaccine candidate antigens. However, extensive genetic polymorphism of this antigen in the field isolates of Plasmodium falciparum represents a major hindrance for the development of an effective vaccine. Therefore, this study aimed to establish the prevalence and genetic polymorphisms of K1, MAD20 and RO33 allelic types of msp-1 block 2 among P. falciparum clinical isolates from Lao PDR. METHODS: Plasmodium falciparum isolates were collected from 230 P. falciparum-infected blood samples from three regions of Lao PDR. K1, MAD20 and RO33 were detected by nested PCR; SSCP was used for polymorphism screening. The nested PCR products of each K1, MAD20 and RO33 allelic types that had different banding patterns by SSCP, were sequenced. RESULTS: The overall prevalence of K1, MAD20 and RO33 allelic types in P. falciparum isolates from Lao PDR were 66.95%, 46.52% and 31.30%, respectively, of samples under study. Single infections with K1, MAD20 and RO33 allelic types were 27.83%, 11.74% and 5.22%, respectively; the remainders were multiple clonal infections. Neither parasite density nor age was related to MOI. Sequence analysis revealed that there were 11 different types of K1, eight different types of MAD20, and 7 different types of RO33. Most of them were regional specific, except type 1 of each allelic type was common found in 3 regions under study. CONCLUSIONS: Genetic polymorphism with diverse allele types was identified in msp-1 block 2 among P. falciparum clinical isolates in Lao PDR. A rather high level of multiple clonal infections was also observed but the multiplicity of infection was rather low as not exceed 2.0. This basic data are useful for treatment and malaria control program in Lao PDR.

Zoonotic Helminthiases in Rodents (Bandicota indica, Bandicota savilei, and Leopoldamys edwardsi) from Vientiane Capital, Lao PDR.

Zoonotic helminths of three rodent species, Bandicota indiaca, Bandicota savilei, and Leopoldamys edwardsi, were investigated in Vientiane capital, Lao PDR. A total of 310 rodents were infected with 11 species of helminth parasites. There were 168 (54.2%) of 310 rodents infected with zoonotic helminths. From our results, there are six recorded zoonotic helminth species, and the highest prevalence was exhibited by Raillietina sp. (30.7%), followed by Hymenolepis diminuta (17.7%), Hymenolepis nana (2.6%), Echinostoma ilocanum (1.9%), Echinostoma malayanum (1.3%), and Angiostrongylus cantonensis (1%). This is the first study of zoonotic helminths in L. edwardsi and the first report of H. diminuta, H. nana, E. ilocanum, and E. malayanum in Bandicota indica and B. savilei, and the first demonstration of A. cantonenensis in B. indica in Lao PDR. From our results, these three rodents are potentially important reservoir hosts of zoonotic helminths. Thus, effective control programs should be considered for implementation to prevent the transmission of these zoonoses in this area.

A survey of malarial infection in endemic areas of Savannakhet province, Lao PDR and comparative diagnostic efficiencies of Giemsa staining, acridine orange staining, and semi-nested multiplex PCR.

Malaria remains one of the most important parasitic diseases in Lao PDR, especially in forested rural areas. Knowing the rate of infection using highly sensitive and specific methods, and the factors related to malarial infection, may be helpful in reducing the infection and mortality rates. We aimed to study the malarial infection rate by comparing three detection methods, i.e., Giemsa staining, acridine orange (AO) staining and semi-nested multiplex PCR. The study also included some factors related to malarial infection in the endemic areas of Savannakhet province, Lao PDR. The respective malarial infection rates by Giemsa staining, AO staining and semi-nested multiplex PCR in Houy Jang vs. Keng Thong villages were 13.1 vs. 20.8, 16.2 vs. 25.4 and 20.8 vs. 30.8%. The infection rate among children not over 10 years of age was higher than infection rate among the older ages (p=0.002, Z-test for two proportions). The higher infection rates by semi-nested multiplex PCR over Giemsa and AO staining suggest the existence of many subclinical cases with low level parasitemia, undetected by microscopic techniques. We found no mixed infections using Giemsa or AO staining, but using semi-nested multiplex PCR we found 1.2% (3/260) mixed P. falciparum and P. vivax infections, suggesting that semi-nested multiplex PCR is suitable for detecting malarial infection from endemic areas whose cases may have low parasitemia and/or mixed infection. The factors significantly related to malarial infection from 260 questionnaires were: (1) children and young adults, (2) not having lived in the area more than 5 years, and (3) not using a mosquito net over the bed, indicating an increased risk of new residents of contracting malaria and a need to promote bed nets.