Intestinal Parasitic Infections and Environmental Water Contamination in a Rural Village of Northern Lao PDR

Village Settlements in Mountainous Tropical Areas, Hotspots of Fecal Contamination as Evidenced by Escherichia coli and Stanol Concentrations in Stormwater Pulses

Fecal bacteria in surface water may indicate threats to human health. Our hypothesis is that village settlements in tropical rural areas are major hotspots of fecal contamination because of the number of domestic animals usually roaming in the alleys and the lack of fecal matter treatment before entering the river network. By jointly monitoring the dynamics of Escherichia coli and of seven stanol compounds during four flood events (July-August 2016) at the outlet of a ditch draining sewage and surface runoff out of a village of Northern Lao PDR, our objectives were (1) to assess the range of E. coli concentration in the surface runoff washing off from a village settlement and (2) to identify the major contributory sources of fecal contamination using stanol compounds during flood events. E. coli pulses ranged from 4.7 × 104 to 3.2 × 106 most probable number (MPN) 100 mL-1, with particle-attached E. coli ranging from 83 to 100%. Major contributory feces sources were chickens and humans (about 66 and 29%, respectively), with the highest percentage switching from the human pole to the chicken pole during flood events. Concentrations indicate a severe fecal contamination of surface water during flood events and suggest that villages may be considered as major hotspots of fecal contamination pulses into the river network and thus as point sources in hydrological models.

Global prevalence of 4 neglected foodborne trematodes targeted for control by WHO: A scoping review to highlight the gaps

BACKGROUND

Foodborne trematodiases (FBTs) are a group of trematodes targeted for control as part of the World Health Organization (WHO) road map for neglected tropical diseases from 2021 to 2030. Disease mapping; surveillance; and capacity, awareness, and advocacy building are critical to reach the 2030 targets. This review aims to synthesise available data on FBT prevalence, risk factors, prevention, testing, and treatment.

METHODS

We searched the scientific literature and extracted prevalence data as well as qualitative data on the geographical and sociocultural risk factors associated with infection, preventive/protective factors, and methods and challenges of diagnostics and treatment. We also extracted WHO Global Health Observatory data representing the countries that reported FBTs during 2010 to 2019.

RESULTS

One hundred and fifteen studies reporting data on any of the 4 FBTs of focus (Fasciola spp., Paragonimus spp., Clonorchis sp., and Opisthorchis spp.) were included in the final selection. Opisthorchiasis was the most commonly reported and researched FBT, with recorded study prevalence ranging from 0.66% to 88.7% in Asia, and this was the highest FBT prevalence overall. The highest recorded study prevalence for clonorchiasis was 59.6%, reported in Asia. Fascioliasis was reported in all regions, with the highest prevalence of 24.77% reported in the Americas. The least data was available on paragonimiasis, with the highest reported study prevalence of 14.9% in Africa. WHO Global Health Observatory data indicated 93/224 (42%) countries reported at least 1 FBT and 26 countries are likely co-endemic to 2 or more FBTs. However, only 3 countries had conducted prevalence estimates for multiple FBTs in the published literature between 2010 to 2020. Despite differing epidemiology, there were overlapping risk factors for all FBTs in all geographical areas, including proximity to rural and agricultural environments; consumption of raw contaminated food; and limited water, hygiene, and sanitation. Mass drug administration and increased awareness and health education were commonly reported preventive factors for all FBTs. FBTs were primarily diagnosed using faecal parasitological testing. Triclabendazole was the most reported treatment for fascioliasis, while praziquantel was the primary treatment for paragonimiasis, clonorchiasis, and opisthorchiasis. Low sensitivity of diagnostic tests as well as reinfection due to continued high-risk food consumption habits were common factors.

CONCLUSION

This review presents an up-to-date synthesis on the quantitative and qualitative evidence available for the 4 FBTs. The data show a large gap between what is being estimated and what is being reported. Although progress has been made with control programmes in several endemic areas, sustained effort is needed to improve surveillance data on FBTs and identify endemic and high-risk areas for environmental exposures, through a One Health approach, to achieve the 2030 goals of FBT prevention.

Microbial pollution in inland recreational freshwaters of Quetta, Pakistan: an initial report

Parasitic contamination of surface waters, especially recreational waters, is a serious problem for under-developed nations like Pakistan, where numerous outbreaks of parasitic diseases are reported each year. In the current study, parasitic presence in two surface waters (Hanna Lake and Wali-Tangi Dam) of Quetta was monitored quarterly for 1 year. The methodology involved the pre-concentration of the water samples and the subsequent preparation for the microscopic search of parasites. Physico-chemical and bacteriological variables were also studied. Wet staining, modified Trichrome staining, and modified acid-fast staining methods were used to identify various parasitic forms (cysts, oocysts, eggs, trophozoites). Collectively 11 parasitic elements (10 in Lake and 8 in Dam) belonging to 10 species were recorded, many of which are potential human pathogens. The species identified include Trichomonas sp., Isospora sp., Balantidium coli, Cryptosporidium sp., Entamoeba spp., amoebas, Microsporidium sp., Endolimax nana, Ascaris lumbricoides, and Giardia spp. Parasitic contamination remained persistent in both locations throughout the year independent of physico-chemical parameters (temperature, EC, pH, turbidity, and DO) and bacterial concentration of water. Reliance on bacterial presence for monitoring of recreational waters can be a risk for tourists. Entamoeba spp. and A. lumbricoides may be used for surface water monitoring in these waters.

Comparative evaluation of vegetable matter involved lesions with oral parasitic infections in the oral cavity

The current research aims to perform a comparative evaluation of vegetable matter involved lesions with oral parasitic infections found in oral mucosa, presenting histochemical methods to differentiate their microscopic similarities. Eight cases were selected out of a sample of 1.975 reports from a single Oral and Maxillofacial Pathology Service of the author's institution from 2012 to 2019. Specimens were examined by hematoxylin and eosin staining (HE), periodic acid-Schiff (PAS) staining, Gomori-Grocott staining, Ziehl-Neelsen staining, Giemsa, and mucicarmine staining. Microscopic analysis included fluorescence, polarized light, and confocal microscopy. Microscopically, in HE coloration, hookworm eggs showed as eosinophilic. Inflammatory multinucleated giant cells and lymphocytes, were usually related to the nematode eggs, forming an intense inflammatory infiltrate. Biofluorescent properties of eggs and larvae revealed to be sensitive in the detection of parasitic structures contrasting with the inflamed connective tissue. Vegetable presence was confirmed by polarized light microscopy and it was found to be associated with microbial biofilms. Confocal microscopy has showed to be an excellent method for morphotype differentiation of parasitic eggs. Parasitic infection and vegetable matter displayed similarities in the inflammatory response, but the latter can rot and agglomerate biofilms. The microscopic diagnosis of such infections requires the interpretation of challenging morphological features since the parasites are usually sectioned and mixed with an inflammatory reaction. These histochemical approaches proved to be excellent to distinguish both lesions.

Zoonotic Transmission of Blastocystis Subtype 1 among People in Eastern Communities of Thailand: Organic Fertilizer from Pig Feces as a Potential Source

Blastocystis sp., the most common intestinal protozoa, remains a public health problem among people in many countries, particularly in rural areas of developing countries. The infection usually reflects poor sanitation in communities by waterborne, zoonotic, and person-to-person transmission. Interestingly, at least 17 subtypes (STs) have been reported and are associated with a broad range of animal hosts, including humans. In this study, we reported potential evidence of zoonotic transmission of Blastocystis ST1 in rural communities of eastern Thailand where the overall prevalence of Blastocystis infection was 15.7%. Two major and three minor subtypes were found to be distributed unequally in this region. Of 5 STs, only ST1 was found to be associated with pig feces in an open farm system that produced organic fertilizer for agriculture uses in the community. This finding suggests that properly protective contact and standard production of organic fertilizer from pig feces by-products could be key factors for reducing the prevalence of Blastocystis infection and prevent Blastocystis reinfection among people in the community.

IMPORTANCEBlastocystis sp. remains a public health problem among people, particularly in rural areas of many developing countries. The infection usually reflects poor sanitation in communities by waterborne, zoonotic, and person-to-person transmission. In this study, we reported potential evidence of zoonotic transmission of Blastocystis subtype 1 (ST1) in rural communities of eastern Thailand. Two major and three minor subtypes were found to be unequally distributed in this region. Interestingly, only ST1 was found to be associated with pig feces in an open farm system that produced organic fertilizer for agriculture uses in the community. The finding makes significant contributions to genetic and molecular investigations of microbial topics of practical value and suggest that properly protective contact and standard production of organic fertilizer from pig feces by-products could be key factors for reducing the prevalence of Blastocystis infection and prevent Blastocystis reinfection among people in the community.

Influence of extraordinary floods on wildlife parasites: the case of gastrointestinal helminths and protozoa of wild canids from the Iberá Ecoregion, Argentina

Parasites are natural components of ecosystems and play a significant role in the dynamics of wild animal populations. Although the environment of parasites is primarily defined by the host, most life cycles involve stages that must endure external conditions. Rainfall and flooding events are important factors that might influence the transport of parasitic stages, altering soil moisture levels, and resulting in a favorable environment for parasite survival and development. We assessed whether an extraordinary flood event modified the occurrence of gastrointestinal parasites (nematodes and protozoa) in wild canids in two protected areas in northern Argentina. From 2016 to 2018, we collected fecal samples of two fox species, Lycalopex gymnocercus and Cerdocyon thous, and examined the presence of nematodes and protozoa. We assessed changes in the occurrence of these parasites after a flood event, while adjusting for potential confounders (i.e., monthly average temperature, season, host species, site). In a second stage of the analysis, we evaluated whether part of the effect was caused by changes in soil moisture, by adding normalized difference water index as an independent variable. We found that the presence of nematodes in foxes was higher after flooding than before flooding, and this association was not explained by changes in the soil moisture. On the other hand, the flood event was not relevant for protozoa. Stronger and long-lasting flood events are expected due to the effect of global warming on El Niño events, and this may increase and intensify the spread of some parasites affecting wildlife, which could also be of public health concern.

The Coexistence of Blastocystis spp. in Humans, Animals and Environmental Sources from 2010-2021 in Asia

Blastocystis spp. are controversial unicellular protists that inhabit the gastrointestinal tract of humans and a wide range of animals worldwide. This review provides an overview of the prevalence and distribution of Blastocystis spp. and their subtypes throughout Asia. Research articles reporting on the presence of Blastocystis spp. in locations within Asia, between 1 January 2010, and 10 May 2021, were obtained from Scopus, PubMed, and Google Scholar. In 427 articles, the prevalence of Blastocystis spp. in 31 countries within the last decade was revealed. Isolates were found in humans, various mammals, birds, reptiles, insects, water sources, vegetables, and ambient air. Prevalence of Blastocystis spp. varied widely across host categories. Subtypes identified throughout Asia were STs 1-14, and ST18-22 (novel subtypes). ST1, ST2, ST3, ST4 were the most frequently isolated in humans; ST5 in pigs; ST10 and ST14 in goats, sheep, and cattle; and ST6 and ST7 in chickens. ST1 and ST3 were most common in water samples. ST1, ST2, ST3, ST4, ST5 and ST6 were shared by humans, animals, and water sources. There is a growing interest in the study of Blastocystis spp. and their subtypes in Asia. Due to the isolation of Blastocystis spp. from biotic and abiotic sources in Asia, the application of the One Health (OH) approach to the study of Blastocystis spp. is proposed for improved perception of this organism.

Occurrence of Giardia duodenalis in selected stations and tributary rivers of Laguna Lake, Philippines

Fecal pollution is a major contributor to the progressive degradation of Laguna Lake, the Philippines' largest inland lake used for aquaculture, recreation, and as a source of irrigation and domestic water. Consequently, intestinal parasites may be present in this body of water, posing risks to water safety and human health. This study was able to detect the protozoan parasite, Giardia duodenalis, in three Laguna Lake stations and seven tributary rivers in a 13-month monitoring period by PCR amplification of the small subunit ribosomal RNA (SSU rRNA) gene of Giardia cysts concentrated from water samples. The pathogen was present in 37.7% of tributary samples (n = 69) and 16.7% of lake samples (n = 36). Notable frequencies of detection were observed in four tributary rivers -Bagumbayan, Taguig (66.7%); Santa Rosa, Laguna (55.6%); San Cristobal, Cabuyao, Laguna (44.4%); and Biñan, Laguna (42.9%). All test SSU rRNA gene sequences were identified as human-infective genotypes of G. duodenalis predominated by Assemblage A (94.1%). Furthermore, analysis of the glutamate dehydrogenase (gdh) gene revealed the possible presence of mixed genotypes in at least two samples. These results support the pressing need to include protozoan pathogen monitoring in Laguna Lake and its tributaries to prevent Giardia infection in humans and animals. This study also recommends microbial source tracking to identify fecal pollution sources and aid in regulation of waste discharges into the lake and its tributaries.

Intestinal Parasitic Infection, The Use of Latrine, and Clean Water Source In Elementary School Children At Coastal And Non-Coastal Areas, Sumenep District, Indonesia

Inadequate latrine and water source cause transmission of intestinal parasitic infection, particularly in children. There is a lack information about it and it is needed to be investigated. This study aimed to compare the prevalence of intestinal parasitic infection, the use of latrine and clean water source in elementary school children at coastal and non-coastal areas in Sumenep District, Indonesia. An analytic observational study with cross sectional design was conducted in Dasuk Timur Elementary School located at coastal area, and Kolor II Elementary School at non-coastal area, Sumenep district, in January 2020. Intestinal parasites in students’ stools were identified by microscopic examination using wet direct smear stained with lugol. The use of latrine and water sources were analyzed with questionnaire. A total of 68 children stools were collected from both elementary schools. Worm infections were not found. Thirty-one children (31/44, 70.5%) from Dasuk Timur Elementary School and eight children (8/24, 33.3%) from Kolor II Elementary School were infected with intestinal protozoan and significant difference (P=0.003, Chi-square test). Blastocystis hominis was highly found in stools of Dasuk Timur Elementary School’s students (31/44, 70.5%) and significantly different from Kolor II Elementary School’s students (P<0.0001, Chi-square test). Three children (3/44, 6.8%) from Dasuk Timur Elementary School were still practicing open defecation. Dasuk Timur Elementary School’s students suffered from intestinal parasitic infection were mostly using non-piped water source (20/31, 64.5%) and were significantly different between two elementary schools (P=0.015, Fisher’s exact test). Prevalence of intestinal parasitic infections in children was found higher in coastal than non-coastal area due to the commonly use of unclean water sources and inadequate latrine. 

Evaluation of the health risks linked to two swimming pools regularly frequented from the city of Yaounde in Cameroon (Central Africa)

The study highlights the presence of pathogenic strains of microorganisms in two swimming pools, highly frequented in the city of Yaounde. Thus, the water samples from these swimming pools have undergone physicochemical and biological treatments using conventional techniques. Three groups of microorganisms (Bacteria, Protozoa, and Helminths) were identified and quantified in these swimming pools with weakly acidic waters (6.79 ± 0.35) with an average temperature of 26.63 ± 0.53 °C and suspended matter ranging from 2 to 150 mg.l^-1. The total bacterial load varies between 8 × 10³ and 6000 × 10³ CFU/100 ml. It consists of mesophilic aerobic heterotrophic bacteria, fecal coliforms, total coliforms, fecal streptococci, Staphylococcus aureus, and Pseudomonas aeruginosa. Protozoan cysts and oocysts range from 122 to 505 per liter of water. These values are slightly lower for helminth eggs and larvae (0 to 108 eggs and larvae/l). In both swimming pools, significant correlations were observed between some abiotic and biotic parameters. The waters of the studied swimming pools are subject to fecal pollution. Swimmers would therefore be exposed to biological contaminations, responsible for pathologies. The most common diseases are linked to gastroenteritis (diarrhea), but infections of all kinds may be overgrown (conjunctivitis, ear infections, dermatitis, respiratory infections).

Impact of informal settlements and wastewater treatment plants on helminth egg contamination of urban rivers and risks associated with exposure

The quality of surface water could be influenced by both anthropogenic and natural factors. This study was designed to determine the impact of informal settlement and wastewater treatment plants on helminth egg contamination of urban rivers and the risks associated with everyday use. We also ascertained the accumulation of these eggs in the river sediments. The study was carried out in two rivers in the eThekwini Municipality of South Africa. Grab samples were taken at different points over a 10-month period. Ascaris spp., hookworm, Toxocara spp., Trichuris spp. and Taenia spp. were the helminth eggs detected in both the water column and sediments, with mean Ascaris spp. eggs of 0-6.3 (± 5.1)/L in the water and 0-6.8 (± 5.2)/kg in sediment samples. The helminth egg concentrations showed seasonal variation, probably due to changes in infection levels of the populations or natural factors, such as rainfall. The informal settlements had a greater impact than treated wastewater. For every 10,000 recreational users of the rivers 19 to 58 may be infected under undisturbed conditions, increasing to 29-88 individuals when the riverbed is disturbed. The risk from agricultural use of the rivers was above the tolerable risk values applicable for wastewater reuse, recommended by the World Health Organization. This calls for a re-evaluation of the policies governing surface water quality assessment, where the inclusion of helminth eggs and sediment monitoring will be critical.

Cross-reaction of POC-CCA urine test for detection of Schistosoma mekongi in Lao PDR: a cross-sectional study

BACKGROUND

The point-of-care circulating cathodic antigen (POC-CCA) test is increasingly used as a rapid diagnostic method for Schistosoma mansoni infection. The test has good sensitivity, although false positive results have been reported among pregnant women and patients with urine infections and hematuria. We validated the POC-CCA test's ability to diagnose Schistosoma mekongi infection in Lao People's Democratic Republic (Lao PDR), where S. mekongi is endemic. Of particular interest was the test's specificity and possible cross-reactivity with other helminth infections.

METHODS

We conducted a cross-sectional study of children and adults in the provinces of Champasack (Schistosoma mekongi and Opisthorchis viverrini endemic), Savannakhet (O. viverrini endemic) and Luang Prabang (soil-transmitted helminths endemic) between October 2018 and April 2019. POC-CCA and urine dipstick tests were administered to all study participants, while an additional pregnancy test was offered to women. Two stool samples were collected from participants and examined with a Kato-Katz test (two smears per stool). Logistic regression was used to associate potential confounding factors (predictors) with POC-CCA test results (outcome).

RESULTS

In S. mekongi-endemic Champasack, 11.5% (n = 366) and 0.5% (n = 2) of study participants had positive POC-CCA and Kato-Katz test results, respectively. Only one of the two Kato-Katz positive patients was also POC-CCA positive. In Champasack and Luang Prabang, where S. mekongi is not endemic, the POC-CCA test yielded (presumably) false positive results for 6.0% (n = 22) and 2.5% (n = 9) of study participants, respectively, while all of the Kato-Katz tests were negative. POC-CCA positive test results were significantly associated with O. viverrini infection (1.69, 95% confidence interval (CI): 1.02-2.77, P = 0.042), increased leukocytes (adjusted Odds Ratio (aOR) = 1.58, 95% CI: 1.15-2.17, P = 0.005) and hematuria (aOR = 1.50, 95% CI: 1.07-2.10, P = 0.019) if the observed trace was counted as a positive test result. Two pregnant women from Champasack province had POC-CCA positive tests.

CONCLUSIONS

We observed a cross-reaction between the POC-CCA test and O. viverrini infection. To some extent, we can confirm previous observations asserting that POC-CCA provides false positive results among patients with urinary tract infections and hematuria. In S. mekongi-endemic areas, POC-CCA can be applied cautiously for surveillance purposes, keeping in mind the considerable risk of false positive results and its unknown sensitivity.

Detection of enteric parasite DNA in household and bed dust samples: potential for infection transmission

BACKGROUND

Enteric parasites are transmitted in households but few studies have sampled inside households for parasites and none have used sensitive molecular methods.

METHODS

We collected bed and living room dust samples from households of children participating in a clinical trial of anthelmintic treatment in rural coastal Ecuador. Dust was examined for presence of DNA specific for 11 enteric parasites (Ascaris lumbricoides, Trichuris trichiura, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Toxocara canis and T. cati, Giardia lamblia, Blastocystis hominis, Cryptosporidium spp., and Entamoeba histolytica) by quantitative PCR (qPCR).

RESULTS

Of the 38 households sampled, 37 had positive dust for at least one parasite and up to 8 parasites were detected in single samples. Positivity was greatest for B. hominis (79% of household samples) indicating a high level of environmental fecal contamination. Dust positivity rates for individual pathogens were: S. stercoralis (52%), A. lumbricoides (39%), G. lamblia (39%), Toxocara spp. (42%), hookworm (18%) and T. trichiura (8%). DNA for Cryptosporidium spp. and E. histolytica was not detected. Bed dust was more frequently positive than floor samples for all parasites detected. Positivity for A. lumbricoides DNA in bed (adjusted OR: 10.0, 95% CI: 2.0-50.1) but not floor dust (adjusted OR: 3.6, 95% CI: 0.3-37.9) was significantly associated with active infections in children.

CONCLUSIONS

To our knowledge, this is the first use of qPCR on environmental samples to detect a wide range of enteric pathogen DNA. Our results indicate widespread contamination of households with parasite DNA and raise the possibility that beds, under conditions of overcrowding in a humid tropical setting, may be a source of transmission.

Current status of Opisthorchis viverrini, minute intestinal fluke and Taenia spp. infections among inhabitants in the Kenethao district of northern Lao PDR

Background

This study reports the prevalence of Ov/minute intestinal fluke (MIF) and Taenia infections among inhabitants of the Kenethao district, northern Lao PDR.

Methods

Fecal samples from 580 inhabitants were examined using the formalin-ethyl acetate concentration technique.

Results

The prevalence of Ov/MIF, Taenia spp. and coinfection was 45.3, 11.9 and 6.1%, respectively. There was no significant difference between males and females for Ov/MIF (p=0.813) and Taenia infection (p=0.759). The prevalence of Ov/MIF was significantly associated with age (p=0.005), but not for Taenia infection (p=0.836). Consumption of raw fish (p=0.001) and raw meat (p=0.046) was significantly associated with parasitic infections.

Conclusions

The results suggest that Ov/MIF and Taenia spp. are highly endemic in this area and there is a need for projects to eliminate these parasites.

Parasitic infections in relation to practices and knowledge in a rural village in Northern Thailand with emphasis on fish-borne trematode infection

The present study integrates several aspects of a parasitological survey in a rural community village combining community knowledge of parasites, their potential transmission routes and health risk factors. A rural community located in Northern Thailand was surveyed for intestinal parasites, and an overall prevalence of 45.2% for helminths and 4.8% for protozoan infections was identified. Socio-demographic characteristics, customs and perceptions were compiled using individual questionnaires and interviews for participants surveyed for parasitic screening. The results allowed us to determine the knowledge and perception of local people concerning helminthic infection and transmission. Despite the fact that the participants in this community were aware of parasitic transmission routes, their widespread custom of eating raw fish and meat render the reduction of helminthiasis difficult. A detailed study on the infection of fish-borne parasitic trematodes, the most prevalent helminth, allowed us to determine that the distance from a given household to the river is a determinant of infection intensity. Health education activities organised in the local community resulted in a change in perception of risks associated with parasite transmission.