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The World Health Organization (WHO) has defined moderate-to-heavy intensity (M&HI) infections with soil-transmitted helminths (Ascaris lumbricoides, Trichuris trichiura and the two hookworms, Ancylostoma duodenale and Necator americanus) based on specific values of eggs per gram of stool, as measured by the Kato-Katz method. There are a variety of novel microscopy and DNA-based methods but it remains unclear whether applying current WHO thresholds on to these methods allows for a reliable classification of M&HI infections. We evaluated both WHO and method-specific thresholds for classifying the M&HI infections for novel microscopic (FECPAKG2, McMaster and Mini-FLOTAC) and DNA-based (qPCR) diagnostic methods. For this, we determined method-specific thresholds that best classified M&HI infections (defined by Kato-Katz and WHO thresholds; reference method) in two multi-country drug efficacy studies. Subsequently, we verified whether applying these method-specific thresholds improved the agreement in classifying M&HI infections compared to the reference method. When we applied the WHO thresholds, the new microscopic methods mainly misclassified M&HI as low intensity, and to a lesser extent low intensity infection as M&HI. For FECPAKG2, applying the method-specific thresholds significantly improved the agreement for Ascaris (moderate → substantial), Trichuris and hookworms (fair → moderate). For Mini-FLOTAC, a significantly improved agreement was observed for hookworms only (fair → moderate). For the other STHs, the agreement was almost perfect and remained unchanged. For McMaster, the method-specific thresholds revealed a fair to a substantial agreement but did not significantly improve the agreement. For qPCR, the method-specific thresholds based on genome equivalents per ml of DNA moderately agreed with the reference method for hookworm and Trichuris infections. For Ascaris, there was a substantial agreement. We defined method-specific thresholds that improved the classification of M&HI infections. Validation studies are required before they can be recommended for general use in assessing M&HI infections in programmatic settings., Author summary The prevalence of moderate-to-heavy intensity (M&HI) infections is a key indicator for measuring the success of large-scale deworming programs for intestinal worms because they account for the majority of the worm-attributable morbidity. Currently, intestinal worm infections are classified as M&HI when the number of worm eggs that are microscopically detected in stool using a standard diagnostic method exceeds a threshold set by the World Health Organization. Over the years, a variety of new promising diagnostic methods have been introduced for the diagnosis of intestinal worms. Although they have some important advantages over the current standard method, it is not clear whether they can reliably classify M&HI infections. This is because their test results either systematically indicate lower egg counts or are expressed in a unit other than eggs per gram of stool (e.g, concentration of worm DNA), warranting the need for method-specific thresholds. We defined method-specific thresholds and verified whether they increased the correct classification of M&HI infections. Overall, our results indicate that method-specific thresholds improved the classification of M&HI infections, but that further validation is required before they can be recommended for evaluating the occurrence M&HI infections in large-scale deworming programs.

Contamination of hands by soil-transmitted helminth eggs was investigated in a small village located in the suburbs of Hanoi, Vietnam. Thirty-three households, consisting of one to eight members, were selected in the village. In addition, 130 school children, including 80 pupils from primary school grade 1 and 50 students from secondary school grade 8, were selected for the survey. A total of 285 villagers were subjected to the collection of hand-wash samples either once or twice during the study. Parasite eggs were found in 37 (13.0%) samples from 21 males and 16 females aged between 2 and 72 years old. One person was positive in both the rainy and dry season. Eggs of seven parasite species were detected; Enterovius. vermicularis (8.4%), Ascaris sp. (2.1%), Trichuris sp. (1.1%), Ascaridia galli (0.7%), Taenia sp. (0.7%), Capillaria sp. (0.4%) and Toxocara sp. (0.4%). A total of 249 villagers were subjected to collection of nail samples either once or twice during the study. Parasite eggs were found in 10 (4.0%) samples from 5 males and 5 females aged between 6 and 46 years old. Six people were also positive on examination of hand-wash samples. Eggs of four parasite species were detected; E.vermicularis (2.0%), Ascaris sp. (0.8%), Trichuris sp.(0.8%) and Toxocara sp. (0.4%). The present study indicates that the infection route by hands plays an important role in the transmission of the soil-transmitted helminth., Tropical Medicine and Health, 38(2), pp.75-79; 2010

Contamination of water and air by soil-transmitted helminth eggs was investigated in a small village located in the suburbs of Hanoi, Vietnam. Water samples were collected from 29 households, two schools, two kindergartens, one restaurant, three ponds and 23 ditch sites during the rainy season. Water samples were also collected at the same places, except for one household and one restaurant, during the dry season. The water samples collected from households, schools, kindergartens and restaurant were comprised of well-water and rain-water. These samples included both water filtrated with sand and gravel and non-filtrated water. Two-liter water samples were examined for helminth eggs by either a centrifugation or flotation method. The contamination of air by helminth eggs was assessed by the method of Kroeger et al. (1992). Eggs in air were trapped on adhesive tapes hanging in rooms and in the area around 29 houses, two schools, two kindergartens, one restaurant and 18 utility poles. Out of 63 water samples collected from households in the rainy season, helminth eggs were found in four water samples; one from non-filtrated well-water and three from filtrated well-water samples. The one non-filtrated water sample contained six eggs of Toxocara sp., while the three filtrated water samples contained one egg each of Trichuris sp., Trichiuris sp. and Taenia sp. No eggs were found in the water samples collected from schools, kindergartens or the restaurant in the rainy season. All water samples collected from ponds and ditches in the rainy season contained many helminth eggs. The eggs found were Ascaris sp., Trichuris sp., Toxocara sp., Ascaridia galli, hookworm, Taenia sp. and Fasciola sp. Examination of the adhesive tapes hanging in the air showed that four sites were contaminated by helminth eggs, i. e. one site near the house, two sites near the school and one site at a utility pole. The species of eggs found were Trichuris sp., Ascaridia galli and Taenia sp. The number of eggs found on tapes was only one or two. In the dry season, a few samples of well-water and rain-water collected from the residential area were contaminated with helminth eggs, and all samples collected from ponds and ditches contained many eggs of various species similar to those collected in the rainy season. The present study clearly indicates that, in our study area, the villagers were subject to infection from soil-transmitted helminthes directly and indirectly through water., Tropical Medicine and Health, vol.37(2), pp.55-61; 2009

Background The Kato-Katz thick smear (Kato-Katz) is the diagnostic method recommended for monitoring large-scale treatment programs implemented for the control of soil-transmitted helminths (STH) in public health, yet it is difficult to standardize. A promising alternative is the McMaster egg counting method (McMaster), commonly used in veterinary parasitology, but rarely so for the detection of STH in human stool. Methodology/Principal Findings The Kato-Katz and McMaster methods were compared for the detection of STH in 1,543 subjects resident in five countries across Africa, Asia and South America. The consistency of the performance of both methods in different trials, the validity of the fixed multiplication factor employed in the Kato-Katz method and the accuracy of these methods for estimating ‘true’ drug efficacies were assessed. The Kato-Katz method detected significantly more Ascaris lumbricoides infections (88.1% vs. 75.6%, p0.32) in FEC between both methods, and indicated no significant difference in FEC, except for A. lumbricoides, where the Kato-Katz resulted in significantly higher FEC (14,197 eggs per gram of stool (EPG) vs. 5,982 EPG). For the Kato-Katz, the fixed multiplication factor resulted in significantly higher FEC than the multiplication factor adjusted for mass of feces examined for A. lumbricoides (16,538 EPG vs. 15,396 EPG) and T. trichiura (1,490 EPG vs. 1,363 EPG), but not for hookworm. The McMaster provided more accurate efficacy results (absolute difference to ‘true’ drug efficacy: 1.7% vs. 4.5%). Conclusions/Significance The McMaster is an alternative method for monitoring large-scale treatment programs. It is a robust (accurate multiplication factor) and accurate (reliable efficacy results) method, which can be easily standardized., Author Summary Currently, in public health, the reduction in the number of eggs excreted in stools after drug administration is used to monitor the efficacy of drugs against parasitic worms. Yet, studies comparing diagnostic methods for the enumeration of eggs in stool are few. We compared the Kato-Katz thick smear (Kato-Katz) and McMaster egg counting (McMaster) methods, which are commonly used diagnostic methods in public and animal health, respectively, for the diagnosis and enumeration of eggs of roundworms, whipworms and hookworms in 1,536 stool samples from children in five trials across Africa, Asia and South America. The Kato-Katz method was the most sensitive for the detection of roundworms, but there was no significant difference in sensitivity between the methods for hookworms and whipworms. The sensitivity of the methods differed across the trials and magnitude of egg counts. The Kato-Katz method resulted in significantly higher egg counts, but these were subject to lack of accuracy caused by intrinsic properties of this method. McMaster provided more reliable estimates of drug efficacies. We conclude that the McMaster is an alternative method for monitoring large-scale treatment programs. It allows accurate monitoring of drug efficacy and can be easily performed under field conditions.

Background The three major soil-transmitted helminths (STH) Ascaris lumbricoides, Trichuris trichiura and Necator americanus/Ancylostoma duodenale are among the most widespread parasites worldwide. Despite the global expansion of preventive anthelmintic treatment, standard operating procedures to monitor anthelmintic drug efficacy are lacking. The objective of this study, therefore, was to define the efficacy of a single 400 milligram dose of albendazole (ALB) against these three STH using a standardized protocol. Methodology/Principal Findings Seven trials were undertaken among school children in Brazil, Cameroon, Cambodia, Ethiopia, India, Tanzania and Vietnam. Efficacy was assessed by the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) using the McMaster egg counting technique to determine fecal egg counts (FEC). Overall, the highest CRs were observed for A. lumbricoides (98.2%) followed by hookworms (87.8%) and T. trichiura (46.6%). There was considerable variation in the CR for the three parasites across trials (country), by age or the pre-intervention FEC (pre-treatment). The latter is probably the most important as it had a considerable effect on the CR of all three STH. Therapeutic efficacies, as reflected by the FECRs, were very high for A. lumbricoides (99.5%) and hookworms (94.8%) but significantly lower for T. trichiura (50.8%), and were affected to different extents among the 3 species by the pre-intervention FEC counts and trial (country), but not by sex or age. Conclusions/Significance Our findings suggest that a FECR (based on arithmetic means) of >95% for A. lumbricoides and >90% for hookworms should be the expected minimum in all future surveys, and that therapeutic efficacy below this level following a single dose of ALB should be viewed with concern in light of potential drug resistance. A standard threshold for efficacy against T. trichiura has yet to be established, as a single-dose of ALB is unlikely to be satisfactory for this parasite. Trial Registration ClinicalTrials.gov NCT01087099, Author Summary Soil-transmitted helminths (roundworms, whipworms and hookworms) infect millions of children in (sub)tropical countries, resulting in malnutrition, growth stunting, intellectual retardation and cognitive deficits. Currently, there is a need to closely monitor anthelmintic drug efficacy and to develop standard operating procedures, as highlighted in a World Health Organization–World Bank meeting on “Monitoring of Drug Efficacy in Large Scale Treatment Programs for Human Helminthiasis” in Washington DC at the end of 2007. Therefore, we have evaluated the efficacy of a commonly used treatment against these parasitic infections in school children in Africa, Asia and South-America using a standardized protocol. In addition, different statistical approaches to analyzing the data were evaluated in order to develop standardized procedures for data analysis. The results demonstrate that the applied treatment was highly efficacious against round- and hookworms, but not against whipworms. However, there was large variation in efficacy across the different trials which warrants further attention. This study also provides new insights into the statistical analysis of efficacy data, which should be considered in future monitoring and evaluation studies of large scale anthelmintic treatment programs. Finally, our findings emphasize the need to update the World Health Organization recommended efficacy threshold for the treatment of STH.

An epidemiological study on intestinal parasitic infections among schoolchildren in a suburban area of Hanoi, Vietnam, was conducted. Of the 217 schoolchildren involved in this study, 166 (76%) were positive for at least one of nine species of parasite (six helminths and three protozoa). Among the helminth parasites, Trichuris trichiura (67%) was detected the most frequently followed by Ascaris lumbricoides (34%) and hookworm (3%). In the case of protozoan parasites, Entamoeba coli (8%) was the most frequently detected followed by E. histolytica (2%). No Cryptosporidium parvum or Cyclospora sp were found. A questionnaire survey revealed that there was no positive relationship between parasite infection and the children's school records, educational background or parental income, which have been known to play a role.

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.