1
|
Jones C, Ngasala B, Derua YA, Tarimo D, Reimer L, Bockarie M, Malecela MN. Lymphatic filariasis transmission in Rufiji District, southeastern Tanzania: infection status of the human population and mosquito vectors after twelve rounds of mass drug administration. Parasit Vectors 2018; 11:588. [PMID: 30424781 PMCID: PMC6234578 DOI: 10.1186/s13071-018-3156-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 10/17/2018] [Indexed: 11/25/2022] Open
Abstract
Background Control of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole. Monitoring the impact of this intervention is crucial for measuring the success of the LF elimination programmes. This study assessed the status of LF infection in Rufiji district, southeastern Tanzania after twelve rounds of MDA. Methods Community members aged between 10 and 79 years were examined for Wuchereria bancrofti circulating filarial antigens (CFA) using immunochromatographic test cards (ICTs) and antigen-positive individuals were screened for microfilaraemia. All study participants were examined for clinical manifestation of LF and interviewed for drug uptake during MDA rounds. Filarial mosquito vectors were collected indoor and outdoor and examined for infection with W. bancrofti using a microscope and quantitative real-time polymerase chain reaction (qPCR) techniques. Results Out of 854 participants tested, nine (1.1%) were positive for CFA and one (0.1%) was found to be microfilaraemic. The prevalence of hydrocele and elephantiasis was 4.8% and 2.9%, respectively. Surveyed drug uptake rates were high, with 70.5% of the respondents reporting having swallowed the drugs in the 2014 MDA round (about seven months before this study). Further, 82.7% of the respondents reported having swallowed the drugs at least once since the inception of MDA programme in 2000. Of the 1054 filarial vectors caught indoors and dissected to detect W. bancrofti infection none was found to be infected. Moreover, analysis by qPCR of 1092 pools of gravid Culex quinquefasciatus collected outdoors resulted in an estimated infection rate of 0.1%. None of the filarial vectors tested with qPCR were found to be infective. Conclusion Analysis of indices of LF infection in the human population and filarial mosquito vectors indicated a substantial decline in the prevalence of LF and other transmission indices, suggesting that local transmission was extremely low if occurring at all in the study areas. We, therefore, recommend a formal transmission assessment survey (TAS) to be conducted in the study areas to make an informed decision on whether Rufiji District satisfied WHO criteria for stopping MDA.
Collapse
Affiliation(s)
- Clarer Jones
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P. O. Box 65011, Dar es Salaam, Tanzania.
| | - Billy Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P. O. Box 65011, Dar es Salaam, Tanzania.,Department of Women's and Children's Health International Maternal and Child Health (IMCH), Uppsala Universitet, Uppsala, Sweden
| | - Yahya A Derua
- National Institute for Medical Research, P. O. Box 9653, Dar es Salaam, Tanzania
| | - Donath Tarimo
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P. O. Box 65011, Dar es Salaam, Tanzania
| | - Lisa Reimer
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Moses Bockarie
- European and Development Countries Clinical Trials Partnership, Cape Town, South Africa
| | | |
Collapse
|
2
|
de Souza DK, Ansumana R, Sessay S, Conteh A, Koudou B, Rebollo MP, Koroma J, Boakye DA, Bockarie MJ. The impact of residual infections on Anopheles-transmitted Wuchereria bancrofti after multiple rounds of mass drug administration. Parasit Vectors 2015; 8:488. [PMID: 26399968 PMCID: PMC4581406 DOI: 10.1186/s13071-015-1091-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 09/11/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Many countries have made significant progress in the implementation of World Health Organization recommended preventive chemotherapy strategy, to eliminate lymphatic filariasis (LF). However, pertinent challenges such as the existence of areas of residual infections in disease endemic districts pose potential threats to the achievements made. Thus, this study was undertaken to assess the importance of these areas in implementation units (districts) where microfilaria (MF) positive individuals could not be found during the mid-term assessment after three rounds of mass drug administration. METHODS This study was undertaken in Bo and Pujehun, two LF endemic districts of Sierra Leone, with baseline MF prevalence of 2 % and 0 % respectively in sentinel sites for monitoring impact of the national programme. Study communities in the districts were purposefully selected and an assessment of LF infection prevalence was conducted together with entomological investigations undertaken to determine the existence of areas with residual MF that could enable transmission by local vectors. The transmission Assessment Survey (TAS) protocol described by WHO was applied in the two districts to determine infection of LF in 6-7 year old children who were born before MDA against LF started. RESULTS The results indicated the presence of MF infected children in Pujehun district. An. gambiae collected in the district were also positive for W. bancrofti, even though the prevalence of infection was below the threshold associated with active transmission. CONCLUSIONS Residual infection was detected after three rounds of MDA in Pujehun--a district of 0 % Mf prevalence at the sentinel site. Nevertheless, our results showed that the transmission was contained in a small area. With the scale up of vector control in Anopheles transmission zones, some areas of residual infection may not pose a serious threat for the resurgence of LF if the prevalence of infections observed during TAS are below the threshold required for active transmission of the parasite. However, robust surveillance strategies capable of detecting residual infections must be implemented, together with entomological assessments to determine if ongoing vector control activities, biting rates and infection rates of the vectors can support the transmission of the disease. Furthermore, in areas where mid-term assessments reveal MF prevalence below 1 % or 2 % antigen level, in Anopheles transmission areas with active and effective malaria vector control efforts, the minimum 5 rounds of MDA may not be required before implementing TAS. Thus, we propose a modification of the WHO recommendation for the timing of sentinel and spot-check site assessments in national programs.
Collapse
Affiliation(s)
- Dziedzom K de Souza
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
| | - Rashid Ansumana
- Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, UK. .,Mercy Hospital Research Laboratory, Bo, Sierra Leone.
| | | | - Abu Conteh
- Ministry of Health and Sanitation, Freetown, Sierra Leone.
| | - Benjamin Koudou
- Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, UK.
| | | | - Joseph Koroma
- Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Daniel A Boakye
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
| | - Moses J Bockarie
- Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, UK.
| |
Collapse
|
3
|
Mosquito-parasite interactions can shape filariasis transmission dynamics and impact elimination programs. PLoS Negl Trop Dis 2013; 7:e2433. [PMID: 24069488 PMCID: PMC3772046 DOI: 10.1371/journal.pntd.0002433] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 08/06/2013] [Indexed: 11/19/2022] Open
Abstract
The relationship between mosquito vectors and lymphatic filariasis (LF) parasites can result in a range of transmission outcomes. Anophelines are generally characterized as poor vectors due to an inability to support development at low densities. However, it is important to understand the potential for transmission in natural vectors to maximize the success of elimination efforts. Primary vectors in Papua New Guinea (n = 1209) were dissected following exposure to microfilaremic blood (range 8-233 mf/20 µl). We examined density dependent and species-specific parasite prevalence, intensity and yield, barriers to parasite development as well as impacts on mosquito survival. We observed strikingly different parasite prevalence and yield among closely related species. Prevalence of infective stage larvae (L3s) ranged from 4.2% to 23.7% in An. punctulatus, 24.5% to 68.6% in An. farauti s.s. and 61.9% to 100% in An. hinesorum at low and high density exposures, respectively. Injection experiments revealed the greatest barrier to parasite development involved passage from the midgut into the hemocoel. The ratio of L3 to ingested mf at low densities was higher in An. hinesorum (yield = 1.0) and An. farauti s.s. (yield = 0.5) than has been reported in other anopheline vectors. There was a negative relationship between mosquito survival and bloodmeal mf density. In An. farauti s.s., increased parasite yield and survival at low densities suggest greater competence at low microfilaremias. In Papua New Guinea the likelihood of transmission will be strongly influenced by vector composition and changes in the mf reservoir as a result of elimination efforts. Global elimination efforts will be strengthened by the knowledge of transmission potential in the context of current control measures.
Collapse
|
4
|
Graves PM, Makita L, Susapu M, Brady MA, Melrose W, Capuano C, Zhang Z, Dapeng L, Ozaki M, Reeve D, Ichimori K, Kazadi WM, Michna F, Bockarie MJ, Kelly-Hope LA. Lymphatic filariasis in Papua New Guinea: distribution at district level and impact of mass drug administration, 1980 to 2011. Parasit Vectors 2013; 6:7. [PMID: 23311302 PMCID: PMC3606332 DOI: 10.1186/1756-3305-6-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 12/23/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Lymphatic filariasis (LF) caused by Wuchereria bancrofti is present at high prevalence in some parts of Papua New Guinea. However, there has been no rigorous data-based representative assessment of nationwide prevalence of LF. The LF programme has been daunted by the scope of the problem, and progress on mass drug administration (MDA) has been slow and lacking in resources. METHODS A systematic literature review identified LF surveys in Papua New Guinea between 1980 and 2011. Results were extracted by location, time period and test used (blood slide, immunochromatographic test (ICT) or Og4C3 ELISA) and combined by district. Three criteria schemes based on the Global Programme to Eliminate Lymphatic Filariasis guidelines, with modifications, were developed to classify and prioritize districts by prevalence level. Results of repeated surveys in the same sites were used to investigate the impact of MDA on LF prevalence over the time period. RESULTS There were 312 distinct survey sites identified in 80 of the 89 districts over the 31-year period. The overall LF prevalence in the sites tested was estimated at 18.5 to 27.5% by blood slide for microfilariae (Mf), 10.1% to 12.9% by ICT and 45.4% to 48.8% by Og4C3. Biases in site selection towards areas with LF, and change in type of assay used, affected the prevalence estimates, but overall decline in prevalence over the time period was observed. Depending on the criteria used, 34 to 36 districts (population 2.7 to 2.9 million) were classed as high endemic (≥5% prevalence), 15 to 25 districts (1.7 to 1.9 million) as low endemic (<5%) and 20 to 31 (1.3 to 2.2 million) as non-endemic. Nine districts (0.7 million) had no information. The strong impact of MDA, especially on microfilaria (Mf) prevalence, was noted in sites with repeat surveys. CONCLUSIONS This analytical review of past surveys of LF in Papua New Guinea enables better estimation of the national burden, identifies gaps in knowledge, quantifies and locates the population at risk, and can be used to predict the likely impact of MDA and/or vector control. Better targeting of districts by level of prevalence will strengthen the control programme, facilitate monitoring of the disease trend and increase the likelihood of reaching the target of LF elimination by 2020.
Collapse
Affiliation(s)
- Patricia M Graves
- Department of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Cairns and Townsville, Queensland, Australia
- James Cook University, PO Box 6811, Cairns, Queensland, 4870, Australia
| | - Leo Makita
- Department of Health, Port Moresby, Papua New Guinea
| | - Melinda Susapu
- Department of Health, Port Moresby, Papua New Guinea
- WHO, Port Moresby, Papua New Guinea
| | - Molly A Brady
- Current address: WHO, Regional Office for the Western Pacific, Manila, Philippines
| | - Wayne Melrose
- Department of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Cairns and Townsville, Queensland, Australia
| | - Corinne Capuano
- Current address: WHO, Regional Office for the Western Pacific, Manila, Philippines
| | | | | | - Masayo Ozaki
- WHO, Pacific Programme to Eliminate Lymphatic Filariasis (PacELF), Suva, Republic of Fiji
- Current address: University of Alabama School of Medicine, Birmingham, Alabama, USA
| | - David Reeve
- Department of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Cairns and Townsville, Queensland, Australia
| | | | | | - Frederick Michna
- Department of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Cairns and Townsville, Queensland, Australia
| | - Moses J Bockarie
- Liverpool School of Tropical Medicine (LSTM), Centre for Neglected Tropical Diseases, Liverpool, United Kingdom of Great Britain and Northern Ireland
| | - Louise A Kelly-Hope
- Liverpool School of Tropical Medicine (LSTM), Centre for Neglected Tropical Diseases, Liverpool, United Kingdom of Great Britain and Northern Ireland
| |
Collapse
|
5
|
Adjobimey T, Hoerauf A. Induction of immunoglobulin G4 in human filariasis: an indicator of immunoregulation. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2011; 104:455-64. [PMID: 20863434 PMCID: PMC3065634 DOI: 10.1179/136485910x12786389891407] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Filarial parasites are known to induce a large range of immunoregulatory mechanisms, including the induction of alternatively activated macrophages and regulatory T cells. These mechanisms are used to evade and down-modulate the host's immune system, to support parasite survival. Several reports have focused on some of these mechanisms, in humans and murine models, but the complex immunoregulatory networks associated with filarial infections remain unclear. Recent publications have conferred a role for regulatory T cells in the ability of helminth parasites to modulate human immune responses, such cells promoting the induction of the non-complement-fixing immunoglobulin G4 (IgG4). High plasma concentrations of IgG4 have been reported in hypo-responsive and asymptomatic cases of helminth infection. In both human lymphatic filariasis and onchocerciasis, the asymptomatic infections are characterised by high plasma concentrations of IgG4 (compared with those of IgE) and of the complement-fixing antibodies IgG1, IgG2 and IgG3. In asymptomatic filarial infection, elevations in IgG4 are also often associated with high worm loads and with high plasma levels of the immunomodulatory interleukin-10. Here, various aspects of the induction of IgG4 in humans and it roles in the immunomodulation of the human responses to filarial parasites are reviewed.
Collapse
Affiliation(s)
- T Adjobimey
- Institute for Medical Microbiology, Immunology and Parasitology, University Clinic Bonn, Germany
| | | |
Collapse
|