Prevalence of and risk factors associated with Cryptosporidium infection in an underdeveloped rural community of southwest China.

BACKGROUND: Cryptosporidium spp. is an important intestinal protozoan causing diarrhea in humans, livestock, and wild animals. Cryptosporidium infection remains a major public health issue, but its epidemiology in humans is still unclear, particularly in rural China. This study was designed to determine the prevalence of and risk factors associated with Cryptosporidium infection in a rural southwestern Chinese community. METHODS: A community-based cross-sectional survey was conducted among 687 residents of a small town in a Yi autonomous prefecture of southwest China in 2014. Blood samples were examined using a broad set of quality-controlled diagnostic methods for hepatitis B virus (HBV) and human immunodeficiency virus (HIV). Stool specimens were processed using the modified acid-fast staining method, and microscopically examined for Cryptosporidium infection. Univariable and multivariable analyses were performed to determine the risk factors associated with Cryptosporidium infection. RESULTS: The majority of the participants were Yi people with poor living conditions and unsatisfactory hygiene habits, and the study area was of very low socioeconomic status. Of the 615 individuals included in the analysis, 14 (2.3%) were HIV positive, 51 (8.3%) were infected with HBV, and 74 (12.0%) had Cryptosporidium infection. The prevalences of HIV/HBV, HIV/Cryptosporidium, and HBV/Cryptosporidium co-infections were 0.3%, 0.3%, and 1.8%, respectively. The prevalence of HBV infection was higher in individuals with Cryptosporidium infection (χ 2 = 5.00, P = 0.03). Owning livestock or poultry was an important risk factor for Cryptosporidium infection (aOR = 2.27, 95% CI: 1.01-5.08, P < 0.05). Cryptosporidium infection was significantly associated with HBV infection (aOR = 3.42, 95% CI: 1.47-7.92, P < 0.01), but not with HIV infection (aOR = 0.57, 95% CI: 0.07-4.39, P = 0.59). CONCLUSIONS: The prevalence of Cryptosporidium infection was high in the rural area of southwestern China that was investigated, and there was a significant association between HBV infection and Cryptosporidium infection. Further investigations are needed to determine the significance of Cryptosporidium infection in patients infected with HBV.

Multi-host model and threshold of intermediate host Oncomelania snail density for eliminating schistosomiasis transmission in China.

Schistosomiasis remains a serious public health issue in many tropical countries, with more than 700 million people at risk of infection. In China, a national integrated control strategy, aiming at blocking its transmission, has been carried out throughout endemic areas since 2005. A longitudinal study was conducted to determine the effects of different intervention measures on the transmission dynamics of S. japonicum in three study areas and the data were analyzed using a multi-host model. The multi-host model was also used to estimate the threshold of Oncomelania snail density for interrupting schistosomiasis transmission based on the longitudinal data as well as data from the national surveillance system for schistosomiasis. The data showed a continuous decline in the risk of human infection and the multi-host model fit the data well. The 25th, 50th and 75th percentiles, and the mean of estimated thresholds of Oncomelania snail density below which the schistosomiasis transmission cannot be sustained were 0.006, 0.009, 0.028 and 0.020 snails/0.11 m(2), respectively. The study results could help develop specific strategies of schistosomiasis control and elimination tailored to the local situation for each endemic area.

Prevalence and risk factors of Ascaris lumbricoides (Linnaeus, 1758), Trichuris trichiura (Linnaeus, 1771) and HBV infections in Southwestern China: a community-based cross sectional study.

BACKGROUND: Intestinal helminths do not cause severe diseases in general, however, when combined with other diseases such as immunodeficiency diseases, there would be massive complications. Infections with Hepatitis B Virus (HBV) may lead to immunological disturbances and defects of cellular immunity and there is a need of clarification whether HBV infections are associated with infections with intestinal helminths. METHODS: A community-based cross sectional study was conducted in Tezi town, Puge County of the Liangshan Prefecture, southwestern China from October 23rd to November 3rd, 2014. Four hundred and thirty eight people (median age = 37 years, IQR = 22-49) were enrolled in this study. Modified Kato-Katz thick smear was used to detect intestinal helminths. HBV DNA was quantified to confirm HBV infection. RESULTS: Among the 438 participants, 9.1%, 13.5% and 30.6% were infected with HBV, A. lumbricoides (L., 1758) and T. trichiura (L., 1771), respectively; 7.1% (30/438) were infected with both A. lumbricoides and T. trichiura and 2.3% (10/438) were co-infected with HBV and A. lumbricoides. The multivariate logistic regression analysis showed that age (21-30 years versus >50 years: OR = 6.66, 95% CI = 2.15-20.68), drug abuse (OR = 6.96, 95% CI = 1.11-43.90), A. lumbricoides infection (OR = 3.60, 95% CI = 1.48-8.75), fertilization with faeces after disposal (OR = 0.15, 95% CI = 0.04-0.47) and working on a farm (OR = 4.59, 95% CI = 1.44-14.63) were significantly associated with HBV infection. Having toilets at home was negatively related to A. lumbricoides infection (OR = 0.52, 95% CI = 0.27-0.98) and T. trichiura infection (OR = 0.48, 95% CI = 0.28-0.80). CONCLUSIONS: Ascaris lumbricoides was independently associated with HBV infection, and faeces might be the medium of HBV transmission. Improving hygiene conditions and habits are essential to reduce the risks of A. lumbricoides and T. trichiura infections.

[Spatial characteristic of distribution of Oncomelania hupensis in mountainous regions].

OBJECTIVE: To analyze the spatial characteristic on the distribution of Oncomelania hupensis in mountainous regions. METHODS: Based on the geographic database of snail distribution in Puge county, Sichuan province, spatial autocorrelation analysis and spatial scan statistics were applied to analyze the spatial characteristic of snail distribution. RESULTS: With regard to the rate of frame with snails, the global Moran's I indicator was 0.095 (P < 0.05), which indicated the spatial autocorrelation of snail distribution in Puge county. Data from the local spatial autocorrelation analysis showed that there were 28 snail habitats with statistically significant differences on local indicators of spatial autocorrelation (LISA) value (P < 0.05), among which existed high-high, low-low, low-high and high-low four types of correlation model. The Spatial Scan Statistics had in total identified 24 snail habitat clusters (P < 0.05), including 14 high rate clusters and 10 low rate clusters, and the result was similar to that of LISA analysis. CONCLUSION: There were spatial autocorrelation and spatial aggregation of snail distribution in mountainous regions, meanwhile spatial heterogeneity of snail distribution also existed. This law could be explored for better control of snails.

Effect of habitat fragmentation on the schistosome-transmitting snail Oncomelania hupensis in a mountainous area of China.

The effect of habitat fragmentation on schistosome-transmitting snails was assessed in an intervention village and a control village in Sichuan Province, China. Snail habitats were fragmented by environmental management. After 2 years, the proportions of quadrats with snails in the fragmented habitats decreased from 9.35% to 2.41% in one patch (c3) and from 12.20% to 6.57% in another patch (c12), whilst the proportions in habitats without fragmentation did not alter significantly. Mean snail density decreased from 0.246 to 0.063 snails/0.11 m2 in patch c3 and from 0.356 to 0.177 snails/0.11 m2 in patch c12, whilst the mean snail density of other patches did not alter significantly. Most snails from the same patch and/or its remaining patches after fragmentation clustered together in the phylogenetic tree, except for c1, c3 and its remaining patches (c5, c6 and c11). Snail habitats in the study zone exhibited visible fragmentation. Habitat fragmentation could decrease the snail population size and limit migration and dispersal of snails between patches.

[Metagenesis of intermediate host to Schistosoma japonicum Oncomelania snail in mountainous areas].

OBJECTIVE: To understand the metagenesis of Oncomelania snails in the mountainous regions so as to control the spread of snails and the epidemics of schistosomiasis. METHODS: Observation spot was established at a typical snail habitat close to Puge county, Sichuan province from February 2008 to July 2009. Random sampling was applied to determine the place of each frame during the observation. All the snails in each frame were collected and numbers counted in the laboratory, with the number of mating pairs in each frame also observed. Snails being collected were measured for the body indices and the dissection was carried out to identify gender composition, survival status and the number of live snails in each frame counted. Line graphs of the body indices, mating pairs in each observed months, bar graphs of the snail density, proportions of gender together with the maturity of the snails in each month were drawn. RESULTS: The number of live snail existed the whole year and its density fluctuated. All the three kinds of body indices showed the same time trend and a dynamic circulation. The young snail existed all year around and arose constantly in proportion from May, becoming the dominant snail in October to replace the adult snails. The young and adult snails also showed a dynamic alternative. The gender composition showed no significant difference during each month. The number of the mating pairs was more on April, May and June annually, when were the snail's main multiplying stage. CONCLUSION: In mountain area, the young snails existed through all the year while adult snails appeared to be dominant in each month except for October. Oncomelania snail showed a circular process of metagenesis which started in May and finished in October. The snail population presented a dynamic equilibrium. It was concluded that ecological studies on Oncomelania snail were extremely relevant, either to optimally apply the existing control measures or to develop alternative measures for snail control, ecologically or biologically.

[Simple sequence repeat variation and small-scale spatial autocorrelation analysis on smooth-shell populations of Oncomelania hupensis in Sichuan province].

OBJECTIVE: To analysis the spatial autocorrelation on the small-scale distribution of the genetic variation in the population of Oncomelania hupensis in Puge county, Sichuan province, using simple sequence repeat (SSR) marker. METHODS: 5 pairs of SSR primer were used to amplify the genomic DNA of Oncomelania hupensis, and the alleles with frequency ranging from 15% to 85% were used to calculate Moran's I spatial autocorrelation coefficients in 14 distance band based on equal numbers of paired samples. RESULTS: A total of 274 alleles were scored by 5 pairs of SSR primer, the average polymorphic information content of the 274 alleles were 0.965 which indicated a high level of genetic diversity. 39 alleles showed different patterns of positive spatial autocorrelation of genetic variation, which was non-random spatial structure. When the distance band increased, the spatial auto-correlativity decreased based on the average Moran's I value at 14 distance band. The alleles which showed a negative spatial autocorrelation were not found in any distance band. CONCLUSION: The spatial distribution of the genetic variation of SSR showed positive spatial autocorrelation in the population of Oncomelania hupensis, and the spatial auto-correlativity decreased with the increase of distance band.

[Spatial distribution and elimination of Schistosome japonicum intermediate hosts Oncomelania hupensis in mountainous regions].

OBJECTIVE: To explore the spatial distribution and elimination of Oncomelania hupensis in mountainous regions. METHODS: Puge County in Tezi township was selected as the study site and the quadratus were placed randomly to investigate snail. The two sods with water were selected as the sites of snail elimination. One sod with area of 1000 m2 and mean density of 9.88 snails/0.11 m2 was selected as the trial group with 'heaping' method, and the other with area of 1000 m2 and mean density of 9.80 snails/0.11 m2 as the control group with sprinkling method. The molluscacidal effect of the two methods was compared by systematic sampling (5 m x 5 m). The sample size was 40 quadratus. RESULTS: The snail distributed mainly in the sods with water, canals and farmlands. Among the three snail habitats, the area with snail was the most in the farmlands with relatively lower density of living snail; the next was the sods with water, with relatively higher density of living snail. Before killing snails, the rate of quadratus with snails was 87.50% in the trial site, and 82.50% in the control site. The mortality of snails was 3.89% in the trial site, and 4.16% in the control site. After three months, no living snails were found in the trial site, while in the control site, the rate of quadratus with snails (chi2 = 0.31, P > 0.05) and the mortality of snails (chi2 = 3.12, P > 0.05) did not decrease significantly, and the density of living snails only reduced by 8.88%. CONCLUSION: The 'heaping' method is an efficacious measure for snail control.

[Snail control by using soil pasting mixed with niclosamide].

OBJECTIVE: To evaluate the effect of snail control through soil pasting mixed with niclosamide. METHODS: Four sites were selected in different epidemic areas in Sichuan province. Soil pasting mixed with niclosamide was carried on, and the dosage was 0 g/m2, 4 g/m2, 6 g/m2, 8 g/m2 and 10 g/m2 respectively. The mortality rate of snail and the density of snail were observed after 7, 15, 30, 90 and 180 days. RESULTS: The mortality rate of snail was more than 43.3% in blank group after 30 days. The mortality rate of snail was from 75.3% to 100.0% at 4 g/m2 group after 30 days. The mortality rate of snail in 4 g/m2 group was significantly higher than that in the blank group (chi2 = 31.27, P < 0.05). There was no significant difference in the mortality rate of snail among all study groups (chi2 = 1.07, P > 0.05). The decrease rate of snail density was more than 90%. The mortality rate of snail was about 30% higher in Chantu group than Qutu group. The unit cost of Pasting-Mixing Drug with Soil was from 5 to 7 times of spray method, but the total cost was similar for the. two methods at the endpoint of the snail control. CONCLUSION: The effect of soil pasting mixed with niclosamide is good, and the dosage of 4-6 g/m2 is suggested in snail control.