Clonorchiasis sinensis and Taenia solium taeniasis/cysticercosis are major foodborne parasitoses. Clonorchiasis sinensis is actively transmitted in some areas of China, Korea, Russia, Vietnam, etc. Currently, it is estimated that more than 200 million people are at risk of infection, 15-20 million people are infected, and 1.5-2 million show symptoms or complications. In China, it is relatively heavily transmitted in Zhujiang River Delta, including Hong Kong and Macao, and Northeast China, where many Korean people live. The transmission is related to the unhealthy habits of residents who like to have raw fish or half-raw fish. The infection of Clonorchis sinensis could result in serious liver and biliary system damages, and chronic cases may induce liver and bile duct cancers. T. solium taeniasis/cysticercosis is distributed around the world except the areas where the residents have a taboo against pork for religious reasons. Recent years, the urban inhabitants infected with T. solium/Cysticercus are increasing in China. T. solium results in intestinal diseases, and cysticercosis is a very serious disease, especially nervous system cysticercosis. Its symptoms include headache, epilepsy, sudden death, etc. Health education and health promotion, environmental reconstruction, and chemotherapy are the main control measures for these diseases. Through several decades of efforts in China, the achievements of control of clonorchiasis and T. solium taeniasis/cysticercosis are great. For example, in one of the main clonorchiasis-endemic provinces, Shandong Province, clonorchiasis has been controlled. In 31 T. solium taeniasis/cysticercosis-endemic counties of Henan Province, through a 6-year control program, the decline rates of T. solium taeniasis and cysticercosis were 90.8 and 96.8 %, respectively. This paper reviews the researches on the control of clonorchiasis and T. solium taeniasis/cysticercosis in China past decades so as to provide references for other countries where these diseases are endemic to improve the control or elimination of clonorchiasis and T. solium taeniasis/cysticercosis.
Among the three main schistosomes (Schistosoma japonicum, Schistosoma mansoni, and Schistosoma haematobium) known to infect humans, S. japonicum causes the most serious pathological lesions. In China, only schistosomiasis japonica is transmitted. From the 1950s, massive epidemiological investigations and active control measures for schistosomiasis japonica have been carried out. At the early stage of schistosomiasis control program, there were about 12 million schistosomiasis patients, and about 5% of schistosomiasis patients belong to advanced patients, which was 600,000. After more than a half century of active schistosomiasis control work, the schistosomiasis situation has been reduced markedly. The nearest epidemiological investigation showed that, by the end of 2012, there were still 240,000 schistosomiasis patients with the descent rate of 98% and 30,000 advanced patients with the descent rate of 95%. This paper reviews the rich experiences of advanced schistosomiasis research and control in China, including that the epidemiology researches confirm there is a family aggregation of advanced schistosomiasis and advanced schistosomiasis patients have no significance to the schistosomiasis transmission in transmission-interrupted areas but still are an infection source in endemic areas; pathogenic mechanism researches verify that genetic factors and immunoregulation play important roles in the disease developing process; ultrasound image examinations are used not only in the diagnosis and differential diagnosis of advanced schistosomiasis but also in the guidance of treatment and evaluation of therapeutic effects and, furthermore, in the risk predictions of portal hypertension and upper gastrointestinal hemorrhage; clinical practices demonstrate that praziquantel can be used in most of advanced schistosomiasis patients, and the therapy not only can interrupt the schistosomiasis transmission somewhat but also is favorable for liver fibrosis improvement; the ascetic fluid concentration afflux is used in the therapy for obstinate ascites, and endoscopic varices ligation is used in the treatment of upper gastrointestinal bleeding, and both have good effects; hundreds and thousands of severe splenomegaly advanced schistosomiasis patients received splenectomy, and the long-term survival rate is more than 90%, most of them are basically cured from the disease and their labor force recovers, some dwarf patients begin growing and developing again, and some sterile women became fertile; the researches of traditional Chinese medicine in the treatment of liver fibrosis have made progress, such as Cordyceps sinensis showing some anti-fibrosis effect in the animal experiments and primary clinical trials; the animal experiments and epidemiological investigations indicate that schistosome infection is one of the carcinogenesis risk factors, especially for liver cancer. In conclusion, these experiences and lessons are plentiful and worth sharing with the peers of other endemic countries for reference.
BackgroundWith the successful implementation of integrated measures for schistosomiasis japonica control, Jiangsu province has reached low-endemicity status. However, infected Oncomelania hupensis snails could still be found in certain locations along the Yangtze river until 2009, and there is concern that they might spread again, resulting in the possible re-emergence of infections among people and domestic animals alike. In order to establish a robust surveillance system that is able to detect the spread of infected snails at an early stage, sensitive and reliable methods to identify risk factors for the establishment of infected snails need to be developed.MethodsA total of 107 villages reporting the persistent presence of infected snails were selected. Relevant data on the distribution of infected snails, and human and livestock infection status information for the years 2003 to 2008 were collected. Spatio-temporal pattern analysis including spatial autocorrelation, directional distribution and spatial error models were carried out to explore spatial correlations between infected snails and selected explanatory factors.ResultsThe area where infected snails were found, as well as their density, decreased significantly between 2003 and 2008. Changes in human and livestock prevalences were less pronounced. Three statistically significant spatial autocorrelations for infected snails were identified. (i) The Moran’s I of infected snails increased from 2004 to 2007, with the snail density increasing and the area with infected snails decreasing. (ii) The standard deviations of ellipses around infected snails were decreasing and the central points of the ellipses moved from West to East. (iii) The spatial error models indicated no significant correlation between the density of infected snails and selected risk factors.ConclusionsWe conclude that the contribution of local infection sources including humans and livestock to the distribution of infected snails might be relatively small and that snail control may limit infected snails to increasingly small areas ecologically most suitable for transmission. We provide a method to identify these areas and risk factors for persistent infected snail presence through spatio-temporal analysis, and a suggested framework, which could assist in designing evidence based control strategies for schistosomiasis japonica elimination.
Praziquantel, due to high efficacy, excellent tolerability, few and transient side effects, simple administration, and competitive cost, is virtually the only drug of choice for treatment of human schistosomiasis. Treatment of schistosomiasis has shown great advances with the introduction of the drug into the therapeutic arsenal in areas that are endemic for the parasite. However, the drug presents various efficacies against different developmental stages of schistosomes, appearing an oddity intermitted mode. The present review article reviews the effects and mechanism of action of praziquantel against schistosomes briefly and suggests the research on this oddity phenomenon.
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