Field assessment of recombinant Schistosoma japonicum 26 kDa glutathione S-transferase in Chinese water buffaloes.

We have shown previously that anti-fecundity immunity can be induced experimentally against recombinant 26 kDa glutathione S-transferase (reSjc26GST) in Chinese water buffaloes (Bos buffelus), important reservoir hosts for Schistosoma japonicum in China. In the field study described here, we immunized buffaloes with reSjc26GST to induce protective immunity against S. japonicum and to evaluate its effectiveness in controlling schistosomiasis japonica. We selected two villages as test and control groups in inside-embankment areas endemic for schistosomiasis japonica. The buffaloes in the test village were vaccinated with reSjc26GST, whereas those in the control village were not. The indicators of the effect of the vaccine included the generation of specific IgG antibodies in the vaccinated buffaloes, changes in the prevalence and infection intensity in buffaloes and village children, changes in the density of infected snails, and changes in the infectivity of water bodies (assessed by sentinel mice) in transmission areas adjacent to both villages. Twenty months after vaccination, the infection rate of buffaloes in the test village was decreased by 60.4% (from an initial prevalence of 13.5% to 5.4%), and 67.9% when compared with that in the control village (initial prevalence of 16.7%). However, the infection rate in village children remained unchanged. The density of infected snails decreased by 71.4%, from 0.0049/0.11 m2 to 0.0014/0.11m2 in the high transmission area outside the embankment in the test village. There was no change in the infectivity of the water body transmission areas between the test and control villages. The levels of specific antibodies to reSjc26GST showed a continuous increase after vaccination. These results indicate that protective immunity was induced and maintained in buffaloes after vaccination with reSjc26GST. The vaccine could thus play a significant role in reducing S. japonicum transmission caused by water buffaloes in the Lake region of China.

Schistosoma japonicum strains: differentiation by RAPD and SSR-PCR.

Eight geographical isolates of Schistosoma japonicum from Taiwan and mainland China and one isolate of Schistosoma mansoni were studied by RAPD analysis using six arbitrary primers and SSR-PCR analysis using a (CA)8RY primer. The genetic distance was determined by the percentage of unshared bands. The RAPD and SSR-PCR results showed that the genetic distance between S. mansoni and S. japonicum was more than 0.900 and 0.850 respectively; the genetic distance between the eight geographical isolates of S. japonicum was 0.000 to 0.232 and 0.066 to 0.368 respectively. These results demonstrated the usefulness of RAPD and SSR-PCR for showing the differences of inter- and intra-species of Schistosoma. The results also suggest that there is genetic diversity among the different geographical strains of S. japonicum in China.

Impact of environmental change and schistosomiasis transmission in the middle reaches of the Yangtze River following the Three Gorges construction project.

With the construction of the Three Gorges high dam on the Yangtze River in China in mind, a serious of ecological environmental factors that might affect the transmission of Schistosoma japonicum in Jian Han Plain were investigated by means of data collection, field surveys and observation in Hubei Province. Several ecological factors including water level of the Yangtze River; riparian water table, annual rainfall and yearly evaporation were investigated in relation to the prevalence of schistosomiasis. The results suggest that after the dam construction, middle water level flows (ie between flood flows and dry-weather flows) will persist in the flood season due to a rise in the water table. The investigation indicated that snail distribution and human schistosomiasis prevalence differed significantly between years which had typically high, middle and low typical water levels in the Yangzte. Moreover, the prevalence of the disease showed a significant linear regression relationship with density of snail intermediate hosts, water table, annual rainfall, yearly evaporation and ground altitude in the survey area. Systematic and careful monitoring and surveillance is necessary to investigate the impact of the environmental changes brought about by the dam construction on schistosomiasis transmission.

Schistosoma japonicum in the black rat, Rattus rattus mindanensis, from Leyte, Philippines in relation to Oncomelania snail colonies with reference to other endoparasites.

This study examined the prevalence of Schistosoma japonicum infections in field rats, Rattus rattus mindanensis, according to different trapping locations. Between October 1995 and January 1996, traps were set in the municipality of Palo, Leyte, Philippines to determine the correlation of rats infected with schistosomiasis to the proximity of the intermediate snail host, Oncomelania hupensis quadrasi, colonies. Of the 22 rats that were caught within a snail colony, 21 (95.5%) were positive for schistosomiasis. Of the 23 rats that were caught 100 meters from a snail colony, 13 (56.5%) were positive for schistosomiasis. Of the 17 rats that were caught approximately 1 km from a snail colony, zero (0%) were positive for schistosomiasis. Infection rates were highest within the habitat of the intermediate host and lowest in rats captured far from snail colonies. Captured rats were also examined for the presence of other endoparasites. Infections of the following were found: Angiostrongylus cantonensis, Gonylonema neoplasticum, Hymenolepis diminuta, Nippostrongylus muris, Strongyloides ratti, Syphacia obvelata, Taenia crassicollis and Trichuris muris, but there was no correlation between trapping location and prevalence. None of the rats were infected with Moniliformis moniliformis, Trichinella spiralis, Trypanosoma lewisi or Vampirolepis nana.

Isotypic antibody responses of a population in an endemic area of schistosomiasis japonica and their epidemiologic significance.

The present study was designed to explore if there exists a correlation between predominant isotype-defined antibody levels and reinfection in low age groups of the population in an endemic area of schistosomiasis japonica in China. One hundred and thirty-eight individuals aged 3-25 years old were selected for serological investigations including the levels of IgG, IgG4, IgM and IgE, detected by ELISA with soluble egg antigen and soluble adult worm antigen. Results show that age is a determinant for SEA-specific IgG, IgG4, and IgE, and SWA-specific IgG and IgG4 antibody levels, which increased with age, and that SEA- and SWA- specific IgG4 antibody levels are risk factors of reinfection, ie, the risk of reinfection occurrence of the population with high level of SEA or SWA-specific IgG4 is 2.83 or 2.40 times, respectively, that with low level of SEA or SWA-specific IgG4, suggesting that in the endemic area of schistosomiasis japonica, there exists a possibility that in the population aged 3-25 years, SEA and SWA-specific IgG4 antibodies mediate a blocking immunity response.

Influence of livestock husbandry on schistosomiasis transmission in mountainous regions of Yunnan Province.

An investigation was conducted in the highly endemic areas of schistosomiasis japonica in Weishan and Eryuan counties, Yunnan Province. The results are summarized as follows: 1) the number of domestic animals was increasing annually; 2) the proportion of animal husbandry gains in the total agriculture income had a yearly escalating tendency; 3) the infection rate of inhabitants was upgrading as a result of the development of and the prevalence in domestic animals in the recent decades. Owing to frequent migration of domestic animals, serious spread of infection sources and high prevalence of schistosomiasis japonica occurred. It is suggested that more attention should be paid to the control of schistosomiasis japonica in mountainous endemic regions during the course of economic development, especially in the development of domestic animals.

Special features of acute infection due to Schistosoma japonicum in urban and rural areas in China.

The statistical analysis of six indices: sex, age, occupation, time of onset, mode of infection and educational level of acute cases infected by Schistosoma japonicum in 1990 and 1994 respectively in Wuhu city was carried out. No significant differences were found in the five indices between 1990 and 1994 in Wuhu city except sex. There were significant differences between the urban and rural areas in all six indices.

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)

A multivariate analysis of the relationship between work ability and S. japonicum infection in Dongting Lake region, in China

A cross-sectional case-control study on the association between the reduced work ability and S. japonicum infection was carried out in a moderate endemic area for schistosomiasis japonica in the southern part of Dongting lake in China. A total of 120 cases with reduced work ability and 240 controls paired to the case by age, sex, occupation and without reduced work ability, participated in the study. The mean age for individuals was 37.6 years old (21-60), the ratio of male:female was 60:40, the prevalence of S. japonicum in the individuals was 28.3. The results obtained in this study showed that the infection of S. japonicum in case and control groups was 49.2 (59/120) and 17.9 (43/240), respectively. Odds ratio for reduced work ability among those who had schistosomiasis was 4.34 (95), confidence interval was 2.58-7.34, and among those who had S. japonicum infection (egg per gram > 100) was up to 12.67 (95), confidence interval was 3.64-46.39. After odds ratio was adjusted by multiple logistic regression, it was confirmed that heavier intensity of S. japonicum infection and splenomegaly due to S. japonicum infection were the main risk factors for reduced work ability in the population studied.

Epidemiological features and control of schistosomiasis japonica in China

Achievements and successes have been obtained in schistosomiasis control in China. An epidemic survey was carried out and its results analyzed