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Bi Y.,Queensland University of Technology | Bi Y.,U.S. Center for Disease Control and Prevention | Hu W.,University of Queensland | Yang H.,Yunnan Institute of Parasitic Diseases | And 4 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2013

Malaria has been a heavy social and health burden in the remote and poor areas in southern China. Analyses of malaria epidemic patterns can uncover important features of malaria transmission. This study identified spatial clusters, seasonal patterns, and geographic variations of malaria deaths at a county level in Yunnan, China, during 1991-2010. A discrete Poisson model was used to identify purely spatial clusters of malaria deaths. Logistic regression analysis was performed to detect changes in geographic patterns. The results show that malaria mortality had declined in Yunnan over the study period and the most likely spatial clusters (relative risk [RR] = 23.03-32.06, P < 0.001) of malaria deaths were identified in western Yunnan along the China-Myanmar border. The highest risk of malaria deaths occurred in autumn (RR = 58.91, P < 0.001) and summer (RR = 31.91, P < 0.001). The results suggested that the geographic distribution of malaria deaths was significantly changed with longitude, which indicated there was decreased mortality of malaria in eastern areas over the last two decades, although there was no significant change in latitude during the same period. Public health interventions should target populations in western Yunnan along border areas, especially focusing on floating populations crossing international borders. Copyright © 2013 by The American Society of Tropical Medicine and Hygiene.

Chen G.W.,Yunnan Institute of Parasitic Diseases
Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi = Chinese journal of parasitology & parasitic diseases | Year: 2011

Malaria situation in 5 monitoring sites of Yunnan showed a decline trend from 2005 to 2008. The average malaria incidence in 2008 was 11.84/10,000 with a decrease of 66.1% in comparison to 2005. The seropositive rate with immuno-fluorescence assay (IFA) was 4.61% for pupils. 82% of the cases chose town or township hospitals as the first place of seeking diagnosis and treatment. 83.6% cases were diagnosed over 3 days of symptom appearing. The main clinical manifestation was fever every other day attack (occupied 72.7%). 98.4% of the cases were with light symptoms. The proportion of primary attacks and relapses among malaria patients were 95.3% and 4.7%, respectively. Plasmodium vivax was the main malaria parasite, occupying 81.2%. 97.2% of the local infected cases were found in the bordering areas of the country. The mosquito net utilization rate was 51.4%. Results showed that malaria has been effectively controlled in the monitoring sites of Yunnan.

Cheng Z.,Peking Union Medical College | Sun X.,Yunnan Institute of Parasitic Diseases | Yang Y.,Peking Union Medical College | Wang H.,Peking Union Medical College | Zheng Z.,Peking Union Medical College
Journal of Clinical Microbiology | Year: 2013

Although malaria remains one of the leading infectious diseases in the world, the decline in malaria transmission in some area makes it possible to consider elimination of the disease. As countries approach elimination, malaria diagnosis needs to change from diagnosing ill patients to actively detecting infections in all carriers, including asymptomatic and low-parasite-load patients. However, few of the current diagnostic methods have both the throughput and the sensitivity required. We adopted a sandwich RNA hybridization assay to detect genus Plasmodium 18S rRNA directly from whole-blood samples from Plasmodium falciparum and Plasmodium vivax patients without RNA isolation. We tested the assay with 202 febrile patients from areas where malaria is endemic, using 20 μl of each blood sample in a 96-well plate format with a 2-day enzyme-linked immunosorbent assay (ELISA)-like work flow. The results were compared with diagnoses obtained using microscopy, a rapid diagnostic test (RDT), and genus-specific real-time PCR. Our assay identified all 66 positive samples diagnosed by microscopy, including 49 poorly stored samples that underwent multiple freeze-thaw cycles due to resource limitation. The assay uncovered three false-negative samples by microscopy and four false-negative samples by RDT and agreed completely with real-time PCR diagnosis. There was no negative sample by our assay that would show a positive result when tested with other methods. The detection limit of our assay for P. falciparum was 0.04 parasite/μl. The assay's simple work flow, high throughput, and sensitivity make it suitable for active malaria screening. Copyright © 2013, American Society for Microbiology. All Rights Reserved.

Xu J.-W.,Yunnan Institute of Parasitic Diseases | Liu H.,Yunnan Institute of Parasitic Diseases
Malaria Journal | Year: 2016

Background: Understanding malaria along the international border of two countries is important for malaria control and elimination; however, it is difficult to investigate a quantitative relationship between two countries' border areas due to a shortage of malaria surveillance data. Methods: A linear regression analysis was conducted to investigate the logarithmic annual parasite incidence (API), numbers of imported cases and local infections in 19 Chinese border counties, with logarithmic API and parasitic prevalence in Myanmar's five special regions. Results: API in 19 Chinese counties was stronger correlated with parasite prevalence than with API in five special regions of Myanmar, correlation coefficient (R) 0.8322 (95 % CI 0.0636-0.9084) versus 0.9914 (95 % CI 0.9204-0.9914). Numbers of imported malaria cases and local malaria infections in 19 Chinese counties were also closer correlated with parasite prevalence than with API in five special regions of Myanmar. Conclusions: There is a strong correlation of malaria between China's side and Myanmar's side along the international border. Parasite prevalence is a better indicator of the true malaria situation in a setting without sound surveillance and reporting system. China should reconsider its definition of imported malaria which neglects imported malaria by mosquitoes and asymptomatic parasite carriers. © 2016 The Author(s).

Xu J.-W.,Yunnan Institute of Parasitic Diseases | Liu H.,Yunnan Institute of Parasitic Diseases | Zhang Y.,Clinical Laboratory | Guo X.-R.,U.S. Center for Disease Control and Prevention | Wang J.-Z.,U.S. Center for Disease Control and Prevention
American Journal of Tropical Medicine and Hygiene | Year: 2015

A retrospective case-control study was conducted to identify risk factors for border malaria in a malaria elimination setting of Yunnan Province, China. The study comprised 214 cases and 428 controls. The controls were individually matched to the cases on the basis of residence, age, and gender. In addition, statistical associations are based on matched analyses. The frequencies of imported, male, adult, and vivax malaria cases were respectively 201 (93.9%), 194 (90.7%), 210 (98.1%), and 176 (82.2%). Overnight stay in Myanmar within the prior month was independently associated with malaria infection (odds ratio [OR] 159.5, 95% confidence interval [CI] 75.1-338.9). In particular, stays in lowland and foothill (OR 5.5, 95%CI 2.5-11.8) or mid-hill (OR 42.8, 95% CI 5.1-319.8) areas, or near streamlets (OR 15.3, 95% CI 4.3-55.2) or paddy field or pools (OR10.1, 95% CI 4.4-55.8) were found to be independently associated with malaria. Neither forest exposure nor use of vector control measures was associated with malaria. In conclusion, travel to lowland and foothill or mid-hill hyperendemic areas, especially along the waterside in Myanmar, was found to be the highest risk factor for malaria. In considering the limitations of the study, further investigations are needed to identify the major determinants of malaria risk and develop new strategies for malaria elimination on China-Myanmar border. Copyright © 2015 by The American Society of Tropical Medicine and Hygiene.

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