Schistosome-infected Snails Research Articles

Intestinal helminthiasis survey withemphasison schistosomiasis in Koga irrigation scheme environs, northwest Ethiopia.

BackgroundDistribution of schistosomiasis is more focal due to spatial heterogeneities in intermediate host snail dynamics and water contact behavior of humans. This makes the search for new transmission foci of schistosomiasis and its connection with malacologically receptive water bodies essential for effective control of its transmission. This study was intended to assess the prevalence of intestinal helminth infections among schoolchildren and Schistosoma mansoni transmission in Koga irrigation scheme surroundings, northwest Ethiopia.Materials and methodsCross-sectional parasitological and malacological surveys were conducted in three schools and nearby water bodies, respectively around Koga irrigation scheme. Stool specimens were collected from 421 randomly selected schoolchildren and microscopically examined using Kato-Katz and formol-ether concentration methods. Malacological surveys were carried out and the identified Biomphalaria pfeifferi snails were screened for schistosome infection. Swiss albino mice were exposed to schistosome cercariae shed by Biomphalaria pfeifferi for definite identification of Schistosoma species.ResultsAmong the examined schoolchildren, 22.6% (95% CI: 18.7%-26.9%) were positive for at least one intestinal helminths species. Ascaris lumbricoides was the most frequent intestinal helminth detected among forty (9.5%) children. Schistosoma mansoni was detected among 4.8% (95% CI: 2.9%-7.2%) of children and its prevalence was significantly higher among male children (p = 0.038) and those attending in Mengesha Jemberie Primary School (p = 0.044). Biomphalaria pfeifferi snails were identified in water bodies in close proximity to Mengesha Jemberie and Wotete Abay Primay schools. Schistosoma mansoni adult worms were harvested after exposure of mice to cercariae shed from Biomphalaria pfeifferi snails collected from water bodies nearby Mengesha Jemberie Primary School.ConclusionsSchistosoma mansoni infection of schoolchildren, findings of schistosome infected snails and establishment of mice infection confirm that transmission is taking place in the study areas. Hence, snail control and other measures such as provision of sanitary facilities and health education are recommended.

Distributional ecology of snails (Gastropoda: Mollusca) in seasonal ponds of Tamil Nadu, South India

The present study was focused to examine diversity and distributional pattern of freshwater snails and to identify the schistosome infected snails in ten different ponds of Madurai district, Tamil Nadu, South India. Snails were collected from native substrates in ponds using dip net from Madurai North, Tamil Nadu province of south India and microscopic examination for detecting cercariae larvae in snails were assessed. In total, 1250 individuals belonging to six species under five families of freshwater snails were collected. The alpha and beta diversity analyses were calculated for estimating the diversity of snails. The cercariae infection was observed in four collected freshwater snail species. Of four infected snails, Lymnaea luteola had the highest percentage of cercariae infection. Statistical tests showed that the environmental factors of total dissolved solids, pH and salinity were significantly related with snail distribution and cercariae infection rather than spatial factor. The study demonstrated that the salinity, conductivity and total dissolved solids of pond water play a key factor for the distribution of snails and cercariae infection. The findings of our study will improve the understanding of the dynamics of schistosomiasis transmission and would ease the implementation of integrated disease control measures based on ecological knowledge of schistosomiasis vector in Madurai and Tamil Nadu zones.

Duplex real-time PCR for sexing Schistosoma japonicum cercariae based on W chromosome-specific genes and its applications.

As a unique feature among otherwise hermaphroditic trematodes, Schistosoma species are gonochoric parasites whose sex is genetically determined (ZZ for males and ZW for females). However, schistosome larvae are morphologically identical, and sex can only be discriminated by molecular methods. Here, we integrated published Schistosoma. japonicum transcriptome and genome data to identify W chromosome-specific genes as sex biomarkers. Three W chromosome-specific genes of S. japonicum were identified as sex biomarkers from a panel of 12 genes expressed only in females. An efficient duplex real-time PCR (qPCR) method for sexing cercariae was developed which could identify the sex of cercariae within 2 h without DNA extraction. Moreover, this method can be used to identify not only single-sex but also mixed-sex schistosome-infected snails. We observed a nearly equal proportion of single-male, single-female, and mixed-sex schistosome infections in artificially infected snails. Sex-known schistosome-infected snail models can be efficiently constructed with the aid of duplex qPCR. A field study revealed that single-sex schistosome infections were predominant among naturally infected snails. Finally, a schistosomiasis mouse model based on sex-known cercariae infection was shown to be more reliable than a model based on sex-unknown cercariae infection. The developed duplex qPCR method for sexing S. japonicum cercariae can be widely used for schistosomiasis modeling, genetic experiments, and field-based molecular epidemiological studies.

Endemic situation of schistosomiasis in People's Republic of China from 2010 to 2017

To understand the epidemic trend of schistosomiasis in China from 2010 to 2017 so as to provide the scientific evidence for schistosomiasis elimination. The information of schistosomiasis control nationwide from 2010 to 2017 was collected, including the endemic of population, status of livestock control, and Oncomelania hupensis snail control. Microsoft Excel was applied for datum management and analysis. From 2010 to 2017, the epidemic of schistosomiasis in China dropped significantly. The decreasing amplitude of estimated number of patients nationwide was 88.46%. Seventy-one acute schistosomiasis patients were reported and 12.68% (9/71) of them were imported. The decreasing rate of cultivated cattle was 50.09%, and the accumulative number of schistosome-infected cattle was 17 239, and the average positive rate of stool examinations decreased from 1.04% to 0.000 22%. The area with snails nationwide was 373 596.18 to 363 068.95 hm2, and the new detected area with snails was 46.71 to 1 346.73 hm2. The area with schistosome-infected snails was 171.68 hm2 in 2012 and it was 9.25 hm2 in 2013. In 72 key monitoring points of 7 endemic provinces, there were 17 schistosome positive points of water body in 2010 and 6 points in 2016. There were some high risk-factors related to schistosomiasis transmission including schisto-some-infected cattle, dogs, and field rats, and the field stools, and the pasture in the area with snails in schistosomiasis monitoring points. The endemic status of schistosomiasis in China has dropped significantly, and the transmission level is very low. However, the infectious source and risk factors in the endemic environments have not be eliminated. Therefore, the infectious source control, health education, snail control, and transmission monitoring should be strengthened, so as to promote the progress of schistosomiasis elimination.

Risk assessment of schistosomiasis transmission in Chuxiong City of Yunnan Province

To evaluate the potential risk of schistosomiasis transmission so as to provide the evidence for formulating the control strategy. Two villages were selected as the investigated sites in Chuxiong City and the risk of schistosomiasis transmission was evaluated by reviewing the data of schistosomiasis epidemic situation and prevention and control work, and carrying out the field survey for Oncomelania hupensis snail status, wild faeces, and schistosome infection of the population from 2015 to 2017. There was 1.49 hm2 area of snail habitats, with an average density of 0.54 snails/0.1 m2. The occurrence rate of frames with snails was 5.41%. No schistosome-infected snails were found. The positive rate of schistosomiasis serological tests of the residents was 3.36%, but the stool examination positive cases were not found. A total of 58 wild faeces samples were collected but no schistosome infested cases were found. The risk levels of schistosomiasis transmission in both villages were Grade III. Although Chuxiong City has been in a low risk state of schistosomiasis transmission, the density of snails is still high, and there is a risk of infection source importation. In the future, the infection source control and snail control should be strengthened.

Surveillance of schistosomiasis in a national surveillance site of Jurong City, 2015-2017

To understand the endemic situation and control effect of schistosomiasis through the surveillance in a national surveillance site of Jurong City, so as to provide the evidence for formulating the prevention and control measures. According to the National Schistosomiasis Monitoring Scheme (2014 Edition), the surveillance of schistosome infection in Oncomelania hupensis snails, residents and livestock was performed in the Kongqing Village, a national surveillance site of Jurong City, from 2015 to 2017. The areas with snails were 0, 0, and 0.63 hm2 in 2015, 2016, and 2017 respectively; the average densities of living snails were 0, 0, and 0.19 snails/0.1 m2 in 2015, 2016, and 2017 respectively. No schistosome-infected snails were found. The positive rates of blood tests for schistosomiasis in the local residents were 7.72%, 7.45% and 3.45%, and the positive rates of blood tests in the floating population were 4.90%, 3.47% and 0.97% in 2015, 2016 and 2017, respectively. No positives were found in the schistosome etiology detection in the crowd and livestock. The effect of schistosomiasis prevention and control is obvious in Jurong City, but O. hupensis snails are still of recurrence. Therefore, the monitoring and control efforts should be strengthened to consolidate the achievements of schistosomiasis prevention and control.

Endemic status of schistosomiasis in People's Republic of China in 2017

This report presents the endemic status of schistosomiasis in the People's Republic of China at national level in 2017, and analyzes the data collected from the national schistosomiasis prevention and control system and 457 national schistosomiasis surveillance sites. Among the 12 provinces (municipality and autonomous region) being endemic of schistosomiasis japonica in P. R. China, 5 provinces (municipality and autonomous region), i.e., Shanghai, Zhejiang, Fujian, Guangdong and Guangxi, continued to consolidate the status of elimination of schistosomiasis. Sichuan Province achieved the transmission interruption and 6 provinces of Yunnan, Jiangsu, Hubei, Anhui, Jiangxi and Hunan kept the transmission control by the end of 2017. There were 450 endemic counties (cities, districts) covering 259 million people, specifically including 28 544 endemic villages of 70 324.5 thousand people at risk. Among the 450 endemic counties (cities, districts), 47.78% (215/450), 34.00% (153/450) and 18.22% (82/450) reached the criteria of elimination, transmission interruption and transmission control, respectively. By the end of 2017, a total of 8 401 113 individuals received schistosomiasis examinations and 14 individuals were parasitologically diagnosed, decreased by 97.67% compared with 600 cases in 2016. It was estimated of 37 601 cases of schistosome infection, decreased by 30.95% compared with 54 454 cases in 2016. One acute schistosomiasis case was reported in 2017. There were 29 407 advanced schistosomiasis cases documented in 2017. Oncomelania hupensis snail surveys were performed in 19 784 endemic villages and O. hupensis snails were found in 7 310 villages, accounting for 36.95% of total villages, with 19 newly detected villages with snails.The snail survey covered an area of 622454.49 hm2 and snails were found in an area of 172501.56 hm2, including a newly detected area of 208.54 hm2. No schistosome-infected snails were found in 2017. A total of 737 016 bovines were raised in the schistosomiasis endemic areas. Of them, 454 830 bovines received the examinations for schistosome infection, and 1 bovine was stool examination positive. There were 119 326 schistosomiasis cases receiving chemotherapy in 2017, with 1 973 968 individuals undergoing expanded chemotherapy; one bovine with schistosomiasis receiving chemotherapy, with 418 925 bovines undergoing expanded chemotherapy. A total of 144 605.31 hm2 area with snail was controlled by using molluscicides, with actual molluscicide-treated area of 73 755.37 hm2; and 5 002.92 hm2 area with snail was treated by environmental modification. Based on the data from the 457 national schistosomiasis surveillance sites, the mean Schistosoma japonicum infection rate was 0.001 6% and 0 in humans and bovines, respectively. No schistosome-infected snails were found by microscopic examinations in all the surveillance sites, and 7 snail samples with schistosome nucleic acid positive were detected by loopmediated isothermal amplification (LAMP) among 6 surveillance sites. The results demonstrate a continuous decline trend on the endemic situation of schistosomiasis in P. R. China. However, the risk of epidemic rebound still exists in some regions and it is still a challenge to achieve the target set by the Thirteenth Five-Year National Plan for Schistosomiasis Control in 2020.

Endemic situation of schistosomiasis in surveillance sites of Jingzhou City, 2017

To grasp the endemic situation of schistosomiasis in Jingzhou City in 2017, so as to provide the evidence for formulating prevention strategies. According to the requirements of National Schistosomiasis Surveillance Program (2014), Hubei Schistosomiasis Surveillance Program (2015) and Jingzhou Schistosomiasis Surveillance Program, the local population infection monitoring, mobile population infection monitoring, livestock disease monitoring, snail monitoring, and wild manure monitoring were carried out at 71 monitoring sites throughout the city. Among the 71 surveillance sites, 44 118 local residents received the indirect hemagglutination test (IHA) for schistosomiasis and 1 925 persons were positive, with the positive rate of 4.36%, However, no stool examination positive cases were found. Totally 2 175 mobile people received the IHA for schistosomiasis and 93 persons were positive, with the positive rate of 4.28%, but no stool examination positive cases were found. A total of 1 937 head of cattle received the stool examination for schistosome infection, but no positives were found. Totally 1 302 Oncomelania hupensis habitats were found in 69 surveillance sites, with 1 923.64 hm2 area with snails. Totally 348 756 frames were surveyed, and the occurrence rate of snails was 17.19%. A total of 142 494 living snails were captured, with the average density of 0.41 snail/0.1 m2. No schistosome-infected snails were found. Totally 596 cases of wild manure were picked up in 41 environments with snails among 23 surveillance sites, but schistosome infested wild manure was not found. In 2017, the level of schistosomiasis epidemic was very low in Jingzhou City. However, the risk of epidemic rebound still exists, and therefore, it is necessary to strengthen the monitoring work to further consolidate the achievements of schistosomiasis control.

Oncomelania hupensis status in national schistosomiasis surveillance sites of Yunnan Province from 2015 to 2017

To master the Oncomelania hupensis distribution and infection status in the national schistosomiasis surveillance sites of Yunnan Province, so as to provide the evidence for making the control and prevention measures. The data of O. hupensis surveillance in the 18 national surveillance sites of Yunnan Province from 2015 to 2017 were collected and analyzed with the descriptive analysis method according to the national schistosomiasis surveillance programme. The total surveillance area was 5 710.94 hm2, the area with O. hupensis snails was 205.69 hm2. The number of surveillance frames was 2 094 553, the occurrence rate of frames with snails was 0.62%, and the density of living snails was 0.025 4 snails/0.1 m2. In the schistosomiasis epidemic controlled areas, the area with snails, the occurrence rate of frames with snails and the density of living snails were all the highest. The snail concentrated distribution areas were the small reservoir, bottomland, paddy field, ditch, and dry land, and the snails mainly distributed in the rice, dry crop, weed and wood vegetation. The number of frames with snails, occurrence rate of frames with snails, total number of snails, number of living snails, and repetition areas with snails presented increasing trends, and however, no schistosome-infected snails were found during the three years. The O. hupensis snail status is obviously serious in the national schistosomiasis surveillance sites of Yunnan Province. The comprehensive snail control measures should continue to be strengthened, so as to effectively control the spread of the snails and reduce the risk of schistosomiasis outbreaks.

Investigation of Oncomelania hupensis snails in Anhui Province in 2016

To investigate the status of Oncomelania hupensis snails in Anhui Province in 2016, so as to provide the evidence for formulating the 13th Five-Year Plans for Schistosomiasis Control. In 2016, a snail survey was conducted in Anhui Province according to the National Programme of the Oncomelania Snail Survey, covering all snail habitats or historical snail habitats and suspected environments of snail breeding, and the results of the survey were analyzed. In 2016, 22 848 environments were surveyed, and no schistosome-infected snails were found. There were 17 927 historical snail habitats in whole province, among which, the environments without changes, changed partly and changed completely accounted for 71.2%, 19.3% and 9.5%, respectively. The area of historical snail habitats was 1.410 billion m2. There were 4 830 environments with snail habitats covering an area of 0.265 billion m2 in 38 counties of 7 cities, including newly emerging area of 1 287.65 hm2 and reemerging area of 1 375.32 hm2. The density of living snails was 0.392 0 snails/0.1 m2, and the rate of frame with living snails was 12.93%. The type of marshland and lake regions, and the type of hilly and mountainous regions accounted for 22.4% and 77.6% of number of snail habitats, and accounted for 86.7% and 13.3% of areas of snail habitats, respectively. Among the different types of vegetation in snail habitats, grass was superior owe to accounting for 82.2% of the number of snail habitats, 57.3% of the area with snail habitats, and the highest density of living snails (0.413 9 snails/0.1 m2). Among the different types of environments in snail habitats, the ditch was superior owe to accounting for 56.8% of the number of snail habitats, the highest density of living snails (0.570 3 snails/0.1m2) and the highest rate of frame with living snails (18.57%), and the beach was superior owe to accounting for 87.8% of the area with snail habitats. In Anhui Province, the first year of snails and schistosome-infected snails being found was 1950 and 1952, respectively, and the latest year of schistosome-infected snails being found was 2012. The map showed that the most environments with snail habitats were distributed along the Yangtze River in Anhui Province. For the first time, the investigation has built the database and map of snail spatial distribution, which truly reflect the historic and current status of snail distribution in Anhui Province and can provide the evidence for formulating the 13th Five-Year Plans for Schistosomiasis Control and improving the schistosomiasis prevention and control work in the future.

Agrochemicals increase risk of human schistosomiasis by supporting higher densities of intermediate hosts

Schistosomiasis is a snail-borne parasitic disease that ranks among the most important water-based diseases of humans in developing countries. Increased prevalence and spread of human schistosomiasis to non-endemic areas has been consistently linked with water resource management related to agricultural expansion. However, the role of agrochemical pollution in human schistosome transmission remains unexplored, despite strong evidence of agrochemicals increasing snail-borne diseases of wildlife and a projected 2- to 5-fold increase in global agrochemical use by 2050. Using a field mesocosm experiment, we show that environmentally relevant concentrations of fertilizer, a herbicide, and an insecticide, individually and as mixtures, increase densities of schistosome-infected snails by increasing the algae snails eat and decreasing densities of snail predators. Epidemiological models indicate that these agrochemical effects can increase transmission of schistosomes. Identifying agricultural practices or agrochemicals that minimize disease risk will be critical to meeting growing food demands while improving human wellbeing.

Endemic status of schistosomiasis in People's Republic of China in 2016

This report presents the endemic status of schistosomiasis in the People's Republic of China at national level in 2016, and analyzes the data collected from the national schistosomiasis prevention and control system and 454 national schistosomiasis surveillance sites. Among the 12 provinces (municipality and autonomous region) of endemic of schistosomiasis japonica in P. R. China, 5 provinces (municipality and autonomous region), i.e., Shanghai, Zhejiang, Fujian, Guangdong and Guangxi, had achieved elimination, and 7 provinces of Sichuan, Yunnan, Jiangsu, Hubei, Anhui, Jiangxi and Hunan had achieved transmission control by the end of 2016. There are 451 endemic counties (cities, districts) covering 257 million people, specifically including 29 692 endemic villages of 69.39 million people at risk. Among the 451 endemic counties (cities, districts), 35.25 % (159/451), 42.35% (191/451) and 22.39% (101/451) reached the criteria of elimination, transmission interruption and transmission control, respectively in 2016. By the end of 2016, it was estimated of 54 454 infections of schistosome, decreased by 29.46% compared with 77 194 in 2015. No acute schistosomiasis case was reported in 2016. There were 30 573 advanced schistosomiasis cases documented in 2016. A total of 8 500 710 individuals received schistosomiasis examinations and 600 individuals were parasitologically diagnosed, decreased by 83.36% compared with 3 606 in 2015. The Oncomelania hupensis snail survey was performed in 22 140 endemic villages and O. hupensis snails were found in 7 106 villages, accounting for 32.109% of the total villages, with 20 newly detected villages with snails. The snail survey covered area of 813 963.91 hm2 and snails were found in an area of 235 096.04 hm2, including a newly detected area of 1 346.48 hm2. No schistosome-infected snails were found in 2016. A total of 881 050 bovines were raised in the schistosomiasis endemic area. Of them, 510 468 bovines received examinations, resulting in 8 schistosome-infected bovines. There were 147 642 schistosomiasis cases receiving drug treatment in 2016, with 2 303 555 individuals undergoing expanded chemotherapy; there were 9 bovines with schistosomiasis receiving drug treatment, with 439 857 bovines undergoing expanded chemotherapy; a total of 139 483.84 hm2 area with snail control by using molluscicides, with actual molluscicide-treated area of 73 941.75 hm2; and 3 101.52 hm2 snail habitants were treated by environmental modification. Based on the data from the 454 national schistosomiasis surveillance sites, the mean Schistosoma japonicum infection rate was 0.02% and 0.0078% in humans and bovines, respectively. No schistosome-infected snails were found in all the surveillance sites. The results demonstrate a decline in the endemicity of schistosomiasis in P. R. China compared with the level of 2015. However, the distribution area of snails in China is still large and the infection source of schistosomiasis still exists to some extent in some endemic areas; in some regions, the task to reach the standard of transmission interruption is still arduous. There are still objective factors of epidemic and transmission and risk factors of endemic reversal and rebound for schistosomiasis. So, further control and effective surveillance as well as accurate prevention and control should be implemented to promote the elimination process on schistosomiasis in P. R. China.

Measures and effects of schistosomiasis elimination in Wujin District, Changzhou City

To understand the measures and effects of schistosomiasis elimination in Wujin District, Changzhou City, so as to provide the reference for other similar areas. The data of schistosomiasis prevention and control were collected and analyzed in Wujin District, Changzhou City from 1995 to 2015. From 1995 to 2015, the accumulated area for investigating Oncomelania hupensis snail habitats was 15 934.01 hm2 in Wujin District, and the accumulated area with snail habitats was 34.61 hm2, but no schistosome-infected snails were found. The area of snail control by molluscicides was 234.59 hm2, and the area of snail control by environmental reform was 84.48 hm2 in 18 key points. There were 259.3 thousand person-times receiving the examinations for schistosomiasis, and there were 17 314 head of livestock receiving the examinations for schistosomiasis, but no schistosome-infected cases were found. There were 204 2 person-times receiving the extensive chemotherapy. The popularizing rate of sanitary toilets was 99.25% in the whole district. The awareness rate of schistosomiasis control knowledge was 98.08% and the formation rate of proper behaviors was 97.82% in the population. In Wujin District, the aim of schistosomiasis elimination has been performed through the active control measures. However, there are still social and natural risk factors of re-endemic of schistosomiasis, and therefore, the schistosomiasis monitoring work still should be strengthened.

Role of new strategy in transmission control of schistosomiasis in Poyang Lake region

To evaluate the role of new strategy in the transmission control of schistosomiasis in Poyang Lake region. The information and epidemic data of schistosomiasis control were collected and analyzed in Poyang Lake region from 2005 to 2016. After eleven years of carrying out the new strategy, thirteen counties achieved the objective of transmission control in Poyang Lake region. In 2016, the number of schistosomiasis cases and human infection rate were 10 301 and 0.03%, decreased by 89.64% and 99.45% compared with those in 2005, respectively. The number of cattle and schistosome -infected cattle were 68 152 and 5, decreased by 50.84% and 99.83% compared with those in 2005, respectively. The average density of Oncomelania hupensis snails was decreased by 61.52%. No schistosome-infected snails were found since 2014. The new strategy accurately locates the key points and targets of schistosomiasis transmission chain, which has controlled the human and animal's fecal eggs from polluting grassland, and cut off the transmission chain, reduced both the infection rates of human and animal and the re-infection risk, and promoted to achieve the target of schistosomiasis transmission control in Poyang Lake region.

Final evaluation of medium- and long-term program of schistosomiasis control in Baise City

To evaluate the monitoring results of medium- and long-term program of schistosomiasis control in Baise City, so as to provide the reference for the elimination of schistosomiasis. The data of schistosomiasis control in Baise City from 2004 to 2015 were collected and analyzed. By the end of 2015, the total number of regular screening serum tests for schistosomiasis in the planning period was 10 244 person-times, with 649 positive cases. The number of feces tests was 2 158 person-times in the permanent resident population, and the number was 2 683 person-times in the floating population. The Oncomelania hupensis snail survey area was 150.04 hm2, and the accumulated snail control area was 2.03 hm2. No schistosomiasis patients or schistosome-infected snails were found. The effect of medium- and long-term program of schistosomiasis control is effective in Baise City, and the criterion of schistosomiasis elimination has been achieved.

Analysis of schistosomiasis endemic status of national surveillance sites in Yunnan Province, 2016

To master the prevalence status of schistosomiasis in Yunnan Province in 2016, so as to provide the evidence for formulating the control strategy and intervention measures. The schistosomiasis heavy-endemic villages were selected from each of 18 endemic counties as the survey sites. Then, the serological and etiological tests were carried out in the local residents and floating population, and the infection status of the livestock, field feces and Oncomelania hupensis snails were surveyed. The serum positive rate of schistosomiasis of local residents was 8.78% and the serum positive rate was 2.26% of floating population. No schistosome eggs were found in the stool examinations in the population. The area with snails was 80.054 6 hm2 in 2016 with an increasing rate of 45.47% compared to that in 2015. The average density of living snails was 0.031 7/0.1 m2. No schistosome-infected snails were found for the last four years and no new area with snails was found for the last three years. No positive livestock or feces were found. The schistosomiasis epidemic situation is stabilized in Yunnan Province in 2016. However, the area with snails and the number of living snails are increasing, and therefore, the schistosomiasis epidemic risk still exists. So, the comprehensive control measures should be strengthened continuously.

Strategy and effect of Oncomelania hupensis snail control in inside-embankment areas in Junshan District, Hunan Province from 1998 to 2017

To explore the strategy and countermeasures of Oncomelania hupensis snail control and evaluate the effect in inside-embankment areas of lake-type schistosomiasis endemic area, for providing the effective method for controlling and interrupting the schistosomiasis transmission. The data of schistosomiasis epidemic and its control and prevention were collected in Junshan District, Hunan Province, and the effect of snail control countermeasures were evaluated and the trend of indexes of snails was drafted in the inside-embankment areas of Junshan District, Hunan Province from 1998 to 2007. The area with snails in the inside embankment areas of Junshan District decreased by 98.43%, from 1 496.66 hm2 in 1998 to 23.48 hm2 in 2017. The occurrence rate and average density of of living snails decreased from 20.61% and 0.45 snail/0.1 m2 in 2003 to 2.06% and 0.03 snail/0.1 m2 in 2017. The highest area with schistosome infected snails was found in 2001 and the total area was 79.36 hm2, however, no infected snails were found since 2007. The total fiscal investment for schistosomiasis prevention and control was 398.857 million RMB in Junshan District, including molluscicide (81.770 9 million RMB) and environment reform (213.5 million RMB) respectively. The comprehensive measures, mainly including the combination of molluscicide and environment reform have gotten a significant effect in snail control and elimination in the inside-embankment areas, but the snail surveillance still need to be strengthened in the historic areas with snails.

Analysis of epidemic situation of schistosomiasis in Wuhu County from 2012 to 2016

Objective To analyze the epidemic situation of schistosomiasis in Wuhu County from 2012 to 2016, so as to provide the reference for adjusting the control strategy. Methods The data of schistosomiasis prevention and control in Wuhu County from 2012 to 2016 were collected and longitudinally analyzed. Results Since 2013, the average infection rate of schistosomiasis in the population decreased year by year, and the infection rate decreased to 0 in 2016. Since 2012, the infection rate of livestock was 0. The area with Oncomelania hupensis snails decreased year by year, but it drastically rebounded in 2016. No schistosome-infected snails were found since 2012. Conclusions Schistosomiasis epidemic is effectively controlled in Wuhu County, but there is a possibility of recovery. In the next stage, we should focus on strengthening the control of snails and imported infectious sources in order to consolidate the achievements of prevention and control.

Surveillance of schistosomiasis in People's Republic of China in 2015

To analyze the investigation data of the national schistosomiasis surveillance sites in 2015, so as to provide scientific evidences for schistosomiasis control, elimination and surveillance. According to National Schistosomiasis Surveillance Programme (version 2014), 457 surveillance sites were selected, and the investigation data in residents, floating population, domestic animals and Oncomelania hupensis snails were collected and analyzed from four types of endemic counties. A total of 4 468 seropositive cases were detected from 133 350 residents, among which 4 457 residents with seropositive results received the etiological tests, and 71 of them were identified with positive results. Most of them were fishermen and farmers in the middle and old-aged group. The schistosomiasis infection rate was 0.05% in local population. Totally 977 seropositive cases were examined from 85 047 migrant individuals, and 16 positive cases were found out from 966 individuals who took etiological tests, which showed the schistosomiasis infection rate was 0.02% in floating population. Imported cases were found among floating people in four provinces, namely Zhejiang, Hunan, Hubei and Anhui provinces. No acute schistosomiasis cases were reported. A total of 13 406 head of cattle received examinations and only 5 were determined as stool positives. The cattle infection rate was 0.04%. The snail survey covered an area of 22 295.13 hm2 and snails were found in an area of 7 426.63 hm2, including 3.47 hm2 newly detected area with snails. No schistosome-infected snails were found. Based on the collected data from 457 national schistosomiasis surveillance sites of China, the Schistosoma japonicum infection rate is 0.05% in local population which maintains a stably descending trend. In floating population, there are imported schistosome-in-fected persons. Cattle are still a vulnerable species infected with schistosome. Although no infected snails are found, snails are widely distributed in endemic areas. Some provinces detect areas with snails for the first time or the reproduction of snails. The staff in endemic provinces should carry out the surveillance work according to National Schistosomiasis Surveillance Programme (version 2014) to improve the surveillance system, and enhance the sensibility and effectiveness of surveillance work.

Oncomelania hupensis status monitoring in Changzhou City, Jiangsu Province from 2013 to 2016

Objective To analyze the Oncomelania hupensis snail distribution and the changes of snail situation in Changzhou City from 2013 to 2016, so as to provide the evidence for formulating the schistosomiasis prevention and control interventions. Methods The data of snail monitoring in Changzhou City from 2013 to 2016 were collected and statistically analyzed. Results The total area with snails was 40.17 hm2 and the newly discovered area was 30.63 hm2 in Changzhou City from 2013 to 2016. In the four years, 3 454 snails were dissected, and no schistosome infected snails were found. There were totally 51 spots with snails, and the areas with snails of different types of marshland, inland and mountain were 12.13 (30.19%), 25.54 hm2 (63.57%) and 2.51 hm2 (6.24%), respectively. In the newly discovered snail environment, the areas of types of marshland and inland were 8.00 hm2 (26.12%) and 22.63 hm2 (73.88%), respectively. The main causes for snail existence were external input and adjacent diffusion. In the past four years, the total snail control area with molluscicides was 71.74 hm2, the consolidated snail control area with molluscicides was 155.15 hm2, and the total environmental modification areas in the current snail spots and historic snail spots were 15.90 hm2 and 11.30 hm2 respectively. Conclusion The diffusion of snails in inland rivers is the key of the newly discovered snail areas in Changzhou City in recent years, and the snail monitoring and control measures should be strengthened in the future.