The control of clonorchiasis in Guangdong province, southern China.

Oriental liver fluke disease (clonorchiasis), caused by Clonorchis sinensis, is endemic in 81 counties in Guangdong province, China. This study was conducted following increasing lack of clonorchiasis awareness and increased consumption of raw freshwater fish and raw fish porridge at home and restaurants, which has been attributed to improved living standards in China, and is considered to have led to a higher C. sinensis infection rate in the country. A total of 61,517 individuals were investigated from 123 sites during a provincial survey in 1988, with average C. sinensis infection rate of 1.82% that increased to 4.08% (335/8217) in 1997. Higher infection rate was observed in adult men than women, with heavy infection rate in fishermen and businessmen because they have access and means to get raw fishes for consumption. Thus, clonorchiasis has become a serious public health problem in Guangdong province. Efforts targeting clonorchiasis prevention and control in Guangdong province started in the 1990s. These included carrying out large-scale surveys and chemotherapy in epidemic regions, research on promotion of environmental sanitation and methods for freshwater aquaculture. Establishment and promotion of clonorchiosis demonstration plots for comprehensive control measures, as well as the development of clonorchiasis-prevention community-out-patient clinics were initiated and their effectiveness was evaluated. However, there seem to be no obvious decline in the prevalence of C. sinensis with 4.90% (608/12,401) in 2015, at Guangdong province due to the people's habit of eating raw fishes in endemic areas. This has led to increasing calls to improve environmental sanitation in the aquaculture industry. It is, however, believed that control efforts on clonorchiosis in the province are at an early stage and require strengthening through the cooperation of different departments to work out effective strategies for sustainable field application of control mechanisms.

Spatial distribution and habitat suitability of Biomphalaria straminea, intermediate host of Schistosoma mansoni, in Guangdong, China.

BACKGROUND: Biomphalaria straminea is an invasive vector in China, posing a significant threat to public health. Understanding the factors affecting the establishment of this snail is crucial to improve our ability to manage its dispersal and potential risk of schistosomiasis transmission. This study sought to determine the spatial distribution of B. straminea in mainland China and whether environmental factors were divergent between places with and without B. straminea. METHODS: A malacological survey of B. straminea was conducted in Guangdong Province, China. Snails were identified using anatomical keys. Water and sediment samples were taken, and their physicochemical properties were analyzed using national standard methods. Landscape and climatic variables were also collected for each site. We compared the environmental characteristics between sites with and without B. straminea using Mann-Whitney U test. We further used generalized linear mixed models to account for seasonal effects. RESULTS: B. straminea was found at six sites, including one in Dongguan and five in Shenzhen. Probability map found a hot spot of B. straminea distribution at Shenzhen and Hong Kong. Sites occupied by B. straminea were characterized by higher median altitude, mean annual precipitation and moderate temperature. Water with snails had higher median concentrations of total nitrogen, nitrate and nitrites, ammoniacal nitrogen, calcium, zinc and manganese but lower dissolved oxygen and magnesium. Sediments with snails had higher median copper, zinc and manganese. B. straminea was associated with maximum temperature of the warmest month (pMCMC < 0.001) and sediment zinc (pMCMC < 0.001). CONCLUSIONS: B. straminea is distributed in Shenzhen and its surrounding areas in Guangdong, China. Sites with and without B. straminea differed in the maximum temperature of the warmest month and sediment zinc. Surveillance should be continued to monitor the dispersal of this snail in China.

[Diagnosis and Treatment of the First Imported Case of Plasmodium knowlesi Infection in China].

Objective: To diagnose and treat the first imported active case of Plasmodium knowlesi infection in China. Methods: The clinical information of the patient was collected. Microscopy of blood smear was conducted after Giemsa staining. Genomic DNA was extracted from blood, and PCR was conducted to amplify rDNA. The PCR products were sequenced and analyzed with BLAST Results: The patient returned from a one-week tour in a tropical rain forest in Malaysia. The first disease attack occurred in Guangzhou on Oct. 16, 2014, with fever, shivering and sweating. The patient was initially diagnosed as malaria and hospitalized on Oct. 26, 2014. Microscopic observation revealed typical forms of P. knowlesi in blood smear. The red blood cells became enlarged, with big trophozoites appearing as a ring with dual cores and dark brown malaria pigment. The trophozoites were slightly bigger and thicker than P. falciparum. The schizont had 6-8 merozoites, with obvious brown malaria pigment. PCR resulted in a specific band of 1 099 bp. BLAST analysis showed that the sequence of the PCR product was 99% homologous to P. knowlesi (acession No. AM910985.1, L07560.1 and AY580317.1). The patient was diagnosed as P. knowlesi infection, and was then given an 8-day treatment with chloroquine and primaquine, together with dihydroartemisinin piperaquine phosphate tablet. The patient was discharged after recovery on Oct. 28, 2014. Conclusion: According to the clinical symptoms, epidemiological history and laboratory test, the patient has been confirmed as P. knowlesi infection. It may also be the first active case of knowlesi malaria reported in China.

[Epidemiological analysis of malaria epidemic situation in Guangdong Province, 2011].

OBJECTIVE: To analyze the features of malaria epidemic in Guangdong Province in 2011 so as to provide the evidence for the elimination of malaria in Guangdong Province. METHODS: The data from the Disease Reporting Information System of Chinese Center for Disease Control and Prevention were analyzed with the descriptive epidemiological method for the epidemiological characteristics of malaria in Guangdong Province in 2011. RESULTS: A total of 96 malaria cases were reported in Guangdong Province in 2011, with an annual mean incidence of 0.092 per 100 thousand. There were 40 cases of Plasmodium vivax infection, 36 cases of Plasmodium falciparum infection and 20 cases of undivided malaria. There were 2 death cases. There were cases reported in 34 counties/cities/districts of 17 prefecture-level cities in the whole province. The cases distributed mainly in Guangzhou and Shenzhen, where there were 57 cases, reaching 59.38% of the cases of the whole province. There were cases reported every month in the whole year. From May to November, 73 cases were reported, accounting for 76.04% of the cases of the whole year. The ratio of male to female cases was 5.86: 1. The age distribution concentrated mainly on 20-50 years old. The youngest patient was 1 years old and the eldest was 65 years old. The occupation distribution concentrated mainly on the worker, commercial service, peasant, housekeeper and unemployed people (68 cases, 70.83%). In addition to the aforementioned 96 cases of local census register population, there were 32 cases of nonlocal census register population found in Guangdong, 2011. Of the total 128 cases, the main original areas of the imported cases were Africa (77, 60.16%) and Asia (30, 23.44%). The country with the most cases was Nigeria in Africa (36 cases), the second was Angola in Africa (19 cases), and the third was Myanmar in Asia (11 cases). CONCLUSION: The malaria epidemic situation in Guangdong Province is relatively stable in 2011, but the imported cases of Plasmodium falciparum infection increase. Therefore, the surveillance, prevention and control for imported cases of P. falciparum infection should be strengthened.

[Time-series analysis on the malaria morbidity affected by meteorological factors in Guangdong province].

OBJECTIVE: To evaluate the associations between malaria risk and meteorological factors. METHODS: A negative binomial distribution regression analysis was built between the temperature, relative humidity, rainfall capacity and the monthly incidence of malaria, based on the temperature information provided by Guangdong Meteorological Department and the malaria incidence information provided by Guangdong Center of Disease Prevention and Control during year 1980 to 2004, adopting the time-series analysis method and by distributed lag non-linear model, in order to analyze the immediate factors. RESULTS: The number of monthly malaria cases in Guangdong province reached 4010 between year 1984 and 2004, while the monthly maximal temperature, minimal temperature, average temperature, relative humidity and average rainfall capacity was separately 26.3°C, 18.8°C, 21.9°C, 88.0% and 5.6 mm. The immediate effect of monthly maximal temperature on malaria incidence showed non-linear relationships. When the temperature reached 32.3°C, the risk was highest, the relative risk (RR) was 2.51 (95%CI: 1.99 - 3.16); when the relative humidity was 60.0%, the relative risk of malaria was highest as 1.19 (95%CI: 0.66 - 2.11) and then decreased gradually; and when the relative humidity was 86.6%, the risk of malaria was lowest at 0.51 (95%CI: 0.34 - 0.76). The risk of malaria increased while the rainfall capacity was 14.5 mm, the risk of malaria was the highest at 1.29 (95%CI: 0.87 - 1.93). Strongest delayed effects on malaria incidence was observed when the monthly maximal temperature reached 31.5°C at lagged 2 months, with the value of RR at 1.81 (95%CI: 1.02 - 3.22). When the monthly rainfall capacity was over 15.2 mm, the delayed effects was strong but short. When the monthly maximal temperature of 33.7°C, the excess risk of malaria was comparatively high, the excess risk was 92.2% (95%CI: 30.5% - 183.2%) when lagging one month. When the relative humidity was low, the delayed effect of malaria lasted for a long time, and the cumulative effect was huge. When the relative humidity reached 87.0%, the excess risk lagging 3 months was only -66.6% (95%CI: -86.4% - -17.7%). When the rainfall capacity was 15.5 mm, the cumulative effect on malaria reached the peak after 3 months, while the excess risk was 40.7% (95%CI: -30.0% - -182.6%); afterwards the cumulative effect gradually weakened. Positive and negative interaction effects were significant between malaria risk and maximal temperature and monthly rainfall capacity, and monthly rainfall capacity and relative humidity at lagged 2 months, respectively. CONCLUSION: High temperature and large rainfall capacity might be the risk factors of malaria in Guangdong province, and there was an obvious interaction between the two factors.

[Investigation on Angiostrongylus cantonensis infection in rodents in Guangdong Province].

OBJECTIVE: To investigate the natural infection of Angiostrongylus cantonensis in Guangdong Province, and to provide the scientific evidence for control measures. METHODS: The investigation was carried out in 56 villages of 28 towns of 28 counties/districts in East Guangdong, West Guangdong, the mountain area of North Guangdong and Peal River Delta of the Province from 2005 to 2010. The rodents were captured with live trap and the species identified. Angiostrongylus cantonensis adult worms were collected from the hearts and lungs of rodents, examined, counted and the sex of worms identified. RESULTS: The rodents were captured from 2005 to 2010, belonged to 2 orders, 2 families (subfamily), 4 genera and 10 species. Seven species of the rodents were found infected with Angiostrongylus cantonensis in all 28 counties/districts. Totally 5 820 rats were examined and 496 infected ones were identified, with a mean infection rate of 8.52%. The infection rate of rodents was highest in the Peal River Delta, reaching 9.8% (205/2084) (chi2=15.25, P<0.01). Rattus norvegicus had the highest infection rate of 16.9% (310/1 835) (chi2=240.91, P<0.01). The mean intensity of infection was 6.1 worms/rat. 1 125 female and 1064 male worms were found respectively (chi2=1.75, P>0.05). CONCLUSION: Natural infection of Angiostrongylus cantonensis in rodents has been found in all the 56 villages selected from the 4 regions of Guangdong Province.

An outbreak of angiostrongyliasis in Guanging, People's Republic of China: migrants vulnerable to an emerging disease.

Angiostrongyliasis has been frequently reported from the People's Republic of China during the last decade. An outbreak of angiostrongyliasis among migrant laborers in Guangning, Guangdong Province is described here. A questionnaire was developed to collect epidemiological and clinical information about 17 migrant laborers from the Bai ethnic group in Dali, Yunnan Province. Serum samples were collected and tested by enzyme-linked immunosorbent assay. Rats and mollusks from the same area where patients had collected Pomacea canaliculata were examined for presence of Angiostrongylus cantonensis. All 17 Bai migrant laborers consumed P. canaliculata and six had meningitis 3-19 days after consumption of P. canaliculata. Headache, myalgia and fatigue were the most common symptoms. Blood samples from 5 patients were positive for antibodies to A. cantonensis. The places where the migrant laborers collected P. canaliculata were identified as endemic areas for A. cantonensis. This outbreak highlights the vulnerability of migrants to angiostrongyliasis.

[Survey on the focus of Angiostrongylus cantonensis in Guangdong Province].

OBJECTIVE: To understand the distribution of Angiostrongylus cantonensis foci in Guangdong Province for making surveillance program. METHODS: Survey sites were chosen by strata sampling according to different geographic locations. Totally 22 survey sites were selected in four regions: East Guangdong, West Guangdong, North Guangdong and the Pearl River Delta. One or two administrative villages in each site were randomly selected for the investigation. Pomacea canaliculata and Achatina fulica collected from fields and other species of freshwater or terrestrial snails obtained in the restaurants and wet markets were examined for the third stage larvae by tissue grinding or lung examination. Rats were captured in the fields, and their hearts and lungs were dissected for adult worms. Rat feces were also collected for the detection of first stage larvae by water precipitation. RESULTS: Large number of P. canaliculata was found in all sites. A. fulica was found in most surveyed sites. Totally 2929 P. canaliculata and 1354 A. fulica were collected with a larva infection rate of 5.9% (172/2929) and 16.5% (223/1354), respectively (P<0.01). The average prevalence among the regions was different (P<0.01) with the highest prevalence in Pearl River Delta (15.6%, 152/975), especially in Dongguan City of the Delta (34.7%, 78/225). 114 Cipangopaludina sp. and 252 Bellamya sp. were bought from wet markets of 9. sites. Larvae were found only in Bellamya snails from Luoding and Kaiping cities with an infection rate of 1.4% (1/70) and 3.3% (3/91), respectively. Totally 491 rats were captured in 9 sites including Rattus norvegicus, R. flavipectus, Suncus murinus, Mus musculus, Bandicota indica, R. losea and R. rattus, with an average infection rate of 11.4% (56/491). Adult worms were found in R. norvegicus, R. flavipectus and B. indica with a prevalence of 19.8% (52/263), 2.5% (3/118) and 10.0% (1/10), respectively. Thirty-four rodent fecal samples were collected in 7 sites and examined with a larva positive rate of 44.1% (15/34). CONCLUSION: Foci of Angiostrongylus cantonensis are widely distributed in Guangdong Province as natural infection has been found in its intermediate and definitive hosts.