Much effort has been devoted by the World Health Organization (WHO) to eliminate soil-transmitted helminth (STH) infections by 2030 using mass drug administration targeted at particular risk groups alongside the availability to access water, sanitation and hygiene services. The targets set by the WHO for the control of helminth infections are typically defined in terms of the prevalence of infection, whereas the standard formulation of STH transmission models typically describe dynamic changes in the mean-worm burden. We develop a prevalence-based deterministic model to investigate the transmission dynamics of soil-transmitted helminthiasis in humans, subject to continuous exposure to infection over time. We analytically determine local stability criteria for all equilibria and find bifurcation points. Our model predicts that STH infection will either be eliminated (if the initial prevalence value, y(0), is sufficiently small) or remain endemic (if y(0) is sufficiently large), with the two stable points of endemic infection and parasite eradication separated by a transmission breakpoint. Two special cases of the model are analysed: (1) the distribution of the STH parasites in the host population is highly aggregated following a negative binomial distribution, and (2) no density-dependent effects act on the parasite population. We find that disease extinction is always possible for Case (1), but it is not so for Case (2) if y(0) is sufficiently large. However, by introducing stochastic perturbation into the deterministic model, we discover that chance effects can lead to outcomes not predicted by the deterministic model alone, with outcomes highly dependent on the degree of worm clumping, k. Specifically, we show that if the reproduction number and clumping are sufficiently bounded, then stochasticity will cause the parasite to die out. It follows that control of soil-transmitted helminths will be more difficult if the worm distribution tends towards clumping.
It has been tested and proven that vaccination is still the best strategy to combat infectious diseases. However, to date, there are still no vaccines against human soil-transmitted helminthic diseases, despite their high prevalence globally, particularly in developing countries and rural areas with tropical climates and poor sanitation. The development of vaccines against helminths is riddled with obstacles. Helminths have a complex life cycle, multiple stages within the same host with stage-specific antigen expression, and the ability to regulate host immune reactions to evade the immune response. These elements contribute to the main challenge of helminthic vaccines: the identification of effective vaccine candidates. Therefore, this article reviews the current progress and potential future direction of soil-transmitted helminthic vaccines, particularly against Trichuris trichiura, Ascaris lumbricoides, Strongyloides stercoralis, Necator americanus and Ancylostoma duodenale. The study design employed was a systematic review, using qualitative meta-summary synthesis. Preclinical studies and clinical trials on the development of protein subunit vaccines against the five soil-transmitted helminths were searched on PubMed and Scopus. Effectiveness was indicated by a reduction in worm burden or larval output, an increase in specific IgG levels, or an increase in cytokine production. Our findings show that only the hookworm vaccine against N. americanus is in the clinical trial phase, while the rest is still in exploratory research and pre-clinical development phase.
Notwithstanding the global efforts made to control intestinal parasitic infections, soil-transmitted helminth (STH) infections are still one of the most prevalent infections globally, especially in developing countries. A double-blinded, randomized controlled trial was conducted on 343 primary schoolchildren (8-12 years old) with vitamin A deficiency (VAD) in rural areas of Malaysia to investigate the effects of red palm olein (RPO)-enriched biscuits on STH reinfection rates and infection intensities. The effects of the RPO-enriched biscuits (experimental group, n = 153) and palm olein (PO)-enriched biscuits (control group, n = 190), were assessed at 3- and 6-month after the administration of complete triple-dose albendazole (one dose of 400 mg for three consecutive days). The overall STH infection rate at baseline was recorded at 65.6%. At 6-month, a significantly lower reinfection rate of A. lumbricoides was observed in the experimental group (35.3%) compared to the control group (60.0%) (P0.05). These findings suggest the potential beneficial effects of RPO-enriched biscuit supplementation on the reinfection of A. lumbricoides, which could be attributed to its high carotenoids content by enhancing host immune response and mucosal epithelium integrity. However, further studies are warranted to confirm whether RPO supplementation could result in similar parasite-specific beneficial effects in other community settings, as well as to explore the underlying mechanisms.
The present study was conducted to determine the prevalence of helminth eggs excreted in the faeces of stray cats, dogs and in soil samples. A total of 505 fresh samples of faeces (from 227 dogs and 152 cats) and soil were collected. The egg stage was detected via microscopy after the application of formalin-ether concentration technique. Genomic DNA was extracted from the samples containing hookworm eggs and used for further identification to the species level using real-time polymerase chain reaction coupled with high resolution melting analysis. Microscopic observation showed that the overall prevalence of helminth eggs among stray cats and dogs was 75.7% (95% CI = 71.2%-79.9%), in which 87.7% of dogs and 57.9% of cats were infected with at least one parasite genus. Five genera of heliminth eggs were detected in the faecal samples, including hookworms (46.4%), Toxocara (11.1%), Trichuris (8.4%), Spirometra (7.4%) and Ascaris (2.4%). The prevalence of helminth infections among stray dogs was significantly higher than that among stray cats (p < 0.001). Only three genera of helminths were detected in soil samples with the prevalence of 23% (95% CI = 15.1%-31%), consisting of hookworms (16.6%), Ascaris (4%) and Toxocara (2.4%). The molecular identification of hookworm species revealed that Ancylostoma ceylanicum was dominant in both faecal and soil samples. The dog hookworm, Ancylostoma caninum, was also detected among cats, which is the first such occurrence reported in Malaysia till date. This finding indicated that there was a cross-infection of A. caninum between stray cats and dogs because of their coexistent within human communities. Taken together, these data suggest the potential role of stray cats and dogs as being the main sources of environmental contamination as well as for human infections.
A study of the prevalence and intensity of soil-transmitted helminthiasis among pre-school children aged 0 to 7 years from an Orang Asli village resettlement scheme in Gua Musang, Kelantan was undertaken. The overall prevalence of soil transmitted helminthic (STH) infections was 56.0%. The predominant helminth found was Ascaris lumbricoides while the commonest type of infection was a mixed infection with Ascaris lumbricoides and Trichuris trichiura. The prevalence rates of Ascaris, Trichuris and hookworm infections were 47.5%, 33.9% and 6.2% respectively. The intensity of Ascaris infections were 64.5% light, 27.3% moderate and 8.3% heavy whilst the intensity of Trichuris infections were 80.5% light, 18.3% moderate and 1.2% heavy. However, the intensity of hookworm infections were 86.7% light, 13.3% moderate and no heavy infection. The prevalence of helminthiasis (STH) shows an-age dependent relationship, with the lowest prevalence in 0-< 1 year age group and highest in the 6-< 7 year age group.
Acanthamoeba, one of free-living amoebae (FLA), remains a high risk of direct contact with this protozoan parasite which is ubiquitous in nature and man-made environment. This pathogenic FLA can cause sight-threatening amoebic keratitis (AK) and fatal granulomatous amoebic encephalitis (GAE) though these cases may not commonly be reported in our clinical settings. Acanthamoeba has been detected from different environmental sources namely; soil, water, hot-spring, swimming pool, air-conditioner, or contact lens storage cases. The identification of Acanthamoeba is based on morphological appearance and molecular techniques using PCR and DNA sequencing for clinico-epidemiological purposes. Recent treatments have long been ineffective against Acanthamoeba cyst, novel anti-Acanthamoeba agents have therefore been extensively investigated. There are efforts to utilize synthetic chemicals, lead compounds from medicinal plant extracts, and animal products to combat Acanthamoeba infection. Applied nanotechnology, an advanced technology, has shown to enhance the anti-Acanthamoeba activity in the encapsulated nanoparticles leading to new therapeutic options. This review attempts to provide an overview of the available data and studies on the occurrence of pathogenic Acanthamoeba among the Association of Southeast Asian Nations (ASEAN) members with the aim of identifying some potential contributing factors such as distribution, demographic profile of the patients, possible source of the parasite, mode of transmission and treatment. Further, this review attempts to provide future direction for prevention and control of the Acanthamoeba infection.
The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay.
The aim of our study was to investigate the intra- and interspecific agonistic behaviors exhibited by the worker and soldier castes of the subterranean termite Microcerotermes crassus Snyder (Isoptera: Termitidae). Aggression between M. crassus colonies from different field locations and also against three termite species--Coptotermes gestroi (Wasmann), Globitermnes sulphureus Haviland, and Odontotermes sp.--were observed in the laboratory. Termite responses were tested in paired combination of castes (soldiers versus soldiers, soldiers versus workers, and workers versus workers) consisting of 10 individuals each. Significant agonistic behaviors were observed only in encounters between pairings of different termite species. M. crassus was aggressive toward individuals from different species but not toward individuals from different M. crassus colonies. Mortality of M. crassus reached 100% in most of the interspecific encounters. However, no or low mortality was recorded in the intraspecific pairings.
Soil-transmitted helminth (STH) infections in Malaysia are still highly prevalent, especially in rural and remote communities. Complete estimations of the total disease burden in the country has not been performed, since available data are not easily accessible in the public domain. The current study utilised geographical information system (GIS) to collate and map the distribution of STH infections from available empirical survey data in Peninsular Malaysia, highlighting areas where information is lacking. The assembled database, comprising surveys conducted between 1970 and 2012 in 99 different locations, represents one of the most comprehensive compilations of STH infections in the country. It was found that the geographical distribution of STH varies considerably with no clear pattern across the surveyed locations. Our attempt to generate predictive risk maps of STH infections on the basis of ecological limits such as climate and other environmental factors shows that the prevalence of Ascaris lumbricoides is low along the western coast and the southern part of the country, whilst the prevalence is high in the central plains and in the North. In the present study, we demonstrate that GIS can play an important role in providing data for the implementation of sustainable and effective STH control programmes to policy-makers and authorities in charge.
Soil-transmitted helminths (STH) infections, anaemia and malnutrition are major public health problems in school-age children in developing countries. This study was conducted on 289 Orang Asli (aboriginal) schoolchildren in order to assess the current prevalence and predictors of anaemia and malnutrition, as well as the nutritional impacts of STH infections among these children.
Soil-transmitted helminth (STH) infections, among the most common neglected tropical diseases, continue to be a major threat to the health and socioeconomic wellbeing of infected people especially children in developing countries.
Vermicomposting using Lumbricus rubellus for 49 days was conducted after 21 days of pre-composting. Three different combination of treatments were prepared with eight replicates for each treatment namely cow dung: kitchen waste in 30:70 ratio (T(1)), cow dung: coffee grounds in 30:70 ratio (T(2)), and cow dung: kitchen waste: coffee grounds in 30:35:35 ratio (T(3)). The multiplication of earthworms in terms of numbers and weight were measured at the end of vermicomposting. Consequently, only T(2) showed significant increase (from it initial stage) compared to other treatments. The presence of coffee grounds in T(2) and T(3) showed higher percentage of nutrient elements in vermicompost produced. The data reveal that coffee grounds can be decomposed through vermicomposting and help to enhance the quality of vermicompost produced rather than sole use of kitchen waste in vermicomposting.
Soil-transmitted helminthiases are a public health problem in rural communities. A cross-sectional study of the prevalence and distribution of Ascaris lumbricoides, Trichuris trichiura and hookworm was conducted in 281 Orang Asli children (aborigines) aged between 2 and 15 years, from 8 Orang Asli villages in Selangor, Malaysia. All the children were infected with soil-transmitted helminthes, with 26.3% of the children infected either with A. lumbricoides, T. trichiura or hookworm and 72.6% having mixed infection. The overall prevalences of A. lumbricoides, T. trichiura and hookworm were 61.9, 98.2 and 37.0%, respectively. Approximately 19.0, 26.0 and 3.0% of the children had severe infection of ascariasis, trichuriasis and hookworm infection, respectively. The prevalences and mean egg per gram (epg) counts for A. lumbricoides and T. trichiura were not significantly dependent on age, therefore age-dependent convexity was not seen in this study. However, the results of this study reveal an age-dependent prevalence and mean epg count in children with hookworm infection. We conclude that ascariasis, trichuriasis and hookworm infection are still prevalent and therefore a public health concern in Orang Asli communities. Severe ascariasis and trichuriasis may lead to other health and medical problems.
Despite the continuous efforts to improve the quality of life of Orang Asli (Aborigines) communities, these communities are still plagued with a wide range of health problems including parasitic infections. The first part of this study aimed at determining the prevalence of soil-transmitted helminth (STH) infections and identifying their associated factors among rural Orang Asli children.
Malaysia is a developing country with a range of parasitic infections. Indeed, soil-transmitted helminths and malaria parasites continue to have a significant impact on public health in Malaysia. In this article, the prevalence and distribution of these parasites, the problems associated with parasitic infections, the control measures taken to deal with these parasites and implications for the future will be discussed.
Soil-transmitted helminths (STHs) pose significant public health challenges in many countries of Southeast Asia (SEA). Overall, approximately one-third of the world's cases of ascariasis, trichuriasis, and hookworm disease occur in the 11 major SEA countries. Various countries are at different stages in their response to controlling these diseases. For instance, in Malaysia and Thailand, the major burden of disease is confined to rural/remote, indigenous and/or refugee populations. In countries, such as Cambodia, Lao People's Democratic Republic and Vietnam, the burden remains high, although extensive deworming programmes are underway and are yielding encouraging results. The present chapter reviews the current status of STH infections in SEA, identifies knowledge gaps and offers a perspective on the development of improved, integrated surveillance and control in this geographical region. It indicates that advances in our understanding of the epidemiology of these parasites, through the strategic use of molecular and predictive (e.g. geographical information systems (GIS) and remote sensing (RS)) technologies, could readily underpin future research and control programmes. It is hoped that the gradual move towards integrated treatment/control programmes will assist substantially in decreasing the chronic disease burden linked to STHs, thus increasing human health and welfare, and supporting socio-economic growth and development in SEA countries.
In Soil-Transmitted Helminth (STH) control programs, microscopic examination is applied as a standard method for detecting the presence and the number of STH eggs. The time limitations of fresh specimen processing, especially for an accurate quantitative diagnosis, cause the specimen processing to be delayed or should be performed at a referral laboratory. This deferment requires preservatives to keep the stool integrity without reducing the accuracy. The aims of this study were: 1) to compare the proportion of positive samples and the intensity of A. lumbricoides, T. trichiura, and hookworm infection based on the examination of fresh samples and stool preserved by 10% formalin for >12 months and 2) to determine the most reliably accurate between Kato-Katz and mini-FLOTAC methods in detecting A. lumbricoides, T. trichiura, and hookworm eggs in preserved stools both qualitatively and quantitatively. Seventy-eight (78) stool samples were examined by mini-FLOTAC, and KatoKatz methods. Proportion of positive samples of A. lumbricoides, T. trichiura, and hookworms in fresh and in >=12 months 10% formalin preserved stools had no significant difference. Helminths density (eggs per gram of stool/EPG) in fresh samples was fewer compared to EPG in preserved samples (p <0.05) which leads to a lower proportion of moderate and high level groups in fresh stools samples compared to those in preserved samples (p <0.05). In preserved samples, as qualitative method, mini-FLOTAC detected more A. lumbricoides and T. trichiura eggs than Kato-Katz, while hookworm eggs were detected more by Kato-Katz than the miniFLOTAC. As a quantitative detection, Kato-Katz showed higher calculation of STH EPG than mini-FLOTAC. Using 10% formalin preservation for stool samples, the STH eggs' morphology could still be well identified. Homogenization process and low number of samples tested, were acknowledged as the limitation of this study.
Soil-transmitted helminth (STH) could possibly cause mild to severe health effects such as diarrhea, weakness, intestinal blood loss, and impaired cognitive development and growth. In Malaysia, previous studies depicted a high prevalence rate of STH was due to poor hygiene practice and low efficacies of anthelminthic drugs. This study was conducted to investigate hand hygiene practice and WASH criteria's (Water, sanitation and hygiene) related to STH infection among two indigenous tribes in Peninsular Malaysia. A cross-sectional study was carried out to study the relationship among STH infection compared to water quality, sanitation, and hygiene conditions. A total of 190 individuals from two indigenous villages participated in the study, with ages ranging from 5 to 60 years old. In addition, Pearson's Chisquare (X2) test was utilized to test the relationship among STH with demographic socioeconomic and behavioral factors. The confidence interval (CI) of 95% is used to estimate the precision of the odds ratio (OR). Multivariate logistic regression models were also used to identify the risk factors associated with STH infections. The overall findings indicated a prevalence rate of 72% for STH, and distributed mainly among children aged < 12 years. Furthermore, multivariate analyses using logistic regression revealed chronic health problems, incorrect hand washing, and walking bare footed were associated with STH infection. Overall results indicated high prevalence of STH among the indigenous villagers, which aligns with the published literature and proves to be a problem need to be addressed as neglected disease. Interestingly, there was a significant relationship between the presences of chronic diseases and STH infection, which prompted other questions the awareness needs to be educated and the simple and low-cost intervention on the proper way of hand washing may help to reduce STH infection in these indigenous communities.
The World Health Organization has recommended the application of mass drug administration (MDA) in treating high prevalence neglected tropical diseases such as soil-transmitted helminths (STHs), schistosomiasis, lymphatic filariasis, onchocerciasis and trachoma. MDA-which is safe, effective and inexpensive-has been widely applied to eliminate or interrupt the transmission of STHs in particular and has been offered to people in endemic regions without requiring individual diagnosis. We propose two mathematical models to investigate the impact of MDA on the mean number of worms in both treated and untreated human subpopulations. By varying the efficay of drugs, initial conditions of the models, coverage and frequency of MDA (both annual and biannual), we examine the dynamic behaviour of both models and the possibility of interruption of transmission. Both models predict that the interruption of transmission is possible if the drug efficacy is sufficiently high, but STH infection remains endemic if the drug efficacy is sufficiently low. In between these two critical values, the two models produce different predictions. By applying an additional round of biannual and annual MDA, we find that interruption of transmission is likely to happen in both cases with lower drug efficacy. In order to interrupt the transmission of STH or eliminate the infection efficiently and effectively, it is crucial to identify the appropriate efficacy of drug, coverage, frequency, timing and number of rounds of MDA.
The influence of soil texture (silt, sand and laterite) and flotation solutions (saturated NaCl, sucrose, NaNO3, and ZnSO4) upon the recovery of Toxocara ova from seeded soil samples with the centrifugal flotation technique was investigated. Soil samples of different texture were artificially seeded with Toxocara spp. ova and subjected to a centrifugal flotation technique which used various flotation solutions. The results showed significant (P < 0.001) interactions between the soil types and the flotation solutions. The highest percentage of ova recovery was obtained with silty soil (34.9-100.8%) with saturated NaCl as the flotation solution (45.3-100.8%). A combination of washing of soil samples with 0.1% Tween 80, and flotation using saturated NaCl and a 30 min coverslip recovery period was used to study the prevalence of contamination of soil samples. Forty-six soil samples were collected from up to 24 public parks/playgrounds in urban areas of Petaling Jaya and suburban areas of Serdang. The prevalence of Toxocara species in the urban and suburban areas was 54.5% and 45.8% respectively.