Cryptosporidium and Giardia in Biogas Wastewater: Management of Manure Livestock and Hygiene Aspects Using Influent, Effluent, Sewage Canal Samples, Vegetable, and Soil Samples.

Cryptosporidium and Giardia are two water- and foodborne protozoan parasites that can cause diarrheal diseases. Poor microbial quality, sanitation conditions, and hygiene practices at exposure to biogas wastewater are important risk factors for human and animal infection. This study highlights the presence and level of both parasites in the environment in relation to biogas waste reuse in Vietnam. A total of 239 samples were collected from different types of samples in the studied districts in Bac Giang province in 2020 via direct immunofluorescent detection to study the occurrence of Cryptosporidium spp. and Giardia spp. (oo)cysts. Among the samples, Cryptosporidium was found in 19 (7.9%) with concentration from 1.104 to 3.105 oocysts/100 mL, while Giardia in 40 (16.7%) with concentration from 1.104 to 2.106 cysts/100 mL, respectively. In detail, the results show that the percentages of positive detection of Cryptosporidium spp. and Giardia spp. in influent, effluent, sewage canal, and vegetables were 13.1% (11/84), 6.0% (5/83), 15.4% (2/13) and 5.9% (1/17) and 26.2% (22/84), 7.2% (6/83), 7.7% (1/13) and 5.9% (1/17), respectively. The results show a trend of decreasing Cryptosporidium and Giardia densities, without statistical significance. Although these parasites decreased after biogas treatment, the remaining loads observed in biogas effluent can reach the watercourses and soil receiving it. Further investigations are needed to contribute to a general understanding of the risk of protozoan parasites, as well as strategies to control and reduce the contamination of environmental water sources and plants and reduce the burden of the pathogens in biogas wastewater in Vietnam.

Diarrhoeal diseases among adult population in an agricultural community Hanam province, Vietnam, with high wastewater and excreta re-use.

BACKGROUND: Despite the potential health risks of wastewater and excreta use as fertiliser in agriculture, it is still widespread in Vietnam. However, the importance of diarrheal risk in adults' associated with the combined exposures to both excreta and wastewater use in agriculture is largely unknown. This study was carried out to determine diarrhoeal incidence and associated risk factors among the adult population exposed to wastewater and excreta used in agriculture in Hanam province, Vietnam. METHODS: An open cohort of 867 adults, aged 16-65 years, was followed weekly for 12 months to determine the incidence of diarrhoea. A nested case-control study was used to assess the risk factors of diarrhoeal episodes. Two hundred and thirty-two pairs of cases and controls were identified and exposure information related to wastewater, human and animal excreta, personal hygiene practices, and food and water consumption was collected. RESULTS: The incidence rate of reported diarrhoea was 0.28 episodes per person-years at risk. The risk factors for diarrhoeal diseases included direct contact with the Nhue River water (odds ratio [OR] = 2.4, attributable fraction [AF] 27%), local pond water (OR = 2.3, AF 14%), composting of human excreta for a duration less than 3 months (OR = 2.4, AF 51%), handling human excreta in field work (OR = 5.4, AF 7%), handling animal excreta in field work (OR = 3.3, AF 36%), lack of protective measures while working (OR = 6.9, AF 78%), never or rarely washing hands with soap (OR = 3.3, AF 51%), use of rainwater for drinking (OR = 5.4, AF 77%) and eating raw vegetables the day before (OR = 2.4, AF 12%). CONCLUSIONS: Our study shows that professional exposure to wastewater and excreta during agricultural activities are significantly contributing to the risk of diarrhoea in adults. The highest attributable fractions were obtained for direct contact with Nhue River and local ponds, handling practices of human and animal excreta as fertilisers, lack of protective measures while working and poor personal hygiene practices, and unsafe food and water consumption were associated with the risk of diarrhoeal episodes in adults. Improve personal hygiene practices and use of relevant treated wastewater and excreta as the public health measures to reduce these exposures will be most effective and are urgently warranted.

Short communication: phylogenetic characterization of HIV type 1 CRF01_AE V3 envelope sequences in pregnant women in Northern Vietnam.

Characterization of HIV-1 strains is important for surveillance of the HIV-1 epidemic. In Vietnam HIV-1-infected pregnant women often fail to receive the care they are entitled to. Here, we analyzed phylogenetically HIV-1 env sequences from 37 HIV-1-infected pregnant women from Ha Noi (n=22) and Hai Phong (n=15), where they delivered in 2005-2007. All carried CRF01_AE in the gp120 V3 region. In 21 women CRF01_AE was also found in the reverse transcriptase gene. We compared their env gp120 V3 sequences phylogenetically in a maximum likelihood tree to those of 198 other CRF01_AE sequences in Vietnam and 229 from neighboring countries, predominantly Thailand, from the HIV-1 database. Altogether 464 sequences were analyzed. All but one of the maternal sequences colocalized with sequences from northern Vietnam. The maternal sequences had evolved the least when compared to sequences collected in Ha Noi in 2002, as shown by analysis of synonymous and nonsynonymous changes, than to other Vietnamese sequences collected earlier and/or elsewhere. Since the HIV-1 epidemic in women in Vietnam may still be underestimated, characterization of HIV-1 in pregnant women is important to observe how HIV-1 has evolved and follow its molecular epidemiology.

Peri-urban aquatic plant culture and skin disease in Phnom Penh, Cambodia.

A cross-sectional study with follow-up was done in five communities involved in aquaculture in peri-urban Phnom Penh, Cambodia, to assess the association between skin disease, particularly dermatitis and occupational wastewater exposure. From 200 selected households 650 household members aged > or = 15 years were visited and examined dermatologically three times in July 2004, January and May 2005. Overall dermatitis prevalence was 6.1%. However, all cases (116) were found in the two wastewater villages involved in aquatic plant culture. Risk factor analysis restricted to the two wastewater villages showed that involvement in wastewater-fed aquatic plant production increased the risk of dermatitis in the univariable analysis but not in the multivariable analysis. Among family members involved in wastewater-fed aquatic plant production a longer duration of daily wastewater contact did not increase the risk of dermatitis in the multivariable analysis. Wet season, older age and having a history of skin problems in the three months prior to each survey were associated significantly with dermatitis. Very few aquaculture workers applied personal protection and the factor had no significant effect on dermatitis. The present study did not show a consistent association between occupational exposure to wastewater and dermatitis, unlike similar Vietnamese studies.

Cyclospora spp. in herbs and water samples collected from markets and farms in Hanoi, Vietnam.

OBJECTIVE: To determine the prevalence of Cyclospora spp. oocysts in herb and water samples as well as in fecal specimens of clinical cases of diarrhoea in Hanoi, Vietnam. METHOD: From November 2004 to October 2005, water and herb samples collected from markets and farms in Hanoi were examined for the presence of Cyclospora spp. oocysts in concentrated sediments and washings using UV epifluorescence examination of a wet mount. In addition, hospital based surveillance studies were carried out using a structured questionnaire which focused on potential risk factors for cyclosporiasis. Stool specimens were collected from individuals with diarrhoea attending primary healthcare facilities and examined for Cyclospora spp. oocysts by modified acid fast smear and wet mount examination using both light and UV epifluorescence microscopy. RESULTS: Cyclospora spp. were found in 34/288 (11.8%) market water and herb samples, and in 24/287 (8.4%) farm samples. All varieties of herbs sold at the market and grown in farms were contaminated with Cyclospora spp. oocysts. A marked seasonal increase in Cyclospora spp. contamination was observed before the rainy season (39/288) from November to April compared to the rainy season (19/268) from May to October (chi(2) = 7.593, P = 0.006). However, Cyclospora spp. was not found in any stool samples collected in hospital-based surveillance studies. CONCLUSIONS: These results confirm the presence of Cyclospora spp. which varies seasonally in environmental samples (water and herbs collected from farms and markets) within the Hanoi metropolitan area.

Seroprevalence of Toxoplasma gondii antibody in Vietnamese villagers.

Toxoplasmosis caused by Toxoplasma gondii is a protozoan infection found worldwide. It usually produces non-specific symptoms, but in pregnant women and immunocompomised individuals, it may cause severe and fatal illness. Many serological studies have been done in various parts of the world, but information is lacking for Vietnam. A seroprevalence study of T gondii antibodies in Vietnamese villagers (n = 650) was performed using the Sabin-Feldman dye test. The average seroprevalence was 4.19% (95% CI = 1.78-4.62), including 6.36% (95% CI = 3.22-11.09), 4.73% (95% CI = 1.92-9.50) and 1.09% (95% CI = 0.23-3.15) from Nghe An, Lao Cai and Tien Giang provinces, respectively. This study confirmed the low prevalence of toxoplasmosis in Vietnam similar to other countries in the region. Further studies are necessary in order to provide a complete picture for the country.

Evaluation of restriction enzymes for standardizing pulsed-field gel electrophoresis protocol for rapid subtyping of Vibrio parahaemolyticus.

We evaluated the cost-effectiveness of the restriction enzymes with rare-cutting sites in the genome of Vibrio parahaemolyticus RIMD 2210633 for pulsed-field gel electrophoresis (PFGE) analysis. The evaluation indicated that PFGE with both NotI and SfiI was discriminatory, but NotI was more cost-effective. Based on the results of this study, we suggest using NotI and SfiI as the 1st and the 2nd restriction enzyme for standardizing the PulseNet PFGE protocol for molecular subtyping and global surveillance of V. parahaemolyticus.

Diarrheagenic Escherichia coli and Shigella strains isolated from children in a hospital case-control study in Hanoi, Vietnam.

This case-control study detected and characterized Shigella and diarrheagenic Escherichia coli (DEC) types among Vietnamese children less than 5 years old. In 249 children with diarrhea and 124 controls, Shigella spp. was an important cause of diarrhea (P < 0.05). We used multiplex PCR and DNA probes to detect enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAggEC), enteropathogenic E. coli (EPEC), attaching and effacing E. coli (A/EEC), verocytotoxin-producing E. coli (VTEC), and enterotoxigenic E. coli (ETEC). The prevalences of DEC in the diarrhea and control groups were 25.7 and 10.5%, respectively. In 62 children with diarrhea, 64 DEC strains included 22 EAggEC (8.8%), 2 EIEC (0.8%), 23 A/EEC (9.2%), 7 EPEC (2.8%), and 10 ETEC strains (4.0%). Among controls, 13 DEC strains included 5 EAggEC strains (4.0%), 7 A/EEC strains (5.6%), and 1 EPEC strain. The characterization of DEC by serotypes, antimicrobial susceptibility patterns, virulence genes, and pulsed-field gel electrophoresis showed the occurrence of many different and highly heterogenic DEC subtypes, but common serotypes were found among ETEC, EIEC and EPEC, respectively. Serotyping was used to distinguish between A/EEC and EPEC. However, A/EEC, EPEC, and EAggEC were isolated at high frequency from both cases and controls. Further in-depth studies are needed to better understand important virulence factors of DEC, especially A/EEC, EPEC, and EAggEC.

Nitrate and bacterial contamination in well waters in Vinh Phuc province, Vietnam.

Measurements were made of the nitrate concentration and bacterial contamination of groundwater samples taken from both dug wells and bores in the commune of Hop Thinh', in the administrative district of Vinh Phuc, Vietnam. A significant number (18%) of samples had nitrate concentrations in excess of the WHO Guideline value for drinking water of 50 mg L(-1), with a higher proportion in the dug wells (29%) than the bores (3.8%). High concentrations of thermotolerant coliforms were found in many of the dug wells and even in the deeper drilled bores. At the time of the study no Shigella or other infectious organisms were found. There was no correlation between nitrate concentration and bacterial content and it is concluded that nitrate concentration is not a good indicator for bacterial contamination.

Microbiological quality of fish grown in wastewater-fed and non-wastewater-fed fishponds in Hanoi, Vietnam: influence of hygiene practices in local retail markets.

Mean water quality in two wastewater-fed ponds and one non-wastewater-fed pond in Hanoi, Vietnam was approximately 10(6) and approximately 10(4) presumptive thermotolerant coliforms (pThC) per 100 ml, respectively. Fish (common carp, silver carp and Nile tilapia) grown in these ponds were sampled at harvest and in local retail markets. Bacteriological examination of the fish sampled at harvest from both types of pond showed that they were of very good quality (2 - 3 pThC g(-1) fresh muscle weight), despite the skin and gut contents being very contaminated (10(2) - 10(3) pThC g(-1) fresh weight and 10(4) - 10(6) pThC g(-1) fresh weight, respectively). These results indicate that the WHO guideline quality of < or = 1000 faecal coliforms per 100 ml of pond water in wastewater-fed aquaculture is quite restrictive and represents a safety factor of approximately 3 orders of magnitude. However, when the fish from both types of pond were sampled at the point of retail sale, quality deteriorated to 10(2) - 10(5) pThC g(-1) of chopped fresh fish (mainly flesh and skin contaminated with gut contents); this was due to the practice of the local fishmongers in descaling and chopping up the fish from both types of pond with the same knife and on the same chopping block. Fishmonger education is required to improve their hygienic practices; this should be followed by regular hygiene inspections.

Molecular study of microsporidiosis due to Enterocytozoon bieneusi and Encephalitozoon intestinalis among human immunodeficiency virus-infected patients from two geographical areas: Niamey, Niger, and Hanoi, Vietnam.

Microsporidiosis cases due to Enterocytozoon bieneusi and Encephalitozoon intestinalis are emerging opportunistic infections associated with a wide range of clinical syndromes in humans. The aim of this study was to specify microsporidial epidemiology in two different geographical areas. From November 2004 to August 2005, 228 and 42 stool samples were collected in Niamey, Niger, and Hanoi, Vietnam, respectively. Screening for microsporidia was performed using UV-light microscopy. Detection was confirmed by molecular biology using two methods specific for E. bieneusi and E. intestinalis. All samples positive for E. bieneusi were subjected to genotyping. In this study, we found high prevalences of microsporidiosis among human immunodeficiency virus-infected patients, 10.5% and 9.5%, respectively, in Niamey and Hanoi. These levels of prevalence are similar to those recorded in European countries before highly active antiretroviral therapy was introduced. In the samples positive for E. bieneusi, we found seven distinct genotypes, including two genotypes not previously described. The E. bieneusi genotype distributions in the two geographical areas suggest different routes of infection transmission, person-to-person in Niger and zoonotic in Vietnam.

Diarrhoeagenic Escherichia coli and other causes of childhood diarrhoea: a case-control study in children living in a wastewater-use area in Hanoi, Vietnam.

A case-control study was conducted to identify the aetiology of diarrhoeal diseases in pre-school children in a suburban area of Hanoi where the use of untreated wastewater in agriculture and aquaculture is a common practice. Stool specimens and clinical information were collected from 111 pairs of children with diarrhoea and healthy controls. A total of 73 cases (66 %) and 41 controls (36 %) had an enteric pathogen. The pathogens most often associated with diarrhoea were rotavirus (17 % of cases) and Entamoeba histolytica (15 %), followed by Shigella (5 %). Diarrhoeagenic Escherichia coli (DEC) was found in 23 % of both patients and controls. Characterization of DEC by serotyping, antimicrobial susceptibility test and PFGE showed that DEC represented by different pathotypes belonged to various serotypes. Except for three enterotoxigenic E. coli strains, typing by PFGE revealed no correlation between pathotype and serotype of DEC strains. This suggests a high prevalence of a variety of DEC subtypes in this area. For this particular region, vaccine development strategies targeting rotavirus and Shigella are likely to be of public health benefit, whereas the role of DEC and preventive measures need to be further elaborated.

Rotavirus disease in young children from Hanoi, Vietnam.

BACKGROUND: Pathogen prevalences and antimicrobial susceptibilities are essential for the rational development of preventive strategies for diarrheal diseases, but little recent information from Vietnam is available. We prospectively studied the prevalence of enteric pathogens in children less than 5 years of age with acute diarrhea and in nondiarrhea controls in a city hospital in Hanoi, Vietnam for 1 year. METHODS: Enteric bacteria and viruses were detected by standard culture methods, and enzyme immunoassay in 291 cases and 291 controls. RESULTS: Detection rates of viral pathogens among cases and controls were 31% and 3% for rotavirus, 12% and 1% for astrovirus and 4% and 1% for adenovirus. For bacterial pathogens, Aeromonas, Shigella, Salmonella, Campylobacter and enterotoxigenic E. coli were isolated from cases and controls in 15% and 8%, 9% and 1%, 7% and 1%, 4% and 0%, and 3% and 0%, respectively. The isolation of bacterial and viral pathogens except for adenovirus was significantly lower in controls than cases. Fluoroquinolones were effective against most bacterial enteropathogens, but resistance was observed in 27% of Campylobacter isolates. CONCLUSIONS: Viral etiologic agents especially rotavirus were the most important cause of acute diarrhea in children less than 5 years of age in Hanoi. The burden of rotavirus in young children in Hanoi warrants consideration of using the recently released rotavirus vaccine.

Incidence of and risk factors for skin ailments among farmers working with wastewater-fed agriculture in Hanoi, Vietnam.

The use of wastewater in agriculture and aquaculture is widespread in many developing countries, but limited information is available about the health hazards associated with this practice. To study the occurrence of skin ailments in relation to wastewater use in agriculture and aquaculture, an open cohort of 636 adults aged 15-70 years living in a wastewater-irrigated area in Hanoi, Vietnam, was followed by weekly visits for 12 months. A nested case-control study with 108 case/control pairs was conducted to investigate possible risk factors for skin ailments. The incidence rate of skin ailments was 32.5 episodes per 100 person-years at risk. Independent determinants of skin ailments included wastewater contact in the past 7 days (odds ratio (OR=2.74, 95% confidence interval (CI) 1.29-5.82), female gender (OR=2.48, 95% CI 1.06-5.76), fish farming-related jobs (OR=3.47, 95% CI 1.27-9.50) and lack of protective measures (OR=2.24, 95% CI 1.21-4.12). It is likely that effective promotion of personal protective measures and improved hygiene practices amongst wastewater users will mitigate the risk of dermatological problems and will thus be of benefit to public health in communities that rely on the use of wastewater for agricultural and aquacultural productions.

Low risk for helminth infection in wastewater-fed rice cultivation in Vietnam.

This study was done to assess the risk of helminth infection in association with wastewater-fed rice cultivation in an agricultural setting of Nam Dinh city, Vietnam. In a cross sectional survey data were collected for 202 households in a commune where wastewater was used for irrigation and for 201 households in a commune that used river water. Parasitological examination was conducted on single stool samples obtained from 1,088 individuals aged -15 years from the households. The irrigation water used in both communes was enumerated for helminth eggs and thermotolerant coliforms. The prevalence of infection with Ascaris spp., Trichuris spp., and hookworm was 42.2%, 19.9% and 10.5% respectively, with an overall prevalence of infection with any helminth of 53.4%. Surprisingly, the prevalence of infection with Ascaris and Trichuris was lower among people exposed to wastewater (containing 40-200 helminth eggs/l and 10(4) thermotolerant coliforms/100 ml) compared to people exposed to river water that contained lower worm egg and bacterial numbers. Poor sanitation and hygiene practices and not using protective measures were important independent risk factors for helminth infection. For hookworm infection, no significant difference was observed between the wastewater exposed and unexposed groups. Children living in the wastewater use area had a significantly better nutritional status than those in the area using river water. This suggests a generally higher welfare level of the wastewater use area. In conclusion, this study showed no evidence that rice cultivation with wastewater poses a risk for helminth infection. More detailed studies are needed on the reduction of fecal indicators and helminth eggs in peri-urban wastewater-irrigated rice culture systems and on the relative importance of wastewater irrigation compared to other risk factors for human helminth infection such as poor sanitation and poverty.

Pyrogenic reactions in hemodialysis patients, Hanoi, Vietnam.

Of 33,111 patients admitted to a large hospital in Vietnam from November 2000 through July 2001, a total of 303 were undergoing hemodialysis and had pyrogenic reactions (ie, fever and/or rigors). Ten case patients (3.3%) had documented bacteremia; pathogens were largely waterborne microorganisms. Pyrogenic reactions in case patients might have occurred because of suboptimal water quality or inadequate dialyzer reprocessing procedures.

Current status of soil-transmitted helminths in Vietnam.

This paper provides a review of surveys on soil-transmitted helminths that were done in Vietnam between 1990 and 2001. Prevalence estimates could be obtained for 29 of the 61 provinces. Extrapolating from this, it is estimated that 33.9 million people in Vietnam are infected with Ascaris (prevalence 44.4%), 17.6 million with Trichuris (prevalence 23.1%), and 21.8 million with hookworm (prevalence 28.6%). Prevalence of Ascaris and Trichuris showed a declining trend from the north to the south of the country. This is probably related to differences in climatic conditions. Hookworm prevalence is more evenly distributed throughout the country, but is concentrated in peri-urban and rural agricultural areas. Vegetable cultivation in which nightsoil is used as fertilizer is a risk factor for hookworm infection, especially among adult women. Helminth control programs should be targeted at school-age children in the northern provinces. Specific interventions are needed throughout the country for women of agricultural communities that are at risk for hookworm infection. There is clearly a need for more detailed analysis of risk factors to quantify the relative contribution of climatic, environmental, and human behavioral factors in the transmission of intestinal nematode infections in Vietnam.

The food-borne trematode zoonoses of Vietnam.

During the past couple of decades, numerous surveys for the occurrence and distribution of food-borne trematodes in Vietnam have been carried out. However, the majority of the data obtained have not been published in international journals, and therefore, the seriousness of these trematode parasitic zoonoses in the country has not been fully appreciated. To correct this, over 40 Vietnamese language reports and local publications were translated and organized as a status review for an international audience. The results show that such serious trematode zoonoses as clonorchiasis, opisthorchiasis, paragonimiasis and fascioliasis are common in many regions of Vietnam, and, in the case of fascioliasis and paragonimiasis, are increasing. Data on the species of intermediate hosts involved in the transmission of these zoonoses, and the effect of host sex and age on infection frequencies are presented, along with findings on food preference/behavior investigations. Finally, the authors present recommendations for further research to provide a more comprehensive picture of the status of these zoonoses, and to obtain the risk assessment information needed to design prevention and control programs.

Current status of cysticercosis in Vietnam.

This English review concerning the current status of cysticercosis in Vietnam has been compiled from various reports of studies conducted over the past 15 years, which have appeared in national publications in Vietnamese, in order to make the information available to the international community. Hospital surveys indicate that cysticercosis is emerging as a serious health problem in the country though most of the information comes from the Hanoi area. Many more men than women are being treated for cysticercosis with most patients being young to middle-aged adults though several juvenile cases have been seen in the south. Clinical manifestations of the disease in humans include subcutaneous nodules, epileptic seizures, severe headache, impaired vision and memory loss. Albendazole has been found to be the best drug for treating cysticercosis though it does not appear to be totally effective for curing cerebral cysts. Information concerning porcine and bovine cysticercosis is very limited and based mostly on passive surveillance at Hanoi slaughterhouses. Surveys for human taeniasis in central and northern provinces indicate a prevalence of 0.2-7.2%. However, techniques of low sensitivity were used and the results are inconclusive since it is unknown with which species of tapeworm the people were infected. In addition to Taenia solium which causes human cysticercosis, T. saginata and T. asiatica are also known to be present in Vietnam. Risk factors investigated thus far with regard to transmission of T. solium suggest that consumption of raw pork, inadequate or absent meat inspection and control, poor sanitation in some areas, and the use of untreated human waste as fertilizer for crops may play important roles in Vietnam but this remains to be validated. The evidence thus far collected suggests that a national surveillance program for cysticercosis is a great need for Vietnam. The authors recommend further research on the epidemiology and impact of cysticercosis in both human and pig hosts in order to determine whether a prevention and control program in Vietnam would be merited and cost effective.

Comparative antibiotic resistance of diarrheal pathogens from Vietnam and Thailand, 1996-1999.

Antimicrobial resistance rates for shigella, campylobacter, nontyphoidal salmonella, and enterotoxigenic Escherichia coli were compared for Vietnam and Thailand from 1996 to 1999. Resistance to trimethoprim-sulfamethoxazole, ampicillin, chloramphenicol, and tetracycline was common. Quinolone resistance remains low in both countries, except among campylobacter and salmonella organisms in Thailand. Nalidixic acid resistance among salmonellae has more than doubled since 1995 (to 21%) in Thailand but is not yet documented in Vietnam. Resistance to quinolones correlated with resistance to azithromycin in both campylobacter and salmonella in Thailand. This report describes the first identification of this correlation and its epidemiologic importance among clinical isolates. These data illustrate the growing magnitude of antibiotic resistance and important differences between countries in Southeast Asia.