What is the impact of acquired immunity on the transmission of schistosomiasis and the efficacy of current and planned mass drug administration programmes?

Schistosomiasis causes severe morbidity in many countries with endemic infection with the schistosome digenean parasites in Africa and Asia. To control and eliminate the disease resulting from infection, regular mass drug administration (MDA) is used, with a focus on school-aged children (SAC; 5–14 years of age). In some high transmission settings, the World Health Organization (WHO) also recommends the inclusion of at-risk adults in MDA treatment programmes. The question of whether ecology (age-dependant exposure) or immunity (resistance to reinfection), or some combination of both, determines the form of observed convex age-intensity profile is still unresolved, but there is a growing body of evidence that the human hosts acquire some partial level of immunity after a long period of repeated exposure to infection. In the majority of past research modelling schistosome transmission and the impact of MDA programmes, the effect of acquired immunity has not been taken into account. Past work has been based on the assumption that age-related contact rates generate convex horizontal age-intensity profiles. In this paper, we use an individual based stochastic model of transmission and MDA impact to explore the effect of acquired immunity in defined MDA programmes. Compared with scenarios with no immunity, we find that acquired immunity makes the MDA programme less effective with a slower decrease in the prevalence of infection. Therefore, the time to achieve morbidity control and elimination as a public health problem is longer than predicted by models with just age-related exposure and no build-up of immunity. The level of impact depends on the baseline prevalence prior to treatment (the magnitude of the basic reproductive number R0) and the treatment frequency, among other factors. We find that immunity has a larger impact within moderate to high transmission settings such that it is very unlikely to achieve morbidity and transmission control employing current MDA programmes.

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The impact of mass drug administration on Schistosoma haematobium infection: what is required to achieve morbidity control and elimination?

Parasites & Vectors ◽

10.1186/s13071-020-04409-3 ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Klodeta Kura ◽

Robert J. Hardwick ◽

James E. Truscott ◽

Jaspreet Toor ◽

T. Deirdre Hollingsworth ◽

...

Keyword(s):

Drug Administration ◽

Mass Drug Administration ◽

Schistosoma Haematobium ◽

Treatment Guidelines ◽

Public Health Problem ◽

Data Availability ◽

World Health ◽

Morbidity Control ◽

Health Organization ◽

The Impact

Abstract Background Schistosomiasis remains an endemic parasitic disease causing much morbidity and, in some cases, mortality. The World Health Organization (WHO) has outlined strategies and goals to combat the burden of disease caused by schistosomiasis. The first goal is morbidity control, which is defined by achieving less than 5% prevalence of heavy intensity infection in school-aged children (SAC). The second goal is elimination as a public health problem (EPHP), achieved when the prevalence of heavy intensity infection in SAC is reduced to less than 1%. Mass drug administration (MDA) of praziquantel is the main strategy for control. However, there is limited availability of praziquantel, particularly in Africa where there is high prevalence of infection. It is therefore important to explore whether the WHO goals can be achieved using the current guidelines for treatment based on targeting SAC and, in some cases, adults. Previous modelling work has largely focused on Schistosoma mansoni, which in advance cases can cause liver and spleen enlargement. There has been much less modelling of the transmission of Schistosoma haematobium, which in severe cases can cause kidney damage and bladder cancer. This lack of modelling has largely been driven by limited data availability and challenges in interpreting these data. Results In this paper, using an individual-based stochastic model and age-intensity profiles of S. haematobium from two different communities, we calculate the probability of achieving the morbidity and EPHP goals within 15 years of treatment under the current WHO treatment guidelines. We find that targeting SAC only can achieve the morbidity goal for all transmission settings, regardless of the burden of infection in adults. The EPHP goal can be achieved in low transmission settings, but in some moderate to high settings community-wide treatment is needed. Conclusions We show that the key determinants of achieving the WHO goals are the precise form of the age-intensity of infection profile and the baseline SAC prevalence. Additionally, we find that the higher the burden of infection in adults, the higher the chances that adults need to be included in the treatment programme to achieve EPHP.

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The Added Value of Water, Sanitation, and Hygiene Interventions to Mass Drug Administration for Reducing the Prevalence of Trachoma: A Systematic Review Examining

Journal of Environmental and Public Health ◽

10.1155/2013/682093 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 4

Author(s):

Anyess Travers ◽

Sheryl Strasser ◽

Stephanie L. Palmer ◽

Christine Stauber

Keyword(s):

Systematic Review ◽

Drug Administration ◽

Mass Drug Administration ◽

Added Value ◽

World Health ◽

Sanitation And Hygiene ◽

Pubmed Database ◽

Health Organization ◽

Hygiene Education ◽

The Impact

Trachoma is the leading cause of infectious blindness worldwide. The SAFE strategy, the World Health Organization-recommended method to eliminate blinding trachoma, combines developments in water, sanitation, surgery, and antibiotic treatment. Current literature does not focus on the comprehensive effect these components have on one another. The present systematic review analyzes the added benefit of water, sanitation, and hygiene education interventions to preventive mass drug administration of azithromycin for trachoma. Trials were identified from the PubMed database using a series of search terms. Three studies met the complete criteria for inclusion. Though all studies found a significant change in reduction of active trachoma prevalence, the research is still too limited to suggest the impact of the “F” and “E” components on trachoma prevalence and ultimately its effects on blindness.

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Lymphatic filariasis elimination endgame in an urban Indian setting: the roles of surveillance and residual microfilaremia after mass drug administration

Infectious Diseases of Poverty ◽

10.1186/s40249-021-00856-x ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Anjali Modi ◽

Keshav G. Vaishnav ◽

Kailash Kothiya ◽

Neal Alexander

Keyword(s):

High Risk ◽

Lymphatic Filariasis ◽

Drug Administration ◽

Mass Drug Administration ◽

Risk Groups ◽

Primary School Children ◽

World Health ◽

Urban Indian ◽

Indian Setting ◽

The Impact

Abstract Background To secure the gains of lymphatic filariasis (LF) elimination programs, attention is needed to the ‘residual microfilaremia phase’, in which high-risk populations may be crucial. The present study documents the impact of mass drug administration (MDA) in the urban Indian setting of Surat City, with high rates of in-migration. Methods Epidemiological assessment included National Filaria Control Program (NFCP) and World Health Organization recommended routine and pre-MDA microfilaremia surveys respectively. Routine filaria surveys were conducted around the year in approximately 2000–4000 people per month, while pre-MDA surveys were carried out annually among approximately 4000 people from four fixed and four random sites. In 2016, Transmission Assessment Survey (TAS) was done in primary school children. The outcomes were microfilaremia (Mf) and antigen prevalence; more specifically, microfilaremia according to place of birth, in pre-MDA and routine night blood smears (NBS) collected from 2008 to 2015. Prevalence ratios and confidence intervals were calculated. Results A total of 25 480 pre-MDA and 306 198 routine NBS were examined during the study. In 2008, the Mf prevalence in the routine survey was 63/18 814 (0.33%), declining to 23/39 717 (0.06%) in 2016. Pre-MDA surveys showed a similar decrease from 47/4184 (1.1%) in 2008 to 12/4042 (0.3%) in 2015. In those born outside Surat, microfilaremia decreased below transmission thresholds, but remained more than treble that of the remainder of the population, in both the pre-MDA surveys [prevalence ratio: 3.17, 95% confidence interval (CI): 1.15–8.72], and the routine surveys (3.31, 95% CI: 1.47–7.48). Though the TAS results indicated that MDA endpoints had been reached, sub-group analysis identified that 90% of antigenemic children were from families of high-risk groups. Conclusions Extensive long-term epidemiological monitoring suggests that all the urban population, including high-risk groups, have benefitted from the ELF program. To prevent re-establishment of infection in large urban areas with unsanitary conditions conducive to filarial vector breeding, there is need to identify residual microfilaremia by customized surveys in addition to pre-MDA monitoring and TAS. The present findings can be used to develop strategies to prioritize screening, surveillance and plan treatment of high-risk groups after achieving MDA endpoints.

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Modelling trachoma post 2020: Opportunities for mitigating the impact of COVID-19 and accelerating progress towards elimination

10.1101/2020.10.27.20219618 ◽

2020 ◽

Author(s):

Anna Borlase ◽

Seth Blumberg ◽

E Kelly Callahan ◽

Michael S Deiner ◽

Scott D Nash ◽

...

Keyword(s):

Public Health ◽

Mathematical Model ◽

Drug Administration ◽

Mass Drug Administration ◽

Health Problem ◽

Public Health Problem ◽

Appropriate Use ◽

Alternative Strategies ◽

The Impact

AbstractBackgroundThe COVID-19 pandemic has disrupted planned annual antibiotic mass drug administration (MDA) activities which have formed the cornerstone of the largely successful global efforts to eliminate trachoma as a public health problem.MethodsUsing a mathematical model we investigate the impact of interruption to MDA in trachoma-endemic settings. We evaluate potential measures to mitigate this impact and consider alternative strategies for accelerating progress in those areas where the trachoma elimination targets may not be achievable otherwise.ResultsWe demonstrate that for districts which were hyperendemic at baseline, or where the trachoma elimination thresholds have not already been achieved after 3 rounds of MDA, the interruption to planned MDA could lead to a delay greater than the duration of interruption. We also show that an additional round of MDA in the year following MDA resumption could effectively mitigate this delay. For districts where probability of elimination under annual MDA was already very low, we demonstrate that more intensive MDA schedules are needed to achieve agreed targets.ConclusionThrough appropriate use of additional MDA, the impact of COVID-19 in terms of delay to reaching trachoma elimination targets can be effectively mitigated. Additionally, more frequent MDA may accelerate progress towards 2030 goals.

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Current status of Schistosoma mansoni infection among previously treated rural communities in the Abbey and Didessa Valleys, Western Ethiopia: Implications for sustainable control

PLoS ONE ◽

10.1371/journal.pone.0247312 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0247312

Author(s):

Alemayehu Assefa ◽

Berhanu Erko ◽

Svein Gunnar Gundersen ◽

Girmay Medhin ◽

Nega Berhe

Keyword(s):

Public Health ◽

Schistosoma Mansoni ◽

Drug Administration ◽

Mass Drug Administration ◽

Health Problem ◽

Public Health Problem ◽

World Health ◽

Current Status ◽

Mass Treatment ◽

Western Ethiopia

Background Schistosoma constitutes a major public health problem and developmental challenges in the majority of developing and subtropical regions. The World Health Organization has set guidelines for the control and elimination of schistosomiasis. Ethiopia is providing school-based Mass Drug Administration (MDA) at the study areas of the Abbey and Didessa Valleys of western Ethiopian since 2015. Moreover, mass treatment was already done in the same villages 30 years ago. However, the current Schistosoma mansoni infection status among humans and snails in the study areas is not known. Hence, the present study aims to determine the current status. Methods A community-based cross-sectional study was conducted in the three communities; Chessega, Agallu Metti and Shimala in Schistosoma mansoni endemic areas of the Abbey and Didessa valleys in Western Ethiopia. Using the list of households obtained from the Kebele administration, a systematic sampling technique was used to select households in each village. Results Even though the area is under the Ethiopian national Mass Drug Administration campaign, the present study reports prevalence above 50%. Although the majority of the infections were moderate, we found that 13% had heavy infection, above 400 eggs per gram of stool, which is at the same level as before the treatment campaign 30 years ago. The infection was significantly higher among those below 12 years of age, among non-attending school-age children and daily laborers. Conclusion Schistosoma mansoni infection is still a public health problem in the study areas, despite control efforts already 30 years ago and present mass treatment in the last years. We suggest making the mass treatment campaign just early after the rainy season, when the snails are washed away. This should be supplemented with provisions of clean water, sanitation, and hygiene (WASH) and reduction of water contact and possible snail control efforts’ to prevent reinfection.

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Can direct smear results that are routinely collected at health centre level be used for monitoring the impact of mass drug administration with praziquantel on schistosomiasis in Burundi? A preliminary assessment

10.21203/rs.2.19785/v1 ◽

2019 ◽

Author(s):

Paul BIZIMANA ◽

Katja POLMAN ◽

Giuseppina ORTU ◽

Meryam KRIT ◽

Frédéric NSABIYUMVA ◽

...

Keyword(s):

Drug Administration ◽

Mass Drug Administration ◽

Negative Binomial ◽

Health Centre ◽

Public Health Problem ◽

Health Care Facilities ◽

Incidence Data ◽

School Based ◽

Intestinal Schistosomiasis ◽

The Impact

Abstract BackgroundIntestinal schistosomiasis is still a public health problem in Burundi. Since 2008, annual mass drug administration (MDA) with praziquantel have been rolled out in 11 endemic districts. The national programme relies on school based surveys with Kato-Katz (KK) to monitor the impact of MDA. We explored whether routine data on intestinal schistosomiasis as determined by direct fecal smears (DS) at health centre (HC) level could be used.MethodsWe collected routine incidence data on intestinal schistosomiasis from the Burundian National Health Information System. These data concerned the number of intestinal schistosomiasis cases as detected by DS examination in the HC of all 45 sanitary districts (SD) between 2011 and 2015. A temporal trends analysis was performed using mixed Negative Binomial regression. Sanitary districts with MDA campaigns with praziquantel (n=11) were compared with those without (n=34). In addition, KK-based prevalence data from a school-based national mapping in 2014 were compared with the DS-based incidence data in the 45 SD.ResultsIn the 11 SD applying MDA with praziquantel, the incidence rate decreased significantly for the years 2014 (β2014=-0.826, p=0.010) and 2015 (β2015=-1.294, p<0.001) and for the five-year period (β=-0.286, p<0.001), whereas in the 34 districts without MDA, there was no significant trend (β=-0.087, p=0.219). In most of the 45 SD, the low prevalences based on KK in school children were confirmed by low incidence rates based on DS in the HC.ConclusionsThe results of this preliminary study suggest that routine surveillance data at HC level, may be able to monitor the impact of MDA with praziquantel on intestinal schistosomiasis in Burundi. However, more sensitive POC diagnostic tests, such as the POC-CCA assay are desirable when moving from control to elimination of schistosomiasis. Elimination of intestinal schistosomiasis calls for integration of adequate diagnosis and treatment into routine activities of primary health care facilities.

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Modelling the ability of mass drug administration to interrupt soil-transmitted helminth transmission: Community-based deworming in Kenya as a case study

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0009625 ◽

2021 ◽

Vol 15 (8) ◽

pp. e0009625

Author(s):

Nyuk Sian Chong ◽

Stacey R. Smith? ◽

Marleen Werkman ◽

Roy M. Anderson

Keyword(s):

Drug Administration ◽

Mass Drug Administration ◽

Neglected Tropical Diseases ◽

Initial Conditions ◽

Drug Efficacy ◽

World Health ◽

High Prevalence ◽

Lower Drug ◽

Health Organization ◽

The Impact

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.

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The coverage and frequency of mass drug administration required to eliminate persistent transmission of soil-transmitted helminths

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2013.0435 ◽

2014 ◽

Vol 369 (1645) ◽

pp. 20130435 ◽

Cited By ~ 108

Author(s):

Roy Anderson ◽

James Truscott ◽

T. Deirdre Hollingsworth

Keyword(s):

Drug Administration ◽

Mass Drug Administration ◽

Cost Effective ◽

Epidemiological Data ◽

Basic Reproductive Number ◽

Reproductive Number ◽

Soil Transmitted Helminths ◽

School Aged Children ◽

Helminth Infections

A combination of methods, including mathematical model construction, demographic plus epidemiological data analysis and parameter estimation, are used to examine whether mass drug administration (MDA) alone can eliminate the transmission of soil-transmitted helminths (STHs). Numerical analyses suggest that in all but low transmission settings (as defined by the magnitude of the basic reproductive number, R 0 ), the treatment of pre-school-aged children (pre-SAC) and school-aged children (SAC) is unlikely to drive transmission to a level where the parasites cannot persist. High levels of coverage (defined as the fraction of an age group effectively treated) are required in pre-SAC, SAC and adults, if MDA is to drive the parasite below the breakpoint under which transmission is eliminated. Long-term solutions to controlling helminth infections lie in concomitantly improving the quality of the water supply, sanitation and hygiene (WASH). MDA, however, is a very cost-effective tool in long-term control given that most drugs are donated free by the pharmaceutical industry for poor regions of the world. WASH interventions, by lowering the basic reproductive number, can facilitate the ability of MDA to interrupt transmission.

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An assessment of coverage and adverse events following country-wide triple-therapy mass drug administration for lymphatic filariasis elimination, Samoa 2018

10.1101/2020.04.21.20072363 ◽

2020 ◽

Author(s):

Gabriela A. Willis ◽

Helen Mayfield ◽

Therese Kearns ◽

Take Naseri ◽

Robert Thomsen ◽

...

Keyword(s):

Adverse Events ◽

Lymphatic Filariasis ◽

Drug Administration ◽

Mass Drug Administration ◽

Total Population ◽

Public Health Problem ◽

Community Survey ◽

World Health ◽

Ministry Of Health ◽

The World

AbstractBackgroundThe Global Programme to Eliminate Lymphatic Filariasis is making considerable progress but has experienced challenges in meeting targets in some countries. Recent World Health Organization guidelines have recommended two rounds of triple-drug therapy with ivermectin, diethylcarbamazine (DEC), and albendazole (IDA), in areas where mass drug administration (MDA) results with two drugs (DEC and albendazole) have been suboptimal, as is the case in Samoa. In August 2018, Samoa was the first in the world to implement countrywide triple-drug MDA. This paper aims to describe Samoa’s experience with program coverage and adverse events (AEs) in the first round of triple-drug MDA.Methodology/Principal findingsWe assessed MDA awareness, reach, compliance, coverage and AEs from three different data sources: a Supervisor’s Coverage Tool (SCT) in three villages; a large cross-sectional community survey in September/October 2018, 7-11 weeks after the first round of triple-drug MDA; and AE surveillance conducted by the Ministry of Health, Samoa. Participants aged ≥5 years had a fingerprick blood sample tested for circulating filarial antigen using the Alere Filariasis Test Strip. Data were analysed descriptively. In our sample of 4420 people (2.2% of the population), age-adjusted estimates indicated that 89.0% of the eligible population were offered MDA and 80.2% of the total population took MDA. Mild AEs were reported by 13.3% and moderate/severe AEs by 2.9% of participants.Conclusions/SignificanceThis study following the 2018 triple-drug MDA in Samoa demonstrated a high reported program awareness and reach of 90.8% and 89.0%, respectively. Coverage of 80.2% of the total population showed that MDA was well accepted and well tolerated by the community.Author summaryLymphatic filariasis is a mosquito transmitted worm disease. A global program underway aims to eliminate lymphatic filariasis as a public health problem by distributing deworming drugs to the whole population once a year for at least five years. In some countries, including Samoa, this strategy has not been sufficient to eliminate transmission. A new drug has been added, and in 2018, Samoa was the first country in the world to apply triple drug mass drug administration using ivermectin, diethylcarbamazine, and albendazole. This study reports on the coverage achieved (percentage of people who reported taking the drugs) and adverse events after taking the drugs. Data were obtained from three different sources. A large community survey of over 4000 people, done 7-11 weeks after the distribution of the first round, found that the program reached and offered MDA to approximately 90% of the whole population, and approximately 80% of the whole population swallowed the drugs. Findings from the community survey on participation in the MDA program were consistent with those from the WHO recommended Supervisor’s Coverage Tool, a smaller survey which was undertaken in three villages by the Samoan Ministry of Health. Data on AEs related to MDA were collected during the community survey, and also through a system set up by the Ministry of Health to enable community members to report any problems related to MDA and receive advice on managing problems. There were relatively few adverse events reported and most of them were mild and of short duration.

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Modelling trachoma post-2020: opportunities for mitigating the impact of COVID-19 and accelerating progress towards elimination

Transactions of the Royal Society of Tropical Medicine and Hygiene ◽

10.1093/trstmh/traa171 ◽

2021 ◽

Author(s):

Anna Borlase ◽

Seth Blumberg ◽

E Kelly Callahan ◽

Michael S Deiner ◽

Scott D Nash ◽

...

Keyword(s):

Public Health ◽

Mathematical Model ◽

Drug Administration ◽

Mass Drug Administration ◽

Health Problem ◽

Public Health Problem ◽

Appropriate Use ◽

Alternative Strategies ◽

The Impact

Abstract Background The COVID-19 pandemic has disrupted planned annual antibiotic mass drug administration (MDA) activities that have formed the cornerstone of the largely successful global efforts to eliminate trachoma as a public health problem. Methods Using a mathematical model we investigate the impact of interruption to MDA in trachoma-endemic settings. We evaluate potential measures to mitigate this impact and consider alternative strategies for accelerating progress in those areas where the trachoma elimination targets may not be achievable otherwise. Results We demonstrate that for districts that were hyperendemic at baseline, or where the trachoma elimination thresholds have not already been achieved after three rounds of MDA, the interruption to planned MDA could lead to a delay to reaching elimination targets greater than the duration of interruption. We also show that an additional round of MDA in the year following MDA resumption could effectively mitigate this delay. For districts where the probability of elimination under annual MDA was already very low, we demonstrate that more intensive MDA schedules are needed to achieve agreed targets. Conclusion Through appropriate use of additional MDA, the impact of COVID-19 in terms of delay to reaching trachoma elimination targets can be effectively mitigated. Additionally, more frequent MDA may accelerate progress towards 2030 goals.

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