Helminth Control Research Articles

Grassland management and helminth control on livestock farms

Most species of gastrointestinal and pulmonary parasitic nematodes of cattle and sheep are host specific and farmers with mixed livestock farms can take advantage of this aspect of parasite biology to mitigate and control pasture-associated parasite infections through mixed or co-grazing. However, some common parasites, such as liver and rumen fluke, are generalists and can parasitise a wide range of mammalian hosts, nevertheless, differences in host responses have the potential to be used to manage high-risk fields, without compromising health or performance. Current research is exploring the possible role of bioactive plants in the control of parasites.

Grassland management and helminth control on cattle farms

Farmers manage their pastures and grazing animals primarily to ensure that swards provide adequate, quality nutrients to support animal performance, but it is also possible to provide useful levels of parasite control without compromising production. On cattle only farms the easiest options for the control of parasitic gastroenteritis in young cattle revolve around the avoidance of high risk pastures from July onwards. On many farms, silage/hay aftermaths that have not been grazed by cattle for 12 months or more can provide low risk fields on which cattle can thrive with minimal reliance on anthelmintics.

Study on the Prevalence of Endoparasites in Small Holder Dairy Farm in and around Harar Town, Oromia Regional State, Eastern Ethiopia

A cross- sectional study of prevalence of Gastro-intestinal helminthiasis of small holder dairy cows was carried out from December 2007 to April 2008 with an attempt to determine the prevalence in Harar town and its surrounding, Eastern Ethiopia. Amongst the 287 coprological analysis or quantitative faecal analysis on dairy cows were performed with an overall prevalence rate 139 (48.4%) by using coprological examination. Coprological examination (Direct, Floatation, sedimentation and Mc Master Techniques) were the methods followed to study the prevalence of GI - parasitic infestation. An overall GI-parasitic infestation of 48.4% was found in this study. The result also revealed that nematodes Strongyles (38.4%) and Trichuris (8.4%), paraphistomum (13.9%) and Coccidia (10.5%) in that order. The helminth eggs present were identified in general terms as strongyloid eggs, since relevant nematode genera produce eggs that are similar in appearance and cannot be discriminated easily, except for eggs of Nematodirus, Strongyloides and Trichuris. In view of the prevalence of hazardous parasitic gastro intestinal parasites with a potential of entailing serious direct and indirect losses, and accompanying in these small holder dairy cows deserve attention and pertinent action to see they are controlled because high economic importance deserving due attention in helminth control programs in the study area.

Phytochemical and Anthelmintic Investigation of Leaves of Glochidion ellipticum Linn

Worm infections remain a major constraint to livestock productivity across all agro-ecological Zones. Now, the main mode for control of gastrointestinal parasites is based on the synthetic anthelmintic. However, wide spread increase of anthelmintic resistance, scarcity and high cost especially to farmers of low income in developing countries led to the need of other alternative helminth control methods. Among other alternative methods, there is considerable and expanding interest in traditional herbal de wormers. In present communication methanolic and aqueous extracts of leaves of Glochidion ellipticum Linn. Flem were investigated for their anthelmintic activity against Pheretima posthuma and Ascardia galli. Different concentrations were used in the assay, which involved paralysis and death time of the worms. Both the extracts showed significant anthelmintic activity.

Нематоды пищеварительной системы домашних жвачных Узбекистана

Objective of research. A study of species composition of nematodes parasitizing the digestive system of domestic ruminants in Uzbekistan, analysis of seasonal dynamics of infestation and features of the nematode fauna in plains and foothill-mountain areas. Material and methods. In the period of 2014–2015, the digestive tracts of 206 head of cattle and 878 head of small cattle from the farms of Tashkent, Syr-Darya, Dzhizak, Namangan, Kashkadarya, Surkhandarya, Navoiy and Bukhara regions as well as Karakalpakstan autonomous republic were investigated by the method of full helminthological dissection. Results and discussion. 30 nematode species were found in digestive tracts of domestic ruminants of Uzbekistan; 28 nematode species in sheep, 26 species in goats, and 22 species in cattle. The highest rates of extensity of infection (EI) and intensity of infection (II) were detected in Ostertagia ostertagi, Marshallagia marshalli, Teladorsagia circumcincta and Parabronema skrjabini. An increase of EI and II in summer and autumn period was typical for the most of the discovered nematode species. However, EI in O. ostertagi, T. circumcincta, Marshallagia spp. and P. skrjabini was relatively stable in all seasons, but II increased to autumn. 26 nematode species were registered in plains; only 3 of them with high EI and II. 28 nematode species were registered in foothill-mountain areas, 8 of them showed high rates of EI and II. 24 species of nematodes are common in both areas. The obtained results allow us to conclude that it is necessary to improve helminth control of ruminants in Uzbekistan. Alternation of pastures and regulation of grazing, as well as preventive dehelmintization should not be ignored; observe the optimal requirements for feeding and management of animals.

The Impact of Lymphatic Filariasis Mass Drug Administration Scaling Down on Soil-Transmitted Helminth Control in School-Age Children. Present Situation and Expected Impact from 2016 to 2020.

Lymphatic filariasis (LF) and soil-transmitted-helminths (STH) are co-endemic in 58 countries which are mostly in Africa and Asia. Worldwide, 486 million school-age children are considered at risk of both diseases. In 2000, the World Health Organization (WHO) established the global programme to eliminate LF by 2020. Since then, the LF elimination programme has distributed ivermectin or diethylcarbamazine citrate (DEC) in combination with albendazole, thereby also treating STH. Consequently, many school-age children have been treated for STH through the LF programme. As treatment targets towards the 2020 LF elimination goal are achieved, many countries are implementing the transmission assessment survey (TAS) and, if the LF prevalence is estimated to be less than 1%, scaling down mass drug administration (MDA). We analysed the 2014 data on preventive chemotherapy (PC) reported from LF STH co-endemic countries and projected the year and location of TAS expected to be conducted between 2016 and 2020 to assess the impact of this scaling down on STH PC. Eighty percent of all co-endemic countries that have already stopped LF MDA nationally were able to establish STH PC through schools. It is estimated that 14% of the total number of children presently covered by the LF programme is at risk of not continuing to receive PC for STH. In order to achieve and maintain the WHO 2020 goal for STH control, there is an urgent need to establish and reinforce school-based deworming programmes in countries scaling-down national LF elimination programmes.

Differential effect of mass deworming and targeted deworming for soil-transmitted helminth control in children: a systematic review and meta-analysis

Soil-transmitted helminth infections are a major global health issue, causing substantial morbidity in the world's poorest populations. Regular delivery of anthelmintic drugs is the mainstay for global soil-transmitted helminth control. Deworming campaigns are often targeted to school-aged children, who are at high risk of soil-transmitted-helminth-associated morbidity. However, findings from modelling studies suggest that deworming campaigns should be expanded community-wide for effective control of soil-transmitted helminth transmission. We aimed to do a systematic review and meta-analysis to compare the effect of mass (community-wide) and targeted (children only) anthelmintic delivery strategies on soil-transmitted helminth prevalence in school-aged children. In this systematic review and meta-analysis, we searched MEDLINE, Embase, and Web of Science for articles published on or before Nov 5, 2015, reporting soil-transmitted helminth prevalence before and after distribution of albendazole or mebendazole, either targeted to children or delivered to the whole community. We excluded studies in which drug delivery was restricted to infected individuals or to a subset of the community or school, or if follow-up time was less than 3 months or greater than 18 months after drug delivery. We extracted data on study year, country, drug administration strategy, drug dose, number of deworming rounds, treatment coverage, diagnostic method, follow-up interval, and soil-transmitted helminth prevalence before and after treatment. We used inverse variance weighted generalised linear models, with prevalence reduction as the outcome variable, to examine the effect of mass versus targeted drug administration, as well as baseline prevalence, number of drug doses, and follow-up time. This study is registered with PROSPERO, number CRD42016026929. Of 10 538 studies identified, 56 studies were eligible for the systematic review and 38 of these were included in meta-analysis. Results of the regression models showed that mass deworming led to a significantly greater reduction in prevalence in children than targeted deworming, for both hookworm (odds ratio 4·6, 95% CI 1·8-11·6; p=0·0020) and Ascaris lumbricoides (16·4, 2·1-125·8; p=0·0092), with no effect seen for Trichuris trichiura. There was significant heterogeneity across studies; for targeted studies I2 was 97% for A lumbricoides and hookworm, and 96% for T trichiura, and for mass studies, I2 was 89% for A lumbricoides, 49% for hookworm, and 66% for T trichiura. The results of this meta-analysis suggest that expanding deworming programmes community-wide is likely to reduce the prevalence of soil-transmitted helminths in the high-risk group of school-aged children, which could lead to improved morbidity outcomes. These findings are in support of recent calls for re-evaluation of global soil-transmitted helminth control guidelines. None.

Anthelmintic resistance in equine helminths and mitigating its effects

Helminth control in horses has been based on the administration of broad-spectrum anthelmintics for over 50 years, but although this has reduced clinical disease, anthelmintic-resistant populations of nematodes (for example,...

The role of pre-school teachers in the control of soil-transmitted helminthes in coastal region, Kenya.

BackgroundSoil transmitted helminthes (STH) are significant health problems among school-age children. In Kenya’s coastal region, the prevalence among pre-school age children (PSAC) ranges from 27.8 to 66.7 %. Whereas some pre-schools are as far as 7 km from the nearest primary schools, the National School-Based Deworming Programme (NSBDP) requires the pre-school teachers to walk with the children to primary schools for deworming by trained primary school teachers. The long distances may contribute in making drug delivery ineffective and unsustainable.MethodsTo assess the pre-school teachers’ knowledge, experiences and perceptions of STH and the NSBDP, a cross-sectional study using qualitative methods was conducted in four sub-counties of the Coast Region. Through purposive sampling, 41 pre-schools which are 2 or more kilometers away from a primary school were selected and in-depth interviews administered to the teachers. Separate in-depth interviews were administered to 34 community health extension workers, 40 opinion leaders and 38 primary school teachers all purposively selected to assess their perceptions of the role of pre-school teachers in the NSBDP. Data was audio recorded, transcribed, coded and analyzed manually by study themes.ResultsA third of the pre-school teachers were aware of signs of STHs and a half indicated that poor hygiene and sanitation practices are major causes. A majority of the pre-school teachers reported that health education and environmental sanitation are key control methods. Majority (39) had received information on NSBDP from various sources and all took part in community sensitization and in treating the pre-school children. A large majority of all study participants indicated that treating the children at pre-schools is ideal for increased coverage. Majority of the pre-school teachers perceived the NSBDP as important in improving the health status of the children. All study participants felt that the parents needed to be given adequate information on STHs and training the pre-school teachers to assist in community sensitization and drug administration would be useful.ConclusionPre-school teachers are a potential resource to the NSBDP that should be utilized to instill proper water and sanitation practices to the young children and assist in community sensitization. They should be empowered and allowed to administer treatment for STH control. County Governments, their current employers should find ways of engaging them in worm control efforts.Trial registration KEMRI SSC 2547, Registered 22 July 2013.

A survey of UK prescribers’ experience of, and opinions on, anthelmintic prescribing practices for livestock and equines

The aim of this study was to determine practices, attitudes and experiences of UK prescribers of anthelmintics for horses and livestock. A questionnaire was sent by direct email to groups licenced to prescribe these medicines. These were veterinarians, Suitably Qualified Persons (SQPs, registered with the Animal Medicines Training Regulatory Authority) and veterinary pharmacists. The survey was also advertised through social media. It comprised questions relating to demographics, training experiences, current prescribing practices, as well as personal opinions on anthelmintic selection, diagnostics and anthelmintic resistance. A total of 193 veterinarians and 326 SQPs were included in final analysis. Pharmacists were excluded from detailed analysis due to the low numbers that responded (n=3). The results indicated that SQP participants were more likely to receive post-certification parasitology training than the veterinarians, and that both channels consulted similar sources for information about helminths and their control (paper articles in journals, online sources). The SQP participants stated a higher frequency of face-to-face interactions with clients/customers (96.1%) than the veterinarians (76.4%), who stated a higher frequency of telephone interactions (55.1% and 73.5%, respectively). Veterinarians were more likely to state that there were specific factors that limited interactions with their clients (54.1%) than SQPs (19.6%), such as competition from other suppliers. SQP participants considered a wider range of factors as important when deciding on which anthelmintic to recommend (i.e. knowledge of specific parasites, knowledge of specific anthelmintics, discussion of measures to avoid anthelmintic resistance and time to talk with clients/customers); however, the veterinarian participants were more likely to consider the results of diagnostic tests. While discussions about anthelmintic resistance were stated with similar frequency in both groups, less frequent were specific discussions about anthelmintic sensitivity testing. In-house faecal egg count analysis was more likely to be available from those that prescribed anthelmintics for equines alone, compared to prescribers who dispensed anthelmintics for livestock alone or livestock and equines. The SQP participants indicated that they felt a large number of organisations were responsible for ensuring that anthelmintics are used responsibly, whilst veterinarian participants were more likely to place responsibility on the prescribers alone. Taken together, these findings provide an insight into how prescribers of anthelmintics in the UK interact with their clients/customers before and at the point of sale and act as a unique source of information on how best practice advice pertaining to sustainable helminth control is disseminated by the various prescribing channels.

Experimental infection of calves with Haemonchus placei or Haemonchus contortus: Assessment of clinical, hematological and biochemical parameters and histopathological characteristics of abomasums

The present study had the primary objective of evaluating clinical, hematological and biochemical parameters, as well as observing anatomical and histopathological characteristics of abomasums, from calves prime-infected with Haemonchus contortus or H. placei. Ten male Holstein newborns were subdivided in three groups (GI placebo; GII infected with H. contortus; GIII inoculated with H. placei). Eye mucosa staining was evaluated. Hematological and biochemical tests were performed on animals. The euthanasia of all ten experimental calves was performed on the 42nd day post-inoculation. Fragments were collected from each of all 10 abomasums for histopathological analysis. Discrete submandibular edema was diagnosed in animals from both infected groups (H. contortus or H. placei). However, there were no significant changes (P > 0.05) in the color of the ocular mucosa of calves from all three experimental groups across the entire experimental period. Hematological and biochemical changes diagnosed on animals could not be linked to infections by species of Haemonchus spp. Regarding histopathological exams, it was possible to diagnose hypertrophy, hyperplasia, binucleated cells, inflammatory infiltrate, multifocal hemorrhage and edema in abomasums from calves of both groups infected with H. placei and H. contortus. It can, thus, be concluded that not only are calves susceptible to infections by both Haemonchus species, but they can also present clinical changes and similar anatomic histopathological lesions independent of being infected by Haemonchus placei or Haemonchus contortus. These results reflect a negative effect on helminth control by mixed grazing between sheep and cattle, especially when using calves.

Feeding horses with industrially manufactured pellets with fungal spores to promote nematode integrated control

The usefulness of pellets industrially manufactured with spores of parasiticide fungi as a contribution to integrated nematode control was assessed in grazing horses throughout sixteen months. Two groups of 7 Pura Raza Galega autochthonous horses (G-T and G-P) were dewormed pour-on (1mg Ivermectin/kg bw) at the beginning of the trial, and other group (G-C) remained untreated. The G-P was provided daily with commercial pellets to which was added a mixture of fungal spores during the industrial manufacturing (2×106 spores of Mucor circinelloides and same dose of Duddingtonia flagrans/kg), and G-T and G-C received pellets without spores. The efficacy of the parasiticidal strategy was assessed by estimating the reduction in the faecal egg counts (FECR) and in the number of horses shedding eggs in the faeces (PHR), and also the egg reappearance periods (ERP). Blood analyses were performed to identify the changes in the red and white cell patterns. To ascertain if horses developed an IgG humoral response against the fungi, antigenic products collected from M. circinelloides and D. flagrans were exposed to the horse sera by using an ELISA.The faecal elimination of eggs of Parascaris equorum and strongyles ceased 2 weeks after treatment in G-T and G-P, thus the values of FECR and PHR were 100%. No P. equorum-eggs were detected later, and the strongyle egg reappearance period was 28 weeks in G-P, and 8 weeks in G-T. Strongyle egg-output values remained lower than 300 eggs per gram of faeces in the G-P, whereas numbers between 330 and 772 in G-C and G-T were recorded. Normal values for the erythrocytes, haemoglobin and haematocrit in horses consuming pellets with spores were recorded, and lower than normal in the other groups. Sensitization of horses to the fungal species was disproven. It is concluded that feeding horses with pellets industrially manufactured with fungal spores represents a very useful tool to implement an integrated control of helminths affecting horses. This strategy allows a decrease in their risk of infection, aids in reducing the frequency of anthelmintic treatment.

Water, sanitation and hygiene related risk factors for soil-transmitted helminth and Giardia duodenalis infections in rural communities in Timor-Leste

There is little evidence on prevalence or risk factors for soil transmitted helminth infections in Timor-Leste. This study describes the epidemiology, water, sanitation and hygiene, and socioeconomic risk factors of STH and intestinal protozoa amongst communities in Manufahi District, Timor-Leste. As part of a cluster randomised controlled trial, a baseline cross-sectional survey was conducted across 18 villages, with data from six additional villages. Stool samples were assessed for soil transmitted helminth and protozoal infections using quantitative PCR (qPCR) and questionnaires administered to collect water, sanitation and hygiene and socioeconomic data. Risk factors for infection were assessed using multivariable mixed-effects logistic regression, stratified by age group (preschool, school-aged and adult). Overall, soil transmitted helminth prevalence was 69% (95% Confidence Interval 67–71%), with Necator americanus being most common (60%; 95% Confidence Interval 58–62%) followed by Ascaris spp. (24%; 95% Confidence Interval 23–26%). Ascaris-N. americanus co-infection was common (17%; 95% Confidence Interval 15%-18%). Giardia duodenalis was the main protozoan identified (13%; 95% Confidence Interval 11–14%). Baseline water, sanitation and hygiene infrastructure and behaviours were poor. Although risk factors varied by age of participants and parasite species, risk factors for N. americanus infection included, generally, age in years, male sex, and socioeconomic quintile. Risk factors for Ascaris included age in years for children, and piped water to the yard for adults. In this first known assessment of community-based prevalence and associated risk factors in Timor-Leste, soil transmitted helminth infections were highly prevalent, indicating a need for soil transmitted helminth control. Few associations with water, sanitation and hygiene were evident, despite water, sanitation and hygiene being generally poor. In our water, sanitation and hygiene we will investigate implications of improving WASH on soil transmitted helminth infection in impoverished communities.

Identification of lead chemotherapeutic agents from medicinal plants against blood flukes and whipworms.

Schistosomiasis and trichuriasis are two of the most common neglected tropical diseases (NTD) that affect almost a billion people worldwide. There is only a limited number of effective drugs to combat these NTD. Medicinal plants are a viable source of parasiticides. In this study, we have investigated six of the 19 phytochemicals isolated from two Bhutanese medicinal plants, Corydalis crispa and Pleurospermum amabile, for their anthelmintic properties. We used the xWORM technique and Scanning Electron Microscope-based imaging to determine the activity of the compounds. Of the six compounds tested, isomyristicin and bergapten showed significant anthelmintic activity against Schistosoma mansoni and Trichuris muris with bergapten being the most efficacious compound one against both parasites (S. mansoni IC50 = 8.6 μg/mL and T. muris IC50 = 10.6 μg/mL) and also against the schistosomulum stage of S. mansoni. These two compounds induced tegumental damage to S. mansoni and affected the cuticle, bacillary bands and bacillary glands of T. muris. The efficacy against multiple phylogenetically distinct parasites and different life stages, especially the schistosomulum where praziquantel is ineffective, makes isomyristicin and bergapten novel scaffolds for broad-spectrum anthelmintic drug development that could be used for the control of helminths infecting humans and animals.

Compounds Derived from the Bhutanese Daisy, Ajania nubigena, Demonstrate Dual Anthelmintic Activity against Schistosoma mansoni and Trichuris muris.

BackgroundWhipworms and blood flukes combined infect almost one billion people in developing countries. Only a handful of anthelmintic drugs are currently available to treat these infections effectively; there is therefore an urgent need for new generations of anthelmintic compounds. Medicinal plants have presented as a viable source of new parasiticides. Ajania nubigena, the Bhutanese daisy, has been used in Bhutanese traditional medicine for treating various diseases and our previous studies revealed that small molecules from this plant have antimalarial properties. Encouraged by these findings, we screened four major compounds isolated from A. nubigena for their anthelmintic properties.Methodology/Principal FindingsHere we studied four major compounds derived from A. nubigena for their anthelmintic properties against the nematode whipworm Trichuris muris and the platyhelminth blood fluke Schistosoma mansoni using the xWORM assay technique. Of four compounds tested, two compounds—luteolin (3) and (3R,6R)-linalool oxide acetate (1)—showed dual anthelmintic activity against S. mansoni (IC50 range = 5.8–36.9 μg/mL) and T. muris (IC50 range = 9.7–20.4 μg/mL). Using scanning electron microscopy, we determined luteolin as the most efficacious compound against both parasites and additionally was found effective against the schistosomula, the infective stage of S. mansoni (IC50 = 13.3 μg/mL). Luteolin induced tegumental damage to S. mansoni and affected the cuticle, bacillary bands and bacillary glands of T. muris. Our in vivo assessment of luteolin (3) against T. muris infection at a single oral dosing of 100 mg/kg, despite being significantly (27.6%) better than the untreated control group, was markedly weaker than mebendazole (93.1%) in reducing the worm burden in mice.Conclusions/SignificanceAmong the four compounds tested, luteolin demonstrated the best broad-spectrum activity against two different helminths—T. muris and S. mansoni—and was effective against juvenile schistosomes, the stage that is refractory to the current gold standard drug, praziquantel. Medicinal chemistry optimisation including cytotoxicity analysis, analogue development and structure-activity relationship studies are warranted and could lead to the identification of more potent chemical entities for the control of parasitic helminths of humans and animals.

Prevalence and risk factors associated with gastrointestinal nematode infection in goats raised in Baybay city, Leyte, Philippines.

Aim:Gastrointestinal parasitism is a serious constraint affecting goat production in the Philippines. This study aimed to determine the prevalence and associated risk factors of gastrointestinal nematode infection in goat-populated barangays of Baybay City, Leyte.Materials and Methods:A total of 81 households or farms were interviewed, and 450 goats were sampled for fecalysis. Fecal egg count along with egg morphological identification and coproculture for third stage larvae identification were conducted. Descriptive statistics and logistic regression analyses were carried out to determine the farm- and animal-level prevalence and risk factors.Results:Fecalysis revealed the presence of strongyle and Trichuris spp. with a farm-level prevalence of 100% and 4.94%, respectively; and animal-level prevalence of 96.22% and 4.44%, respectively. The identified strongyle genera per barangay were Haemonchus spp. (34.79%), Trichostrongylus spp. (33.29%), Oesophagostomum spp. (24.21%), Cooperia spp. (6.93%), and Chabertia spp. (0.79%). Goats older than 12 months were four times more likely to present high strongyle burden when compared to goats <6 months. With each month increase in goat’s age, the odds of acquiring strongyle infection also increased by 1.07 times. Animals kept in goat house with cemented flooring have lower odds of acquiring strongyle (odds ratio=0.12). Goats raised for leisure purposes and fed with carabao grass (Paspalum conjugatum) were 8.12 and 5.52 times more likely to acquire Trichuris, respectively.Conclusion:Most of the backyard goat raisers in Baybay City, Leyte, do not practice sound helminth control measures as shown by the high prevalence of gastrointestinal nematodes. The most relevant risk factors for gastrointestinal nematode infection were the age of the goat, type of goat house’s flooring, purpose of raising goats, and feeding practices.

Assessing the usefulness of mineral licks containing herbal extracts with anti-parasitic properties for the control of gastrointestinal helminths in grazing sheep – a field trial

Summary One of the alternative methods of parasite control, of particular importance in sustainable farming, is the use of medicinal plants. The specific aim of the present field trial was to assess the anti-parasitic effects of herbal extracts contained in a commercially available lick formulation for sheep. At the outset of this study conducted during the grazing season, all animals were de-wormed and then randomly assigned to one of the two separately kept groups (treatment and control), each consisting of 25 animals (11 ewes and 14 lambs). The treatment group received mineral licks containing the extracts of the plants with anti-parasitic properties, while control animals received standard mineral licks ad libitum. Rectal fecal samples were collected monthly from all animals for the McMaster analyses. There were no significant differences in the prevalence and intensity of helminth infections between the treatment and control groups. Thus, we were not able to ascertain the efficacy of the commercial herbal de-wormer tested for the control of gastrointestinal helminths in grazing ewes and their lambs.

Markov Model Predicts Changes in STH Prevalence during Control Activities Even with a Reduced Amount of Baseline Information.

BackgroundEstimating the reduction in levels of infection during implementation of soil-transmitted helminth (STH) control programmes is important to measure their performance and to plan interventions. Markov modelling techniques have been used with some success to predict changes in STH prevalence following treatment in Viet Nam. The model is stationary and to date, the prediction has been obtained by calculating the transition probabilities between the different classes of intensity following the first year of drug distribution and assuming that these remain constant in subsequent years. However, to run this model longitudinal parasitological data (including intensity of infection) are required for two consecutive years from at least 200 individuals. Since this amount of data is not often available from STH control programmes, the possible application of the model in control programme is limited. The present study aimed to address this issue by adapting the existing Markov model to allow its application when a more limited amount of data is available and to test the predictive capacities of these simplified models.MethodWe analysed data from field studies conducted with different combination of three parameters: (i) the frequency of drug administration; (ii) the drug distributed; and (iii) the target treatment population (entire population or school-aged children only). This analysis allowed us to define 10 sets of standard transition probabilities to be used to predict prevalence changes when only baseline data are available (simplified model 1). We also formulated three equations (one for each STH parasite) to calculate the predicted prevalence of the different classes of intensity from the total prevalence. These equations allowed us to design a simplified model (SM2) to obtain predictions when the classes of intensity at baseline were not known. To evaluate the performance of the simplified models, we collected data from the scientific literature on changes in STH prevalence during the implementation of 26 control programmes in 16 countries. Using the baseline data observed, we applied the simplified models and predicted the onward prevalence of STH infection at each time-point for which programme data were available. We then compared the output from the model with the observed data from the programme.ResultsThe comparison between the model-predicted prevalence and the observed values demonstrated a good accuracy of the predictions. In 77% of cases the original model predicted a prevalence within five absolute percentage points from the observed figure, for the simplified model one in 69% of cases and for the simplified model two in 60% of cases. We consider that the STH Markov model described here could be an important tool for programme managers to monitor the progress of their control programmes and to select the appropriate intervention. We also developed, and made freely available online, a software tool to enable the use of the STH Markov model by personnel with limited knowledge of mathematical models.

Cost-effectiveness of scaling up mass drug administration for the control of soil-transmitted helminths: a comparison of cost function and constant costs analyses

The coverage of mass drug administration (MDA) for neglected tropical diseases, such as the soil-transmitted helminths (STHs), needs to rapidly expand to meet WHO's 2020 targets. We aimed to compare use of a cost function to take into account economies of scale to the standard method of assuming a constant cost per treatment when investigating the cost and cost-effectiveness of scaling up a STH MDA programme targeting Ascaris lumbricoides. We fitted a cost function describing how the costs of MDA change with scale to empirical cost data and incorporated it into a STH transmission model. Using this cost function, we investigated the consequences of taking into account economies of scale on the projected cost-effectiveness of STH control, by comparison with the standard method of assuming a constant cost per treatment. The cost function was fitted to economic cost data collected as part of a school-based deworming programme in Uganda using maximum likelihood methods. We used the model to investigate the total reduction in the overall worm burden, the total number of prevalent infection case-years averted, and the total number of heavy infection case-years averted. For each year, we calculated the effectiveness as the difference between the worm burden or number of cases and the number in absence of treatment. When using the cost function, the cost-effectiveness of STH control markedly increased as the programme was scaled up. By contrast, the standard method (constant cost per treatment) undervalued this and generated misleading conclusions. For example, when scaling up control in the projected district from 10% to 75% coverage of at-risk school-age children, the cost-effectiveness in terms of prevention of heavy burden infections was projected to increase by over 70% when using the cost function, but decrease by 18% when assuming a constant cost per treatment. The current exclusion of economies of scale in most economic analyses must be addressed if the most cost-effective policies for the control of neglected tropical diseases are to be formulated. These findings are also relevant to other large-scale disease interventions. GlaxoSmithKline, Bill & Melinda Gates Foundation, Partnership for Child Development, and Wellcome Trust.

Studi Kajian Upaya Pemberian Obat Pencegah Masal Filariasis Terhadap Pengendalian Penyakit Infeksi Kecacingan

Abstract Filariasis and helminth infections are public health problem s in Indonesia. Starting in 2005, the Ministry of Health launched filariasis elimination by implementing preventive mass drug administration ( MDA ) or “POPM”. A t least as 65% of the population in the district /city are given diethyl carbamazine citrate (DEC) and combined with albendazole. With t he existence of this program , it is expected filariasis can be eliminated and worm infection s can be control ed . This study aims to determine the constraints and problems encountered in the implementation of filariasis elimination and helminth infections control. The method applied is a review of scientific article , policy inventory, discussions with experts and practitioners, as well as confirmation data in the field. This study known 233 districts/cities in Indonesia were endemic filariasis with mf rate average of 3.61 %, and the prevalence of helminth disease in 173 districts/cities with an average of 28.12%. Among the 233 districts/cities endemic filariasis, 104 districts/cities were also endemic helminth diseases ; and only 135 regencies/cities implement ed MDA filariasis. Within the 135 districts/cities reported to implement MDA filariasis , only 16 districts/cities actually executed MDA with prevalence of helminth infections above 30% ( MDA helminth requirement). Recommendation s is necessary to accelerate MDA filariasis in the district/city with endemic filariasis and also those with endemic helminth diseases above 30%.