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H C Yuan

Publications and source records attributed to H C Yuan.

16 recordsLinked to original sources
PubMed2000

[Studies on risk factors for liver fibrosis of schistosomiasis japonica].

OBJECTIVE: To explore the risk factors for schistosomal liver fibrosis. METHODS: 192 hepatitis-negative patients with schistosomiasis were selected and divided into 3 groups according to the result of B ultrasound examination, that is, grade 2 and 3 fibrosis group(81 patients), grade 1 fibrosis group (61 patients) and control group (non-fibrosis, 50 patiets). The univariate and multivariate ordinal regression model was made to analyse the possibly harmful factors influencing the liver damages of these patients. RESULTS: Four factors were found to be positively associated with schistosomal liver fibrosis. They were: number of treatments of schistosomiasis (OR = 1.75), interval of schistosomal infection(OR = 1.40), history of drinking wine (OR = 1.95) and familial history of advanced schistosomiasis (OR = 2.11). CONCLUSION: Patients with repeated schistosome infection, long duration of schistosomal infection, long history of drinking and familial history of advanced schistosomiasis had higher risk for liver fibrosis than schistosomiasis patients without these factors.

Adult↗
PubMed1998

Variations in fecal Schistosoma japonicum egg counts.

Variations in fecal Schistosoma japonicum egg counts were studied in ZhuXi administrative village, JiangXi Province, China. Population stool examinations were collected with duplicate, standard, 41.5-mg Kato-Katz thick smears on seven consecutive days for 570 individuals from two natural (individual) villages: village I with high endemicity and village II with low endemicity. The proportion of individuals with at least one positive count increased from 42.4% after a single measurement to 68.3% after seven measurements in village I (n = 356), and from 17.0% to 36.0% in village II (n = 214), respectively. This demonstrates a very high variation in repeated S. japonicum egg counts and a considerable lack of sensitivity of the Kato-Katz technique; light and moderate infections are especially missed with a single or a few measurements. The observed day-to-day variation in individual egg counts is highly aggregated (variance higher than the mean) and suggestive of a negative binomial distribution. For five individuals on three days, repeated sampling from different locations of a stool specimen shows a clear trend with egg counts decreasing from the beginning of the stool to the end and from the outside layer to the center. Ten multiple samples from a particular subsection (10-30 g) of a stool specimen for 44 positive individuals still showed aggregation in egg counts, particularly for high intensities of infection. This means that the aggregation in repeated daily S. japonicum egg counts cannot be explained alone by a specific day-to-day component and variation in the concentration of eggs at different locations in the stool. There also exists clustering of eggs within parts of the stool.

Adolescent↗
PubMed1993

Epidemiological features and control strategies of schistosomiasis japonica in China.

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.

Animals↗
PubMed1992

[Role of human and domestic animal reservoirs of schistosomiasis japonica in Dongting and Boyang Lake regions].

In Dongting and Boyang Lake regions, the main reservoirs of schistosomiasis were farm cattle (mostly buffaloes), pigs and mobile nonnatives. However, the role of these reservoirs in different types of endemic areas were not the same in the transmission of schistosomiasis. In islet-beach type area, the main infectious sources were pigs and local residents. The proportion of IRC (Index of Real Contamination) of local residents and pigs to the total IRC was 30.9% and 39.9% respectively. In fork-beach type area having luxuriant grass and abundant aquatic products, there were a number of buffaloes and people from other places. The proportion of IRC of the nonnative buffaloes and mobile nonnatives made up 51.9% and 21.8% of the total IRC respectively, the main reservoirs being from other places. The embankment-beach type area had a vast snail-infected area and a large number of buffaloes from both local and other places as well as mobile nonnatives. The proportion of IRC of buffaloes and nonnatives made up 69.8% and 21.4% of the total IRC respectively, serving as the main reservoirs. As regard to season differences, the infected buffaloes were the main reservoirs during dry seasons, especially from March to May, whereas the mobile nonnatives including fishermen and boatmen were the main infectious sources during flood seasons from June to October.

Animals↗
PubMed1991

Comparison of the therapeutic efficacy and side effects of a single dose of levo-praziquantel with mixed isomer praziquantel in 278 cases of schistosomiasis japonica.

A randomized double-blind study comparing the therapeutic efficacy of single dose of levo-praziquantel and mixed isomer praziquantel was carried out on 139 matched pairs of patients with schistosomiasis japonica. A single dose of either levo-praziquantel (20 mg/kg) or praziquantel (40 mg/kg) was given to each patient. Four and six months after treatment, the stool ova negative conversion rates were 94.85% and 96.27% for the levo-praziquantel group, and 97.06% and 94.03% for the praziquantel group, respectively; there was no statistically significant difference between the two treatments (P greater than 0.05). For lightly and moderately infected patients, a single 20 mg/kg dose of levo-praziquantel was as efficacious as 40 mg/kg of praziquantel. Moreover, levo-praziquantel produced fewer side effects than praziquantel. These results suggest that levo-praziquantel is the component of the mixed isomer preparation that is antihelminthic. Levo-praziquantel could be used therapeutically at half the current dose of the mixed isomer drug.

Adolescent↗
PubMed1991

Comparative efficacy of levo-praziquantel and praziquantel in treatment of schistosomiasis japonica at a single dose.

The result of a randomized double blind comparison of therapeutic efficacy of single doses of levo-praziquantel (L-PZQ) and praziquantel (PZQ) in the treatment of 139 matched pairs of proved cases of schistosomiasis japonica was reported, 268 were chronic early cases and 10 were late cases. The dosage of L-PQZ was 20 mg/kg, and that of PZQ was 40 mg/kg. Four and 6 months after treatment the stool-ova negative conversion rates were 94.8% and 96.3% for the L-PZQ group, and 97.1% and 94.0% for the PZQ group respectively (P greater than 0.05).

Adolescent↗
PubMed1988

Schistosoma mansoni: development of the cercarial glycocalyx.

The development of the cercarial glycocalyx of Schistosoma mansoni was studied by transmission electron microscopy and immunofluorescence light microscopy employing antibodies raised against extracted and chromatographed glycocalyx. By electron microscopy, cercariae present in the brood chamber of daughter sporocysts were surrounded by an electron-dense granular and fibrillar matrix. This material appeared structurally distinct from the glycocalyx which was coarsely fibrillar and located only on the surface of organisms that had developed a final tegument. The thickness of the glycocalyx apparently increased with the maturation of the tegument, since teguments that had many spines also had the thickest glycocalyx. Immunofluorescent staining of frozen sections of infected snail hepatopancreas showed that glycocalyx antigens were present on the surface of the cercariae and not in the matrix within the brood chamber or in snail tissues. Immunofluorescent staining of isolated larval cercariae showed staining of some but not all parasites with partially elongated tails. These studies suggest that the glycocalyx develops late in cercarial development (late in Stage 6 or in Stage 7 of Cheng and Bier), is made by the cercariae themselves, and is not a product of either the sporocyst wall cells or snail hepatopancreas.

Animals↗
PubMed1984

Susceptibility of snail vectors to Oriental anthropophilic Schistosoma.

Laboratory experiments were carried out to study the susceptibility of snail vectors to Oriental anthropophilic Schistosoma. Oncomelania hupensis hupensis was readily infected with the local strain of Schistosoma japonicum (Chinese strain), and also infected with S. japonicum (Philippines strain). O.h. quadrasi was only susceptible to its S. japonicum (Philippines strain). The Oncomelania races were refractory to S. mekongi, S. japonicum-like species (Malaysian strain). Tricula aperta (beta race) was readily infected with S. mekongi, S. sinensium and S. japonicum-like species from Malaysia, but not S. japonicum. T. bollingi was susceptible to S. sinensium and S. mekongi. Robertsiella kaporensis was only susceptible to the local strain, S. japonicum-like species from Malaysia. Geographical isolation may be the cause of these differences in compatibility between the snail vectors and the schistosome parasites.

Animals↗
PubMed1983

Morbidity in schistosomiasis japonica in relation to intensity of infection. A study of two rural brigades in Anhui Province, China.

Schistosomiasis japonica remains endemic in several provinces south of the Yangtze River in China because of relatively sparse populations of human beings and dense populations of snails. We studied two brigades in a rural commune in Gui-chi County, Anhui Province, to determine the prevalence, intensity, and morbidity associated with this infection before concerted control efforts were instituted. Quantitative fecal examinations, histories, and physical examinations relevant to schistosomiasis japonica were performed in 96 per cent of the available population 2 to 65 years of age. The prevalence was 26.3 per cent in Brigade A (778 persons) and 14.4 per cent in Brigade B (1532 persons). Clinical symptoms and signs were compared among uninfected persons and persons at three levels of infection as determined by fecal egg output. Some increased weakness was seen only at the heaviest levels of infection; abdominal pain was not an important symptom. Hepatomegaly was somewhat more frequent in moderate and heavy infections, but splenomegaly was rare and unrelated to intensity of infection. Neither stool consistency nor occult blood was related to the presence or intensity of infection. Approximately 50 per cent of the population had been treated for schistosomiasis japonica, 25 per cent repeatedly.

Adolescent↗
PubMed1983

Microtopography of the surface of adult Schistosoma japonicum-like (Malaysian) as observed by scanning electron microscopy.

The surface of adult Schistosoma japonicum-like (Malaysian) was studied by scanning electron microscopy. The basic pattern of surface microtopography is similar to other strains of S. japonicum as previously reported. However, among male member there are some unique differences in the types, number and distribution of surface papillae and morphology of ridges. Three kinds of papillae were observed: (1) the large fungiform papillae (3.5-4 micron in diameter, most without cilia) are more numerous than in other strains of S. japonicum, they concentrate on the lateral aspect of the anterior and middle parts close to the edge of the gynecophoral canal, and on the dorso-lateral aspect of the posterior part towards the tail tip; (2) the small hemispherical papillae (1.5-2 micron in diameter, all bearing cilia) are especially numerous in the suckers, the gynecophoral canal and parts of the tegument around the suckers and close to the tail tip; on the rest of the surface they are evenly distributed; (3) the cratered papillae (3-4 micron in diameter, about half having cilia) are more numerous than on other strains, they concentrate on the lateral aspect of the middle part and on the edges of the gynecophoral canal. The surface ridges (about 0.2-0.3 micron in width) are tall, highly branching and perforated; they are most developed in the middle part. Spines were observed only in the suckers and the gynecophoral canals. In contrast to the male, the female has numerous spines on all parts of the surface except the most anterior, where a large number of long cilia were observed. All three kinds of papillae were present; fungiform papillae are more numerous than in females of other strains; they concentrate on the latero-dorsal aspect of middle and posterior parts, and around the excretory pore. Ridges are much less developed than in the male and are prominent only in the middle part.

Animals↗
PubMedDate not supplied

Schistosomiasis control in China.

After three decades' efforts, schistosomiasis japonica were controlled in one-third (4/12) of endemic provinces and 68.2% (259/380) of endemic counties throughout the country. The remaining 121 endemic counties are located primarily in the lake and mountainous regions. The epidemiological and ecological features of the lake and mountainous areas are different from the other endemic areas. The major schistosomiasis control efforts in China can be characterized as follows: (1) Application of centralized leadership and management, since schistosomiasis control is a task not only of the Ministry of Public Health, but also of all local governments in the endemic areas; (2) Integration of actions taken by various departments or bureaus, such as agriculture, water conservation and public health; (3) Promotion of mass participation; (4) Organization of strong professional teams; (5) Raising sufficient funds. Strategies on schistosomiasis control applied in different areas are divided into three levels: (1) In the areas where the schistosomiasis has been successfully controlled, surveillance must be maintained and immediate action should be taken where new infections occur and/or vector snails are found, so that control can be reestablished quickly; (2) In the areas where schistosomiasis has been partially controlled, any residents and/or live-stock infected should be examined and treated promptly with due care, and environment modifying and/or mollusciding must be used to eliminate the remaining snails; (3) In the areas where transmission has not been controlled, the main strategy is to control morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗