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

Animals ; China ; epidemiology ; Female ; Humans ; Incidence ; Male ; Schistosoma japonicum ; Schistosomiasis japonica ; epidemiology ; transmission ; Urban Health

The aim of the present study was to confirm observations on the vertical transmission of Schistosoma japonicum in the rabbit. S. japonicum-infected pregnant rabbits were used in this study. Perfusion of mother rabbits was done 9 weeks after infection in order to obtain worm burdens in relation to their initial cercarial dose. Anti-schistosoma specific IgM antibodies in serum samples collected from rabbit kittens were detected by ELISA. Our results showed that gestation period lasted the normal 29-31 days. All the exposed mother rabbits became infected with S. japonicum. Positive IgM antibody OD values were detected in 12 out of the 60 kittens examined (20.0%). In group C and A, 40.0% and 17.9% of the kitten were congenitally infected, respectively. 18.1% of the kittens born to mothers infected with a single dose of 200 cercariae per rabbit were positives; this is not significantly different from that obtained for the 600 dose group (22.2%). Three randomly selected IgM+ kittens harbored between one and two adult worms. The livers of these kittens displayed granulomatous lesions. It is concluded that congenital S. japonicum infection does occur in the rabbit and is affected by the mother stage of pregnancy and to a lesser extent by its infection load.
Antibodies, Helminth/blood ; *Disease Transmission, Vertical ; Immunoglobulin M/blood ; Schistosoma japonicum/immunology ; Schistosoma japonicum/isolation & purification ; Schistosomiasis japonica/*transmission

BACKGROUNDRecently congenital infection with Schistosoma japonicum (S. japonicum) has been demonstrated in pigs, rabbits, mice and dogs. We explored the rabbit as an animal model for the congenital infection of schistosomiasis japonica and assessed the effect of a congenital S. japonicum infection on the resistance of rabbit kittens to a postnatal challenge infection.

METHODSSixteen pregnant New Zealand white rabbits were infected with a single dose of S. japonicum cercariae. The exposed animals were divided into three groups according to the gestation age at the time of infection. Diagnosis of prenatally acquired S. japonicum infection in the rabbit kittens was primarily based on serological tests in combination with parasitological and histopathological findings. Congenitally infected kittens were challenged percutaneously with 100 S. japonicum cercariae to assess the effect of a congenital S. japonicum infection on kitten resistance to a postnatal challenge infection.

RESULTSThe overall prevalence of congenital infection in offspring of infected mothers was 20% (12/60). The congenital infection rate in group L (late gestation) was much higher than in group E (early gestation) and group M (mid-gestation) (P <0.05). After a postnatal challenge infection, prenatally infected kittens had a 54.66% worm reduction rate, 41.45% egg reduction rate, and 51.76% granuloma size reduction rate compared to naïve kittens.

CONCLUSIONSThis study demonstrates the possibility of congenital infection of S. japonicum in rabbits and the resistance of congenitally infected kittens to a postnatal challenge infection. These results have important implications not only for epidemiological investigations, but also in designing government control programs for schistosomiasis.

Animals ; Antibodies, Helminth ; blood ; Female ; Immunoglobulin M ; blood ; Infectious Disease Transmission, Vertical ; Male ; Pregnancy ; Rabbits ; Schistosomiasis japonica ; congenital ; immunology ; parasitology

The aim of the present study was to confirm observations on the vertical transmission of Schistosoma japonicum in the rabbit. S. japonicum-infected pregnant rabbits were used in this study. Perfusion of mother rabbits was done 9 weeks after infection in order to obtain worm burdens in relation to their initial cercarial dose. Anti-schistosoma specific IgM antibodies in serum samples collected from rabbit kittens were detected by ELISA. Our results showed that gestation period lasted the normal 29-31 days. All the exposed mother rabbits became infected with S. japonicum. Positive IgM antibody OD values were detected in 12 out of the 60 kittens examined (20.0%). In group C and A, 40.0% and 17.9% of the kitten were congenitally infected, respectively. 18.1% of the kittens born to mothers infected with a single dose of 200 cercariae per rabbit were positives; this is not significantly different from that obtained for the 600 dose group (22.2%). Three randomly selected IgM+ kittens harbored between one and two adult worms. The livers of these kittens displayed granulomatous lesions. It is concluded that congenital S. japonicum infection does occur in the rabbit and is affected by the mother stage of pregnancy and to a lesser extent by its infection load.
Animals ; Antibodies, Helminth ; blood ; Female ; Immunoglobulin M ; blood ; Infectious Disease Transmission, Vertical ; Pregnancy ; Rabbits ; Schistosoma japonicum ; immunology ; isolation & purification ; Schistosomiasis japonica ; transmission

OBJECTIVETo analyze the relationship between the normalized difference vegetation index (NDVI) and the snail distribution in marshland of Jiangning county in Jiangsu province, and to explore the utility of Terra-MODIS image map in the small scale snail habitats surveillance.

METHODSNDVI were extracted from MODIS image by vector chart of the snail distribution using ArcView 8.1 and ERDAS 8.5 software. The relationship between NDVI and the snail distribution were Investigated using Bivariate correlations and stepwise linear regression.

RESULTSThe snail density on marshland was positively correlated with the mean NDVI in the first ten-day of May and the maximum NDVI (N(20max)) in the last ten-day of May. Incidence of pixel with the live snail on marshland was positively correlated with the mean NDVI (N(2mean)) in the first ten-day of May. An equation Y(1) = 0.009 47 x N(20max) (R(2) = 0.73), Y(2) = 0.018 6 x N(2mean) (R(2) = 0.906) was established.

CONCLUSIONThis study showed that the Terra-MODIS satellite images reflecting the status of the vegetation on marshland in Jiangning county could be applied to the study to supervise the snail habitat. The results suggested that MODIS images could be used to survey the small scale snail habitats on marshland.

Animals ; Breeding ; China ; epidemiology ; Ecology ; Environmental Monitoring ; Epidemiological Monitoring ; Humans ; Satellite Communications ; Schistosomiasis japonica ; epidemiology ; transmission ; Seasons ; Snails ; growth & development ; parasitology ; physiology

OBJECTIVETo investigate the changes in natural ecology and social environment after the construction of the dam in the Three Gorges Reservoir area, and to understand the social behavior status and education backgrounds of the local residents, and to analyze the potential impact of these factors on schistosomiasis spreading.

METHODSData of nature and social economy after the construction of the dam in the Three Gorge area were collected, and a cross-sectional study with questionnaire survey on information including social demographic characteristics, people's production and life style, knowledge about schistosomiasis was conducted among natives, emigrations.

RESULTSAfter the construction of the dam, as the stream became slower, the water-level fluctuating zone on the bank of the reservoir was formed. The main source of drinking water and daily life activity are mainly depends on the river supplying (accounting about 68.7% and 75.8%, respectively); due to the needs of farming, washing cloths and vegetables, 45.6% of resident had a close contact with river water. People with away-from-home employment among emigrations were increased from 5.7% to 18.7%. The proportion of using hygienic lavatory was 88.6%. The main source of water for drinking and daily life among emigrations was tap water (85.4% and 87.0%). The residents had no awareness about the health hazard for schistosomiasis, with less health information

CONCLUSIONThe natural environment of reservoir areas and the life style are risk factors for the spread of schistosomiasis. The improved sanitation condition and the economy construction after the construction of the dam is propitious to keeping away from the introduction of schistosomiasis. However, people with away-from-home employment among emigrations are still at risk of schistosomiasis.

Animals ; China ; Fresh Water ; Humans ; Life Style ; Rain ; Schistosoma japonicum ; Schistosomiasis japonica ; epidemiology ; transmission ; Social Behavior ; Surveys and Questionnaires ; Water Movements ; Water Pollution ; Workplace

OBJECTIVETo use a mathematical model and computer simulation to study transmission dynamics and control of schistosomiasis in mountainous regions of Sichuan.

METHODSBased on studies of schistosomiasis japonica transmission in 20 villages in mountainous regions of Sichuan, a mathematical model was developed to characterize the impact of local environmental factors on transmission intensity. The model integrated site-specific factors and was calibrated to field epidemiological data from 3 subset villages. The dichotomic method was then used to predict different control measures.

RESULTSThe study showed high variations in prevalence of infection and infection intensity across villages, ranging between 3%-73%, 0.1-100 epg (eggs per gram stool), respectively. Important factors including occupation of local residents, exposure to contaminated water, microclimatic characteristics were integrated in the model. The predictions of dichotomic models showed that continuing chemotherapy (coverage between 50%-60%) could reduce infection intensities to 30%-80%, but could not change local transmission potential; therefore, the termination of chemotherapy would be followed by bouncing back of transmission. Sustaining targeted environmental interventions through snail and parasite oval control at certain coverage (30%-50%, respectively) could reduce the transmission to relatively stable levels. The model predictions showed that an integrated control (e.g., including both chemotherapy and environmental interventions) could suppress the transmission to an undetectable level even interruption of transmission between 5-10 years.

CONCLUSIONThe study demonstrated the feasibility of using a dynamic model, calibrated to local data, to gain insights into complicated processes underlying the transmission and informing site-specific control strategies.

Adolescent ; Adult ; Animals ; Child ; Child, Preschool ; China ; Environment ; Humans ; Middle Aged ; Models, Theoretical ; Schistosoma japonicum ; Schistosomiasis japonica ; epidemiology ; prevention & control ; transmission ; Snails ; parasitology

Schistosomiasis is a kind of common disease around the riverside or lakeside areas, especially popular in rural areas, and causes huge economic loss. Based on existing schistosomiasis dynamic models and data, a new method of working out coefficients, and an improved model were provided in our study. The improved model can be applied to the study of the characteristics of transmission of schistosomiasis, and the effect of new control methods for schistosomiasis was evaluated.
Animals ; Cattle ; China ; Computer Simulation ; Humans ; Models, Theoretical ; Numerical Analysis, Computer-Assisted ; Schistosoma japonicum ; isolation & purification ; Schistosomiasis japonica ; epidemiology ; prevention & control ; transmission ; Snails ; parasitology

OBJECTIVETo analyze the impact of water transfer project from the Yangtze River to the Huaihe River on schistosomiasis transmission, and to evaluate the risk of the disease input to the potential endemic area in Anhui Province, namely the Chaohu Lake region.

METHODSFrom 2008 to 2012, 1 fixed and 3 mobile surveillance sites in the Chaohu Lake area were selected, and the schistosomiasis infection situation of 615 local residents in the fix surveillance site was investigated in autumn of 2008 and 2012, while the schistosomiasis infection situation of 1603 mobile population in the 3 mobile surveillance sites were investigated in autumn of 2008 to 2012. All people were screened by indirect hemagglutination assay (IHA), and the positive ones were then examined by sedimentation method. 303 local livestock and livestock from schistosomiasis endemic areas were examined by stool hatching method in autumn of 2008 to 2012. From 2008 to 2012, the distribution of Oncomelania snails was investigated in risk areas and suspicious areas, and the snail spreading pattern was conducted through salvaging floaters in rivers connected with the Yangtze River. In addition, the Oncomelania snails were raised in the cages on the beaches of the Chaohu Lake, a control area, from 2007 to 2010, and their survival and reproduction capacity was observed.

RESULTSIn 2008 and 2012, 301 and 314 local residents were detected by IHA, but there were no positive found. From 2008 to 2012, a total of 1603 mobile population were examined by IHA, and the positive rate of antibody was 3.1% (49/1603); 75 individuals were examined by sedimentation method, and the positive rate was 36.00% (27/75). A total of 303 livestock were examined by stool hatching method, but no one showed positive. A total of 1630 km(2) in risk areas and 3551 km(2) in suspicious areas were surveyed, but there were no Oncomelania snails found. A total of 457.6 kg floating debris were investigated, and 11 Oncomelania snails were found. From 2007 to 2010, the survival rate of Oncomelania snails in two trail areas in the Chaohu Lake and in the control area was 88% (86/98), 51% (45/89), 30% (25/71), 24% (20/84) and 92% (85/92), 54% (50/92), 23% (12/52), 17% (13/79) and 96% (85/89), 52% (44/85), 26% (18/69), 18% (14/76), respectively, there were no statistical significance between the trial areas and the control area (χ1(2) = 3.78, P > 0.01; χ2(2) = 0.27, P > 0.01; χ3(2) = 2.51, P > 0.01; χ4(2) = 1.50, P > 0.01), and filial generation snails were found in each observation area from 2008 to 2010, the number was 156-312.

CONCLUSIONThe imported infectious sources of schistosomiasis have been found in the Chaohu Lake region, the possibility of imported exogenous Oncomelania snails spreading into the Lake and surviving and reproducing there is high. The risk of schistosomiasis input to the potential endemic area in Anhui Province is predicted to be high.

Animals ; Cross-Sectional Studies ; Environmental Monitoring ; Humans ; Lakes ; parasitology ; Risk Assessment ; Rivers ; parasitology ; Schistosomiasis japonica ; epidemiology ; prevention & control ; transmission ; Snails ; parasitology