Immuno–parasitological assessment of bancroftian filariasis in a highly endemic area along the River Sabaki, in Malindi district, Kenya

Cytokines and immunoglobulin g response in donkeys with spontaneous Setaria equine infection

Setaria equina (S. equina) is a filarial worm that exists in peritoneal cavity of equines. This study aimed to evaluate cytokine mediators tumour necrosis factor alpha (TNF-α), interleukin-4 (IL-4) and immunoglobulin G (IgG) responses in spontaneously S. equina infected and non-infected donkeys with emphasis on choosing the best antigen that could be used in diagnosis of such filarial infection. A total of 87 donkeys were examined. Two S. equina antigens: crude somatic S. equina antigen (CSS) and excretory secretory S. equina antigen (ESS) were prepared. They were evaluated in diagnosis of the infection using indirect ELISA and electrophoretically characterised through sodium dodecyl sulphate poly acrylamide gel electrophoresis (SDS-PAGE) and western blotting technique. The results indicated that both TNF-α and IL-4 in the serum of infected donkeys were significantly higher compared with the non-infected group at P<0.05 and P<0.01, respectively. However, the IL-4 level of infected donkeys was significantly higher than that of TNF-a (P<0.01). Apparent prevalence, specificity and positive predictive values (96.55%, 100%, and 100% each) of CSS showed higher diagnostic accuracy than that of ESS. In addition, electrophoretic protein profile and IgG reactivity of CSS antigen via western blot presented a prominent reactive protein band at 28 kDa. It was concluded that the CSS antigen was the best antigen that could be used in serodiagnosis of S. equina infection. The cytokine responses were explored in order to differentiate infected from non-infected donkeys.

A case study of risk factors for lymphatic filariasis in the Republic of Congo

BACKGROUND

Little is known regarding risk factors for lymphatic filariasis (LF) in Central Africa. We studied the epidemiology of LF in an endemic village in the Republic of Congo.

METHODS

Dependent variables were Wuchereria bancrofti antigenemia (ICT card test) and microfilaremia (night blood smears). The following factors were investigated: sex, age, bed net, latrines, source of water, uptake of anthelmintic drugs, hunting/fishing activities, and occasionally sleeping in the bush. Mixed multivariate logistic regression models were used.

RESULTS

134 of 774 subjects aged ≥ 5 years (17.3%) had W. bancrofti antigenemia and 41 (5.3%) had microfilaremia (mf). Infection rates increased with age up to roughly 20 years and remained stable thereafter. Multivariate analysis of antigenemia demonstrated an increased risk for males (OR = 2.0 [1.3-3.0]) and for people who hunt or fish (OR = 1.5 [1.0-2.4]) and a protective effect of latrines (OR = 0.5 [0.4-0.8]). Among males, those hunting or fishing at night had an increased risk for antigenemia (OR = 1.9 [1.1-3.5]), and use of latrines was protective (OR = 0.5 [0.3-0.9]). For females, bed nets were protective (OR = 0.4 [0.1-0.9]), and there was a strong household effect (intraclass correlation coefficient [ICC]: 0.24). When mf was used as the dependent variable, males had a higher risk for infection (OR = 5.4 [2.1-13.4]), latrines had a protective effect (OR = 0.4 [0.1-0.9]) and there was a marked household effect (ICC = 0.49).

CONCLUSIONS

Age, sex, and occupation-dependent exposure to mosquitoes were important risk factors for infection with W. bancrofti in this study. It is likely that men often acquire infection in high transmission areas outside of the village, while children and women are infected in areas with lower transmission inside or near the village. Additional studies are needed to determine whether these findings apply to other areas in Central Africa.

Spatial distribution of podoconiosis in relation to environmental factors in Ethiopia: a historical review

BACKGROUND

An up-to-date and reliable map of podoconiosis is needed to design geographically targeted and cost-effective intervention in Ethiopia. Identifying the ecological correlates of the distribution of podoconiosis is the first step for distribution and risk maps. The objective of this study was to investigate the spatial distribution and ecological correlates of podoconiosis using historical and contemporary survey data.

METHODS

Data on the observed prevalence of podoconiosis were abstracted from published and unpublished literature into a standardized database, according to strict inclusion and exclusion criteria. In total, 10 studies conducted between 1969 and 2012 were included, and data were available for 401,674 individuals older than 15 years of age from 229 locations. A range of high resolution environmental factors were investigated to determine their association with podoconiosis prevalence, using logistic regression.

RESULTS

The prevalence of podoconiosis in Ethiopia was estimated at 3.4% (95% CI 3.3%-3.4%) with marked regional variation. We identified significant associations between mean annual Land Surface Temperature (LST), mean annual precipitation, topography of the land and fine soil texture and high prevalence of podoconiosis. The derived maps indicate both widespread occurrence of podoconiosis and a marked variability in prevalence of podoconiosis, with prevalence typically highest at altitudes >1500 m above sea level (masl), with >1500 mm annual rainfall and mean annual LST of 19-21°C. No (or very little) podoconiosis occurred at altitudes <1225 masl, with annual rainfall <900 mm, and mean annual LST of >24°C.

CONCLUSION

Podoconiosis remains a public health problem in Ethiopia over considerable areas of the country, but exhibits marked geographical variation associated in part with key environmental factors. This is work in progress and the results presented here will be refined in future work.

Epidemiological assessment of continuing transmission of lymphatic filariasis in Samoa

Ongoing transmission of lymphatic filariasis (LF) was assessed in five Samoan villages by measuring microfilaraemia (Mf), circulating filarial antigen (CFA) and antibody prevalence. Compared to the other villages, Fasitoo-Tai had a significantly higher Mf prevalence (3·2%), CFA prevalence (14·6%) and antibody prevalence in children (62·0%) (P<0·05). Puapua had a significantly lower CFA prevalence (2·5%), no detectable Mf-positive individuals and significantly low antibody prevalence in children (7·9%) (P<0·05). Siufaga, previously believed to be LF-free, recorded >1% CFA prevalence and a high antibody prevalence in children (46·6%). Overall, antibody prevalence in children appeared to reflect the transmission dynamics in the villages and, in Siufaga, identified an area of ongoing transmission. The Filariasis Cellabs Enzyme-Linked Immunosorbent Assay (CELISA), based on recombinant antigen Bm14, to detect antibodies, could potentially be a promising diagnostic tool for inclusion in future surveillance in the South Pacific.

Application of the Filariasis CELISA Antifilarial IgG(4) Antibody Assay in Surveillance in Lymphatic Filariasis Elimination Programmes in the South Pacific

Elimination of lymphatic filariasis (LF) in the Pacific Island Countries and Territories (PICT) has been defined as <0.1% circulating filarial antigen (CFA) prevalence in children born after the implementation of successful mass drug administrations (MDAs). This research assessed the feasibility of CFA and antibody testing in three countries; Tonga, Vanuatu, and Samoa. Transmission is interrupted in Vanuatu and Tonga as evidenced by no CFA positive children and a low antibody prevalence and titre. Transmission is ongoing in Samoa with microfilaraemic (Mf) and CFA positive children and a high antibody prevalence and titre. Furthermore, areas of transmission were identified with Mf positive adults, but no CFA positive children. These areas had a high antibody prevalence in children. In conclusion, CFA testing in children alone was not useful for identifying areas of residual endemicity in Samoa. Thus, it would be beneficial to include antibody serology in the PICT surveillance strategy.

Adult population as potential reservoir of NTD infections in rural villages of Kwale district, Coastal Kenya: implications for preventive chemotherapy interventions policy

Background

Neglected tropical diseases (NTDs) are major public health problems in developing countries where they contribute to suffering of populations living in poor settings. As part of a research project started in September 2009 in Kwale district, Coast Region, Kenya, a baseline cross-sectional survey was conducted in 5 rural villages to provide information on the status of NTDs, including urinary schistosomiasis, soil-transmitted helminthiasis (STH), and lymphatic filariasis. This paper presents the results of a parasitological investigation among adults in the study villages.

Methods

A total of 599 adults in the 5 study villages were tested for NTD infections in urine, stool and blood. The presence of Schistosoma haematobium infection was determined by the urine filtration method. The presence of STH in stool was determined by Kato-Katz method while filarial antigenaemia was determined using immunochromatographic (ICT) test.

Results

The study revealed high prevalence of hookworm (41.7%) and schistosomiasis (18.2%) infections among adults in the study villages. Of the 599 individuals examined, 50.1% had one or more helminthic infections. There was low level of polyparasitism with helminthic NTDs in the study population with 9.5% and 1.7% of the participants having two and three infections, respectively.

Conclusions

In the current study, hookworm and schistosomiasis infections were identified as important infections among adults living in areas of high endemicity for these infections. Thus, if this section of the population is left untreated it may remain an important potential reservoir and a source of re-infection for school-age children treated in school deworming programmes. Therefore, there is a need to design novel strategies for preventive chemotherapy interventions that could allow inclusion of adults in an effort to reduce force of infection in high endemic communities.

Evaluation of effectiveness of diethylcarbamazine/albendazole combination in reduction of Wuchereria bancrofti infection using multiple infection parameters

OBJECTIVES

To evaluate the effect of multiple rounds of annual single dose of DEC (6 mg/kg) or albendazole (400mg) given alone or in combination on Wuchereria bancrofti microfilaraemia, anti-filarial IgG1 and IgG4 and antigenaemia.

METHODS

A total of 170 participants were randomly assigned to albendazole (n = 62), DEC (n = 54), and DEC plus albendazole (DEC/ALB) combination (n = 54). Blood samples were collected at pre-treatment in 1998, at 1 week and 6 months after the first treatment and thereafter before subsequent treatments in 1999 and 2000. Effects of treatment on W. bancrofti infection were determined by changes in levels of microfilaraemia, antifilarial antibodies and circulating filarial antigen.

RESULTS

Comparison of geometric mean microfilariae intensities between DEC/ALB combination and DEC or albendazole single therapy groups after two rounds of annual treatment and 24 months follow-up showed that combination therapy resulted in a greater reduction of microfilaraemia than single therapy with either albendazole (p < 0.001) or DEC alone (p = 0.146). The overall levels of anti-filarial antibodies decreased significantly (p = 0.028 for IgG1 and p < 0.043 for IgG4) in all treatment groups at 24 months follow-up. Additionally, overall reduction in geometric mean circulating filarial antigen levels at 24 months was 44%, 60% and 85% for albendazole, DEC and DEC/ALB groups, respectively.

CONCLUSIONS

These study findings suggest that albendazole improved efficacy of DEC and mass administration of a combination of the two drugs would therefore enhance the interruption of transmission of W. bancrofti in endemic areas. This information has important implications for the ongoing Global Program for Elimination of Lymphatic Filariasis.

Sustained reduction in prevalence of lymphatic filariasis infection in spite of missed rounds of mass drug administration in an area under mosquito nets for malaria control

BACKGROUND

The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was established by the World Health Organisation (WHO) in 2000 with the goal of eliminating lymphatic filariasis (LF) as a public health problem globally by 2020. Mass drug administration (MDA) of antifilarial drugs is the principal strategy recommended for global elimination. Kenya launched a National Programme for Elimination of Lymphatic Filariasis (NPELF) in Coast Region in 2002. During the same year a longitudinal research project to monitor trends of LF infection during MDA started in a highly endemic area in Malindi District. High coverage of insecticide treated nets (ITNs) in the coastal region has been associated with dramatic decline in hospital admissions due to malaria; high usage of ITNs is also expected to have an impact on LF infection, also transmitted by mosquitoes.

RESULTS

Four rounds of MDA with diethylcarbamazine citrate (DEC) and albendazole were given to 8 study villages over an 8-year period. Although annual MDA was not administered for several years the overall prevalence of microfilariae declined significantly from 20.9% in 2002 to 0.9% in 2009. Similarly, the prevalence of filarial antigenaemia declined from 34.6% in 2002 to 10.8% in 2009. All the examined children born since the start of the programme were negative for filarial antigen in 2009.

CONCLUSIONS

Despite the fact that the study villages missed MDA in some of the years, significant reductions in infection prevalence and intensity were observed at each survey. More importantly, there were no rebounds in infection prevalence between treatment rounds. However, because of confounding variables such as insecticide-treated bed nets (ITNs), it is difficult to attribute the reduction to MDA alone as ITNs can lead to a significant reduction in exposure to filariasis vectors. The results indicate that national LF elimination programmes should be encouraged to continue provision of MDA albeit constraints that may lead to missing of MDA in some years.

High prevalence of Wuchereria bancrofti infection as detected by immunochromatographic card testing in five districts of Orissa, India, previously considered to be non-endemic

India accounts for over one-third of the world's burden of lymphatic filariasis (LF). Although most coastal districts of Orissa state (eastern India) are LF-endemic, the western districts of Orissa are considered non-endemic. During a large-scale insecticide-treated bed net/microfinance trial, we tested one randomly selected adult (age 15-60 years) for LF from a random sample of microfinance-member households in five districts of western Orissa, using immunochromatographic card testing (ICT). Overall, 354 (adjusted prevalence 21%, 95%CI 17-25%) of 1563 persons were ICT positive, with district-wide prevalence rates ranging from 15-32%. This finding was not explained by immigration, as only 3% of subjects had ever lived in previously known LF-endemic districts. These results therefore suggest ongoing autochthonous transmission in districts where LF control programs are not operational. Our results highlight the importance of broad, systematic surveillance for LF in India and call for the implementation of LF control programs in our study districts.

Mapping, monitoring, and surveillance of neglected tropical diseases: towards a policy framework

As national programmes respond to the new opportunities presented for scaling up preventive chemotherapy programmes for the coadministration of drugs to target lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis, and trachoma, possible synergies between existing disease-specific policies and protocols need to be examined. In this report we compare present policies for mapping, monitoring, and surveillance for these diseases, drawing attention to both the challenges and opportunities for integration. Although full integration of all elements of mapping, monitoring, and surveillance strategies might not be feasible for the diseases targeted through the preventive chemotherapy approach, there are opportunities for integration, and we present examples of integrated strategies. Finally, if advantage is to be taken of scaled up interventions to address neglected tropical diseases, efforts to develop rapid, inexpensive, and easy-to-use methods, whether disease-specific or integrated, should be increased. We present a framework for development of an integrated monitoring and evaluation system that combines both integrated and disease-specific strategies.

Filaria control and elimination: diagnostic, monitoring and surveillance needs

Gold standard diagnosis using blood films or skin snips has dimished relevance as mass drug distribution programmes for control of filaria infections expand. The view of 'diagnosis' and its relevance at the individual level has changed, as it has been recognised that the spectrum of programmatic processes (mapping, mass drug interventions, monitoring and evaluation, and surveillance) require different approaches as different questions are asked at each stage. The feasibility and relevance of skin biopsy or blood film examination is challenged when mass drug distribution seeks to treat all eligibles in communities. The need to expand programmes rapidly by identifying the highest risk communities has seen the development of rapid assessment methods, such as rapid epidemiological mapping of onchocerciasis (REMO) and rapid epidemiological assessment (REA) for onchocerciasis, immunochromatographic test (ICT)-based mapping for lymphatic filariasis (LF), and Rapid Assessment Procedure for Loiasis (RAPLOA) for Loa, to reduce the risk of serious adverse events and to guide projects in high-risk communities. As programmes reduce the prevalence through mass drug distribution, more sensitive techniques are required to define endpoints, for LF in particular where the programmatic goal is elimination; for onchocerciasis, sensitive surveillance tools are required particularly in those areas where such risks of recrudescence are high. Whilst much progress has been made in the development and deployment of rapid methods, there are still specific needs for antigen detection in onchocerciasis, whilst standardisation of a panel of tools for LF will allow the definition of endpoint parameters so that countries can decide when mass drug administration (MDA) can be stopped and have a sensitive post-MDA surveillance system.

Impact of two rounds of mass treatment with diethylcarbamazine plus albendazole on Wuchereria bancrofti infection and the sensitivity of immunochromatographic test in Malindi, Kenya

Annual single-dose mass treatment of endemic populations with a combination of either diethylcarbamazine (DEC) or ivermectin plus albendazole is recommended as the mainstay of lymphatic filariasis elimination programmes. We evaluated the impact of two rounds of annual mass drug administration (MDA) of DEC and albendazole on bancroftian filariasis in a pilot elimination programme in an endemic area of Kenya. Overall prevalence of microfilaraemia decreased by 65.4%, whereas community microfilarial load decreased by 84% after the two MDAs. The prevalence of parasite antigenaemia determined by immunochromatographic test (ICT) declined significantly by 43.5% after the two MDAs. We also studied the effect of mass treatment on the sensitivity of the ICT. Although the sensitivity of the test before treatment was high (89.9%; kappa=0.909) sensitivity was lower after two MDAs (59.3%; kappa=0.644). The finding raises concern about the reliability of the ICT in long-term monitoring of infection and for establishing programmatic endpoints. The results of the present study indicate a relatively high effectiveness of MDA using a DEC/albendazole combination against Wuchereria bancrofti infection and, therefore, it may be a useful strategy to eliminate lymphatic filariasis in onchocerciasis-free areas.