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Biogenic molluscicides refer to the use of plants,animals and micro?organisms or their metabolites,and synthesis biomimetic molluscicides to kill Oncomelania hupensis snails. With the rapid development of science and technology,new bio?genic molluscicides are continuously emerging and the category also continues to expand. According to the molluscicidal active ingredient and sources,at present,the biogenic molluscicides with in?depth studies include plant?derived molluscicides,micro?organism molluscicides,microbial metabolite molluscicides and animal molluscicides. This paper reviews the advances in the re?searches of biogenic molluscicides in recent years.
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Objective To quantitatively estimate the range and area of environmental contamination by the feces of Schistoso?ma japonicum?infected that were freely grazed,so as to provide the theoretical evidence for the scientific assessment of the role of the freely grazed goat in the transmission of schistosomiasis japonica and development of control strategy. Methods All the fecal samples excreted by the infected goat at daytime(12 h)were collected by using a self?made goat fecal collector,weighed and counted. The quantity and dispersal of the feces excreted by the freely grazed goat at daytime under a natural condition were investigated,and the walking route and speed of the freely grazed goat at daytime were recorded with a multifunction GPS data logger. The maximum range and area of the environment contaminated by the feces of the freely grazed goat at daytime were esti?mated,and the maximum range and area of the Oncomelania hupensis snails that may be infected by the schistosome miracidium released from the eggs in the fecal samples of the freely graze goat at daytime were calculated. Results During the walking along the marshland at daytime(12 h),the quantity of the feces execrated by the freely grazed infected goat was(232.8 ± 39.8) g per goat,and the fecal samples were composed of(819.2 ± 152.1)pellets. The goat had a mean walking speed of(0.522 7 ± 0.099 7)km/h,and the longest distance,largest radius and largest range of walking activity were(6.272 4 ± 1.195 8)km, 3.136 2 km and(3 191.113 0 ± 1 189.709 4)hm2at daytime,respectively. The area of the snails that may be infected by the mi?racidium released from the eggs in the fecal samples of the freely graze goat(range of key regions for infected snails detection and control)at daytime was estimated to be(3 210.717 5 ± 1 190.907 3)hm2. Conclusions The intensity of environmental contamination by the eggs in the fecal samples of the freely grazed goat is linked to the number of infected goat. The contamina?tion range caused by the feces of the freely grazed goat with fixed fences is relatively stably kept within the walking range at day?time,and the range and area of goat fecal contamination is associated with the number of households that breed goat and the dis?tribution of goat fence. The area of the snails that may be infected by the miracidium released from the eggs in the fecal samples of the freely graze goat is larger than the area of setting contaminated by the eggs in the goat feces ,indicating that the range of in?fected snail examination and control is larger than the range of goat feces detected.
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Objective To describe the growth and development of Schistosoma japonicum in goat and the intensity and tem?poral distribution of eggs excreted by goat feces,so as to provide baseline data for the control and elimination of the role of goat in the transmission of schistosomiasis. Methods The goat animal models of schistosomiasis were established,and stool sam?ples were collected for parasitological examinations. The number of adult worms recovered,variation of schistosomes in goat at different time points post?infection,number of eggs in schistosomes,variation in number and temporal profiles of eggs excreted from goat feces were observed. Results Of the 6 schistosome?infected goat,415 adult worms were recovered,with a mean adult worm recovery of 34.58%(range,23.00%to 45.50%). Among the 5 goat infected with 200 cercariae each,47,93,77, 74 and 73 adult worms were recovered 2,5,8,11 and 14 months post?infection,respectively. There were(200.00 ± 42.33), (226.20±45.88),(168.20±25.85),(183.80±55.13)and(190.80±53.53)eggs detected in female schistosomes. The mean pre?patent period of eggs excreted by 10 infected goat was(37.7±3.02)d. From 2 to 14 months post?infection,7 batches of goat fe?ces were hatched,and there were 30,23,14,1 and 2 times for miracidium intensity of“++++”,“+++”,“++”,“+”and“-”, respectively,with 42.86%,32.86%,20.00%,1.43%and 2.86%constituent ratios of miracidium intensity. Conclusions Ap?proximately 1/3 S. japonicum cercariae may develop to adults in goats post?infection,and the prepatent period of eggs is(37.7± 3.02)d. There is no remarkable decrease seen in the number of adult worms,eggs in female schistosomes and eggs in goat feces within 14 months post?infection. Our findings suggest a long duration for infected goat in the transmission of schistosomiasis ,and there is no evidence to prove the“self?cure”phenomenon in goat,indicating that goat is an important source of infection for schistosomiasis japonica.
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Objective To develop a simple,feasible goat feces collector to improve the collection accuracy and integrity of goat fecal samples without pollution,and to modify the miracidium hatching test with a plastic tube to achieve simple,standard and comparative procedures,so as to provide technical support for pathogenic diagnosis and scientific research of goat schistoso?miasis japonica. Methods According to the body features of goat in marshland regions,a goat fecal collector,which was made of coarse fabric cottons,was devised,which was able to be fixed onto the goat buttocks and avoid urine pollution. Prior to mira?cidium hatching test,the goat fecal samples were pieced by using a mechanical method instead of the conventional artificial piec? ing method,and the effect of mechanical piecing treatment on miracidium hatching was evaluated. A filter membrane was added between the tube and rubbery ring to block the floater in fecal residues into the tube. The effects on miracidium hatching by us?ing thin fat?free cotton,thick fat?free cotton,nylon gauze at 100 pores/25.4 mm2 and 150 pores/25.4 mm2 were compared. Re?sults The goat feces collector was composed of foreleg fixing garment,hindleg fixing garment and stool bag. The functions of the fixing garment were as a fixed collector to allow non?shift and tolerance of weight during goat activity ,while the major func?tion of stool bag was in storage of stool. The goat activity was not influenced by the use of collector ,and all fecal samples were ex?creted to the bag. This collector was easy to perform and could avoid urine pollution,which was reusable after cleaning. Prior to miracidium hatching,the goat fecal samples,together with water,were pieced at 18 000 to 23 000 r/min for successive three times in a cooking machine,of 10 s each time at an interval of 5 s. Mechanical piecing had no clear?cut effect on miracidium hatching of eggs in fecal samples. A total of 541,620,344 and 211 miracidia were detected by using the miracidium hatching test with nylon gauze at 100 pores/25.4 mm2 and 150 pores/25.4 mm2,thin fat?free cotton and thick fat?free cotton respectively, indicating a better detection efficacy by using nylon gauze at 100 pores/25.4 mm2 and 150 pores/25.4 mm2. Conclusions The goat fecal collector is an easy?to?perform,accurate,unpolluted and reusable device to collect goat feces,which is suitable for pathogenic diagnosis of goat schistosomiasis. Mechanical piecing and use of nylon gauze at 150 pores/25.4 mm2 allow a simple, accurate and stable technique for parasitological diagnosis of schistosomiasis japonica,which provides a reliable tool for schisto?somiasis control and research.
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Objective To investigate the survival of Schistosoma japonicum eggs in goat feces in natural marshlands and the factors affecting its survival,so as to provide evidences for understanding of the role of eggs in goat feces in the transmission of schistosomiasis and the development of the interventions pertaining to disease control and elimination. Methods The goat ani?mals of schistosomiasis japonica were modeled in laboratory,and the feces of infected goat were collected. In laboratory,the ef?fects of environmental temperature and water content in goat feces on egg hatching were evaluated,and in the field,the effect of duration of goat feces on marshland on egg hatching and the effect of direct sunshine on egg survival were evaluated. Results At 25℃in laboratory,the hatching rate of eggs in goat feces was high?positively correlated with the water content in goat feces (r=0.87). If the water content reduced to 7.6%in goat feces,the eggs in goat feces lost the ability to hatch. Under the same wa?ter content in goat feces,the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces to-5℃,which reduced to 0 following 5 h exposure. At 5,15 and 25℃,the hatching rates of eggs gradually decreased with the extension of the duration of exposure of goat feces,and the miracidium hatching rates of eggs were 2.3%,5%and 0.9%respec?tively following the exposure for 52 d. At 35℃,the hatching rate of eggs gradually decreased with the extension of the duration of exposure,which reduced to 0 following 13 d exposure. In winter(-2?10℃),the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces on marshlands,which reduced to 0 after 21 d of exposure,and in spring(16?19℃),the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces on marshlands,which reduced to 0.9%after 5 d of exposure. At the same time point on the same marshland,the hatching rate of eggs in goat feces exposed to marshlands with direct sunshine was lower than that without direct sunshine. Conclusion The sur?vival of S. japonicum eggs in goat feces is associated with environmental temperature and water content(humidity)in goat feces, and the temperature and humidity are major natural factors affecting egg hatching.
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Objective To prokaryotically express the valosin-containing protein(VCP)of Schistosoma japonicum,and ana-lyze its VCP mRNA expressions in the cercaria,schistosomulum,adult worm(female and male worms)and egg. Methods RNA of S. japonicum eggs were extracted,and reversely transcribed into cDNA. The VCP gene of S. japonicum was amplified by using polymerase chain reaction(PCR),and subcloned into the prokaryotically expressed vector pET15b. The recombined plasmid was transformed into BL21 cells,and the expression of the target gene was induced with isopropyl-beta-D-thiogalactopyranoside (IPTG). The recombinant protein was yielded through the purification of inclusion body,and identified by using sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE). The RNA(s)of cercaria,schistosomulum,female adult worm,male adult worm,and egg of S. japonicum were extracted,digested with DNase,purified,and reversely transcribed into cDNA. The mRNA expressions of the VCP gene in various developmental stages of S. japonicum were determined by using fluorescence-based quantitative real-time PCR. Results The VCP gene of S. japonicum was yielded by PCR amplification,and the recombinant pro-tein was obtained through recombinant plasmid expression and purification of inclusion body. The highest VCP mRNA expression in S. japonicum cercaria was detected by the fluorescence-based quantitative real-time PCR,while low expressions were found in the schistosomulum,egg,female and male adult worms. Conclusion The recombinant protein encoded by the VCP gene of S. ja-ponicum is successfully obtained,and the VCP mRNA expression is determined in various developmental stages of S. japonicum.
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OBJECTIVE@#To assess the diagnostic efficacy of the currently most widely used indirect hemagglutination assay (IHA) and enzyme-linked immunosorbent assay (ELISA) for detection of Schistosoma japonicum human infections.@*METHODS@#A comprehensive search was undertaken from China National Knowledge Infrastructure, Wanfang Database, VIP Database, PubMed, Cochrane Library, Science Citation Index Expanded, Proquest, and the inclusion and exclusion criteria were strictly settled. The funnel plot was used to assess the publication bias, Cochran's Q test was employed to measure the homogeneity between studies, a summary receiver operating characteristic (SROC) curve was used to compare the diagnostic accuracy between the IHA and ELISA qualitatively by means of the Weighted Least Square method, the Ordinary Least Square method and the Robust regression method, and the diagnostic odds ratio (DOR) was drawn to compare the accuracy quantitatively.@*RESULTS@#Out of 785 publications, 19 papers were eventually selected for analysis. Literature quality assessment indicated that minor publication bias existed in studies pertaining IHA test, but no bias was found in literatures regarding ELISA test. The heterogeneity test showed a heterogeneity between studies was present (χ(2)=466.07 and 34.67, both P values<0.0001). The areas under the SROC curves of IHA were all higher than that of ELISA test using the three methods (Weighted Least Square method: 0.766 vs. 0.695, Ordinary Least Square method: 0.826 vs. 0.741, Robust regression: 0.815 vs. 0.715). The TPR* values for IHA and ELISA were 0.710, 0.759, 0.749, and 0.650, 0.686 and 0.666, respectively, and OR values were 5.997, 9.937, 8.893, and 3.432, 4.784 and 3.959, respectively. The DOR of IHA was 9.41 (95% CI: 4.88-18.18), and 4.78 (95% CI: 3.21-7.13) for ELISA.@*CONCLUSIONS@#All above results revealed that the diagnostic performance of IHA is better than that of ELISA. However, taking into account their unsatisfactory diagnostic value in areas with low infection intensity, a search for a better diagnostic test that can be applied in field situations in China should be given high priority.