[Objective] To determine the effect of Schistosoma japonicum infection on the testoterone level in the sera from male C57BL/6 mice. [Methods] Radioimmunoassay was used to examine testosterone levels in sera of 9 male mice experimentally infected with Schistosoma japonicum. [Results] The serum testosterone levels reduced significantly in all experimentally infected animals 45 days after infection, as compared with the uninfected controls. [Conclusion] Infection with Schistosoma japonicum decreases testosterone levels in the mouse host.

[Objective] To evaluate the diagnostic value of the recombinant antigen of 39 amino acid repeats encoded by a kinesin-like gene of Leishmania changasi (rK39) in serodiagnosis of visceral leishmaniasis (VL). [Methods] In Kashi, Xinjiang, 13 VL patients with splenomegaly and bone marrow aspirate culture positive were subjected to dipstick assay. A drop of whole blood or serum from patient was placed at the absorbing pad at the bottom of the dipstick.Flooding of the bottom protein with buffer allows serum proteins to migrate upwards, producing the positive band and Western blot analysis of rK39 subsequently performed with the sera collected. [Results] The end-point titers of antirK39 antibodies of these sera were determined by ELISA and found to fall within the range of 10-2 to 10-4, which were consistent with the intensity of their reaction with rK39 in dipstick assay. The positive sera could also recognize the specific rK39 band as analyzed by Western blot analysis. [Conclusion] The rK39 dipstick assay is more rapid, specific, sensitive and less invasive than the conventional methods of diagnosis for VL in the areas of low endemicity.

[Objectice] To study the relationship between the livestock trade and schistosomiasis transmission and to provide an evidence for making a strategy of schistosomiasis control in mountainous areas. [Methods] A retrospective survey and analysis was conducted to investigate the prevalence of schistosomiasis in both humans and livestock (cattle, horses, mules, donkeys and pigs), and the number and migration of livestock in Weishan County, Yunnan Province in 1980～ 1991. [Results] A positive correlation was found between the infection rate of residents and the numbers of livestock migration (R=0. 9151, P＜0.01). During 1980 to 1991 the infection rate was increased gradually along with the development of livestock husbandry, especially, from the economic reforms since 1984. In 1984 there was positive correlation in the infection rate both human and livestock (R=0. 8458, P＜0.05). The results show that the infection rates of livestock on sale including cattle, horses, mules, donkeys and pigs are 9.54%, 29.39%, 16.38%, 14.47%, 25.73% and 11.11%, respectively. [Conclusion] The infection rate of human and livestock arises by parallel. The high frequency of livestock trade resulted in serious spreading of the infection source of schistosomiasis. The migration of the infected livestock might be an important factor in transmitting schistosomiasis.

[Objective] To obtain the genetic information on Necator americanus and to search for the purpose genes.[Methods] Mrna was isolated from the third stage larvae of Necator americanus maintained in hamsters.Double strand Cdna was synthesized and ligated to ΛzapⅡ vector to construct the Cdna library.Expresed se-quence tages (ESTs) were obtained by single pass sequencing of randomly isolated Cdna clones from the es-tablished library.[Results] A Cdna librazy of N.americanus was successfully constructed with high recombi-nant efficiency.The titer of unamplified library was 1×107.The insert size was about 750～3000bp.Of 11 ESTs obtained from the library,7 have a significant homology with certain functional genes.[Conclunsion]A high quality and high representative Cdna library of N.americanus was constructed at the first time and ome functional genes were identified from the library by ESTs.

[Objective] To answer the following questions:① For Oncomelania snails collected two years apart from the same locality,has there been genetic divergence?②How much experimental error has there been in studying subsets of these populations? ③As this is an unstable population,what has the net effect been on Hardy-Weinberg equilibrium(Hwe)?[Methods] Allozymes were studied using horizontal starch gel electrophoresis.Data collected from numbers of experiments were conapiled.Data from each collection were divided into two equal subsets based on chronology of the experiments.Thirty-four loci were studied using 72 to 180 snails per subset.[Results] The mean number of alleles per locus ranged frcra 1.5～1.9.With each consecutive subset,the 96 polymorphic loci dropped from 38.2 to 17.6.The mean heterozygosity was very low:0.033 to 0.049 and not significantly different from Hardy-Weinberg expectations.Ten loci and 11 alleles exclusive to the first group were eliminated from the overall study reducing the number of polymorphic loci from 19 to 10.There were significant departures from Hwe at five loci having a substantial number of individuals for each allele.Nei's and Wright's D were 0.003±0.001 and 0.054±0.006 respectively.[Conclusion] ①There were significant errors seen primarily in the results scored' in the earliest experiments.②These earlier errors involving scoring difficult to resolve loci,and interpretation of rare alleles that were not found in later experiment had no significant effect on overall genetic distance.③The use of Wright's D for closely related populations is explained.Results with Nei's D indicated no significant difference among the four subunits; Wright's D yielded significant difference between the collections made two years apart,attributed to the annual flooding of the Yangtze River mixing snails from different localities.④ Major polymorphic loci were not in Hwe as predicted using the unstable population model.⑤One must study 25 or more individuals to find relatively rate alleles and study population genetics.

[Objective] To study the synergic effect of praziquantel (PZQ) and host acquired immunity on Clonorchis sinensis. [Methods] Acquired immunity to C. sinensis was induced by immunization with crude adult worm antigen (AW Ag) and excretory-secretory antigen (ES Ag) or infection with C. sinensis metacercariae. The effect was assessed by the worm reduction rate compared with the control groups after challenge infection with 50 metacercariae and treated orally with a subcurative dose of praziquantel (50 mg/kg). Significant test was performed by analysis of variance (ANOVA) and Nparl way Kruskal-Wallis test. All calculations were performed by PC-SAS system. [Results] 1. PZQ was more effective against C. sinensis larvae than against adult worms in the control (P＜0. 001), ES Ag (P＜0.01) or crude AW Ag immunization group (P＜0. 001). 2. As compared with the control, the worm reduction rate after challenge infection was significantly higher (P＜0. 001) in ES Ag immunized group (35.60%) and metacercaria infection group (97.5 % ) and less in crude AW Ag group (23.4 %). The PZQ efficacy was significantly enhanced in ES Ag immunized group. [Conclusion] The efficacy of PZQ against C. sinensis could be synergically enhanced in rats by inducing host acquired immunity.

[Objective] To evaluate the infectivity of Cryptosporidium parvum oocysts in NMRI suckling mouse.[Methods] Four-day- old SPF NMRI suckling mice were inoculated with different amounts of oocysts by oral gavage.On clay 7 after inoculation, suckling mice were sacrificed, and a suspension was prepared by homogenizing the intestinal tract from pylorus to anus. A mouse was considered infected when oocysts were found in smears of the intestinal content suspension stained with carbo lfuchsin solution. The infectivity of oocysts was evaluated as measured by the percentage of infected mice in each group. [Results] Mice receiving 1 500 or 2 000 oocysts were all infected. The percentages of infected mice were 88, 74, 51 and 28 respectively after ingestion of 1 000, 500, 250 and 100 oocysts. The percentage of infected mice was 9.5 % after ingesting as few as 50 oocysts. [Conclusion] This model is convenient for evaluation of the infectivity of C. parvum oocysts.

Objective To assess the effect of artemether on the tegument of adult Schistosoma haematobium harbored in mice. Methods Ten mice were infected subcutaneously with 100-120 S. haematobium cercariae each. At day 81 post-infection, 8 mice were treated orally with 400 mg/kg artemether. Mice were sacrificed at 1, 3, 7 and 14 days post-treatment, and schistosomes were collected by the perfusion technique, fixed and examined under a scanning electron microscope. Schistosomes obtained from the 2 untreated mice served as a control. Results Twenty-four hours post-treatment, tubercles on the tegument of male worms showed lesions, characterized by enlargement, collapse and partial peeling off from the border with the tegument. In both male and female worms, the tegument showed focal or extensive swelling, fusion, vacuolization, erosion, peeling, and destruction of sensory structures. Three days post-treatment,tegumental alterations further aggravated; particularly severe damage was the swelling or collapse of the oral sucker observed in both sexes. In addition, extensive swelling, erosion and peeling of tegumental ridges and destruction of discoidlike sensory structures were seen in female worms. Seven to 14 days post-treatment, moderate-to-severe damage was still evident in some worms, whereas other worms surviving the treatment showed apparent recovery in most parts of their tegument. Conclusion Artemether causes extensive and severe tegumental damage in adult S. haematobium.

Objective To perform a temporal examination of ultrastructural alterations in adult Schistosoma haematobium due to artemether Methods Eight mice infected with 100-120 S. haematobium cercariae for 81 days were treated intragastrically with 400 mg/kg artemether. At 24 hours, 3, 7 and 14 days post-treatment, groups of 2 mice were sacrificed and schistosomes collected by the perfusion technique. Worm samples were fixed and examined by transmission electron microscopy. Schistosomes were also obtained from 2 untreated mice that served as control.Results Typical ultrastructural alterations included swelling, lysis and vacuolization of the tegumental matrix, and disappearance of basal membrane. In sensory organelles and tubercles, there was extensive or local lysis of internal structure. In the musculature, parenchymal tissues, syncytium and gut epithelial cells, focal or extensive lysis, decrease in granular endoplasmic reticulum, vacuolization and degeneration of mitochondria were observed. These alterations became apparent both in male and female worms 24 hours post-treatment. In female worms, severe damage to the vitelline cells was also observed, resulting in the emergence of vacuoles, a decrease in granular endoplasmic reticulum,fusion of vitelline balls or even collapse of damaged vitelline cells. The most extensive tegumental alterations were observed 3-7 days post-treatment. Whilst 14 days post-treatment ultrastructural damage was still apparent, the tegument of some worms showed similar features to those recovered from untreated control mice. Conclusion Administration of artemether to mice infected with adult S. haematobium results in extensive damage to the ultrastructure in the tegument and subtegument tissues of the worms, confirming previous results with other schistosome species.

Objective To confirm the transmission of Toxoplasma gondii by semen and to investigate the impact of vaginal status on the transmission of T. gondii in female rabbits. Methods Sixteen male rabbits were infected with T. gondii by intraperitoneal injection each with 1 ×105 RH tachyzoites. Eight rabbits died in 8-14 d after infection.Artificial vagina was used to collect semen from male rabbits weekly before and after infection for 8 weeks. If more than 2 portions of semen from 8 survived male rabbits were collected after infection, the collected semen was mixed weekly for later use. Twenty-seven female rabbits were divided into 4 groups: group 1 with normal vagina (7 rabbits), group 2with wounded vagina (7), group 3 with trichomonas vaginitis (7) and group 4 with colpomycosis infection (6). Tachyzoites were found in mixed semen digested by trypsinase, and were used for endovaginal artificial insemination to female rabbits by uterine cavity tube once a week for 8 consecutive weeks. 2-3 d after every insemination, 2 ml blood was collected from helix vein of each rabbit, and stored at -40 ℃ for use. Anti-T. gondii antibody was examined by ELISA and the B1 gene of T. gondii was detected by PCR. Results Anti-T. gondii antibody was detected in some rabbits (2, 3, 1, and 1 rabbits from each of the groups respectively) on the 16th day after the first insemination. The positive rate of ELISA was 25.9%. The amplification of B1 gene (200 bp) by PCR appeared positive from the blood samples on the 3rd day after the first insemination and the last positive one was proved on the 51th day after the first insemination.Number of positive samples was 2, 1, 3 and 1 in the 4 groups respectively, with an overall PCR positive rate of 18.5%.Only 3 of the 27 rabbits were positive by both ELISA and PCR. Conclusions T. gondii can be transmitted by semen and the health status of vagina shows no impact on it.