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Evaluation of circumsporozoite protein of Plasmodium vivax to estimate its prevalence in the Republic of Korea: an observational study of incidence

Pyo-Yun Cho1, Sang-Wook Lee2, Seong Kyu Ahn1, Jin Su Kim1, Seok Ho Cha3, Byoung-Kuk Na4, Yun-Kyu Park1, Sung Keun Lee5, Won-Ja Lee6, Ho-Woo Nam7, Sung-Jong Hong8, Jhang Ho Pak9, Yoon-Joong Kang10, Youngjoo Sohn11, Young-Yil Bahk12, Han-Ik Cho13, Tong-Soo Kim1* and Hyeong-Woo Lee2*

Author Affiliations

1 Departments of Parasitology, Inha University School of Medicine, Incheon 400-712, Republic of Korea

2 Department of Pathology, Immunology, & Laboratory Medicine, College of Medicine, University of Florida, J-566, 1275 Center Drive, Gainesville FL 32610, USA

3 Department of Biomedical Technology, Inha University School of Medicine, Incheon 400-712, Republic of Korea

4 Department of Parasitology and Institute of Health Sciences, Gyeongsang University School of Medicine, Jinju 660-751, Republic of Korea

5 Department of Pharmacology, Inha University School of Medicine, Incheon 400-712, Republic of Korea

6 Department of Parasitology, National Institute of Health, Osong 363-951, Republic of Korea

7 Department of Parasitology and Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, Seoul 137-701, Republic of Korea

8 Department of Medical Environmental Biology, College of Medicine, Chung-Ang University, Seoul 156-756, Republic of Korea

9 Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea

10 Department of Biomedical Science, Jungwon University, Goesan Chungbuk 367-805, Republic of Korea

11 Department of Anatomy, College of Korean Medicine, Institute of Korean Medicine, Kyung Hee University, Seoul 130-701, Republic of Korea

12 Department of Biotechnology, College of Biomedical and Health Sciences, Konkuk University, Chungju 380-701, Republic of Korea

13 Korea Association of Health Promotion, Seoul 157-928, Republic of Korea

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Malaria Journal 2013, 12:448  doi:10.1186/1475-2875-12-448

Published: 13 December 2013

Abstract

Background

Plasmodium vivax re-emerged in 1993. Although the number of infections has been steadily decreasing, it is likely to continue to affect public health until it is eradicated. The aim of this study is to measure anti-circumsporozoite protein (CSP) antibody and compare malaria prevalence. As to understand the prevalence, an epidemiology study has to be conducted in the Republic of Korea.

Methods

A total of 1,825 and 1,959 blood samples were collected in 2010 and 2011, respectively, from the inhabitants of Ganghwa and Cheorwon counties. The antibody titers of the inhabitants were measured by enzyme-linked immunosorbent assay (ELISA) using recombinant protein purified from Escherichia coli transformed with a CSP gene-inserted pET-28a(+) expression vector. Microscopic examination was performed to identify malaria parasites.

Results

The annual parasite incidence (API) in Ganghwa decreased from 4.28 in 2010 to 2.23 in 2011, and that in Cheorwon decreased from 1.88 in 2010 to 1.15 in 2011. The antibody-positive CSP rate in these areas also decreased from 18.14% (331/1825) in 2010 to 15.36% (301/1959) in 2011. Pearson analysis showed a strong correlation between the API and the antibody-positive CSP rate in these areas (r = 1.000, P < 0.01). The intensity of the immune responses of the inhabitants of Cheorwon, as measured by the mean optical density, decreased from 0.9186 ± 0.0472 in 2010 to 0.7035 ± 0.0457 in 2011 (P = 0.034), but increased in Ganghwa from 0.7649 ± 0.0192 in 2010 to 0.8237 ± 0.1970 in 2011 (P = 0.006). The immune response increased according to age (r = 0.686, P = 0.041).

Conclusions

The positive CSP-ELISA rate was closely related to the API in the study areas. This suggests that seroepidemiological studies based on CSP-ELISA may be helpful in estimating the malaria prevalence. Moreover, such studies can be used to establish and evaluate malaria control and eradication programmes in high-risk areas in Korea.