Elimination of lymphatic filariasis:Where do we stand so far?

Lymphatic filariasis(LF),an asymptomatic,acute,and chronic condition in human beings,is the second most common vector-borne disease after malaria.According to the World Health Organization,there are 120 million LF cases detected in 81 tropical and subtropical countries,and one billion people are at risk.Therefore,the Global Program to Eliminate Lymphatic Filariasis was launched in 2000,with the primary objective of stopping LF transmission among all at-risk groups using mass drug administration(MDA),managing morbidities,and preventing LF-related impairments using a minimum treatment package.Additionally,other programs such as epidemiological assessment including National Filaria Control Program and World Health Organization recommended routine and pre-MDA microfilaremia surveys also implemented to stop the LF transmission.The routine filaria surveys were also carried out in around 2000-4000 individuals/month throughout the year whereas pre-MDA surveys were also conducted every year in approximately 4000 individuals in four fixed and four random sites.Furthermore,the Transmission Assessment Survey was also conducted to check the risk of LF among primary school children.Moreover,potential diagnostic methods,systematic surveillance regimes,the Direct Network Report system,and regular trainings and awareness may be also effective in preventing the recurrence of LF.Hence,this review emphasizes the potential advocacy tools and various strategies as well as procedures for monitoring,which could be impactful in eliminating LF.

Expression and Evaluation of Wb-SXP-1 and Wb-123 Recombinant Antigens as Potential Diagnostic Biomarkers for Lymphatic Filariasis

Lymphatic filariasis (LF) remains a public health concern as it can cause permanent morbidity and disability to those infected. While the global elimination of LF in these endemic areas is ongoing through mass drug administration, there is the need to develop diagnostic tools that would be utilized to track the progress of total global eradication as well as perform surveillance for the recurrence of lymphatic filariasis transmission. Currently, approved LF diagnosis tools are faced with lack of specificity, low sensitivity, and periodicity dependence. Recombinant filarial antigen-based assays can address these drawbacks and offer practical instruments for LF diagnosis and surveillance. This present study, evaluated rWb-SXP-1 and rWb-123 antigens as potential diagnostic biomarker tools for Wuchereria banchrofti in human sera using microspheres-based multiplex serological assay. Based on statistical analysis using XLSTAT 2019 (Addinsoft) on data generated from multiplex technology assay, generated ROC curves for both rWb-SXP-1 and rWb-123 demonstrated 87.1% sensitivity to Wuchereria banchrofti human sera with rWb-SXP-1 antigens having the highest specificity of 96%. Indication that rWb-SXP-1 and rWb-123 antigens are capable of detecting immunoglobulin G4 (IgG4) antibodies in human sera synthesized specifically against W. banchrofti infections. Therefore, rWb-SXP-1 and rWb-123 antigens can be utilized to detect W. banchrofti infections by antibody profiling with excellent diagnostic sensitivity and specificity using microsphere-based multiplex serological tests. This method can be particularly practical for screening a large number of sera samples and/or for quick, extensive field-testing due to the high-throughput and quick formats applied.

Understanding gender and its intersection with social stratifiers on prevention and care seeking behavior of lymphatic filariasis in Nepal

BackgroundLymphatic filariasis (LF) is a debilitating and painful neglected tropical disease and is one of the leading causes of permanent disability. In many countries, the intersection of gender with various social stratifiers has influenced exposure to LF and ultimately impacting the disease burden and its elimination. This study aimed to explore the influence of gender and its intersection with other social stratifiers for the prevention and care seeking behavior of LF in Nepal.MethodsThis study employed qualitative research methods: in-depth interviews (IDIs) and focus group discussions (FGDs) for data collection in Bardiya, Nepal. A total of 22 IDIs (11 male, 11 female) and 2 FGDs (1 male and 1 female) were conducted with the community people between January and March 2020. The participants were purposively selected to represent different social stratifiers including age, sex, ethnicity, occupation. The data collected were analyzed using a thematic framework approach with use of intersectional gender analysis matrix.ResultsThe study findings revealed that men spend more time outside their household compared to women while fulfilling their roles and responsibilities, largely determined by societal expectations and gender norms. This resulted in limited access to preventive health services for men, as they often missed annual mass drug administration programme in their community and limited access to preventive methods. Further traditional occupation, specific to particular ethnicity, influenced the vulnerability to LF for certain ethnic groups. The ability to prevent exposure varied among individuals. Although women made decisions regarding the use of protective methods, it was influenced by patriarchal and gender norms. They often felt a responsibility to take care and priorities males and other family members when resources are limited. The intersectionality of gender with other social stratifiers such as marital status, ethnicity, and geographical areas influenced individual’s ability to access information related to LF and care seeking.ConclusionsOverall, the findings emphasized how access to resources, division of work, norms and values and decision-making power alone and its interaction with various social stratifiers shaped peoples’ vulnerability to disease, ability to prevent exposure and response to illness.

Five years of post-validation surveillance of lymphatic filariasis in Thailand

Background The World Health Organization (WHO) validated Thailand in 2017 as having eliminated lymphatic filariasis (LF) as a public health problem with recommendations for continued surveillance. This article describes measures and progress made in Thailand with post-validation surveillance (PVS) of LF from 2018 until 2022.Methods The implementation unit (IU) is a sub-village in 11 former LF endemic provinces. Human blood surveys are targeted in 10% of IUs each year. InWuchereria bancrofti areas, filaria antigen test strips (FTS) are used, and inBrugia malayi areas, antibody test kits (Filaria DIAG RAPID) are used. Positive cases are confirmed by thick blood film (TBF) and polymerase chain reaction (PCR). Vector surveys for mosquito species identification and dissection for microfilaria (Mf)/filarial larvae are done in 1% of IUs where human blood surveys are conducted. Human blood surveys using FTS are conducted among migrants in five provinces. Surveillance of cats is done in areas that previously recorded > 1.0% Mf rate among cats. Morbidity management and disability prevention (MMDP) are done every 2 years in LF-endemic areas where chronic disease patients reside.Results From 2018 to 2022, in a total of 357 IUs in 11 provinces, human blood surveys were conducted in 145 IUs (41%) with an average population coverage of 81%. A total of 22,468 FTS and 27,741 FilariaDIAG RAPID were performed. 27 cases were detected: 3 cases ofW. bancrofti in Kanchanaburi province and 24 cases ofB. malayi in Narathiwat province. 4 cases ofW. bancrofti were detected in two provinces through routine public health surveillance. Vector surveys in 47 IUs detectedB. malayi Mf filarial larvae only in Narathiwat province. Chronic LF patients reduced from 114 in 2017 to 76 in 2022. Surveys among 7633 unregistered migrants yielded 12 cases ofW. bancrofti. Mf rate among cats in Narathiwat province declined from 1.9% in 2018 to 0.7% in 2022. MMDP assessments revealed gaps in healthcare provider’s management of chronic cases due to staff turnover.Conclusions In 2022, after 5 years of PVS, Thailand re-surveyed 41% of its previously endemic IUs and demonstrated ongoing transmission in only one province of Narathiwat, where Mf prevalence is below the WHO provisional transmission threshold of 1%. This study highlights the importance of continued disease surveillance measures and vigilance among health care providers in LF receptive areas.

The history of the elimination of lymphatic filariasis in China

China used to be one of the most heavily endemic countries for lymphatic filariasis(LF)in the world.There were 864 endemic counties/cities in 16 provinces/autonomous regions/municipalities(P/A/M)with a total population of 330 million at risk of infection.Since the founding of the People’s Republic of China in 1949,the Chinese Government has designated the control of the disease to be a top priority.Due to decades of sustained efforts,close cooperation related to LF control among government departments,and active participation of endemic populations,an all-round campaign for prevention and control has been carried out vigorously and successfully.Over many years,great achievements have been made through persistent endeavors of Chinese scientists and disease control workers.The ultimate goal to eliminate LF in the country was achieved in 2006.

Lessons from lymphatic filariasis elimination and the challenges of post-elimination surveillance in China

Background:The Global Programme to Eliminate Lymphatic Filariasis(GPELF)was launched in response to the call proposed at the 50th World Health Assembly.The goal of the GPELF is to ensure that all the countries where the disease is endemic would have been transmission-free or would have entered post-intervention mass drug administration(MDA)surveillance by 2020.However,several countries are still not on track to discontinue MDA as planned.Thus,issues remain regarding the achievement of stated goals and how to effectively monitor the disease in the post-control and post-elimination phases.Main text:China was once a lymphatic filariasis(LF)endemic country with heavy disease burden.There were three milestones in the LF control phase of China,including:the proposal that the major focus of the control strategy should be on infectious sources;the three regimens of diethylcarbamazine(DEC)administration according to LF endemic extent;and the establishment of the threshold for LF transmission interruption.It has been ten years since China entered the post-elimination stage(declaration of LF elimination in China was in 2007).Two schemes and a diagnostic criterion were issued to guide all levels of disease control and prevention workers that conduct LF surveillance,as well as those caring for chronic filariasis patients.Regular training courses are held to maintain LF control skills in grass-root institutions.The Notifiable Diseases Reporting System,which included LF in 2004,plays an important role in LF post-elimination surveillance.Until now,no resurgence of LF cases has been detected,except for LF residue foci being found in Fuchuan County of the Guangxi Zhuang Autonomous Region.To confirm that transmission is no longer achievable after a decade since the declaration of LF elimination in China,it is expected within the next two years a transmission assessment survey,conducted in previous LF-endemic areas.Conclusions:DEC-fortified salt can help accelerate the progress of GPELF before the sprite phase.Sophisticated diagnostic criteria,systematic surveillance regimes,the Direct Network Report system,and regular trainings can effectively prevent the recrudescence of LF during surveillance phases.

Lymphatic filariasis, infection status in Culex quinquefasciatus and Anopheles species after six rounds of mass drug administration in Masasi District, Tanzania

Background:Lymphatic filariasis(LF)elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020.Evidence shows a persistent LF transmission despite more than a decade of mass drug administration(MDA).It is advocated that,regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely.This study was therefore designed to assess the status of Wuchererio bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District,South Eastern Tanzania.

Potential factors influencing lymphatic filariasis transmission in"hotspot"and"control"areas in Ghana:the importance of vectors

Background:Mass drug administration(MDA)programmes for the control of lymphatic filariasis in Ghana,have been ongoing in some endemic districts for 16 years.The current study aimed to assess factors that govern the success of MDA programmes for breaking transmission of lymphatic filariasis in Ghana.Methods:The study was undertaken in two"hotspot"districts(Ahanta West and Kassena Nankana West)and two control districts(Mpohor and Bongo)in Ghana.Mosquitoes were collected and identified using morphological and molecular tools.A proportion of the cibarial armatures of each species was examined.Dissections were performed onAnopheles gambiae for filarial worm detection.A questionnaire was administered to obtain information on MDA compliance and vector control activities.Data were compared between districts to determine factors that might explain persistent transmission of lymphatic filariasis.Results:High numbers of mosquitoes were sampled in Ahanta West district compared to Mpohor district(F=16.09,P=0.002).There was no significant difference between the numbers of mosquitoes collected in Kassena Nankana West and Bongo districts(F=2.16,P=0.185).Mansonia species were predominant in Ahanta West district.An.coluzzii mosquitoes were prevalent in all districts.An.melas with infected and infective filarial worms was found only in Ahanta West district.No differences were found in cibarial teeth numbers and shape for mosquito species in the surveyed districts.Reported MDA coverage was high in all districts.The average use of bednet and indoor residual spraying was 82.4 and 66.2%,respectively.There was high compliance in the five preceding MDA rounds in Ahanta West and Kassena Nankana West districts,both considered hotspots of lymphatic filariasis transmission.Conclusions:The study on persistent transmission of lymphatic filariasis in the two areas in Ghana present information that shows the importance of local understanding of factors affecting control and elimination of lymphatic filariasis.Unlike Kassena Nankana West district where transmission dynamics could be explained by initial infection prevalence and low vector densities,ongoing lymphatic filariasis transmission in Ahanta West district might be explained by high biting rates ofAn.gambiae and initial infection prevalence,coupled with high densities ofAn.melas andMansonia vector species that have low or no teeth and exhibiting limitation.

The fight against lymphatic filariasis:perceptions of community drug distributors during mass drug administration in coastal Kenya

Background:Lymphatic filariasis(LF)#a neglected tropical disease(NTD)and leading cause of global disability,is endemic in 32 countries in Africa with almost 350 million people requiring regular drug administration,and only 16 countries achieving target coverage.Community Drug Distributors(CDDs)are critical for the success of NTD programs,and the distribution of medicines during mass drug administration(MDA)in Africa;however they could also be a weak link.The primary aim of this study is to explore and describe perceptions of CDDs during MDA for LF in Mvita sub-county in Mombasa county and Kaloleni sub-county in Kilifi county,Kenya;and provide recommendations for the effective engagement of communities and CDDs in low-resource settings.Methods:In September 2018,we conducted six focus group discussions with community members in each sub-county,three with men aged 18-30,31-50,and 51 years and above and three with women stratified into the same age groups.In each sub-county,we also conducted semi-struaured interviews with nine community health extension workers(CHEWs),the national LF focal point,the county NTD focal points,and seven community leaders.Content analysis of the data was conducted,involving a process of reading,coding,and displaying data in order to develop a codebook.Results:We found that several barriers and facilitators impact the engagement between CDDs and community members during MDA.These barriers include poor communication and trust between CDDs and communities;community distrust of the federal government;low community knowledge and perceived risk of LF,poor timing of MDA,fragmented supervision of CDDs during MDA;and CDD bias when distributing medicines.We also found that CDD motivation was a critical factor in their ability to successfully meet MDA targets.It was acknowledged that directly observed treatment and adequate health education were often not executed by CDDs.The involvement of community leaders as informal supervisors of CDDs and community members improves MDA.Conclusions:In order to achieve global targets around the elimination of LF,CDDs and communities must be effectively engaged by improving planning and implementation of MDA.

How elimination of lymphatic filariasis as a public health problem in the Kingdom of Cambodia was achieved

Background:Endemicity of lymphatic filariasis(LF)in Cambodia was proven in 1956 when microfilariae were detected in mosquitos in the Kratiéprovince.In 2001,an extensive study confirmed the presence of both Brugia malayi and Wuchereria bancrofti microfilariae.In 2003,the Ministry of Health established a national task force to develop policies and strategies for controlling and eliminating neglected tropical diseases(NTDs),with the goal of eliminating LF by 2015.This article summarizes the work accomplished to eliminate LF as a public health problem in Cambodia.Methods:The National Program to Eliminate Lymphatic Filariasis made excellent progress in the goal towards elimination due to strong collaboration between ministries,intensive supervision by national staff,and advocacy for mobilization of internal and external resources.Mass drug administration(MDA)with diethylcarbamazine citrate and albendazole was conducted in six implementation units,achieving>70%epidemiological coverage for five consecutive rounds,from 2005 to 2009.In 2006,in 14 provinces,healthcare workers developed a line list of lymphedema and hydrocele patients,many of whom were>40 years old and had been affected by LF for many years.The national program also trained healthcare workers and provincial and district staff in morbidity management and disability prevention,and designated health centers to provide care for lymphedema and acute attack.Two reference hospitals were designated to administer hydrocele surgery.Results:Effectiveness of MDA was proven with transmission assessment surveys.These found that less than 1%of school children had antigenemia in 2010,which fell to 0%in both 2013 and 2015.A separate survey in one province in 2015 using Brugia Rapid tests to test for LF antibody found one child positive among 1677 children.The list of chronic LF patients was most recently updated and confirmed in 2011-2012,with 32 lymphoedema patients and 17 hydrocele patients listed.All lymphedema patients had been trained on self-management and all hydrocele patients had been offered free surgery.Conclusions:Due to the success of the MDA and the development of health center capacity for patient care,along with benefits gained from socioeconomic improvements and other interventions against vector-borne diseases and NTDs,Cambodia was validated by the World Health Organization as achieving LF elimination as a public health problem in 2016.

Mass drug administration for lymphatic filariasis elimination in a coastal state of India: a study on barriers to coverage and compliance

Background:Lymphatic filariasis is targeted for elimination in India through mass drug administration(MDA)with diethylcarbamazine(DEC)combined with albendazole(ABZ).For the strategy to be effective,>65%of those living in endemic areas must be covered by and compliant to MDA.Post the MDA 2011 campaign in the endemic district of Odisha,we conducted a survey to assess:(i)the filariasis knowledge in the community,(ii)the coverage and compliance of MDA from the community perspective,and(iii)factors affecting compliance,as well as the operational issues involved in carrying out MDA activities from the drug distributor’s perspective.Methods:A sample of 691 participants-both male and female,aged two years or above-were selected through multistage stratified sampling and interviewed using a semi-structured questionnaire.Additionally,drug distributors and the medical officers in charge of the MDA were also interviewed to understand some of the operational issues encountered during MDA.Results:Ninety-nine percent of the study participants received DEC and ABZ tablets during MDA,of which only just above a quarter actually consumed the drugs.The cause of non-compliance was mostly due to fear of side effects,lack of awareness of the benefits of MDA,and non-attendance of health staff in the villages.Lack of adequate training of drug distributors and poor health communication activities before the MDA campaign commenced and the absence of follow-up by health workers following MDA were a few of the operational difficulties encountered during the MDA campaign.Conclusion:Currently MDA is restricted to the distribution of drugs only and the key issues of implementation in compliance,health education,managing side effects,and logistics are not given enough attention.It is therefore essential to address the issues linked to low compliance to make the program more efficient and achieve the goal of filariasis elimination.

How Thailand eliminated lymphatic filariasis as a public health problem

Background:Lymphatic filariasis is endemic in nine of the eleven Member States of the World Health Organization South East Asia Region.This article describes the intensive interventions with the National Programme for Elimination of Lymphatic Filariasis in Thailand since its launch in 2001 till the validation of its elimination in 2017.Methods:A baseline epidemiological survey was initiated in 2001 to identify both brugian and bancroftian filarial areas and delineate its endemicity.Mass drug administration(MDA)with diethylcarbamazine citrate(DEC)and albendazole(ALB)was implemented in a total of 357 implementation units(IUs)in 11 lymphatic filariasis(LF)endemic provinces.The implementing unit(IU)was a sub-village.Stop-MDA surveys were conducted in 2006 in the 11 LF endemic provinces among population over 6 years of age and children of≤6 years using immunochromatographic test(ICT)for Wuchererio bancrofti antigen and microfilariae(mf)detection for Brugia maloyi.In Narathiwat province,Stop-MDA surveys were done in 2011 using ELISA.Transmission assessment surveys(TAS)were conducted in 2012-2013,2015 and 2016-2017 among school students in the 6-7-year age-group.Surveillance of migrant populations through the national migrant health checkup were intensified in seven provinces over 2002-2017 for LF antigenaemia using ICT test cards.In four B.m oloyi endemic provinces,annual surveys to detect LF reservoir in domestic cats commenced in 1994.A 2001 survey of the chronic disease burden for LF established a register of the cumulative number of people with lymphedema/elephantiasis.Results:A total of five rounds of MDA annually were implemented over 2002-2006 in all Ills.Additional annual rounds of MDA were required in 87 Ills of Narathiwat province from 2007 to 2011 due to persistent infection.The annual national drug coverage with MDA over 2002-2012 was in the range of 68.0 to 95.4%.Stop-MDA surveys in 2006 in the 11 LF endemic provinces found nine mf positive cases in seven Ills in Narathiwat province with the highest prevalence of 0.8%(range:0.1-0.8%).In Narathiwat TAS-1,TAS-2 and TAS-3 detected below transmission threshold rates for B.m oloyi mf among antibody positive children(0.3,0.2 and 0.7%respectively).Contact tracing both all mf cases in all three TAS yielded no positive cases.Through the migrant health checkup,a total of 23477 persons were tested,showing a positive rate of 0.7%(range:0.1-2.7%)over years 2002-2017.In Narathiwat province,annual ivermectin treatment among cats commenced in 2003 resulting in a decline of mf prevalence among cats from 8.0%in 1995 to 0.8%in 2015.As of April 2011,a total of 99 lymphoedema/elephantiasis patients were registered and followed-up under 34 health facilities.Conclusions:Thailand over the years 2002 to 2011 conducted extensive MDA with high coverage rates.Through periodic and regular monitoring surveys it delineated LF transmission areas at sub-village level and demonstrated through its evaluation surveys-the Stop-MDA surveys and TAS,below transmission threshold rates that enabled its validation of LF elimination.In September 2017,World Health Organization acknowledged the Ministry of Health Thailand had eliminated lymphatic filariasis as a public health problem.

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

Background:To secure the gains of lymphatic filariasis(LF)elimination programs,attention is needed to the Yesidual 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.

The health and economic benefits of the global programme to eliminate lymphatic filariasis (2000–2014)

Background:Lymphatic filariasis(LF),also known as elephantiasis,is a neglected tropical disease(NTD)targeted for elimination through a Global Programme to Eliminate LF(GPELF).Between 2000 and 2014,the GPELF has delivered 5.6 billion treatments to over 763 million people.Updating the estimated health and economic benefits of this significant achievement is important in justifying the resources and investment needed for eliminating LF.Method:We combined previously established models to estimate the number of clinical manifestations and disability-adjusted life years(DALYs)averted from three benefit cohorts(those protected from acquiring infection,those with subclinical morbidity prevented from progressing and those with clinical disease alleviated).The economic savings associated with this disease prevention was then analysed in the context of prevented medical expenses incurred by LF clinical patients,potential income loss through lost-labour,and prevented costs to the health system to care for affected individuals.The indirect cost estimates were calculated using the human capital approach.A combination of four wage sources was used to estimate the fair market value of time for an agricultural worker with LF infection(to ensure a conservative estimate,the lowest wage value was used).Results:We projected that due to the first 15 years of the GPELF 36 million clinical cases and 175(116–250)million DALYs will potentially be averted.It was estimated that due to this notable health impact,US$100.5 billion will potentially be saved over the lifetimes of the benefit cohorts.This total amount results from summing the medical expenses incurred by LF patients(US$3 billion),potential income loss(US$94 billion),and costs to the health system(US$3.5 billion)that were projected to be prevented.The results were subjected to sensitivity analysis and were most sensitive to the assumed percentage of work hours lost for those suffering from chronic disease(changing the total economic benefit between US$69.30–150.7 billion).Conclusions:Despite the limitations of any such analysis,this study identifies substantial health and economic benefits that have resulted from the first 15 years of the GPELF,and it highlights the value and importance of continued investment in the GPELF.

The burden of mental health in lymphatic filariasis

Background:Neglected Tropical Diseases(NTDs)afflict around one billion individuals in the poorest parts of the world with many more at risk.Lymphatic filariasis is one of the most prevalent of the infections and causes significant morbidity in those who suffer the clinical conditions,particularly lymphedema and hydrocele.Depressive illness has been recognised as a prevalent disability in those with the disease because of the stigmatising nature of the condition.No estimates of the burden of depressive illness of any neglected tropical disease have been undertaken to date despite the recognition that such diseases have major consequences for mental health not only for patients but also their caregivers.Methods:We developed a mathematical model to calculate the burden of Disability-Adjusted Life Years(DALY)attributable to depressive illness in lymphatic filariasis and that of their caregivers using standard methods for calculating DALYs.Estimates of numbers with clinical disease was based on published estimates in 2012 and the numbers with depressive illness from the available literature.Results:We calculated that the burden of depressive illness in filariasis patients was 5.09 million disability-adjusted life years(DALYs)and 229,537 DALYs attributable to their caregivers.These figures are around twice that of 2.78 million DALYs attributed to filariasis by the Global Burden of Disease study of 2010.Conclusions:Lymphatic filariasis and other neglected tropical diseases,notably Buruli Ulcer,cutaneous leishmaniasis,leprosy,yaws,onchocerciasis and trachoma cause significant co morbidity associated with mental illness in patients.Studies to assess the prevalence of the burden of this co-morbidity should be incorporated into any future assessment of the Global Burden of neglected tropical diseases.The prevalence of depressive illness in caregivers who support those who suffer from these conditions is required.Such assessments are critical for neglected tropical diseases which have such a huge global prevalence and thus will contribute a significant burden of co-morbidity attributable to mental illness.

Prevalence of malaria and lymphatic filariasis in bateyes of the Dominican Republic

Background:The island of Hispaniola,shared by Haiti and the Dominican Republic(DR),is the only remaining malaria-endemic island in the Caribbean and accounts for 95%of the lymphatic filariasis(LF)burden in the Americas.Both countries aim to eliminate the diseases by 2020.Migration from Haiti,where both diseases are more prevalent,may promote transmission in the DR.Historically,Haitian migrant labourers live in rural Dominican agricultural'company towns'called boteyes,many of which received mass drug administration(MDA)for LF elimination.This study sought to determine the prevalence of malaria and LF in bateyes of the DR and to describe related risk faaors for disease.Methods:From March to April 2016,a cross-seaional,cluster survey was conduaed across Dominican boteyes stratified into three regions:southwest,north and east.A household questionnaire(n=776),captured demographics,ethnic origin,mobility patterns,malaria intervention coverage,and knowledge,and recent fever and treatment-seeking.Two individuals per household(n=1418)were tested for malaria parasites by microscopy and rapid diagnostic test(RDT)and LF antigen by filariasis test strip(FTS).Population-level estimates and confidence intervals(Cl)were computed adjusting for the survey design.Two-sided Hests compared differences in knowledge scores.Results:No(0%)blood sample was Plosm odium-positw e by microscopy or RDT.Six individuals were FTS-positive(0.5%;95%CI:0.2-1.5),but none(0%)of these were microfllariae-positive.Most botey residents were born in the DR(57.8%),documented(85.0%),and permanent residents(85.1%).Very few respondents(9.4%)reported travel to Haiti in the past year.Overall,half(53.8%)of respondents owned a bed net,and 82.3%of net owners reported using it the previous night.Indoor residual spraying(IRS)differed by region(range:4.7%-61.2%).Most of those with recent fever sought care(56.0%),yet only 30.5%of those seeking care were tested for malaria.Compared to Dominican-born populations,Haitian-born respondents more frequently reported recent fever,did not seek care for the fever,had not heard of malaria,and could not name symptoms or prevention methods.Conclusions:Malaria and LF transmission appear absent or extremely low in Dominican bateyes,which are a mixture of Haitian and Dominican residents.Travel to Haiti is rare,meaning risk of malaria and LF importation is low.Addressing identified gaps in intervention coverage,malaria knowledge,treatment seeking and service delivery will improve the quality of surveillance for these diseases,particularly among marginalized populations and promote island-wide elimination.

PROGRESS IN LYMPHATIC FILARIASIS CONTROL IN CHINA

Lymphatic filariasis (bancroftian filariasis and malayan filariasis)is one of the major parasitic diseases in China.It is distributed in 15 provinces.

Exploring the dynamic complexity of risk factors for vector-borne infections in sub-Saharan Africa:Case of urban lymphatic filariasis

Dynamic complexity is often a characteristic of public health issues;to visualize these problems as a system rather than isolated elements,system dynamics modeling may be an appropriate tool.The dynamic complexity of risk factors for lymphatic filariasis(LF)as an urban vector-borne disease has been addressed using system dynamics methodology.Some causal loop diagrams(CLDs)were designed to display the network of interactions of risk factors for urban transmission of LF and a potential set of public health interventions.A stock and flow diagram was also designed to capture the transmission dynamics as an accumulation and flow system,and a simulation model was built and executed.The system dynamics(SD)methodology is suitable for addressing the dynamic complexity of risk factors for LF in urban settings and is well-suited for public health interventions.

Mapping and modelling the impact of mass drug adminstration on filariasis prevalence in Myanmar

Background:Lymphatic filariasis(LF)is endemic in Myanmar and targeted for elimination.To highlight the National Programme to Eliminate Lymphatic Filariasis(NPELF)progress between 2000 and 2014,this paper describes the geographical distribution of LF,the scale-up and impact of mass drug administration(MDA)implementation,and the first evidence of the decline in transmission in five districts.Methods:The LF distribution was determined by mapping historical and baseline prevalence data collected by NPELF.Data on the MDA implementation,reported coverage rates and sentinel site surveillance were summarized.A statistical model was developed from the available prevalence data to predict prevalence at township level by year of measurement.Transmission assessment survey(TAS)methods,measuring antigenemia(Ag)prevalence in children,were used to determine whether prevalence was below a level where recrudescence is unlikely to occur.Results:The highest baseline LF prevalence was found in the Central Valley region.The MDA implementation activities scaled up to cover 45 districts,representing the majority of the endemic population,with drug coverage rates ranging from 60.0%to 98.5%.Challenges related to drug supply and local conflict were reported,and interrupted MDA in some districts.Overall,significant reductions in LF prevalence were found,especially after the first 2 to 3 rounds of MDA,which was supported by the corresponding model.The TAS activities in five districts found only two Ag positive children,resulting in all districts passing the critical threshold.Conclusion:Overall,the Myanmar NPELF has made positive steps forward in the elimination of LF despite several challenges,however,it needs to maintain momentum,drawing on international stakeholder support,to aim towards the national and global goals of elimination.

Killing filarial nematode parasites: role of treatment options and host immune response

Background:There is compelling evidence that not only do anti-filarials significantly reduce larval forms,but that host immune responses also contribute to the clearance of filarial parasites;however,the underlying mechanisms have not been fully elucidated.Main text:Filarial infections caused by Wuchereria bancrofti and Brugia species(lymphatic filariasis)and Onchocerca volvulus(onchocerciasis)affect almost 200 million individuals worldwide and pose major public health challenges in endemic regions.Indeed,the collective disability-adjusted life years for both infections is 3.3 million.Infections with these thread-like nematodes are chronic and,although most individuals develop a regulated state,a portion develop severe forms of pathology.Mass drug administration(MDA)programmes on endemic populations focus on reducing prevalence of people with microfilariae,the worm's offspring in the blood,to less than 1%.Although this has been successful in some areas,studies show that MDA will be required for longer than initially conceived.Conclusion:This paper highlights the mode of action of the various antifilarial treatment strategies and role of host immune response.