Volume 106 · Issue 08 · 1993

Schistosomiasis japonica in China has a long history and wide distribution. In the last three decades, great achievements have been obtained in schistosomiasis control. Among 12 formerly endemic provinces, municipalities, and autonomous regions, transmission has been successfully controlled in 2 provinces, 1 municipality and 1 autonomous region. Among 380 formerly endemic counties, transmission has been interrupted in 158 and is under control in 101. Most remaining endemic areas are located in marshlands, lake and mountainous regions. By the ecological and epidemiological features, the endemic areas in lake and mountainous regions can be classified into different categories. Infection is related to exposure to infected lake and ditch water. The inhabitant activities and level of education have much to do with the frequency of water contact. The density of the infected snail is the main index of determining the high-risk place in the mountain and lake regions, and livestock such as buffalo and pigs, the principal reservoir in the endemic areas. Properly arranged annual chemotherapy with praziquantel can reduce the prevalence rate of inhabitants and livestock. However, the prevalence rate can climb again rapidly. Therefore, a maintenance phase is urgently needed. Modification of the snail-ridden environment should be linked with agricultural development and construction of water conservancy. Surveillance should be strengthened in the area where schistosomiasis has been controlled.

A nation-wide sampling survey using a stratified group randomized sampling technique was conducted in 1989 in 8 provinces where schistosomiasis was still endemic. Among 343 sampling spots, 197 were in controlled areas and 146 in endemic areas. 16,953 (10.2%) of 165,834 persons were found infected according to stool examination in the endemic areas with a population of 1.03% of the total in China. The positive rates of stool examination in Hunan, Hubei, Jiangxi, Anhui, Jiangsu, Zhejiang, Yunnan and Sichuan provinces were 14.4%, 13.5%, 5.5%, 8.6%, 0%, 0%, 4.4%, and 16.8%, respectively. Thirty-two (0.1%) out of 34,556 children aged 10-14 years were found infected in the areas where schistosomiasis was under control. Also included in this survey were the relationship between schistosome infection and age, sex, and occupation of the population in the endemic areas, the distribution of snail habitats, the roles of domestic animals in the transmission and epidemiological characteristics of different endemic areas.

The biology of the Chinese mainland strain of Schistosoma japonicum in mammalian phase of the life cycle has been studied in the past three decades. The mode of cercarial penetration is found to involve enzyme secretion and movement. The entry of schistosomulum into the blood vessel in the hypodermal connective tissue is evidenced after skin penetration. The growth and development of this fluke in mice and rabbits are investigated by physiological, histochemical and ultrastructural methods. The development of the fluke may be divided into eight stages. In the definitive host-range, at least 45 species and subspecies of 34 genera in 18 families of 7 mammalian orders have been demonstrated, and the susceptibility to infection in domestic animals is compared. The process of egg formation and embryonic development of this fluke are studied histologically and histochemically. It is suggested that the chemical nature of the egg shell should be a quinontanned protein system. The characteristics and dynamic changes of cytochemical substances in embryonation of eggs are described.

Using an affinity purified circulating cathodic antigen (CCA) preparation and an anti-CCA monoclonal IgM antibody, we modified dot-binding assays for anti-CCA and CCA detections with biotinylated conjugates. A study on 3 groups of 138 schistosomiasis japonica patients and 105 healthy individuals demonstrated a high predictive rate of over 95% in both assays, highly comparable to those of circumoral precipitin test (COPT). A blind test in 342 samples of various groups revealed higher detection rates in Ab-binding assay with both acute and chronic case groups (over 90%), but comparatively lower rates in Ag-binding assay with chronic groups (50%-76%). Distinct reductions of either GMRT and dot-indexes were found in 48 praziquantel treated patients whose sera were collected 9 months after chemotherapy. The major target molecules detected by the two binding assays were proved to be the protein incorporated moieties readily precipitated by trichloroacetic acid (TCA), ammonium sulphate and higher concentration of polyethylene glycol (PEG) suggestive of pathological, specific immunoglobulins in the free or complex forms. Non-specific dot reactions were found in some acute and chronic patients with non-relevant bovine serum albumin (BSA) conjugated peroxidase and streptavidin-PO controls, and also in normal sera with the McAb peroxidase conjugate or when working concentration of the biotinylated McAb was not properly titrated. The reliability and proper management of the dot binding assay as an immunodiagnostic tool were discussed.

Levo-praziquantel is the left isomer of racemic praziquantel. Animal experiments showed that it is an active component of schistosomicidal activity, while dextro-praziquantel is almost ineffective. Clinical trials in three endemic areas of Schistosomiasis japonica indicated that the therapeutic efficacy of levo-praziquantel is superior to racemic praziquantel. Pharmacokinetic and pharmacodynamic activities of the stereoselectivity of praziquantel isomers (enantiomers) are discussed.

We quantified serum lipoprotein(a) [Lp(a)] in 1266 healthy persons and established the reference value of Lp(a) in groups of age and sex. The Lp(a) in myocardial infarction (MI) survivors, stroke and primary hypertension patients were determined in comparison with that of age-matched normal controls. Moreover, cholesterol, triglyceride, HDL-cholesterol, apo Al and apo B were measured. The Lp(a) concentrations were not correlated with other lipids in normal controls and patients. Our results suggest that increased Lp(a) is an independent risk factor for MI and stroke patients. The total detective rate of abnormal lipids in MI and stroke patients was as high as 50% and 53.8% (Lp(a) excluded) as well as 65.7% and 64.9% (Lp(a) included) respectively.

The relationship between cytosolic free [Ca2+]i and intracellular cAMP of platelet at various stages of experimental atherosclerosis in rabbits was studied. The results showed that the increase of [Ca2+]i was negatively correlated with the level of cAMP in cholesterol-fed rabbits (r=-0.667, P<0.001) for 2, 4, 8 and 12 weeks. The viscosity of the whole blood at shear rates of 230.4/s and 5.76/s increased only in rabbits fed with cholesterol for 2 weeks, but the plasma viscosity increased in those fed for 2 and 4 weeks.

A study was made in Neijiang City, Sichuan Province to observe the safety and immunogenicity of a live attenuated hepatitis A virus (HAV) vaccine (H2 strain). 3,031 children, aged 6 to 9 years, were injected subcutaneously with 106.0 TCID50, 105.5 TCID50, and 105.0 TCID50 of HAV vaccine; the seroconversion rate and antibody GMT were 97.52%-90.68%, GMT=1:5.19±1.90-1:3.36±1.94; 84.75%-76.27%, GMT=1:4.29±1.96-1:2.0±2.67; 53.23%-51.61%, GMT=1:2.57±1.89-1:1.68±1.41 respectively after 4 weeks to 12 months of inoculation. Forty-eight children in the control group were anti-HAV negative at 4, 8, and 12 weeks; 21 children in the oral group were not antibody positive 4 and 8 weeks after oral administration of the vaccine. The stool specimens of 3 of the 14 vaccinated children were HAA positive. The results suggest that the live attenuated HAV vaccine (H2 strain) is of good immunogenicity and safety.

We analysed the early viremia and clinical tests in 82 patients with epidemic hemorrhagic fever (EHF). The results showed that the changes in viremia and clinical tests are related to the severity of the disease and prognosis. Higher concentrations of the virus in infected patients might cause a more unfavourable prognosis and more abnormalities in clinical tests. CK-MB, SGOT, SGPT, serum creatinine and urea nitrogen contents increased markedly, while serum total protein, albumin and calcium contents decreased markedly, indicating that the heart, liver and kidney in EHF patients were severely damaged. Markedly increased WBC and monocytes showed that the patients were seriously infected. Platelet count, antithrombin-III and plasminogen decreased markedly, demonstrating that there were marked changes in the coagulation-anticoagulation and fibrinolytic system of the EHF patients. Changes in RBC, Hb and HCT contents indicated that the blood in the EHF patients had a higher concentration. This study gives further evidence that EHFV plays an important role in the pathogenesis of EHF.

DNA content and cell cycle distributions in paraffin-embedded blocks of 111 skin biopsy specimens of 70 patients with cutaneous malignant lymphomas (CML) and 41 patients with cutaneous pseudolymphomas (CPL) including chronic actinic dermatitis (CAD) were estimated by DNA flow cytometry. A statistical significant difference between DNA indices (DIs) or proliferative indices (PIs) for CML including mycosis fungoides (MF) II, MF III, Sezary's syndrome (SS), cutaneous peripheral T-cell lymphomas other than MF and SS, cutaneous germinal center cell-derived lymphomas and cutaneous genuine histiocytic lymphoma from CPL. DIs were also helpful in differentiating MF I from CPL. There was a linear relationship between DIs and PIs, both of which had a parallel relationship to the degrees of malignancy and mortality of varieties of CML. The finding of aneuploidy is likely to be useful in differentiating CML from CPL. It is worth noting that DIs, PIs and proportions of aneuploidy in CAD were all higher than those of higher malignancy of CML. These data could not be considered as markers of malignancy.

Diagnosis is an essential prerequisite for the control programs of schistosomiasis. Chinese scientists have been making efforts for decades towards the development of immunological approach in an attempt to offer alternatives of or supplements to parasitological diagnosis. The authors outline briefly the main advances in the research of immunodiagnosis for schistosomiasis japonica in China in two catalogues: antibody detection and antigen detection. A number of immunodiagnostic assays based on antibody detection, which have been used widely in the control programs in China, are appraised in terms of sensitivity and specificity, and the achievements in the development of immunodiagnostic assays based on antigen detection are introduced. Readers will find some information concerning the efforts so far made by Chinese scientists in the improvement of immunodiagnosis by use of molecular approach, including search for biochemically and/or immunochemically isolated and/or purified antigens, recombinant antigens and anti-idiotypic reagents of diagnostic interest to construct defined antigen-antibody systems for diagnosis, and development of monoclonal antibody-based assays for antibody or antigen detections.