Historical review of malaria control and elimination in the border areas of China: A case study of Yunnan Province.

To understand how malaria could be eliminated in the original hyperendmic area for malaria along international borders in Yunnan Province, malaria situation and control were described on the basis of seven phases. At last the experiences and lessons of the program that reduced border malaria from hyperendmicity to malaria-free status were summarized. Malaria control and elimination area were particularly difficult in the Yunnan border. The achievement can be attributed to high political commitment, strategic and technical innovations based on the actual locality, effective collaboration and communication with neighbouring countries to carry out cross border interventions. Other border areas might perform their own pilot interventions based on their local context, including malaria burden, governing system, health service structure contextualized based on their socioeconomic development and ecology, and then a local decision could be made according to their own trial results.

Genetic polymorphism of merozoite surface proteins 1 and 2 of Plasmodium falciparum in the China-Myanmar border region.

BACKGROUND: Malaria is a major public health problem in the China-Myanmar border region. The genetic structure of malaria parasite may affect its transmission model and control strategies. The present study was to analyse genetic diversity of Plasmodium falciparum by merozoite surface proteins 1 and 2 (MSP1 and MSP2) and to determine the multiplicity of infection in clinical isolates in the China-Myanmar border region. METHODS: Venous blood samples (172) and filter paper blood spots (70) of P. falciparum isolates were collected from the patients of the China-Myanmar border region from 2006 to 2011. The genomic DNA was extracted, and the msp1 and msp2 genes were genotyped by nested PCR using allele-specific primers for P. falciparum. RESULTS: A total of 215 P. falciparum clinical isolates were genotyped at the msp1 (201) and msp2 (204), respectively. For the msp1 gene, MAD20 family was dominant (53.49%), followed by the K1 family (44.65%), and the RO33 family (12.56%). For the msp2 gene, the most frequent allele was the FC27 family (80.93%), followed by the 3D7 family (75.81%). The total multiplicity of infection (MOI) of msp1 and msp2 was 1.76 and 2.21, with a prevalence of 64.19% and 72.09%, respectively. A significant positive correlation between the MOI and parasite density was found in the msp1 gene of P. falciparum. Sequence analysis revealed 38 different alleles of msp1 (14 K1, 23 MAD20, and 1 RO33) and 52 different alleles of msp2 (37 3D7 and 15 FC27). CONCLUSION: The present study showed the genetic polymorphisms with diverse allele types of msp1 and msp2 as well as the high MOI of P. falciparum clinical isolates in the China-Myanmar border region.

Assessment of malaria control consultation and service posts in Yunnan, P. R. China.

BACKGROUND: This paper seeks to assess the function of malaria control consultation and service posts (MCCSPs) that are located on the border areas of Yunnan province, P.R. China, as a strategy for eliminating malaria among the mobile and migrant population in these areas. METHODS: A retrospective descriptive analytical study was conducted. Blood smear examinations conducted at all MCCSPs in Yunnan from 2008 to 2014 were analysed. A cross-sectional survey was conducted in 2014 to understand how the MCCSPs function and to elucidate the quality of the blood smear examinations that they conduct. RESULTS: Out of the surveyed MCCSPs, 66 % (39/59), 22 % (13/59), and 12 % (7/59) were attached to local township hospitals, village health clinics, and the county centre for disease control and prevention or private clinics, respectively. More than 64 % (38/59) of the posts' staff were part-time workers from township hospitals and village health facilities. Less than 31 % (18/59) of the posts' staff were full-time workers. A total of 35 positive malaria cases were reported from seven MCCSPs in 2014. Four MCCSPs were unable to perform their functions due to under staffing in 2014. There was a small fluctuation in blood smear examinations from January 2008 to June 2009, with two peaks during the period from July 2009 to October 2010. The number of blood smear examinations has been increasing since 2011. The yearly mean number of blood smear examinations in each post increased from 44 per month in 2011 to 109 per month in 2014, and the number of positive malaria cases detected by blood smear examinations has declined (χ 2 = 90.67, P = 0.000). The percentage of people from Yingjiang county getting blood smear examinations increased between 2008 and 2014, while percentages of the mobile population including Myanmar people, people from other provinces, and people from other Yunnan counties getting blood smear examinations decreased. CONCLUSION: MCCSPs face challenges in the phase of malaria elimination in Yunnan, China. New case detection strategies should be designed for MCCSPs taking into account the current trends of migration.

[Species Identification and Sequence Analysis of Plasmodium spp. in Border Areas of Yunnan Province by 18S rRNA-based Nested PCR]

Objective: To analyze blood samples from patients with falciparum malaria and vivax malaria in border areas of Yunnan Province, using 18S rRNA-based nested PCR, and compare 18S rRNA sequences. Methods: Blood or filter blood samples with positive microscopic results for Plasmodium falciparum or P. vivax infection were collected from Laza, Nankajiang, Mangdong and Nawei of Myanmar, and from Mengla, Tengchong and Yingjiang of Yunnan Province between 2004 and 2011. 18S rRNA-based nested PCR was conducted on the samples, and PCR products were sequenced and blasted. Phylogenetic tree was constructed using the neighbor-joining method with MEGA software (version 6.06). Results: Microscopic examination revealed P. falciparum infection in 256 samples and P. vivax infection in 219 samples. The 18S rRNA-based PCR further confirmed P. falciparum infection in 242 samples, P. vivax infection in 176 samples, and mixed infection in 57 samples. The consistency rate was 81.7% （388/475） between microscopic and PCR results. The inconsistency rate significantly correlated with parasite density （Spearman's r=-0.408， P<0.05）. Sequence alignment revealed 11 and 10 homologous sequences for P. falciparum and P. vivax 18S rRNA gene, comprising 2.9%（6/205） and 22.5%（27/120） variable sites, respectively. The 18S rRNA of P. falciparum clustered with that from Cameroon（GenBank accession number KC428742）, but was distantly related with the S-type 18S rRNA from the Netherlands （U36465） and Brazil （U36466 and U36467）. The 18S rRNA of P. vivax clustered with A-type 18S rRNA from Thailand （U07367）, but was distantly related with the C-type 18S rRNA from Thailand（U07368）. Conclusion: Nested PCR revealed mixed infection in 57 samples among those identified with single infection by microscopy. There is no significant difference in 18S rRNA sequence in seven counties/cities in Yunnan Province.

[Evaluation on Malaria Hotspots in Yingjiang County of the China-Myanmar Border Area in 2015].

Objective: To understand the control status of malaria at hotspots in Yingjiang County and provide measures for malaria elimination in the China-Myanmar border areas of Yunnan Province. Methods: A survey was made in 4 villages with indigenous malaria cases or imported cases in Nabang and Tongbiguan of Yingjiang County in Yunnan Province in June and July 2015. Peripheral blood samples were collected from the neighboring residents around patients and examined by malaria rapid diagnostic test （RDT）. The results were further verified by nested-PCR. Mosquitoes were collected by overnight trapping with light traps in Jingpo, Lilisu, Jiema, and Mengxiangyang villages or by human landing catches in Jingpo and Lisu villages. Nested-PCR was performed on part of the captured Anopheles minimus to detect the malaria parasites. Results: One hundred and ninety-four filter blood samples were collected from 11 malaria cases in two sites. All were detected to be negative for Plasmodium by RDT. In contrast, two samples originated from Jingpo and Lisu villages with indigenous cases were detected to be positive for Plasmodium vivax by nested-PCR. A total of 2 374 mosquitoes were captured, belonging to 22 species of 4 genera: Anopheles, Culex, Aedes and Armigeres. The mosquitoes were predominated by genus Culex, followed by genus Anopheles（11.33%, 269/2 374） which was dominated by A. minimus（49.07%, 132/269）, then was A. sinensis（4.09%, 11/269）, A. maculatus（2.23%, 6/269）, A. jeyporiensis（0.74%, 2/269）and so on. The mean indoor man-biting rate of mosquitoes was 5.78 and 3.20 per person per hour for Jingpo and Lisu villages, and the mean outdoor man-biting rate of mosquitoes was 2.30 per person per hour for Lisu Village. The 14 A. minimus were negative for sporozoite infection as detected by nested-PCR. Conclusion: Nested-PCR showed that there are asymptomatic Plasmodium carriers in Yingjiang's border area of Yunnan Province. Four major mosquito species as malaria vectors exist with A. minimus as the dominant one.

[In vitro sensitivity of Plasmodium falciparum isolates from China-Myanmar border region to chloroquine, piperaquine and pyronaridine].

OBJECTIVE: To assess the in vitro sensitivity of Plasmodium falciparum to chloroquine, piperaquine and pyronaridine in China-Myanmar border area. METHODS: Fifty-one blood specimens of P. falciparum isolates were collected from Laza City of Myanmar during September to December in 2009, and the sensitivity of the parasites to the drugs was detected by Rieckmann's in vitro microtest. RESULTS: Among the 42 blood samples with valid results of sensitivity test, the resistance rate to chloroquine, piperaquine and pyronaridine was 95.2%, 7.1%, and 54.8%, with a corresponding 50% inhibition dose (IDn) of 320.5, 128.2, and 96.0 nmol/L, respectively. Pyronaridine-resistant P. falciparum exhibited some degree of cross-resistance to chloroquine [91.3%(21/23)] and piperaquine [13.0% (3/23)], and chloroquine-resistant P. falciparum showed cross-resistance to piperaquine [7.5%(3/40)] and pyronaridine [52.5%(21/40)]. High level of cross-resistance was present to chloroquine (100%) and pyronaridine (100%) in piperaquine resistant P. falciparum. CONCLUSION: In Laza City, P. falciparum shows high resistance to chloroquine, half isolates are resistant to pyronaridine, and most isolates are still sensitive to piperaquine.