OBJECTIVETo explore the impact of the impoundment of Three Gorges reservoir on Oncomelania snail habitats of Poyang Lake.

METHODSFour counties with schistosomiasis endemic around the Poyang Lake, naming as Xingzi, Duchang, Jinxian and Xinjian, were selected as study areas. The average daily water level of four major hydrological stations near the above 4 counties from 1997 to 2008 were collected, as well as the elevation of 215 marshlands with snails in those 4 counties, the data of schistosomiasis endemic situation and snail survey of 4 counties in the year before the impoundment of Three Gorges reservoir (2002) and the 6th year after the impoundment of Three Gorges reservoir (2008). The fluctuations of water levels of Poyang Lake, flooding day of marshland with snails as well as the changes of the indicators in snail survey and prevention and control measures before and after the impoundment of Three Gorges reservoir were compared.

RESULTSBefore the impoundment of Three Gorges reservoir, the fluctuations of average water level of the four hydrological stations around Poyang Lake was 6.91-12.93 m; which reduced to 5.72 - 10.75 m after the impoundment. The D-value of the fluctuations of average water level was (1.06 ± 0.47) m. The date of the annual maximum water level delayed by an average of 12 d; while the date of annual minimum water level arrived an average of 12 d earlier than the impoundment of Three Gorges reservoir. The average flooding days of marshland with snails were separately (100.04 ± 42.06) d before the impoundment and (64.13 ± 22.30) d after the impoundment. The difference was statistically significant (t = 3.70, P < 0.05). The density of snails in the 4 counties around Poyang Lake was 0.8437/0.1 m(2) after the impoundment; declining by 31.04% from the snail density (1.2234/0.1 m(2)) before the impoundment. The density of infectious snails was 0.0014/0.1 m(2) after the impoundment; dropping by 67.34% from it (0.0042/0.1 m(2)) before the impoundment; the infection rate of snails was separately 0.34% after the impoundment and 0.16% before the impoundment. The difference was statistically significant (χ(2) = 53.25, P < 0.05). The coverage rate of chemotherapy increased from 4.45% (35 558/798 200) in 2002 to 9.80% (79 457/810 400) in 2008; the difference was statistically significant (χ(2) = 17 336.63, P < 0.05). The coverage rate of snail killing increased from 1.35% (389.04/28 824.66) in 2002 to 7.49% (2260.90/30 166.22) in 2008; the difference was also statistically significant (χ(2) = 28 824.66, P < 0.05).

CONCLUSIONThe impact of the impoundment of Three Gorges reservoir shortened the flooding days of marshland with snails and helped the prevention and control of schistosomiasis in Poyang Lake regions as the environment went against the breeding of the snails.

Animals ; Disease Reservoirs ; Ecosystem ; Environmental Monitoring ; Lakes ; Snails ; physiology

Dengue ; prevention & control ; Disease Reservoirs ; Humans ; Risk Assessment ; Singapore

Fishborne trematode (FBT) metacercariae were investigated in yellowfin goby, Acanthogobius flavimanus, collected from Shinan-gun and Muan-gun, Jeollanam-do (province), Korea. All collected fishes were examined using the artificial digestion method. In all of 15 gobies from Aphae-myeon in Shinan-gun, metacercariae of Stictodora spp. (334 metacercariae/fish), Heterophyes nocens (153/fish), and Heterophyopsis continua (20/fish) were detected. In 2 of 14 gobies from Jido-myeon in Shinan-gun, 8 Echinostoma hortense metacercariae in total were detected. In 15 gobies from Haeje-myeon in Muan-gun, the metacercariae of H. continua were found in 100%, Stictodora spp. in 86.7%, and H. nocens in 6.7% of fish examined. The average numbers of metacercariae per infected fish were 23.3 (H. continua), 416.0 (Stictodora spp.), and 2.0 (H. nocens), respectively. The metacercariae of E. hortense found in gobies were elliptical, with 150 x 138 micrometer in average size, and had 27 collar spines on the head crown. The above results suggest that yellowfin gobies from 2 localities may be the potential infection sources of FBT. Moreover, it is proved for the first time that the yellowfin goby, A. flavimanus, acts as a second intermediate host for E. hortense.
Animals ; Disease Reservoirs/*parasitology ; Echinostomiasis/parasitology ; Humans ; Korea ; Perciformes/*parasitology ; Trematoda/*isolation & purification

OBJECTIVETo understand the risk factors of schistosomiasis transmission in the Three Gorges Reservoir Area (TGRA) and to provide evidence for the development of control strategy.

METHODSApproaches including epidemiology, immunology and field survey were applied to investigate the potential risk factors which would involve the importation of infectious resources live mobile and migrant population, and livestock in the reservoir area. Meanwhile, observation on survival and reproductive status of snail under simulation habitats was also carried out, using ecological methods on snails. Strategy in preventing the spread of snail as infectious resources was also provided.

RESULTS175 mobile people from schistosomaisis endemic area of were tested and one person showed immunology tests positive with indirect hemagglutination test (IHA) and circumoral precipitin test (COPT), with a positive rate of 0.57%. Through the two-year period under observation, data showed that the snails with ribbon/smooth shells could survive and reproduce under habitats of simulation.

CONCLUSIONSOnce the infectious resource of schistosomiasis was introduced into the TGRA, the area became a new schistosomiasis epidemic area in TGRA which called for countermeasures to be taken.

Animals ; China ; epidemiology ; Disease Reservoirs ; Humans ; Risk Factors ; Schistosomiasis japonica ; epidemiology ; prevention & control ; transmission ; Snails ; parasitology

Disease Reservoirs ; Genetic Therapy ; HIV Infections ; therapy ; Hematopoietic Stem Cell Transplantation ; Humans

A mathematical model for transmission of schistosomes is useful to predict effects of various control measures on suppression of these parasites. This review focuses on epidemiological and environmental factors in Schistosoma japonicum and Schistosoma mekongi infections and recent advances in mathematical models of Schistosoma transmission.
Animals ; Asia, Southeastern/epidemiology ; *Communicable Disease Control ; Disease Reservoirs/parasitology ; Humans ; Models, Theoretical ; Schistosoma/*physiology ; Schistosomiasis/epidemiology/parasitology/*transmission

Environmental studies regarding Paragonimiasis have been done in Sulak-Myun, Kapyung-Goon (I district) and Yongmoon-Myun, Yangpyung-Goon (II district), both of which are considered "active" endemic areas, and in Byukje-Myun, Koyang-Goon (III district) an "arrested" area. 1. Paragonimiasis is still active in the Uhmos River, Sulak-Myun, Kapyung-Goon, where 49% of crayfish contained Paragonimus metacecaria. Snails which are the first intermediate host of Paragonimus westermani were moderately present. In the Oonke River, Yongmoon-Myun, Yangpyung-Goon, crayfish which are the second intermediate host of Paragonimus westermani, were found in every area of the river, but snails were not found in any area of either branch of the river. They were caught in areas which are located below the junction. In the Daeja river, Bykje-Myun, Koyang-Goon, crayfish were found only in the upper stream of the river and snails were not caught in any area of the river. 2. The results described above are attributed to the fact that snails, which have minimal mobility and vitality, were complete1y obliterated by the long, unprecedented drought in 1965. In contrust, crayfish with great mobility and vitality survived. Thus without the snail, the life cycle of Paragonimus western1ani become incomplete, and the clinical disease disappeared. 3. Rainfall is very important in maintaining water flow in the river, a necessary factor for the life cycle of Paragonimus westermani. Therefore we have charted tile amount of rainfall in the Seoul and Choonchun areas in 1965, compared with the average of the past 30 years, in order to ascertain the degree of drought which influnced the Paragonimus westermani hosts and cohabitants. 4. Geographic conditions which are also very important in maintaining water flow in small rivers was investigated. The conclusion was drawn, that a long river has an advantage over a short during drought; a tortuous river provides a better opportunity for miracidia of Paragonimus westermani eggs to migrate to snails, and for Pargonimus cercaria to invade crayfish than a straight rapidly flowing river. 5. We must conclude that man may ingest Paragonimus metacercaria by drinking water from shallow wells and streams in areas endemic to paragonimiasis, when we note that one crayfish of four caught in shallow wells in Kapyung-Goon contained many Paragonimus metacercaria. 6. Other factors are the increase in traffic due to the expanding population in Korean farm areas, and the increase in the use of farm chemicals, which seep into the rivers and reduce the number of snails, crayfish and crabs available as potential hosts. 7. In recent years, the wild fauna in the mountains, one of the important terminal hosts of Paragonimus westermani, have been markedly reduced in number. This may have contributed to decreasing paragonimiasis as directly infective to man. 8. Health education on paragonimiasis, informing the people of the dangers of eating raw or inadequately cooked crayfish and crabs, or those soaked less than 10 days in soysauce, and drinking the water from shallow wells and streams, is demonstrated to have decreased the incidence of this disease. 9. Because of the preceding facts, paragonimiasis in Kyunggi-Prvince is being decreased.
Animals ; Asian Continental Ancestry Group ; Crustacea ; *Disease Reservoirs ; *Disease Vectors ; Ecology ; Human ; Korea ; Paragonimiasis/*epidemiology ; Paragonimus/isolation & purification ; Snails

Animals ; Disease Reservoirs ; microbiology ; Genome, Bacterial ; Geography ; Marmota ; microbiology ; Plague ; epidemiology ; microbiology ; Polymorphism, Genetic ; Yersinia pestis ; genetics

Animals ; China ; epidemiology ; Disease Reservoirs ; Hepatitis E ; epidemiology ; transmission ; Hepatitis E virus ; genetics ; isolation & purification ; Humans ; Rodentia ; virology ; Swine ; virology

OBJECTIVETo analyze the change of tendency on schistosomiasis epidemics in China in the last 5 years.

METHODSData on schistosomiasis epidemics in the history and particularly in the last 5 years were collected. Tendency and the re-emerging status after 1998 were analyzed.

RESULTSData in 2003 showed that in 42%, 40% and 53% of the provinces, counties and townships with epidemics, the transmission of the disease has been interrupted or controlled. The number of estimated patients of schistosomiasis and areas with snails were also reduced by 92.74% and 73.56%, in 2003. The annual estimated number of chronic cases was around 800 000 and 31 321.5 hectare of snail infested areas were newly identified in recent 5 years. Among 20 national villages under longitudinal surveillance, 30%, 70% and 35% of the villages were presented a tendency of increase in the rates of human infection, bovine infection and Oncomelania snails infection, respectively. A total of 38 counties from 7 provinces have re-emerged in schistosomiasis transmission after those counties having reached criteria of transmission under control or interrupted. In 6 non-endemic counties, snails were presented, and 16 marshlands in Xan river were found with appearance of acute cases of schistosomiasis. More snail infested areas were found in Shanghai, Zhejiang, and Fujian. Both snail infested areas and newly infected cases were occurred in urban areas along the Yangtze River.

CONCLUSIONThe tendency of increase was presented in focal areas along the Yangtze River, due to changes of environmental, ecological, societal and economic status, as well as on the forces of control.

Animals ; China ; epidemiology ; Disease Reservoirs ; Humans ; Praziquantel ; therapeutic use ; Prevalence ; Schistosomiasis japonica ; drug therapy ; epidemiology ; prevention & control ; Snails ; parasitology