Evaluation of diagnostic tests for Wuchereria bancrofti infection in Brazilian schoolchildren

Introduction Since the launch of the Global Programme to Eliminate Lymphatic Filariasis, more than 70% of the endemic countries have implemented mass drug administration (MDA) to interrupt disease transmission. The monitoring of filarial infection in sentinel populations, particularly schoolchildren, is recommended to assess the impact of MDA. A key issue is choosing the appropriate tools for these initial assessments (to define the best intervention) and for monitoring transmission. Methods This study compared the pre-MDA performance of five diagnostic methods, namely, thick film test, Knott's technique, filtration, Og4C3-ELISA, and the AD12-ICT card test, in schoolchildren from Brazil. Venous and capillary blood samples were collected between 11 pm and 1 am. The microfilarial loads were analyzed with a negative binomial regression, and the prevalence and associated 95% confidence intervals were estimated for all methods. The accuracies of the AD12-ICT card and Og4C3-ELISA tests were assessed against the combination of parasitological test results. Results A total of 805 schoolchildren were examined. The overall and stratified prevalence by age group and gender detected by Og4C3-ELISA and AD12-ICT were markedly higher than the prevalence estimated by the parasitological methods. The sensitivity of the AD12-ICT card and Og4C3-ELISA tests was approximately 100%, and the positive likelihood ratios were above 6. The specificity of the Og4C3-ELISA was higher than that of the AD12-ICT at different prevalence levels. Conclusions The ICT card test should be the recommended tool for monitoring school-age populations living in areas with ongoing or completed MDA. .

Monitoramento da infecção filarial por Wuchereria bancrofti através da cinética de anticorpos com o antígeno recombinante Bm14, em áreas endêmicas da RMR-PE submetidas ao tratamento coletivo para filariose / Filarial infection monitoring by Wuchereria bancrofti through kinetic antibodies with the recombinant antigen Bm14, in endemic areas of the RMR-PE subject to collective treatment for filariasis

A Filariose Linfática (FL) no Brasil é causada pela espécie Wuchereria bancrofti e consiste em um problema de saúde pública. O principal foco ativo de transmissão atualmente no país é a Região Metropolitana do Recife - PE, que desde 2003 iniciou o Programa de Controle/Eliminação da FL, tendo como estratégia principal o Tratamento Coletivo (TC) com Dietilcarbamanzina (DEC). Este trabalho, aprovado pelo Comitê de Ética em Pesquisa do Centro de Pesquisas Aggeu Magalhães, analisou o TC nessas áreas, acompanhando 30 moradores, no período de 2003 a 2009. Para essa análise além das ferramentas tradicionais da pesquisa filarial - Filtração (MF/mL de sangue) e Antígeno Circulante Filarial (Og4C3) - também foi utilizada a pesquisa de anticorpos através de um antígeno recombinante (Bm14). Essa nova metodologia desenvolvida é recomendada para ser empregada como uma forma de avaliar o progresso dos programas de controle e eliminação da FL nas áreas sob intervenção. Os resultados obtidos indicam redução na positividade para a FL pelas três metodologias: o Bm14 reduziu de 90 por cento para 80,00 por cento, o Og4C3 de 100 por cento para 60,00 por cento e a microfilaremia (MF) de 100 por cento para 0 por cento. A análise da densidade de MF/mL de sangue e a positividade para o Bm14 revelou que o grupo com maior densidade de MF/mL no sangue (= 57 MF/mL) apresentou maior percentual de redução na positividade para o anticorpo do que o grupo de menor densidade ( 57 MF/mL) em 2009. A taxa de anticorpos-positivos apresentou um percentual de redução de 11,11 por cento no último ano. A diminuição nas taxas de positividade apresentadas pelo Bm14 e o padrão de decaimento observado na análise das Densidades Óticas média e mediana do anticorpo durante os seis anos da pesquisa indicam que o monitoramento dos anticorpos com o antígeno recombinante Bm14 foi capaz de reconhecer indivíduos infectados e também de identificar redução dos níveis de anticorpos produzidos por eles após exposição aos parasitos filariais. Sugerindo que o TC com DEC teria surtido efeito na eliminação dos vermes adultos e conseqüente desaparecimento das microfilárias da circulação sanguínea.

Subperiodic, asymptomatic microfilaremia in an adult male from Mysore: a nonendemic area.

Wuchereria bancrofti is found throughout tropics and subtropics like Asia, Pacific islands, Africa, areas of South America and Caribbean basin. In all these areas, except Pacific islands, microfilaria occurs in the periodic form, in which case the microfilaria are found in large numbers in the peripheral blood during night. In the Pacific islands, they occur in the subperiodic form, i.e., microfilaria are present in the peripheral blood at all times and reach the maximum level of parasitemia in the afternoon. Microfilaria of Wuchereria bancrofti and Brugia malayi occurring in India displays a nocturnal periodicity, appearing in large numbers at night. This is the biological adaptation to the nocturnal biting habits of the vector mosquitoes. The maximum density in blood is reported between 10 PM and 2 AM. Here is a case report of asymptomatic microfilaremia showing subperiodicity, which is very unusual in India.

The control and surveillance of filariasis in Hainan Province, China.

Hainan is a single bancroftian filariasis endemic province where filariasis is prevalent in all 18 cities and counties. A program to control filariasis was started in 1953. The strategy of eliminating infection sources has been adopted as the principal intervention measure in filariasis control. Over 30 years, the sustained effort throughout the province reached the point of basic elimination of filariasis in 1987. After the basic elimination of filariasis, the patterns of filariasis transmission in residual microfilaremia cases in Hainan Province were studied so as to provide a scientific basis for formulating strategies to eliminate filariasis. According to the "Technical scheme for surveillance in areas where fialariasis has been basically eliminated" issued by the Ministry of Health, a longitudinal and cross-sectional and entomological surveillance of fialariasis was carried out using parasitological and entomological and serological methods in the whole province during 1983-2004. In the cross-sectional and entomological surveillances, the last microfilaremia case was found in 1999, no mosquitoes were found to be infected with filarial larvae. A total of 132 microfilaremia cases found in the longitudinal surveillance become negative by 10 years. Since 1997 no mosquitoes were found to be infected with filarial larvae in the longitudinal surveillance. Serological surveillance of the population showed the mean positive rate of IFAT dropped from 10.63% in 1990 to 0.28% in 2000, which being similar to that of nonendemic areas. The results show that residual sources of infection after basic elimination of filariasis were tending to be naturally eliminated and transmission of filariasis has been interrupted in Hainan Province.

Microfilaria in thyroid gland nodule.

Presence of microfilaria in the thyroid gland is a rare finding. Filariasis is a common public health problem in the Indian sub-continent. Most of the cases of microfilaria in thyroid gland reported in the literature are associated with goiter and thyroid neoplasms. Here, we present a rare case that showed microfilaria on fine needle aspiration cytology of solitary thyroid nodule.

Filarial granuloma in breast.

A case of filarial granuloma in breast in a 59-year-old female is reported. Adult worm was identified in a breast nodule.

Microfilariae in fine needle aspirates: a report of 22 cases.

The objective of the study is to document the value of fine needle aspiration cytology (FNAC) in the diagnosis of filariasis at all possible sites in both exfoliative cytologic material and fine needle aspirates. Both unguided and guided FNACs of all foci were studied over a period of two years between 1999 to 2000. Total 22 cases of filariasis were detected which included subcutaneous swellings(7), breast(3), thyroid(3), lymphnodes(3), effusions(3), cervical scrape(1), eyeball(1), sputum(1) and bronchial washing(1). In none of these cases was filariasis considered a diagnostic possibility. Cytologic smears showed eosinophils in 9 cases, oval ova and embryonated eggs in 2 cases. Microfilariae were associated with other diseases in 13 cases, including 6 cases of malignancy. Significant adherence of inflammatory cells and macrophages to microfilariae was present in 6 of the 22 cases. In endemic areas,filariasis should be considered one of the differential diagnosis of a swelling. Thus demonstration and identification of the parasite in cytologic smears played a significant role in the prompt recognition of the disease and institution of specific treatment, thus obviating the more severe manifestations of lymphatic frilariasis.

Breast filariasis diagnosed by fine needle aspiration cytology--a case report.

We report a case of female who presented with a lump in the right breast. Fine needle aspiration cytology of lump revealed numerous adult filarial worms. Common habitat of the adult filarial worms is the lymphatic vessels and lymph nodes of limbs and their occurrence in breast is uncommon.

Bancroftian filariasis in an endemic area of Brazil: differences between genders during puberty

Diferenças entre os sexos quanto à susceptibilidade às doenças infecciosas têm sido observadas em vários estudos. Um inquérito de prevalência foi realizado em uma área endêmica de filariose bancroftiana na cidade de Olinda, Brasil. Todos os residentes com idade > 5 anos foram examinados pela gota espessa. Moradores com idade entre 9 e 16 anos foram entrevistados e testados para a presença de antigenemia filarial. Os dados foram analisados utilizando tabelas de contingência e modelos de regressão. O risco de microfilaraemia nos homens foi significativamente mais elevado. Meninos com idade entre 15 e 16 anos tiveram maior risco de infecção filarial do que as meninas. Os dados sugerem que variações entre os sexos na filariose podem resultar de um aumento na susceptibilidade dos homens a partir da puberdade tardia. Essa característica epidemiológica deve ser considerada ao se formularem os planos de eliminação da endemia.

Comparison of an immunochromatographic card test with night blood smear examination for detection of Wuchereria bancrofti microfilaria carriers.

BACKGROUND: At present, two diagnostic tests--Og4C3 ELISA and an immunochromatographic card test (ICT)--are available to detect circulating filarial antigens of Wuchereria bancrofti in serum/whole blood samples collected during the day. We aimed to assess the sensitivity of the new format card test 'NOW ICT Filariasis' in detecting microfilaria carriers of W. bancrofti in comparison with conventional microscopic techniques and Og4C3 ELISA. METHODS: A total of 200 persons were selected from two villages following a quota sampling design (100 in each village). The required number of houses was selected using a systematic sampling procedure with a random start of the first household. Blood samples were taken from all the available persons in each selected house until the quota of 100 was reached. The new format ICT test, Og4C3 ELISA and night blood smear examination for microfilaria were carried out following standard procedures. RESULTS: The sensitivity of the new format ICT test was 100% among microfilaria carriers (detected by both early and late readings). The kappa statistic measure of agreement between the two readings of all the samples (n =200) tested was 0.811 (p<0.05). The new format test also reported 25% of microfilaria-negative individuals as being positive for circulating filarial antigens. However, the diagnostic lines were not stable beyond 10 minutes (particularly in the case of amicrofilaraemic persons). Though there was an overall agreement between the results of ICT and Og4C3 tests (kappa =0.612; p< 0.05), the sensitivity of the Og4C3 test was lower than that of ICT. CONCLUSION: The new format ICT test is highly sensitive in detecting microfilaria carriers in endemic communities. Improvement in the format to provide stable diagnostic lines, specificity of the format and cost of the test kit are to be considered before its large-scale use.