Table of Content

31 May 1996, Volume 14 Issue 2

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SURVEILLANCE OF FILARIASIS ERADICATION IN GUANGXI

1996, 14(2):  94-97. 

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AIM: To observe the long term effect and the dynamics of prevalence of filariasis after the disease has been basically eradicated and to provide scientific evidence for the eradication of filariasis. METHORD: Microfilaremia and the antibody level were detected by IFAT. The vector mosquitoes were dissected for the filarial larvae. RESULTS: The microfilaria rate was further reduced from 0.021% in the first year after filariasis was basically eradicated to 0.001% in the ninth year. No microfilaremia case was found in the following decade. The surveillance covering rates of the population of the township, village and endemic area were 71.0%, 29.9% and 14.6%, respectively in the first ten years, whereas in the following ten years the covering rates were 37.0%, 8.5% and 3.8% and no microfilaremia case could be detected. No natural infection of filarial larvae in Culex pipiens quinquefasciatus (n= 711 823), Anopheles anthropophagus and A. sinensis (n=13 007) was found as a whole. The annual average positive rate of filarial antibodies in inhabitants(n=259 934) living in endemic area detected by IFAT ranged from 1.69% to 3.90%. There was no significant difference between the filarial antibody levels of inhabitants both living in endemic area and in non endemic area. CONCLUSION: It is suggested that the transmission of filariasis in Guangxi has been interrupted and filariasis has been eradicated.

THE RELATIONSHIP BETWEEN SOCIOECONOMIC FACTORS AND SCHISTOSOMIASIS IN MOUNTAINOUS REGION in YUNNAN

1996, 14(2):  106-110. 

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AIM: To elucidate the relationship between schistosomiasis transmission and socioeconomic factors in Yunnan mountainous region. METHOD: A house visiting investigation with a questionaire concerning socioeconomic factors was conducted in four natural villages in Weishan and Eryuan counties, Yunnan Province in 1993. RESULTS: (1) The rate of disease history was significantly higher in women, inhabitants with lower education level, with lower income, with lower sense of individual protection and with more frequent labor exchange than in men, inhabitants with higher education level, with higher income, with higher sense of individual protection and with less frequent labor exchange; (2) the frequency of water contact with cercariae and defecation in the wild was significantly higher in cases with disease history than in those without the disease history. The results from multi logistic regression analysis suggest that labor exchange, contacting infested water, defecating in ve getable field, using water in ditches and canals for daily life and working in paddyfields were the important factors influencing the prevalence. The infected domestic animals were another risk factor. CONCLUSION: The transmission of schistosomiasis in Yunnan mountainous region are notably related to socioeconomic factors and behaviour aspects of local inhabitants.

DETECTION OF CRYPTOSPORIDIUM PARVUM IN FECAL SAMPLES BY POLYMERASE CHAIN REACTION

1996, 14(2):  111-114. 

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AIM: To develop a sensitive and specific procedure based on the polymerase chain reaction (PCR) for detection and identification of Cryptosporidium parvum in fecal samples from infected humans and animals. METHOD: DNA extracted directly from fecal samples with C. parvum oocysts from humans and guinea pigs was served as the source of template for the PCR. A pair of oligonucleotide primers was synthesized and used to prime the amplification of a 452 bp target fragment specific for C. parvum. The PCR products were analyzed by electrophoresis in agarose gels stained with ethidium bromide. RESULTS: The target fragment was present in DNA extracts of fecal samples from humans and guinea pigs infected with C. parvum, but not in DNA from any other parasite, Candida albicans, E. coli, normal humans or guinea pigs tested. The level of detection by this method is shown to be about 100 times more sensitive than the currently used laboratory methods for diagnosis of cryptosporidiosis. CONCLUSION: The PCR assay developed is a relatively simple, highly sensitive and specific method for detection of C. parvum and could serve as a valuable tool for clinical diagnosis and epidemiological survey.

STUDY ON THE STABILITY OF PARAMETERS IN GRY FORECASTING MODELS OF MALARIA INCIDENCE

1996, 14(2):  115-118. 

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AIM: To establish a forecasting model of GM(1,1) with stable parameters for improving the prediction of malaria incidence. METHOD: Using the RCI.GM(1,1)[i.e.modelling GM(1,1) with rate of case increase] method to replace the direct GM(1,1) method. RESULTS: The RCI.GM(1,1) model increases the stability of parameters and reduces the modelling and forecasting error rates. The output of RCI.GM(1,1) model would not be influenced seriously by slight fluctuation of data.CONCLUSION: The RCI.GM(1,1) model is better than that of GM(1,1) for improving the modelling and predictive value of malaria forecasting model.

CONSTRUCTION OF cDNA LIBRARY OF TOXOPLASMA GONDII

1996, 14(2):  124-127. 

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ATM: To construct a cDNA library of Toxoplasma gondii. METHOD: We extracted the RNA of Toxoplasma gondii (RH strain)by using a single step acid guanidinium thiocyanate method and isolated the poly(A) +RNA by using messenger RNA affinity membrane containing poly U to synthesize ds cDNAs.After ligating the cDNA into the adaptor of EcoRI/NotI and then into λgt11 DNA arms of the expressive vector,the ligated products were packaged in vitro and used to infect the E.coli Y 1090 .The 32 P dCTP genomic DNA of T.gondii RH strain hybridized the λgt11 recombinant plaques in situ .RESULTS:The ds cDNAs were found to be 0.5-2 kb in size.The cDNA library of T.gondii constructed showed 6.97×10 5 recombinant plaqes.The recombination rate and the cloning efficiency were 98.73% and 6.97×10 6 clones/μg cDNA,respectively.For in situ hybridization of the λgt11 recombinant plaques,the rate of hybridization was 95.2%.CONCLUSION:The method of extracting the RNA of T.gondii is simple and efficient.The cDNA library constructed has large content and good quality.

SURVEILLANCE OF MALARIA AFTER BEING BASICALLY ERADICATED IN KAILICITY AND OTHER 11 COUNTIES IN GUIZHOU

1996, 14(2):  128-131. 

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AIM:To evaluate the results of surveillance in 12 counties in southeast Guizhou wheremalaria had basically beeneliminated since 1985. METHODS: Intermsof the indices of conventional malariometric survey used in thenationwide anti malaria campaign. RESULTS:(1)The annual parasite incidence(API) varied from 0.0056‰ to 0.00033‰;(2)the average positive rate of febrile cases during case detection among inhabitants was 0.73,and the average parasite rate of mass blood examination was 0.82;(3)the average positive rate of febrile cases and the average parasite rate in mobile population was 413.1and 7.06,respectively;(4)there were 10.7% active foci among a total of 994 residual malaria foci. CONCLUSION:The increasing imported malaria is a risk factor in this basically eliminated malaria area and should be promptly managed andkeptundersurveillance.

OBSERVATION ON SEVERAL ECOLOGICAL ASPECTS OF HUMAN DEMODEX 

1996, 14(2):  135-138. 

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AIM:To exploreseveralecologicalaspectsof human Demodex . METHOD:A comparison of human Demodex detection rates between populations with normalbodytemperatureandabove was conducted. RESULT: Demodex folliculorum mostly parasitized in hair follicles with their gnathosomas facing the bottom part of the follicles,with a few facing the side wall and the orifice of the follicles.The skin distribution of Demodex brevis was found practically similar to that of Demodex folliculorum except for the fact thatthe gnathosomas orientation of the former was only seen moving in and out toward the sebaceous glands. The detection rates were higher at night (74%)than in daytime(52%);higher in individuals with body temperatures38℃ (91.1%) thanin those with normal temperatures(66.7%); higher in individuals after bathing (60.9%) than in those before bathing (29.9%).The detection rates under the ambient temperatures 0±1℃,10±1℃,20±1℃,30±1℃ were 28%,52%,62%,76%,respectively,the differences beingdistinctly significant ( P 0.01). CONCLUSION:Thechanges in the body temperature of the hosts and in the ambient temperature have immediate effects on the detection rate of Demodex .

DETECTING CIRCULATING ANTIGEN IN PATIENTS OF CHRONIC SCHISTOSOMIASIS USING STAPHYLOCOCCUS PROTEIN A CO AGGLUTINATION TEST

1996, 14(2):  143-145. 

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AIM: To determine the sensitivity, specificity and efficacy evaluation capacity of the staphylococcus protein A co agglutination test(SPA CoA) in detecting circulating antigens in the patients of chronic schistosomiasis.METHOD: Sera from 72 chronic schistosomiasis patients were examined before and after treatment. RESULTS: A positive rate of 93.1%(67/72)was achieved in chronic cases before treatment.No significant correlations were found between EPG and the antigen titres(r=0.0256, P 0.05).In healthy controls,3 out of 95 were positive,accounting for a false positive rate of 3.2%.For cross reactions,only 1 out of 10 clonorchiasis patients was positive and none was found positive in 11 non parasitic di sease controls .Three months after treatment,80.7%(46/57)of the patients followed up with negative fecal examinations showed negative conversion in serum antigen detections.All the patients remained fecal egg positive still showed SPA CoA positive,but the antigen titers were much reduced than those before treatment. CONCLUSION: With simplicity,rapidity and low cost,SPA CoA is recommended to be used in the diagnosis of schistosomiasis as well as in the evaluation of therapeutic efficacy.