[Effect of mid- and long-term schistosomiasis control plan and discussion of consolidation strategy in marshland endemic regions].

OBJECTIVE: To evaluate the effectiveness of mid- and long-term schistosomiasis control plan and explore the consolidation strategy in marshland endemic regions, so as to provide an effective approach for interrupting and eliminating schistosomiasis in the regions. METHODS: A prospective field study was designed. Dantu District of Zhenjiang City, a marshland schistosomiasis endemic region, was selected, and the "key village, key environment, and key water regions" comprehensive control strategy was implemented according to the endemic level of schistosomiasis. The morbidity due to schistosomiasis in humans and domestic animals, and Oncomelania hupensis snails were surveyed, and the data of the implementation of control measures were collected. The schistosomiasis morbidity and snail status were compared before and after the implementation of the mid- and long-term plan for schistosomiasis prevention and control, and the changing trends of human, domestic animal and snail infections were plotted. RESULTS: During the implementation of the plan from 2005 to 2014, 16.84 km concrete and bank protection and 9 snail sinks were built, 10 culverts re-built, 3.85 hm2 fences were constructed, 29.5 thousand domestic animals were examined and treated, 170 cattle were eliminated, 4930 hm2 fishing farms were built for snail control, 1 560.00 hM2 land were improved, and 376.00 hm2 forests were built for snail control. In addition, 19,364.80 hm2 snail areas were surveyed, 4694.6 hm2 area received molluscicide, 207.9 thousand of people (person-times) received the examination and treatment, 69.1 thousand of harmless toilets were built, 282.2 thousand health education materials and protection materials were allocated, 958 warning signs were established, and 5435 slogans were pasted or hung. After the implementation of the mid- and long-term plan, the percentages of human, bovine and snail infections appeared decline tendencies year by year, and reduced from 0.08%, 1.28% and 0.13% in 2005 to 0 in 2014, respectively, while the areas with snails and infected snails reduced from 284.34 hm2 and 55.10 hm2 in 2005 to 73.60 hm2 and 0 hm2 in 2014, with reduction rates of 74.12% and 100%, respectively. The infection rate of sheep appeared a fluctuation between 2005 and 2014, with the rate of 1.13% in 2005, 0 in 2007 and 2008, rising in 2009 and then between 0.25% and 0.95% from 2009 to 2012, and reducing to 0 in 2013 and 2014. During the 10-year period, the number of cattle reduced year by year from 2005 to 2010, and slightly increased after 2011, showing an overall stable level, while the number of sheep increased year by year after 2006, peaked in 2010, and appeared a decline tendency since 2011, which was almost consistent with the fluctuation of schistosome infection rate in sheep. CONCLUSIONS: The sustainable comprehensive control strategy with the "key village, key environments, and key water regions" is an effective approach for schistosomiasis control in marshland endemic regions. However, the endemic situation of schistosomiasis is extremely easy to repeat. The prevention and control of the impact of sheep and wild animals on schistosomiasis transmission should be strengthened in order to consolidate the schistosomiasis control achievements gained.

[Surveillance of schistosomiasis in national surveillance sites of Zhenjiang City, 2005-2010].

OBJECTIVE: To master the changes of schistosomiasis epidemic situation in national surveillance sites of Zhenjiang City, Jiangsu Province. METHODS: According to the scheme of the national schistosomiasis surveillance, the Shicheng Village of Yangzhong County and Sanzhou Village of Dantu District were selected as the national schistosomiasis surveillance sites, and from 2005 to 2010, the schistosomiasis morbidity and Oncomelania hupensis status were surveyed and the results were analyzed statistically. RESULTS: In 2010, in the Shicheng Village, the reduction rates of mean living snail density, infected snail density, area with infected snails, and positive blood tests in residents were 98.4%, 0, 0, 71.8% respectively, and in the Sanzhou Village, the reduction rates were 70.4%, 100%, 100% and 81.5%, respectively compared with those in 2005. No acute infections were found in the 2 villages during the period of 6 consecutive years. CONCLUSION: In the national surveillance sites of Zhenjiang City, the schistosomiasis morbidity has been effectively controlled. However, the areas with snails change little. Therefore, the comprehensive management of snail environment in the marshland should be strengthened in the future.

[Effect evaluation of comprehensive control of schistosomiasis in Dantu District, Zhenjiang City].

Since the project of comprehensive control of schistosomiasis was carried out in Dantu District, Zhenjiang City, Jiangsu Province, the infection rate of residents decreased from 0.083% in 2005 to 0 in 2010. After 2007, the number of acute schistosomiasis patients was 0, and the infection rate of livestock was 0. The areas with infected Oncomelania snails and average density of infected snails significantly decreased year by year, and none infected snail was discovered since 2010. In 2010, Dantu District achieved the national criteria for schistosomiasis transmission control, and the epidemic situation was effectively controlled.

The sensitivity of Schistosoma japonicum to praziquantel: a field evaluation in areas with low endemicity of China.

The purpose of the current study was to investigate the susceptibility of Schistosoma japonicum to praziquantel in low endemic foci of China. During the non-transmission period of schistosomiasis, a total of 43 of 1,242 subjects were identified as being infected with the parasite using parasitological stool examinations in two low-endemicity areas of China, with a prevalence rate of 3.46%. All stool-egg-positive subjects were treated with praziquantel in a single oral dose of 40 mg/kg or 30 mg/kg for two successive days. Six weeks post-treatment, no S. japonicum eggs were detected in the 43 treated villagers. The results indicate that the current efficacy of praziquantel against S. japonicum seems satisfactory and has not changed over the past three decades in the low endemic areas of China. It is also suggested that no evidence of tolerance or resistance to praziquantel in S. japonicum is detected in areas with low endemicity in China.

The South-to-North Water Diversion Project: effect of the water diversion pattern on transmission of Oncomelania hupensis, the intermediate host of Schistosoma japonicum in China.

BACKGROUND: The South-to-North Water Diversion Project (SNWDP) is the largest national water conservancy project in China. However, the Eastern Route Project (ERP) of SNWDP will refer to the habitats of Oncomelania hupensis, the intermediate host of Schistosoma japonicum. The present study was aimed at investigating the effects of some factors relating to the water diversion pattern on the spread north of O. hupensis and transmission of S. japonicum. METHODS: Marked snails were attached to the floating debris, and then placed on the water surface, the passage of snails through water pumps was observed. Some marked living adult snails were placed under water in the 5 spots, 15, 30, 60, 90 and 120 days later, their survival and transfer under water were investigated. 2, 4, 8, 16, 32, 64 and 128 juvenile snails, with a male: female ratio of about 1, were caged, 1 year later, their reproductions were calculated. RESULTS: The snails attached on the floating debris at 100-, 50- and 20-cm-distance from the inlet pipe of the big pump (with a diameter of 80 cm), could be absorbed into the pumps, with passing rates of 2.45%, 3.93% and 43.46%, respectively, compared with 72.07% and 91.00% for the snails at 20 cm and 10 cm-distance from the inlet pipe of the small pump (with a diameter of 20 cm). A total of 36,600 marked living snails were put into 5 ponds and ditches, with the water depths of 1-1.6 m, 15-120 days later, no marked ones were found along the ponds and ditches or in the straw packages. The juvenile snails did not reproduce until their density reached up to 8 snails (ratio of male: female of 1)/0.16 m2. CONCLUSIONS: During the construction of ERP of SNWDP, the risk of northward spread of schistosomiasis japonica will be decreased or eliminated as long as long-term reliable interventions for snail control are implemented.

A strategy for emergency treatment of Schistosoma japonicum-infested water.

BACKGROUND: Schistosomiasis japonica, caused by contact with Schistosoma japonicum cercaria-infested water when washing, bathing or production, remains a major public-health concern in China. The purpose of the present study was to investigate the effect of a suspension concentrate of niclosamide (SCN) on killing cercaria of S. japonicum that float on the water surface, and its toxicity to fish, so as to establish an emergency-treatment intervention for rapidly killing cercaria and eliminating water infectivity. RESULTS: At 30 min after spraying 100 mg/L SCN, with niclosamide dosages of 0.01, 0.02, 0.03, 0.04 g/m², the water infectivity reduced significantly and no infectivity was found at 60 min after spraying SCN. The surface of static water was sprayed with 100 mg/L SCN, the peak concentration was found at 0 min, and the solution diffused to site with a water depth of 10 cm after 10 min. 30 min later, SCN diffused to the whole water body, and distributed evenly. After spraying 100 mg/L SCN onto the surface of the water with a volume of(3.14 × 202 × 50)cm³, with niclosamide dosages of 0.02 g/m², 96 h later, no death of zebra fish was observed. CONCLUSIONS: By spraying 100 mg/L SCN, with a niclosamide dosage of 0.02 g/m² onto the surface of S. japonicum-infested water, infectivity of the water can be eliminated after 30-60 min, and there is no evident toxicity to fish. This cercaria-killing method, as an emergency-treatment intervention for infested water, can be applied in those forecasting and early warning systems for schistosomiasis.

[Surveillance of schistosomiasis in a national, surveillance site of Dantu District, Zhenjiang City, 2005-2009].

The surveillance of schistosomiasis in Sanzhou Village, a national schistosomiasis surveillance site, in Gaoqiao Town of Dantu District, Zhenjiang City from 2005 to 2009 showed that the schistosomiasis morbidity remained in a low level in the surveillance site; however, the Oncomelania snails and infected snail areas remained high. It is suggested that, in addition to snail control, comprehensive control measures should be strengthened, and the causes of infected snails in marshland should be investigated, so as to clarify the roles of various hosts in transmission of schistosomiasis.

Is there reduced susceptibility to praziquantel in Schistosoma japonicum? Evidence from China.

Praziquantel is widely used for the treatment of human schistosomiasis. However, in recent years, there has been increasing concern about the resistance of Schistosoma species to praziquantel. The study described here was designed to evaluate the current susceptibility to praziquantel in S. japonicum in China. During the non-transmission period of schistosomiasis, a random sample of 4760 subjects from the main endemic foci of China were examined using parasitological stool examination. In total, 584 subjects were identified as being infected with S. japonicum, with a prevalence rate of 12.27%. Among them, 565 stool-egg-positive subjects were treated with praziquantel in a single oral dose of 40 mg/kg. Six weeks post-treatment, among the 505 villagers re-examined, 480 (95.05%) had no detectable S. japonicum eggs. Twenty-one subjects still excreting eggs after the first treatment were treated with praziquantel for the second time. All stool samples, including those from those participants with second treatment were re-examined 6 weeks after the second treatment, and no stool-egg-positives were found. The results indicate that the current efficacy of praziquantel against S. japonicum is still high and has not changed after more than 2 decades of repeated, expanded chemotherapy in the main endemic areas of China. It is suggested that no evidence of tolerance or resistance to praziquantel in S. japonicum was detected in China.