Molecular identification of the species of Biomphalaria snails in Shenzhen reservoir based on 16S rDNA sequences / 中华地方病学杂志

Objective To identify the species of Biomphalaria snails collected in Shenzhen reservoir,based on the mitochondrial 16S rDNA sequences.Methods The 16S rDNA fragments were amplified by PCR from the genome DNA of Biomphalaria snails,and inserted in plasmid pMD-18T for sequencing.The sequence of 16S rDNA fragment and its phylogenetic relationships with those of other species of Biomphalaria snails were analyzed with BLAST and MEGA4 software.Results The amplified 16S rDNA fragment of the Biomphalaria snails was about 466 bp in length.As aligned with the corresponding sequences of the related Biomphalaria species,the identity of nucleotides was 99％ with 1 isolate of Biomphaltria straminea (B.straminea),98％ with 3 isolates of B.kuhniana,95％ with 1 isolate of B.intermedia,and 94％ with 1 isolate of B.edisoni.Based on the 16S rDNA sequence,the results of phylogenetic analysis with neighbor-joining (NJ) and unweighted pair-group method with arithmetic means (UPGMA) indicated that the snails had close genetic relationships with the B.straminea isolate (Genbank accession NO.AY030213.1) Conclusion The Biomphalaria snails collected in Shenzhen reservoir could be classified as B.straminea based on the characteristics of 16S rDNA sequence.

Development of Lateral Flow Immunoassay for Antigen Detection in Human Angiostrongylus cantonensis Infection

Angiostrongyliasis is difficult to be diagnosed for the reason that no ideal method can be used. Serologic tests require specific equipment and are not always available in poverty-stricken zone and are time-consuming. A lateral flow immunoassay (LFIA) may be useful for angiostrongyliasis control. We established a LFIA for the diagnosis of angiostrongyliasis based on 2 monoclonal antibodies (mAbs) against antigens of Angiostrongylus cantonensis adults. The sensitivity and specificity were 91.1% and 100% in LFIA, while those of commercial ELISA kit was 97.8% and 86.3%, respectively. Youden index was 0.91 in LFIA and 0.84 in commercial ELISA kit. LFIA showed detection limit of 1 ng/ml of A. cantonensis ES antigens. This LFIA was simple, rapid, highly sensitive and specific, which opened an alternative approach for the diagnosis of human angiostrongyliasis.

Detection of circulating antigen of Angiostrongylus cantonensis by 12D5 and 21B7 monoclonal antibodies / 中华流行病学杂志

Objective To detect the rate of Angiostrongylus cantonensis infection and to study the effects of treatment so as to prepare monoclonal antibodies (McAbs) ,and gold immunochroma-tography assay (GICA) with 12D5 and 21B7 McAbs could be prepared in advance. Methods Two McAbs (12D5 and 21B7) were applied to detect the circulating antigen (CAg) in the sera of rats infected with A. cantonensis and angiostrongyliasis patients respectively by double antibody sandwich ELISA. Either 12D5 or 21B7 McAbs was used as antibody and protein A was conjugated with colloid gold as the detection marker. A special pad for GICA was designed according to the reaction procedure, and CAg were detected by GICA in the sera of rats infected with A. cantonensis and angiostrongyliasis patients respectively. Results 12D5 McAb was identified as IgG1 and 21B7 McAb was IgM. Results from Western blotting showed that two McAbs could be used to identified 55 KD protein of adult worms of A. cantonensis. The detection rates of CAg in the sera of infected rats was 100% (48/48) and the detection rates of CAg in the sera of angiostrongyliasis patients was 100% (32/32). No cross-reaction to sera of patients with other infection of parasites, such as clonochiasis, fasiolopsiasis, ancylostotniasis, ancylostomiasis, anisakiasis as well as schsitosomiasis wee seen and normal sera did not react with 12D5 and 21B7 McAbs. Conclusion Results from sandwich ELISA and GICA with 12D5 and 21B7 McAbs showed high specificity and acting as detecting CAg of A. cantonensis in sera of infected animals and patients. We noticed that GICA with 12D5 and 21B7 was not only rapid and simple that without requirement of special instrument, but also rather sensitive and specific for the detection of current infection with A.cantonensis.

Study on the epidemiological characteristics and natural infectious focus of Angiostrongylus cantonensis in Shenzhen area of Zhujiang Delta in China / 中华流行病学杂志

Objective To delimit the natural infectious focus, including the distribution of wildlife,species, ecology of intermediate hosts and final host of Angiostrongylus cantonensis, as well as the routes of transmission and epidemiological characteristics and wildlife of human Angiostrongylus cantonensis, based on human diverging cases identified in Shenzhen, southern area of China. Methods Data including rate of infection and density of Angiostrongylus cantonensis among different hosts in 12 different areas in Shenzhen was collected, using microscope to inspect homogenate liquids of snails. Wild mice were captured with mouse cage to examine the adult Angiostrongylus cantonensis. Using larva isolated from wild-snails-infected rats to observe the life cycle of Angiostrongylus cantonensis. Results Wild life of Angiostrongylus cantonensis existed in the southwest part of Shenzhen with its majority intermediate hosts as Achatina fulica. The overall rate of infection was 31% in wildlife and final host was found to be Rattus andersoni, Achatina fulica which were extensively distributed in the shrub region of Shenzhen because of suitable climate,humidity and vegetation for generating the life cycle of Achatina fulica. Human infected Angiostrongylus cantonensis was mainly due to eating raw snails or vegetables contaminated by larva of Angiostrongylus cantonensis.The peak of infection was seen from April to November in Shenzhen area.Conclusion Wildlife of Angiostrongylus cantonensis existed in the southwest part of Shenzhen with major wildlife reservoir including fresh water snail and wild mouse. The existence of natural focus Angiostrongylus cantonensis was now recognized as an important source of human angiostrongliasis in Shenzhen area.

Epidemiological studies on Clonorchis sinensis infection along the Zhujiang River in Lou village of Shenzhen / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the transmission route and epidemiological features of Clonorchis sinensis infection in Shenzhen area--the biggest immigration city of Southern China.</p><p><b>METHODS</b>In this study, we examined 1473 individuals (710 males and 763 females) to determine the current status of C. sinensis infection among the people in one village in Zhujiang river region, Guangdong province, China. Blood samples were detected on antibody of C. sinensis with enzyme linked immunosorbent assay,and stool specimens from sera positive cases were examined by modified Kato-Katz thick smear to confirm the density of infection. People were interviewed on their life styles under the structured questionnaire which was administered by trained staff members. Major content of the questionnaire included eating raw fish, using the same utensils for both raw fish and cooked food, using feces of domestic animals and human feces to feed fish and so on.</p><p><b>RESULTS</b>Among 1473 people examined, 70 (4.75%) were found infected with C. sinensis. By counting eggs per gram feces (EPG), it was found that heavy intensities of infection in males was stronger than that of females,and the overall average EPG was 41.87. Of 1473 interviewees, 54% of them did not know about fluke disease or its transmission route, 12% of those who knew about the fluke but believed that the infection caused no harm or only slight harm to their health. 27% of the interviewees ate raw fish at least 1-2 times per months with 5% of the families using the same utensils for both raw fish and cooked food. 40% of the fish ponds owners fed their fish with the feces of domestic animals and human feces.</p><p><b>CONCLUSION</b>Together with these results, unhealthy behaviors, poor knowledge, inappropriate farming/fishery practices, eating raw fish were important factors influencing the C. sinensis prevalence in humans.</p>