Lymphatic Filariasis Transmission Research Articles

Progress towards elimination of lymphatic filariasis in the Eastern Mediterranean Region.

Lymphatic filariasis (LF), a neglected tropical disease, is targeted for global elimination as a public health problem. This article reviews the history of LF control and elimination activities in the countries of the World Health Organization's (WHO) Eastern Mediterranean Region (EMR) over the last 2 decades. In 2000, the estimated at-risk population in EMR countries was 12.6 million people, accounting for approximately 1% of the global disease burden. Of the 22 EMR countries, 3 countries (Egypt, Sudan and Yemen) were LF endemic and the disease was suspected in 4 other countries (Djibouti, Oman, Somalia and Saudi Arabia). After almost 2 decades of implementing sustained control and prevention measures, Egypt and Yemen were successfully validated by the WHO as having achieved the elimination criteria in 2017 and 2019, respectively. In 2018, Sudan completed mapping of LF, reaching 26.2% geographical coverage where mass drug administration (MDA) is required and is scaling-up MDA. Extensive epidemiological assessment indicated the absence of LF transmission in the four suspected countries and no MDA required. Challenges faced during the elimination and post-elimination phases are described and discussed.

Progress towards elimination of lymphatic filariasis in the Americas region.

In South and Central America, lymphatic filariasis (LF) is caused by Wuchereria bancrofti, which is transmitted by Culex quinquefasciatus, the only vector species in this region. Of the seven countries considered endemic for LF in the Americas in the last decade, Costa Rica, Suriname and Trinidad and Tobago were removed from the World Health Organization list in 2011. The remaining countries, Brazil, Dominican Republic, Guyana and Haiti, have achieved important progress in recent years. Brazil was the first country in the Americas to stop mass drug administration (MDA) and to establish post-MDA surveillance. Dominican Republic stopped MDA in all LF-endemic foci: La Ciénaga and Southwest passed the third Transmission Assessment Survey (TAS) and the Eastern focus passed TAS-1 in 2018. Haiti passed the TAS and interrupted transmission in >80% of endemic communes, achieving effective drug coverage. Guyana implemented effective coverage in MDAs in 2017 and 2018 and in 2019 scaled up the treatment for 100% of the geographical region, introducing ivermectin in the MDA in order to achieve LF elimination by the year 2026. The Americas region is on its way to eliminating LF transmission. However, efforts should be made to improve morbidity management to prevent disability of the already affected populations.

Lymphatic filariasis epidemiology in Samoa in 2018: Geographic clustering and higher antigen prevalence in older age groups.

Samoa conducted eight nationwide rounds of mass drug administration (MDA) for lymphatic filariasis (LF) between 1999 and 2011, and two targeted rounds in 2015 and 2017 in North West Upolu (NWU), one of three evaluation units (EUs). Transmission Assessment Surveys (TAS) were conducted in 2013 (failed in NWU) and 2017 (all three EUs failed). In 2018, Samoa was the first in the world to distribute nationwide triple-drug MDA using ivermectin, diethylcarbamazine, and albendazole. Surveillance and Monitoring to Eliminate LF and Scabies from Samoa (SaMELFS Samoa) is an operational research program designed to evaluate the effectiveness of triple-drug MDA on LF transmission and scabies prevalence in Samoa, and to compare the usefulness of different indicators of LF transmission. This paper reports results from the 2018 baseline survey and aims to i) investigate antigen (Ag) prevalence and spatial epidemiology, including geographic clustering; ii) compare Ag prevalence between two different age groups (5-9 years versus ≥10 years) as indicators of areas of ongoing transmission; and iii) assess the prevalence of limb lymphedema in those aged ≥15 years. A community-based cluster survey was conducted in 30 randomly selected and five purposively selected clusters (primary sampling units, PSUs), each comprising one or two villages. Participants were recruited through household surveys (age ≥5 years) and convenience surveys (age 5-9 years). Alere Filariasis Test Strips (FTS) were used to detect Ag, and prevalence was adjusted for survey design and standardized for age and gender. Adjusted Ag prevalence was estimated for each age group (5-9, ≥10, and all ages ≥5 years) for random and purposive PSUs, and by region. Intraclass correlation (ICC) was used to quantify clustering at regions, PSUs, and households. A total of 3940 persons were included (1942 children aged 5-9 years, 1998 persons aged ≥10 years). Adjusted Ag prevalence in all ages ≥5 years in randomly and purposively selected PSUs were 4.0% (95% CI 2.8-5.6%) and 10.0% (95% CI 7.4-13.4%), respectively. In random PSUs, Ag prevalence was lower in those aged 5-9 years (1.3%, 95% CI 0.8-2.1%) than ≥10 years (4.7%, 95% CI 3.1-7.0%), and poorly correlated at the PSU level (R-square = 0.1459). Adjusted Ag prevalence in PSUs ranged from 0% to 10.3% (95% CI 5.9-17.6%) in randomly selected and 3.8% (95% CI 1.3-10.8%) to 20.0% (95% CI 15.3-25.8%) in purposively selected PSUs. ICC for Ag-positive individuals was higher at households (0.46) compared to PSUs (0.18) and regions (0.01). Our study confirmed ongoing transmission of LF in Samoa, in accordance with the 2017 TAS results. Ag prevalence varied significantly between PSUs, and there was poor correlation between prevalence in 5-9 year-olds and older ages, who had threefold higher prevalence. Sampling older age groups would provide more accurate estimates of overall prevalence, and be more sensitive for identifying residual hotspots. Higher prevalence in purposively selected PSUs shows local knowledge can help identify at least some hotspots.

Genetic epidemiology of lymphatic filariasis in American Samoa after mass drug administration

Over 892 million people in 48 countries are at risk of infection by nematodes that cause lymphatic filariasis. As part of the Global Programme to Eliminate Lymphatic Filariasis, mass drug administration is distributed to communities until surveillance indicates infection rates are below target prevalence thresholds. In some countries, including American Samoa, lymphatic filariasis transmission persists despite years of mass drug administration and/or has resurged after cessation. Nothing is known about the population genetics of Wuchereria bancrofti worms in Polynesia, or whether local transmission is persisting and/or increasing due to inadequate mass drug administration coverage, expansion from residual hotspots, reintroduction from elsewhere, or a combination. We extracted DNA from microfilariae on blood slides collected during prevalence surveys in 2014 and 2016, comprising 31 pools of five microfilariae from 22 persons living in eight villages. We sequenced 1104 bp across three mitochondrial markers (ND4, COI, CYTB). We quantified parasite genetic differentiation using variant calls and estimated haplotypes using principal components analysis, F-statistics, and haplotype networks. Of the variants called, all but eight were shared across the main island of Tutuila, and three of those were from a previously described hotspot village, Fagali’i. Genotypic data did not support population genetic structure among regions or villages in 2016, although differences were observed between worms collected in Fagali’i in 2014 and those from 2016. Because estimated haplotype frequency varied between villages, these statistics suggested genetic differentiation, but were not consistent among villages. Finally, haplotype networks demonstrated American Samoan sequence clusters were related to previously published sequences from Papua New Guinea. These are, to our knowledge, the first reports of W. bancrofti genetic variation in Polynesia. The resurgent parasites circulating on the main island of American Samoa represent a single population. This study is the first step towards investigating how parasite population structure might inform strategies to manage resurgence and elimination of lymphatic filariasis.

Simulating a Transmission Assessment Survey: An evaluation of current methods used in determining the elimination of the neglected tropical disease, Lymphatic Filariasis

IntroductionThe World Health Organization (WHO) recommends Transmission Assessment Surveys (TAS) to determine when an evaluation unit (EU) (a designated population survey area) has achieved elimination of transmission of the vector-borne macroparasitic disease Lymphatic Filariasis (LF). These determinations are based on combining data from multiple survey units within an EU; it is unclear how underlying cluster-level variation influences the outcome of the TAS at EU level. We simulate LF infection distribution in an EU and compare three methods for assessing whether LF elimination has occurred based on currently recommended decision thresholds and sampling methods. MethodsWe simulate an EU divided into clusters of varying size and disease prevalence. We produce 1000 samples according to LF TAS examples and WHO guidelines and compare three decision-making approaches: lot quality assurance sampling (LQAS) (recommended by WHO), one-sided interval estimate (CI), and nth order statistic (MAX). Summary statistics demonstrating the “pass” rate for the EU under different disease transmission conditions are generated using a versatile SAS® macro. ResultsAs the prevalence of LF decreases, the LQAS and CI approaches produce increased likelihood of a pass outcome for an EU while some cluster units may still have a high likelihood of transmission. The MAX provides an alternative that increases the likelihood of determining a pass only once the whole area has a low likelihood of transmission. LQAS and CI approaches designed to estimate the LF prevalence in the EU miss hotspots that will continue to transmit infection while the MAX approach focuses on identifying clusters with high risk of transmission. ConclusionsThe current TAS methodology has a flaw that may result in false predictions of LF transmission interruption throughout an EU. Modifying the TAS methodology to address results from extreme clusters rather than being based on mean prevalence over an EU will result in greater success for global elimination of LF.

Defining a prevalence level to describe the elimination of Lymphatic Filariasis (LF) transmission and designing monitoring & evaluating (M&E) programmes post the cessation of mass drug administration (MDA).

The global decline in prevalence of lymphatic filariasis has been one of the major successes of the WHO’s NTD programme. The recommended strategy of intensive, community-wide mass drug administration, aims to break localised transmission by either reducing the prevalence of microfilaria positive infections to below 1%, or antigen positive infections to below 2%. After the threshold is reached, and mass drug administration is stopped, geographically defined evaluation units must pass Transmission Assessment Surveys to demonstrate that transmission has been interrupted. In this study, we use an empirically parameterised stochastic transmission model to investigate the appropriateness of 1% microfilaria-positive prevalence as a stopping threshold, and statistically evaluate how well various monitoring prevalence-thresholds predict elimination or disease resurgence in the future by calculating their predictive value. Our results support the 1% filaremia prevalence target as appropriate stopping criteria. However, because at low prevalence-levels random events dominate the transmission dynamics, we find single prevalence measurements have poor predictive power for predicting resurgence, which suggests alternative criteria for restarting MDA may be beneficial.

A first nation-wide assessment of soil-transmitted helminthiasis in Fijian primary schools, and factors associated with the infection, using a lymphatic filariasis transmission assessment survey as surveillance platform.

BackgroundSoil-transmitted helminthiasis (STH) is endemic in Fiji but its prevalence is not known and likely to have changed after a decade of mass drug administration (MDA) for lymphatic filariasis (LF). By linking with LF transmission assessment surveys (LF-TAS), we undertook the first nation-wide assessment of STH in Fijian primary schools, as well as an analysis of factors associated with STH infections.Methodology/Principal findingsA cross-sectional assessment for STH was conducted in all four Divisions of Fiji from 2014 to 2015. In the Western, Central, and Northern Divisions, schools were sub-sampled after LF-TAS, while, in the Eastern Division, schools were selected via simple random sampling. For the diagnosis of STH, stool samples were examined by coproscopy with a single Kato-Katz thick smear (KK) and the formol-ether-acetate concentration technique, except for the samples from the Eastern Division where only KK was used. Mean prevalence of any STH among class 1–2 students at the national level was 10.5% (95% CI: 6.9–15.5). Across the three Divisions via LF-TAS, the prevalence levels for ascariasis were 8.7% (95% CI: 4.3–16.6), hookworm 3.9% (95% CI: 2.3–6.6) and trichuriasis 0%. In the Eastern Division, ascariasis prevalence was 13.3% (95% CI: 6.4–25.6), and hookworm 0.7% (95% CI: 0.2–2.5), with one case of trichuriasis. Among class 3–8 students, ascariasis prevalence was lower. Lower risk of any STH was associated with wearing shoes (adjusted OR 0.54, 95% CI: 0.32–0.90) and having piped water from the Fiji Water Authority at home (adjusted OR 0.48, 95% CI: 0.25–0.92).ConclusionsAfter a decade of community-based LF-MDA, STH in school-age children in Fiji is now close to 10%, but localities of endemicity remain. Preventive chemotherapy should be maintained in areas with elevated STH prevalence alongside targeted delivery of integrated WASH interventions. LF-TAS has provided an opportunity to develop future public health surveillance platforms.

Exploring factors affecting quality implementation of lymphatic filariasis mass drug administration in Bole and Central Gonja Districts in Northern Ghana.

Ghana has been implementing Mass Drug Administration (MDA) since the year 2001, and Lymphatic Filariasis transmission has been interrupted in 76 out of the 98 targeted districts. The remaining districts have a microfilaria prevalence above the 1% threshold needed for the interruption of transmission. This study assesses the level of lymphatic filariasis MDA coverage and explored factors affecting the quality of implementation of the MDA in the Bole and Central Gonja Districts of Northern Ghana. A concurrent mixed methods study design approach was used to provide both a quantitative and qualitative insight. A descriptive analysis was carried out, and the results are presented in tables and charts. The transcripts of the qualitative interviews were imported into Nvivo and framework methods of analysis were used. The results were summarized based on the themes and buttressed with narratives with key quotes presented within the texts. The overall MDA coverage in Central Gonja is 89.3% while that of Bole district is 82.9%. Refusal to ingest the drug and adverse drug reactions were higher in Bole district than the Central Gonja District. The persistent transmission of lymphatic filariasis in Bole District was characterized by poor community mobilization and sensitization, nonadherence to the directly observed treatment strategy, refusal to ingest the drug due to the fear of adverse drug reactions, inadequate knowledge and misconceptions about the disease. Reported mass drug administration coverage will not necessarily result into interruption of transmission of the disease without strict compliance to the directly observed treatment strategy, strong stakeholder engagement coupled with evidence-based context-specific multi-channel community education strategies with key educational messages on the cause of the disease and adverse drug reactions. While the clock for the elimination of lymphatic filariasis by the year 2020 and meeting of the Sustainable Development Goal 3 target 3.3 by 2030 is ticking, there is an urgent need for a concerted effort to improve the fidelity of the ongoing lymphatic filariasis MDA campaigns in the Bole District of Northern Ghana.

Predicting lymphatic filariasis elimination in data-limited settings: Areconstructive computational framework for combining data generation and model discovery.

Although there is increasing importance placed on the use of mathematical models for the effective design and management of long-term parasite elimination, it is becoming clear that transmission models are most useful when they reflect the processes pertaining to local infection dynamics as opposed to generalized dynamics. Such localized models must also be developed even when the data required for characterizing local transmission processes are limited or incomplete, as is often the case for neglected tropical diseases, including the disease system studied in this work, viz. lymphatic filariasis (LF). Here, we draw on progress made in the field of computational knowledge discovery to present a reconstructive simulation framework that addresses these challenges by facilitating the discovery of both data and models concurrently in areas where we have insufficient observational data. Using available data from eight sites from Nigeria and elsewhere, we demonstrate that our data-model discovery system is able to estimate local transmission models and missing pre-control infection information using generalized knowledge of filarial transmission dynamics, monitoring survey data, and details of historical interventions. Forecasts of the impacts of interventions carried out in each site made by the models estimated using the reconstructed baseline data matched temporal infection observations and provided useful information regarding when transmission interruption is likely to have occurred. Assessments of elimination and resurgence probabilities based on the models also suggest a protective effect of vector control against the reemergence of LF transmission after stopping drug treatments. The reconstructive computational framework for model and data discovery developed here highlights how coupling models with available data can generate new knowledge about complex, data-limited systems, and support the effective management of disease programs in the face of critical data gaps.

ENTOMOLOGICAL SURVEY OF MOSQUITO VECTORS OF LYMPHATIC FILARIASIS IN TALATAN-MAFARA AND TSAFE LOCAL GOVERNMENT AREAS OF ZAMFARA STATE, NIGERIA

Entomological survey of mosquito vectors was carried out to determine species abundance and identify those responsible for the transmission of lymphatic filariasis in Talatan-mafara and Tsafe Local Government Areas of Zamfara State, Nigeria. Houses were randomly selected for mosquito collection. Aerosol (Baygon) was sprayed in the rooms to knockdown indoor resting mosquitoes. A total of 5,230 mosquitoes comprising of 3,104 females and 2,126 males were collected and 1,182 engorged females were dissected to isolate filarial worm, Wuchereria bancrofti. The species of mosquitoes encountered include Culex quinquefasciatus (84%), Anopheles funestus (10%) and Anopheles gambiae sl. (6%). The overall infection and infectivity rates of the mosquitoes with Wuchereria bancrofti were 1.86% and 1.44% respectively. The infection/infectivity rates of Culex quinquefasciatus, Anopheles funestus and Anopheles gambiae sl. were 1.01%/0.51%, 2.97%/2.97% and 4.54%/4.14% respectively.

Prevalence and Correlates of Lymphatic Filariasis Infection and Its Morbidity Following Mass Ivermectin and Albendazole Administration in Mkinga District, North-Eastern Tanzania.

Lymphatic filariasis (LF) is a neglected tropical disease targeted for elimination as public health problem through morbidity management and preventive annual mass drug administration (MDA). This cross-sectional community-based surveillance assessed the prevalence and correlates of LF infection in Mkinga district, Tanga-region, Tanzania. A total of 4115 individuals (49.7% males, 35.2% children) were screened for circulating filarial antigens (CFA), microfilaremia (mf) and disease manifestations in 15 villages between November 2018 and January 2019. MDA uptake in the previous year was assessed. Overall prevalence of CFA-positivity was 5.8% (239/4115; 95% CI: 5.1–6.6), with significant heterogeneity between villages (range 1.2% to 13.5%). CFA-positivity was higher in males (8.8%) than females (3.3%), and correlated with increasing age (p < 0.001). Prevalence of mf among CFA-positives was 5.2%. Only 60% of eligible inhabitants in the study area took MDA in the previous year, and CFA-positivity was 2-fold higher in those who missed MDA (p < 0.0001). Prevalence of scrotal enlargement, hydrocele, arms or legs swelling, lymphoedema and lymphadenopathy was 6.4%, 3.7%, 1.35%, 1.2% and 0.32%, respectively. Compared to baseline data, 16 years of MDA intervention significantly reduced LF transmission and morbidity, although the intended elimination target of <1% mf and <2% antigenemia to level where recrudescence is unlikely to occur by the year 2020 may not be attained. The finding of hotspots with ongoing transmission calls for intensified control measures.

Post-Treatment Surveillance for Lymphatic Filariasis in Plateau and Nasarawa States, Nigeria: Results of Transmission Assessment Surveys.

.Following the halt of mass drug administration (MDA) for lymphatic filariasis (LF), the WHO recommends at least 4 years of post-treatment surveillance (PTS) to confirm that transmission recrudescence or importation does not occur. The primary means of evaluation during PTS is repeated transmission assessment surveys (TASs) conducted at 2- to 3-year intervals after TAS-1 stop-MDA surveys. This study reports the results of TAS-2 and TAS-3 surveys in Plateau and Nasarawa states (pop. 6.9 million) of Nigeria divided into a minimum of seven evaluation units (EUs) per TAS. A total of 26,536 first- and second-year primary school children (approximately 6–7 years old) were tested for circulating filarial antigen (CFA) between 2014 and 2017. Of 12,313 children tested in TAS-2 surveys, only five (0.04%) were CFA positive, with no more than two positive samples from any one EU, which was below the critical value of 20 per EU. Of 14,240 children tested in TAS-3 surveys, none (0%) were CFA positive. These results indicate that LF transmission remains below sustainable transmission levels and suggest that elimination of transmission has been achieved in Plateau and Nasarawa, Nigeria.

The Potential Sources of Transmission and Distribution of Lymphatic Filariasis in Semarang City, Central Java, Indonesia

Lymphatic Filariasis (LF) is a neglected tropical disease caused by filarial worms. Semarang City has an increasing number of LF. The aim of this study was to investigate potential sources of transmission and distribution of LF. It was descriptive research using cross-sectional design. The sample were 28 LF cases. The variables studied were level of knowledge, physical and biological environmental factors, and provision of health service. Data were collected with interview and observation. Data were analysed descriptively and spatially. The results showed that LF cases were distributed in centre of Semarang City, especially in the coastal area. Poor drainage and stagnant water around the houses were potential breeding places for mosquitos, which are suspected as a vector of LF transmission. Physical and biological environmental factors around the houses of LF patient may possibly be sources of distribution and transmission of LF. It was indicated with the existence of mosquito larvae in any habitats.

Molecular xenomonitoring as a post-MDA surveillance tool for global programme to eliminate lymphatic filariasis: Field validation in an evaluation unit in India.

BackgroundLymphatic filariasis (LF) is targeted for elimination by the year 2020. As of 2017, 67 of the 72 endemic countries have implemented annual Mass Drug Administration (MDA) for interrupting LF transmission. Transmission Assessment Survey (TAS) is the recommended protocol to evaluate the impact of MDA and to decide when to stop MDA in an Evaluation Unit (EU, population ≤2 million). As the human infection levels go down with repeated MDA rounds, it becomes a challenge to select the appropriate survey methods to assess transmission interruption. This study validates a standard protocol for molecular xenomonitoring of infection in vectors (MX) at an EU as a complementary tool for TAS to stop MDA and its utility for post-MDA or post-validation surveillance.MethodologyThe study was conducted in Cuddalore district, Tamil Nadu, India, which was found eligible for TAS after 15 annual rounds of MDA (4 with DEC alone and 11 with DEC plus albendazole). The district was divided into two EUs as per the TAS protocol and one EU was randomly selected for the study. A two-stage cluster design vector sampling, developed and validated at a sub-district level, was implemented in 30 randomly selected clusters in the EU. Female Culex quinquefasciatus were collected placing gravid traps overnight (1800–0600 hrs) inside the premises of systematically selected households. Pools of 20–25 blood-fed, semi-gravid and gravid Cx. quinquefasciatus were subjected to real-time quantitative PCR (polymerase chain reaction) assay for detecting Wuchereria bancrofti DNA. Pool infection rate (% of pools positive for W. bancrofti DNA), and the estimated prevalence of W. bancrofti DNA in mosquitoes and its 95% confidence interval were calculated. Additionally, in these 30 clusters, microfilaria (Mf) survey among individuals >5 years old was carried out. School-based TAS was conducted using Immunochromatographic Card Test (ICT) in the EU. Prepared itemized cost-menu for different cost components of MX survey and TAS were estimated and compared.ResultsMX survey showed that only 11 (3.1%) of the 358 pools (8850 Cx.quinquefasciatus females), collected from 30 clusters, were found positive for W. bancrofti DNA. The estimated vector infection rate was 0.13% (95% CI: 0.07–0.22%), below the provisional threshold (0.25%) for transmission interruption. Of 1578 children tested in the TAS, only four (0.25%) were positive for filarial antigenemia, and it is well below the critical cut-off (18 positives) for stopping MDA. Among 9804 persons tested in the 30 clusters, only four were found positive for Mf (0.04%; 95% CI: 0.01–0.1%). The Mf-prevalence was <1% threshold for transmission interruption in humans. The estimated costs for TAS and MX per EU were $14,104 USD and $14,259 USD respectively.ConclusionsThe result of MX protocol was in good agreement with that of TAS, providing evidence to recommend MX as a complementary tool to TAS to decide on stopping MDA. MX can also be a potential surveillance tool for post-MDA and post-validation phases as it could detect sites with residual infection and risk of resurgence of transmission. MX is economically feasible as its cost is slightly higher than that of TAS.

Circadian Biting patterns of Major Lymphatic Filariasis Vectors from Northwest Nigeria

The circadian biting pattern of mosquito vectors is an important determinant of malaria and lymphatic filariasis (LF) transmission. Good knowledge of the vector host-seeking behavior, its outdoor/indoor biting preference, and nocturnal biting time is essential component for vector control strategies in Northwest Nigeria. The aim of this study was to assess the circadian biting time and identify the mosquito composition morphologically and molecularly. Mosquitoes were collected outdoor by human landing catches (HLC) using mouth aspirator from Batagarawa town and Gajerar Giwa village. Mosquitoes were morphologically and molecularly identified as Anopheles gambiae (M and S forms), Anopheles funestus s.s and Culex quinquefasciatus. The peak biting time for Culex quinquefasciatus were relatively similar across the study communities and the nocturnal biting rates showed an increased night time peak between 11pm to 12am. However, the peak biting time of Anopheles gambiae s.l also varied between study communities and the nocturnal biting rates showed an increased night time peak between 9pm to 10pm and then 11pm to 12am but, the peak biting time for Anopheles funestus s.l which was found only in Gajerar Giwa village and the nocturnal biting rates showed an increased night time peak between 12am to 1am. This finding serves as a basis for creating an improved vector control strategies that target specific species, and if combine with other interventions could result in the elimination of malaria and LF transmission from Northwest Nigeria.

DNA of Brugia malayi detected in several mosquito species collected from Balangan District, South Borneo Province, Indonesia

Background and Aim:Lymphatic filariasis (LF) is a lesser-known parasitic disease, which contributes to significant decreases in overall health. This study investigated the presence of Brugia malayi in mosquitoes collected in the South Borneo Province, Indonesia.Materials and Methods:Mosquitoes were collected through bare leg collection methods after sunset in several areas of the Hukai and Gulinggang villages in the Balangan District. The collected mosquitoes were identified based on morphological features and dissected to find microfilaria and then pooled through species for polymerase chain reaction (PCR) microfilaria detection.Results:A total of 837 female mosquitoes consisting of at least 14 species were selected; they were dissected, and no microfilariae were found. Mosquitoes were divided into 69 pools for PCR analysis. PCR revealed that 8.7% (6/69) of the pools were positive for B. malayi, including Mansonia annulifera (4 pools), Aedes albopictus (1 pool), and Culex tritaeniorhynchus (1 pool).Conclusions:These results suggested that mosquito dissection was not an optimum method for finding microfilaria. M. annulifera, C. tritaeniorhynchus, and A. albopictus mosquitoes might play an important role in the transmission of LF in the Balangan District. Information from this study could be used for the prevention of transmission or vector control programs in Indonesia.

An Expanded Transmission Assessment Survey to Confirm the Interruption of Lymphatic Filariasis Transmission in Wallis and Futuna.

Historically, the human prevalence of Wuchereria bancrofti infection in Wallis and Futuna (WAF) was among the highest in the Pacific and mass drug administration (MDA) against lymphatic filariasis (LF) either with diethylcarbamazine citrate (DEC) or the combination of DEC and albendazole had been implemented for decades. To determine whether LF antigen prevalence in WAF was lower than 1%, the infection threshold for elimination in an area where Aedes spp. are the principal vectors, we conducted the WHO-recommended transmission assessment survey in 2012. We present the results of a school-based survey, which targeted 1,014 students in all 13 elementary schools in WAF. From a fingerprick, the circulating filarial antigen (CFA) positivity was checked for grade 2-5 students using BinaxNOW filariasis test (immunochromatographic test). Of 935 children tested, three were positive for CFA in two schools. At the territory level, this was below the critical cutoff of nine cases, if the whole territory was considered as a single evaluation unit. The prevalence of CFA in WAF is less than 1%, reaching the goal for LF elimination set by the WHO. We were able to recommend stopping LF MDA and move to post-MDA surveillance to detect any recrudescence. This survey successfully paved the way for WAF to be validated as achieving LF elimination as a public health problem by 2020.

Assessment of transmission in areas of uncertain endemicity for lymphatic filariasis in Brazil.

BackgroundThe objective of the Global Program to Eliminate Lymphatic Filariasis (GPELF) is to phase out this endemic disease as a public health problem by 2020. Validation of elimination is obtained from the World Health Organization through evidence of non-transmission in countries that have already been subjected to mass drug administration (MDA) and in places adjoining these endemic areas. While three municipalities in Brazil have completed MDA, the epidemiological situation remains uncertain in nine adjoining municipalities. To determine the epidemiological status, this study was to perform a review of the literature and a school-based survey to describe the past and recent endemicity of lymphatic filariasis (LF) theses nine municipalities in Brazil.Methodology/Principle findingsFor review of the literature, both formal and informal literature sources were accessed since the first reports of filariasis in the Metropolitan Region of Recife, Brazil. We conducted a school-based survey in 2016 using immunochromatographic card tests (ICTs) among schoolchildren aged 6–10 years living in nine municipalities contiguous with the endemic areas in which MDA was conducted. Our review of the literature identified eight studies involving surveys demonstrating that microfilariae had been circulating in eight of the municipalities since 1967, with a low prevalence of microfilaremia, isolated autochthonous cases, and treatment of individual cases. The school-based survey included 17,222 children in 185 urban schools in the nine areas of Brazil with uncertain endemicity. One child affected by allochthonous transmission was antigen positive based on ICT and lived in a municipality adjacent to Recife; this child’s family came from Recife, but no other case was diagnosed within the family.Conclusions/SignificanceThe study results suggest that there is no transmission of LF in the municipalities investigated. However, these areas have population migration and socioenvironmental conditions favorable to mosquito breeding grounds; therefore, surveillance is strongly recommended in these areas.

Study on vector mosquito of zoonotic Brugia malayi in Musi Rawas, South Sumatera, Indonesia.

Background and Aim:Studies to determine abundance, distribution, species composition, and mosquito interactions are very important in understanding the risk of disease transmission to implement appropriate mosquito management in endemic areas. Lymphatic filarial worms are one of the parasites that are contracted and/or transmitted by mosquitoes when sucking the blood of infected humans or animals and then biting others. This research was conducted to study the abundance, species composition, mosquito biting cycles, density and periodicity of mosquitoes caught in Lubuk Pauh Village, Bulang Tengah Suku Ulu, Musi Rawas, South Sumatera, Indonesia, which is an endemic area of zoonotic Brugia malayi.Materials and Methods:The mosquito collection was done in July 2018 using the human landing collection method for 11 h from 18.00 pm to 5.00 am Western Indonesian Time. The catching of mosquitoes was done both indoors and outdoors, and mosquitoes were identified under a dissecting microscope using an identification key to confirm their species. Detection of B. malayi larvae in mosquitoes was confirmed by dissection and polymerase chain reaction methods.Results:The caught mosquitoes consisted of four species: Armigeres subalbatus, Culex quinquefasciatus, Culex vishnui, and Mansonia uniformis. Based on the Shannon–Wiener index, Lubuk Pauh Village has low mosquito species diversity (0.210). Ar. subalbatus was the dominant mosquito in Lubuk Pauh Village with dominance number 95.08, and it had the most frequent activity in each of periods of indoor and outdoor collection, with the highest density (man-hour density) at 18.00-19.00 (51.750). B. malayi infective stage larvae were not found in all mosquito species caught.Conclusion:Existence of Ar. subalbatus, Cx. quinquefasciatus, and Ma. uniformis in Lubuk Pauh Village which is an endemic area of B. malayi shows that the area is at risk of lymphatic filariasis transmission.

Elimination of lymphatic filariasis as a public health problem from Tonga

BackgroundTonga was highly endemic for lymphatic filariasis (LF) caused by diurnally sub-periodic Wuchereria bancrofti transmitted by Aedes vector species. LF prevalence declined very appreciably as a result of chemotherapeutic intervention measures implemented in 1977, but low levels of infection persisted. Along with other Pacific Island countries and in partnership with the Pacific Programme to Eliminate LF (PacELF), Tonga implemented a programme to eliminate LF as a public health problem.MethodsOn the basis of historical data and baseline survey, all the divisions of the country were declared as endemic. Five to six consecutive rounds of effective MDA were implemented in all the divisions during 2001–2006. The impact of MDA was assessed through interim and post-MDA antigen (Ag) detection surveys among adults and transmission assessment surveys among children. The chronic disease burden was assessed by health workers through observation.ResultsThe base-line Ag prevalence was 2.70%. The treatment coverage was > 80% in all MDA rounds. The mid-term surveys showed an Ag prevalence of 2.46%. The pre-stop MDA Ag survey revealed an Ag prevalence of 0.34%. The stop MDA survey and transmission assessment surveys among children showed Ag prevalence at < 0.05%, indicating transmission is negligible. Health workers concluded that filarial lymphedema or hydrocele condition in the communities is absent or very rare.ConclusionTonga had successfully met the criteria for elimination of LF as a public health problem. The accomplishment was acknowledged by the WHO in 2017. Tonga looks forward to work with stakeholders to eliminate transmission of LF and achieve zero incidence of infection.