The Burden of Bancroftian Filariasis in Nigeria: A Review.

BACKGROUND: Lymphatic filariasis (LF) is a neglected tropical disease (NTD) vectored by mosquito; and people in rural areas are mostly at risk of infection. Pooling prevalence data across the six geo-political zones of Nigeria is expected to provide a clearer insight into the burden of the disease as this information could guide towards planning eradication programmes. METHODS: Search for pertinent literature was done on Google Scholar, African Journal Online (AJOL) and PubMed databases using relevant keywords. Studies on the prevalence of LF due to Wuchereria bancrofti in Nigeria were selected and reviewed. Prevalence data from the different states were further organized into the six geopolitical zones and analyzed. RESULTS: Of the 36 states in Nigeria, prevalence data were available only for 19 states. Furthermore, in the six geopolitical zones, North-West had the highest disease burden (44 per 10 000) of Years Lived with Disability (YLD), while North-Central (4 per 10 000) had the lowest disease burden. CONCLUSION: Result are largely attributed to the prevailing conditions in the different zones. In view of ensuring a successful control plan and eventual eradication of the disease, a comprehensive national survey in every state should be carried out using more sensitive tools.

Applications of machine learning techniques to predict filariasis using socio-economic factors.

Filariasis is one of the major public health concerns in India. Approximately 600 million people spread across 250 districts of India are at risk of filariasis. To predict this disease, a pilot scale study was carried out in 30 villages of Karimnagar district of Telangana from 2004 to 2007 to collect epidemiological and socio-economic data. The collected data are analysed by employing various machine learning techniques such as Naïve Bayes (NB), logistic model tree, probabilistic neural network, J48 (C4.5), classification and regression tree, JRip and gradient boosting machine. The performances of these algorithms are reported using sensitivity, specificity, accuracy and area under ROC curve (AUC). Among all employed classification methods, NB yielded the best AUC of 64% and was equally statistically significant with the rest of the classifiers. Similarly, the J48 algorithm generated 23 decision rules that help in developing an early warning system to implement better prevention and control efforts in the management of filariasis.

Molecular xenomonitoring for Wuchereria bancrofti in Culex quinquefasciatus in two districts in Bangladesh supports transmission assessment survey findings.

BACKGROUND: Careful monitoring for recrudescence of Wuchereria bancrofti infection is necessary in communities where mass drug administration (MDA) for the elimination of lymphatic filariasis (LF) as a public health problem has been stopped. During the post-MDA period, transmission assessment surveys (TAS) are recommended by the World Health Organization to monitor the presence of the parasite in humans. Molecular xenomonitoring (MX), a method by which parasite infection in the mosquito population is monitored, has also been proposed as a sensitive method to determine whether the parasite is still present in the human population. The aim of this study was to conduct an MX evaluation in two areas of Bangladesh, one previously endemic district that had stopped MDA (Panchagarh), and part of a non-endemic district (Gaibandha) that borders the district where transmission was most recently recorded. METHODOLOGY/PRINCIPAL FINDINGS: Mosquitoes were systematically collected from 180 trap sites per district and mosquito pools were tested for W. bancrofti using real-time PCR. A total of 23,436 intact mosquitoes, representing 31 species, were collected from the two districts, of which 10,344 (41%) were Culex quinquefasciatus, the vector of W. bancrofti in Bangladesh. All of the 594 pools of Cx. quinquefasciatus tested by real-time PCR were negative for the presence of W. bancrofti DNA. CONCLUSIONS/SIGNIFICANCE: This study suggested the absence of W. bancrofti in these districts. MX could be a sensitive tool to confirm interruption of LF transmission in areas considered at higher risk of recrudescence, particularly in countries like Bangladesh where entomological and laboratory capacity to perform MX is available.

The untapped cell biology of neglected tropical diseases.

The World Health Organization lists a constellation of 17 tropical diseases that afflict approximately one in six individuals on the planet and, until recently, few resources have been devoted to the treatment and eradication of those diseases. They are often referred to as the diseases of the "bottom billion," because they are most prevalent among the poorest individuals in impoverished tropical nations. However, the few studies that have been performed reveal an extraordinary world of molecular and cellular adaptations that facilitate the pathogens' survival in hosts ranging from insects to humans. A compelling case can be made that even a modest investment toward understanding the basic molecular and cell biology of these neglected pathogens has a high probability of yielding exciting new cellular mechanisms and insights into novel ways of combating these diseases.

A cohort study on anti-filarial IgG4 and its assessment in good and uncertain MDA-compliant subjects in brugian filariasis endemic areas in southern Thailand.

The prevalence of Brugia malayi was surveyed in three highly endemic provinces in southern Thailand as part of an ongoing evaluation of the effectiveness of two rounds of mass drug administration (MDA). Prior to MDA IV, and thereafter every 6 months up to 18 months, including MDA V at 12 months, nocturnal blood sampling was assayed for microfilaria (mf) and IgG4 antibodies in 200 subjects from Nakorn Srithammarat and Surathani provinces. From an additional 300 subjects from Narathiwatt province, daytime blood was also examined for IgG4 antibodies for 1 year. Subjects who tested positive, with reciprocal IgG4 titres above 100, were dichotomized in the 'good compliant' or 'uncertain compliant' groups. Stool samples were examined for intestinal parasites from all 500 subjects simultaneously. Only two subjects (1%) tested positive for mf, while 98 subjects (19.6% of 500) tested positive for IgG4. In general, the good drug-compliant subjects were less likely to exhibit the IgG4 response than subjects in the uncertain compliant group. Only six subjects (1.2%) exhibited lymphoedema while 68 subjects (13.6%) had a total of 105 parasitic infections, with female instances of protozoan infections exceeding male instances of helminth infections. It was concluded that the two MDA rounds were highly successful in not only in reducing mf to negligible levels but also in lowering antifilarial IgG4 titres in the good compliant subjects. The IgG4 assay is a sensitive and cost-effective surveillance tool for the early detection of brugian infections that is not contingent on nocturnal blood collections.

Tropical parasitic diseases and women.

Tropical parasitic diseases constitute the greatest threat to the health and socio-economic status of women as a gender and social group. There are some gender specific ways in which parasitic diseases affect women in contrast to men due to differences in exposure, occupational risk, sociocultural behavior, gender roles and practices. These parasitic diseases confer some social stigma, which affects the health seeking behavior of women. Women are therefore important in the control of these parasitic diseases and they are key agents of change, if they are included in community control programs. Women need more attention in endemic areas as a group that had been neglected. This deprived and excluded group have got vital role to play, as discussed in this review.

Effect of yearly mass drug administration with diethylcarbamazine and albendazole on bancroftian filariasis in Egypt: a comprehensive assessment.

BACKGROUND: Egypt was one of the first countries to implement a national programme to eliminate lymphatic filariasis based on WHO's strategy of repeated rounds of mass drug administration (MDA) with diethylcarbamazine and albendazole (target population, 2.5 million in 181 localities). We assessed the effect of five yearly rounds of MDA on filariasis in four sentinel villages in Egypt. METHODS: We studied two areas with different infection rates before MDA: the Qalubyia study area had a low infection rate because of previous treatment with diethylcarbamazine; this was typical of most filariasis-endemic villages in Egypt before MDA. The Giza study area had a high baseline infection rate. We undertook repeated surveys in villages for treatment compliance and tests for microfilaraemia and circulating filarial antigenaemia, antibodies to filarial antigen Bm14 in schoolchildren, and infections in indoor-resting mosquitoes (assessed by PCR). FINDINGS: MDA compliance rates were excellent (>80%). In Giza after MDA, prevalence rates of microfilaraemia and circulating filarial antigenaemia fell from 11.5% to 1.2%, and from 19.0% to 4.8%, respectively (p<0.0001). Corresponding rates in Qalubyia fell from 3.1% to 0% and 13.6% to 3.1%, respectively (p<0.0001). Rates of antifilarial antibody and circulating filarial antigenaemia in schoolchildren (aged about 7-8 years), fell from 18.3% to 0.2% (p<0.0001) and from 10.0% to 0.4% (p<0.0001) in Giza, respectively, and from 1.7% to 0% and 1.7% to 0% (both p=0.13) in Qalubyia, respectively. Mosquito infection rates fell from 3.07% (95% CI 2.38-3.88) to 0.19% (0.08-0.38) in Giza and from 4.37% (3.07-5.99) to 0% (0-0.05) in Qalubyia. INTERPRETATION: MDA greatly affects variables related to infection (microfilaraemia and circulating filarial antigenaemia prevalence rates) and transmission (antifilarial antibodies in young children and mosquito infection rates). Our results suggest that after five rounds of MDA filariasis is likely to have been eliminated in most endemic localities in Egypt.

Independent assessment of Mass Drug Administration in filariasis affected Surat city.

The Mass Drug Administration (MDA) done in Surat city (Gujarat) during 2005, revealed good impact on infection and infectivity in mosquitoes and also on microfilaria rate & mean infection density. The overall impact seen was 23% on mf rate, 28% on mean mf density, 65% on infection rate and 50% on infectivity rate in vectors. Indigenous population contribution to microfilaria cases was 9.7%, whereas migratory population contributed 72.2%; predominant 51.9% from Orissa and 20.3% from U.P. Of the total 3640 persons interviewed for MDA compliance in seven zones of the Surat city revealed that actual drug consumption was 76.7% (2792/3640). Another 11.9% although took the drug but did not consume and 11.4% refused. Important reasons for consuming was fear to get the disease (40.7%) and for not consuming; 'will consume after meal' (6.9%), too many tablets (1.7%), seek consent from doctor (1.5%), lack of awareness (1.4%) etc. Refusal was mainly due to the reason as respondents felt apparently healthy. Assessment of IEC activities suggested that main awareness was created by media (local or national TV, banners or handbills, local news papers or mike announcement) alongwith some impact made through NGO's. These observations clearly indicated the utility of effective health education for optimum community participation and shown that it was crucial for successful community based elimination campaign. However some gray areas also suggest the scope for further improvements.

[Scientific knowledge and public health policies: reflections on the occurrence of filariasis in Recife, Pernambuco, Brazil]. / A produção do conhecimento científico e as políticas de saúde pública: reflexões a partir da ocorrência da filariose na cidade do Recife, Pernambuco, Brasil.

This article discusses the relationship between the production of scientific knowledge on filariasis in Brazil and health policy-making and implementation related to control of the disease. The study presents a review of scientific output on filariasis from the creation of the Program to Combat Filariasis in the mid-20th century until the creation of the Unified National Health System (SUS) within the framework of decentralized control of endemic diseases in the country. The focus on empirical observations in Recife, a city where filariasis is present, highlights the relevant institutional processes and the role of various players. The hypothesis is that in the first half of the 20th century there was a lack of scientific knowledge and technological development to control the problem, but that after these advances were obtained, new requirements of a political nature came into play and acted as determinants for persistence of the endemic in the city.

The use of grid sampling methodology for rapid assessment of the distribution of bancroftian filariasis.

The recent World Health Assembly Resolution to eliminate lymphatic filariasis as a public health problem once more brings to the fore the need for reliable data for the effective planning of disease control programmes. Most countries do not have data on the distribution of lymphatic filariasis and are therefore not in the position to initiate control programmes based on sound baseline data. We tested in Ghana in 1998-99 a method for the Rapid Assessment of the Geographical Distribution of Bancroftian Filariasis (RAGFIL) that uses a spatial sampling grid with 50 km between sampled villages, rapid assessment surveys for filariasis prevalence in the sampled villages and spatial analysis to estimate the geographical distribution of filariasis throughout the study area. The prevalence contours obtained with the 50 x 50-km sampling grid were operationally similar to those obtained with a 25 x 25-km grid. The predicted prevalence was not statistically different from the sample survey prevalence in 57 independent villages and the 50 x 50-km grid appears adequate for rapid mapping of filariasis. For the purpose of filariasis mapping, the antigen test would seem a better diagnostic test than clinical examination for hydrocoele. We recommend that a regional approach to mapping be used because of the importance of cross-border foci as demonstrated by our findings from the north of Ghana. Application of the method will provide the minimal information required for effective planning of treatment programmes, and will facilitate estimation of the number of people to be treated. It will also help improve estimates of the number of people at risk and affected, and of the burden of disease due to lymphatic filariasis in Africa.

Programa especial para investigación y adiestramiento en enfermedades tropicales (TDR) / Special programme in research and training in tropical diseases

A description of the six tropical diseases involved in the programme and the achierement of research goals are evaluated. The author points out the important accomplishment of these aims in the impact in the malaria and filiariasis control, in the elimination of leprosy and the future erradication of Chagas disease in the Americas. At the same time the relevance of the manpower training were imphasized in the strenghtening on the research infrastructure of the member countries

Cost and cost effectiveness of mass diethylcarbamazine chemotherapy for the control of bancroftian filariasis: comparison of four strategies in Tanzania.

This study examines the costs and cost effectiveness of four different mass diethylcarbamazine (DEC) chemotherapy regimens-standard dose, semi-annual single dose, low monthly dose and DEC-medicated salt-in reducing microfilarial (mf) prevalence at the community level. Costs were estimated for each intervention in relation to both ingredient and activity, by the derivation and use of detailed itemized cost menus. The most expensive and most effective strategy in reducing community mf prevalence over 2 years was DEC salt intervention, followed in order of costs by the standard, low monthly and semi-annual DEC strategies. The most cost effective strategy was the low monthly DEC treatment. Cost and sensitivity analyses, however, suggest that the optimal choice of mass DEC strategy for reducing mf is very sensitive to programme design parameters. In particular, the results demonstrate that if the salt delivery structure is simplified, DEC salt has the potential to be the dominant intervention for filariasis control. The results suggest that economies of scale considerations might militate against the adoption of this intervention for large-scale applications, unless perhaps offset by its potential for cost recovery by direct patient purchase. Further analyses require a more realistic evaluation of filariasis intervention effectiveness by addressing changes in infection intensity and by accounting for the population dynamics of parasite transmission and control.

Urbanizaçao, favelas e endemias: a produçao da filariose no Recife, Brasil / Urbanization, slums, and endemics: the production of filariasis in Recife, Brazil

Discute a ocorrência da filariose como um problema de saúde pública na cidade do Recife, capital do Estado de Pernambuco, que apresenta ainda hoje, em algumas áreas, níveis de prevalência preocupantes. Procura mostrar o papel da evoluçao urbana da cidade, caracterizada por um crescimento desordenado e pela formaçao de um número crescente de favelas, na criaçao de condiçoes propícias para a transmissao desta parasitose. Identifica categorias de análise, ligadas à organizaçao social do espaço urbano, que devem ser incluídas como "mediadoras" em um modelo compreensivo da transmissao da filariose. Os aglomerados de habitaçoes inadequadas, construídas em favelas superpovoadas, sem saneamento básico e sem sistema de drenagem de águas propiciam as condiçoes adequadas à proliferaçao dos mosquitos vetores da infecçao e à manutençao da endemia

Assessment of intradermal test in longitudinal surveillance of bancroftian filariasis.

Longitudinal surveillance was carried out consecutively during 1982-1987 in two pilot villages where bancroftian filariasis was prevalent in different severity before 1982. Intradermal test (IT) with filaria polypeptide (FPT) antigen prepared from Dirofilaria immitis was made. It was shown that the level of immediate hypersensitivity reaction to the antigen in population as shown by IT appeared to be directly proportional to both the prevalence of the disease and the infection rate of mosquitoes harbouring larval filariae before mass and selective treatment with diethylcarbamazine. Time for negative conversion of IT after chemotherapy was significantly longer in previous microfilaraemic patients than that in amicrofilaraemic cases. The selected three criteria of IT used in filariasis surveillance, namely, the positive rate, frequency of strong reaction and positive conversion rate, were diminished gradually after chemotherapy year by year, so that the three criteria were demonstrated to be useful for longitudinal surveillance of lymphatic filariasis.

[Assessment of intracutaneous test in longitudinal surveillance for lymphatic filariasis].

In order to evaluate the usefulness of intracutaneous test (IT) in longitudinal surveillance of filariasis, two administrative villages selected from Queshan County, Henan Province of China, endemic for Wuchereria bancrofti, were surveyed in 1982, 1983 and 1987 respectively, by IT with antigen FPT derived from Dirofilaria immitis. The result showed that the original level of IT to antigen FPT in the population was consistent with the data of either etiological or entomological investigation before chemotherapy. When the microfilaraemia rate and natural filarial infection rate of mosquitoes in a village were high, the positive rate and frequency of strong positivity (skin wheel diameter greater than or equal to 1.3 mm) for immediate hypersensitivity reaction would be high too; and the reverse was true. It is suggested that both criteria of IT mentioned above may be useful in assessing endemicity of lymphatic filariasis before mass chemotherapy. The speed of negative conversion of IT in both groups, the previously microfilaraemic patients and the microfilaraemic inhabitants positive to immediate hypersensitivity reaction before chemotherapy, were different, the former being significantly slower than that of the latter after mass and selective chemotherapy with diethylcarbamazine. All of the three criteria for immediate hypersensitivity, positive rate, frequency of strong positivity and positive conversion rate, decreased gradually after a mass and selective DEC treatment. Until 1987, the 5th year after the chemotherapy, the average positive rate in the two villages dropped to 20.0% from 55.4% in 1982, the frequency of strong positivity to 2.8% from 23.8% in 1982, and the positive conversion rate to 9.7% (1984-1987) form 19.2% (1982-1983).(ABSTRACT TRUNCATED AT 250 WORDS)

Aspectos epidemiológicos sócio-economicos e culturais da Filariose de Bancrofti em Castro Alves - BA / Epidemiological, socio-economic and cultural aspects of Filariasis de Bancrofti in Castro Alves, Bahia, Brazil

Através de um estudo epidemiológico retrospectivo, com o objetivo de descrever algumas características epidemiológicas e os determinantes sócio-econômicos e culturais da filariose (Wuchereria bancrofti), foram investigados 102 indivíduos portadores de bancroftose registrados pela Superintendência de Campanhas de Saúde Pública - SUCAM, no período de junho de 1977 à julho de 1980, na cidade de Castro Alves, BA e 198 indivíduos sadios, sorteados na comunidade, obedecendo criterios de pareamento por sexo, cor da pele e idade, os quais passaram a compor o grupo controle. Verificou-se que a maioria dos indivíduos doentes achavam-se concentrados nas áreas I e II da cidade onde säo precárias as condiçöes de saneamento e habitaçäo, o mesmo acontecendo para moradias que apresentavam foco ou criadouro peridomiciliar e que na maioria das vezes, eram construidos com materiais de qualidade inferior. Nos diferentes níveis de renda registrou-se associaçäo estatísticamente significativa entre a presença de foco ou criadouro peridomiciliar e a microfilaremia, com maior intensidade entre aqueles que apresentavam os menores níveis de renda per capita...

Bovine parafilariosis in Southern Africa: a preliminary report.

A total of 32,042 cattle, slaughtered at the Pretoria, Johannesburg and Durban abattoirs, was examined for parafilariosis and as many animals as possible were traced to the farms from which they originated. The disease is most prevalent in the Bushveld areas of the northern Transvaal. The most important factors limiting its distribution are the annual rainfall and the duration of the frost period. Mention is made of some aspects of the economic loss involved. The effect of routine anthelmintic treatment and dipping on the prevalence of the parasite is briefly discussed.