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Acta Trop. 2015 Jan;141(Pt B):190-7. doi: 10.1016/j.actatropica.2014.08.004. Epub 2014 Aug 14.

An ultra-sensitive assay targeting the circulating anodic antigen for the diagnosis of Schistosoma japonicum in a low-endemic area, People's Republic of China.

Author information

1
Department of Parasitology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. Electronic address: G.J.van_Dam@lumc.nl.
2
National Institute of Parasitic Diseases, Chinese Center for Diseases Control and Prevention, Key Laboratory of Parasite & Vector Biology, Ministry of Public Health, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai 200025, People's Republic of China. Electronic address: xfmjing@163.com.
3
Ingerod 407, S-45494 Brastad, Sweden.
4
Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
5
Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland; University of Basel, P.O. Box, CH-4003 Basel, Switzerland.
6
National Institute of Parasitic Diseases, Chinese Center for Diseases Control and Prevention, Key Laboratory of Parasite & Vector Biology, Ministry of Public Health, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai 200025, People's Republic of China.
7
Hunan Institute of Parasitic Diseases, WHO Collaborating Centre for Research and Control on Schistosomiasis in Lake Region, Yueyang 41400, People's Republic of China.

Abstract

The downward trend in prevalence and intensity of Schistosoma japonicum infection in the People's Republic of China (P.R. China) has reached a level where accurate methods are required for monitoring the national schistosomiasis control programme and to verify whether transmission has been interrupted. We have assessed the prevalence of active S. japonicum infection by use of an up-converting phosphor lateral-flow (UCP-LF) assay for determination of circulating anodic antigens (CAA) in urine and serum, and compared the findings with those of the Kato-Katz technique for egg detection in stool and an immunohaemagglutination assay (IHA) for specific antibodies in serum. The study was carried out in three villages located in a remaining S. japonicum-endemic area in P.R. China. Overall, 423 individuals were investigated by Kato-Katz, 395 by IHA, 371 with the UCP-LF CAA assay adapted for urine and 178 with the UCP-LF CAA assay applied on serum. The IHA showed the highest number of positive results (n=107, 27.1%). The UCP-LF CAA urine assay detected 36 CAA positives (9.7%) and the serum-based CAA assay 21 positives (11.8%). The Kato-Katz technique revealed only six positive stool samples (1.4%). Among those 166 individuals with complete data records, sensitivities of the different assays were determined versus a combined 'gold' standard, showing the highest sensitivity for the urine CAA assay (93%), followed by the serum CAA (73%) and IHA (53%), whilst triplicate Kato-Katz thick smears had a very low sensitivity (13%). Serum CAA concentrations were about 10-fold higher than in urine and were significantly correlated. Highest prevalences as determined by CAA were found in older age groups (>40 years). Half of the CAA- or egg-positive cases were negative for antibodies by IHA, thereby revealing an important obstacle for the effectiveness of the current schistosomiasis control and elimination efforts. The significantly higher prevalence of active schistosome infections as shown by the urine and serum UCP-LF CAA assays has implications for the national control and elimination programme in P.R. China, particularly in respect to case-finding and intervention strategies.

KEYWORDS:

Circulating anodic antigen (CAA); Diagnosis; Immunohaemagglutination assay; Kato–Katz technique; People's Republic of China; Schistosoma japonicum; Schistosomiasis; Up-converting phosphor lateral-flow assay

[Indexed for MEDLINE]

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