RÉSUMÉ
Objective To evaluate the potential risk of transmission of angiostrongyliasis by common freshwater snails in Dali Bai Autonomous Prefecture, Yunnan Province, so as to provide insights into local surveillance of angiostrongyliasis. Methods Common freshwater snails were collected from Dali Bai Autonomous Prefecture, Yunnan Province from March to April, 2020, and identified and bred in laboratory. SD rats were infected with third-stage larvae of Angiostrongylus cantonensis that were isolated from commercially available Pomacea canaliculata snails in Dali Bai Autonomous Prefecture, and freshwater snails were infected with the first-stage larvae of A. cantonensis that were isolated from the feces of SD rats 39 days post-infection at room temperature. The developmental process and morphological characteristics of worms in hosts were observed, and the percentages of A. cantonensis infections in different species of freshwater snails were calculated. Then, SD rats were infected with the third-stage larvae of A. cantonensis that were isolated from A. cantonensis-infected freshwater snails, and the larval development and reproduction was observed. Results More than 3 000 freshwater snail samples were collected from farmlands, ditches and wetlands around Erhai Lake in Dali Bai Autonomous Prefecture, and Cipangopaludina chinensis, P. canaliculata, Parafossarulus striatulus, Oncomelania hupensis robertsoni, Galba pervia, Physa acuta, Radix swinhoei, Assiminea spp., Tricula spp. and Bellamya spp. were morphologically identified. A total of 105 commercially available P. canaliculata snails were tested for A. cantonensis infections, and 2 P. canaliculata snails were found to be infected with A. cantonensis, in which the third-stage larvae of A. cantonensis were isolated. Ten species of freshwater snails were artificially infected with the third-stage larvae of A. cantonensis, and all 10 species of freshwater snails were found to be infected with A. cantonensis, with the highest positive rate of A. cantonensis infections in Bellamya spp. (62.3%, 137/204), and the lowest in C. chinensis (35.5%, 11/31). After SD rats were infected with the third-stage larvae of A. cantonensis isolated from different species of freshwater snails, mature adult worms of A. cantonensis were yielded. Conclusions Multiple species of freshwater snails may serve as intermediate hosts of A. cantonensis under laboratory conditions in Dali Bai Autonomous Prefecture of Yunnan Province. Further investigations on natural infection of A. cantonensis in wild snails in Dali Bai Autonomous Prefecture seem justified.
RÉSUMÉ
Objective To understand the status of water contact and labor practice of residents in plateau mountain schisto?somiasis endemic areas in Yunnan Province so as to provide the evidence for formulating the strategy of prevention and control of schistosomiasis in the next step of work. Methods A total of 412 residents aged 6-65 years old in 2 villages were randomly sampled and investigated with questionnaires for their water contacts and labor practices in plateau valley schistosomiasis endem?ic areas. Then the schistosome infection status of the residents was surveyed with the indirect hemagglutination assay IHA . Re?sults Among the 412 residents investigated the rate of water contact was 88.35% and the main causes of water contact were watering and swimming and playing. The percentages of residents who had schistosomiasis history were 1.16% 0.00%30.80% 3.85% and 0 in them who had swimming and playing water?contacts bathing watering washing hands and others respectively χ2=38.96 P<0.01 . The positives of IHA in the above?mentioned residents were 18.60% 0.00% 37.60%23.08% and 0 respectively χ2=12.61 P<0.05 . Conclusions The productive infested water contact is the main way of schistosome infection. Therefore the changes of labor practices and water contact of the residents are very important for the ef?fective prevention and control of schistosomiasis transmission.
RÉSUMÉ
Objective To evaluate the effect of comprehensive schistosomiasis control measures based on infection source control in plateau mountain areas of Yunnan Province. Methods From 2006 to 2004,four administrative villages were selected as test areas from plateau canyon and plateau basin endemic areas in Jindun Town,Heqing County,two villages each type,and the comprehensive control measures were implemented,including the examination and treatment of schistosomiasis,Oncomela?nia hupensis snail survey and control,health education,improving drinking water and lavatories,banning grazing,constructing sanitary pen of livestock,replacing cattle with machine,etc. The schistosome infection state and snail status in 2006 were treat?ed as the baseline information,and the effect of the comprehensive measures were evaluated. Results The infection rate of hu?man in plateau canyon areas decreased from 4.94%in 2006 to 0.06%in 2014,and that of livestock decreased from 1.11%to 0. In plateau basin areas,there was only 1 case of schistosomiasis found in Xiaolian Village in 2007,and no any other cases found in the other years,the infection rates of livestock dropped from 7.38%to 0. Compared with 2006,the snail areas in the two type areas decreased by 74.89%and 75.30%,respectively,meanwhile,the percentage of snail area,the occurrence rate of frames with snails,as well as the average density of living snails also decreased,and no infected snails were found since 2008. Xidian and Xinzhuang villages in plateau canyon area reached the criteria of schistosomiasis transmission controlled in 2009,and Xiao?lian and Kangfu villages in plateau basin reached the criteria of transmission interrupted in 2014. Conclusions The comprehen?sive schistosomiasis control measures based on infection source control can effectively control the endemic situation of schistoso? miasis in plateau areas of Yunnan Province. In the future,we should pay an equal attention to the infection sources control and snail control to consolidate and amplify the achievement of schistosomiasis control.