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01.12.2017 | Research article | Ausgabe 1/2017 Open Access

BMC Infectious Diseases 1/2017

Clinical diagnostic value of viable Schistosoma japonicum eggs detected in host tissues

Zeitschrift:
BMC Infectious Diseases > Ausgabe 1/2017
Autoren:
Kongzhen Gu, Yuesheng Li, Patrick Driguez, Qingren Zeng, Xinlin Yu, Hui Sun, Liting Cai, Yongkang He, Wenyang Wang, Donald P. McManus
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12879-017-2362-4) contains supplementary material, which is available to authorized users.

Abstract

Background

Schistosomiasis, one of the neglected tropical diseases, is endemic in more than 70 countries. However, the clinical diagnosis of patients with a low degree of infection is an unsolved technical problem. In areas endemic for schistosomiasis japonica, proctoscopy detection of eggs has been one method used for clinical diagnosis. However, it is often a challenge to find typical live eggs and it is difficult to distinguish live eggs from large numbers of partially degraded and/or completely degraded eggs within colon biopsy tissue. To address this problem, we tested six different morphological and biochemical/molecular markers (ALP; morphological characteristics of egg; CalS (calcified substance); AOS (antioxidase); SDHG (succinic dehydrogenase) and SjR2 mRNA (retrotransposons 2 of S.japonicum genome mRNA)), including four new markers (CalS; AOS; SDHG and SjR2 mRNA.), to determine the viability of S. japonicum eggs deposited in human and mouse colon tissues. Our ultimate aim is to obtain a new method that is more sensitive, practical and accurate to clinically diagnose schistosomiasis.

Methods

Tissue samples were collected from mice at six different time points during S. japonicum infection with or without treatment with praziquantel (PZQ). Four new biochemical or molecular markers were used for the detection of egg viability from mouse liver and intestinal samples: CalS; AOS; SDHG and SjR2 mRNA. Subsequently, all markers were employed for the detection and analysis of eggs deposited in biopsy materials from patients with suspected schistosomiasis japonica for clinical evaluation. Microscopic examination of the egg morphology, worm burden in vivo and ALP (alkaline phosphatase) levels were used as a reference standard to evaluate the sensitivity and reliability of four new markers detecting egg viability.

Results

The results of the study showed that the morphology of S. japonicum eggs deposited in tissues of hosts with schistosomiasis, especially cases with chronic schistosomiasis, is complex and egg viability is difficult to judge morphologically, particularly eggs with a fuzzy structure or partially modified eggs. We found that the majority of the viable schistosome eggs determined by four new markers (CalS, AOS, SDHG and SjR2 mRNA) were morphologically difficult to identify.

Conclusions

Among the markers, the most sensitive and specific method was the detection of SjR2 mRNA and the most simple, rapid and practical method was the detection of SDHG. Therefore, the detection of SDHG is the most practical for clinical application and its use could improve the accuracy in diagnosing active schistosome infection.
Zusatzmaterial
Additional file 6: Figure S5. AOS staining results for S. japonicum eggs in mouse colonic tissue. A, B and C indicate free eggs isolated from either tissues of infected mice with S. japonicum at 45 days and 180 days post infection or tissues of treated mice at 90 days post treatment. After staining with DAB, eggs in Fig. A developed a positive deep yellow or brown color. Some eggs in Fig. B were positive response and are indicated by blue arrows. In Fig. C, no eggs were positive. Figs 1, 2, 3, 4, 5 and 6 (1: 45 dPI group; 2: 90 dPI group; 3: 120 dPI group; 4: 30 dPT group; 5: 90 dPT group; 6: 180 dPT group) show DAB stained eggs in colon tissue from mice. Among them, all eggs in Figs 1 and 2 developed a positive deep yellow color. Some eggs in Figs 3 and 4 were positive indicated by blue arrows. None of the eggs in Figs 5 and 6 were positive. Eggs that were negative were morphologically empty and had a fuzzy structure or appeared black (400× magnification). (JPEG 82 kb)
Literatur
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