Lymphatic filariasis, infection status in Culex quinquefasciatus and Anopheles species after six rounds of mass drug administration in Masasi District, Tanzania.

BACKGROUND: Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. Evidence shows a persistent LF transmission despite more than a decade of mass drug administration (MDA). It is advocated that, regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely. This study was therefore designed to assess the status of Wuchereria bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District, South Eastern Tanzania. METHODS: Mosquitoes were collected between June and July 2019 using Center for Diseases Control (CDC) light traps and gravid traps for indoor and outdoor respectively. The collected mosquitoes were morphologically identified into respective species. Dissections and PCR were carried out to detect W. bancrofti infection. Questionnaire survey and checklist were used to assess vector control interventions and household environment respectively. A Poisson regression model was run to determine the effects of household environment on filarial vector density. RESULTS: Overall, 12 452 mosquitoes were collected of which 10 545 (84.7%) were filarial vectors. Of these, Anopheles gambiae complex, An. funestus group and Cx. quinquefasciatus accounted for 0.1%, 0.7% and 99.2% respectively. A total of 365 pools of Cx. quinquefasciatus (each with 20 mosquitoes) and 46 individual samples of Anopheles species were analyzed by PCR. For Cx. quinquefasciatus pools, 33 were positive for W. bancrofti, giving an infection rate of 0.5%, while the 46 samples of Anopheles species were all negative. All 1859 dissected mosquitoes analyzed by microscopy were also negative. Households with modern latrines had less mosquitoes than those with pit latrines [odds ratio (OR) = 0.407, P < 0.05]. Houses with unscreened windows had more mosquitoes as compared to those with screened windows (OR = 2.125, P < 0.05). More than 80% of the participants own bednets while 16.5% had no protection. CONCLUSIONS: LF low transmission is still ongoing in Masasi District after six rounds of MDA and vector control interventions. The findings also suggest that molecular tools may be essential for xenomonitoring LF transmission during elimination phase.

Interruption of lymphatic filariasis transmission in Manaus, a former focus of Wuchereria bancrofti in the Western Brazilian Amazon / Interrupción de la transmisión de la filariasis linfática en Manaos, anteriormente un foco de Wuchereria bancrofti en la Amazonia occidental de Brasil / Interrupção da transmissão da filariose linfática em Manaus, anteriormente um foco de Wuchereria bancrofti na parte leste da Amazônia brasileira

ABSTRACT Objective. To confirm the absence of Wuchereria bancrofti autochthonous cases in Manaus, a former focus of lymphatic filariasis in the Western Brazilian Amazon. Methods. A field survey was carried out in 2016 using immunochromatographic rapid tests (ICT card) for the detection of circulating filarial antigens in blood. The sample included a group of 3 000 schoolchildren aged 6 to 10 years enrolled in schools from different urban areas of Manaus (including the former lymphatic filariasis focus in the city) and a group of 709 adolescents and adults, between the ages of 11 and 85 years, born and raised in different areas of Manaus. Results. All of the individuals tested negative for W. bancrofti antigen. Conclusions. Although Manaus was once considered endemic, this focus no longer seems to be active for lymphatic filariasis transmission. The results of this study could support the certification by the World Health Organization of the lymphatic filariasis transmission elimination exercise in Brazil.

RESUMEN Objetivo. Confirmar la ausencia de casos autóctonos de Wuchereria bancrofti en Manaos, anteriormente un foco de filariasis linfática en la Amazonia occidental de Brasil. Métodos. En el 2016 se llevó a cabo una encuesta en el terreno con pruebas rápidas inmunocromatográficas (tiras inmunocromatográficas) para detectar antígenos filáricos circulantes en sangre. La muestra constó de un grupo de 3 000 escolares de 6 a 10 años matriculados en escuelas de diferentes zonas urbanas de Manaos (incluida la zona que anteriormente era el foco de filariasis linfática en la ciudad) y de un grupo de 709 adolescentes y adultos, de edades comprendidas entre 11 y 85 años, nacidos y criados en diferentes áreas de Manaos. Resultados. Todas las personas dieron negativo en la prueba de antígeno de Wuchereria bancrofti. Conclusiones. Aunque hubo un tiempo en que Manaos se consideraba zona endémica, parece que este foco de transmisión de la filariasis linfática ya no está activo. Los resultados de este estudio podrían brindar apoyo a la certificación de la Organización Mundial de la Salud respecto de los esfuerzos realizados en Brasil para eliminar la transmisión de la filariasis linfática.

RESUMO Objetivo. Confirmar a ausência de casos autóctones de Wuchereria bancrofti em Manaus, anteriormente um foco da filariose linfática na parte leste da Amazônia brasileira. Métodos. Uma pesquisa de campo foi realizada em 2016 com o uso de teste rápido por imunocromatografia (cartão ICT) para detecção de antígenos de microfilárias circulantes no sangue. A amostra estudada consistiu de um grupo de 3 000 crianças escolares entre 6 e 10 anos de idade matriculados em escolas de diferentes áreas da zona urbana de Manaus (englobando a área anteriormente com o foco de filariose linfática) e um grupo de 709 adolescentes e adultos entre 11 e 85 anos de idade nascidos e crescidos em diferentes áreas de Manaus. Resultados. Todos os indivíduos pesquisados tiveram teste negativo para o antígeno da W. bancrofti. Conclusões. Apesar de Manaus ter sido anteriormente uma área endêmica, parece que não existe mais foco ativo de transmissão da filariose linfática na cidade. Os resultados deste estudo podem servir para embasar a certificação pela Organização Mundial da Saúde da eliminação da transmissão da filariose linfática no Brasil.

Implementing a community vector collection strategy using xenomonitoring for the endgame of lymphatic filariasis elimination.

BACKGROUND: The global strategy for elimination of lymphatic filariasis is by annual mass drug administration (MDA). Effective implementation of this strategy in endemic areas reduces Wuchereria bancrofti in the blood of infected individuals to very low levels. This minimises the rate at which vectors successfully pick microfilariae from infected blood, hence requiring large mosquito numbers to detect infections. The aim of this study was to assess the feasibility of using trained community vector collectors (CVCs) to sample large mosquito numbers with minimal supervision at low cost for potential scale-up of this strategy. METHODS: CVCs and supervisors were trained in mosquito sampling methods, i.e. human landing collections, pyrethrum spray collections and window exit traps. Mosquito sampling was done over a 13-month period. Validation was conducted by a research team as quality control for mosquitoes sampled by CVCs. Data were analyzed for number of mosquitoes collected and cost incurred by the research team and CVCs during the validation phase of the study. RESULTS: A total of 31,064 and 8720 mosquitoes were sampled by CVCs and the research team, respectively. We found a significant difference (F(1,13) = 27.1606, P = 0.0001) in the total number of mosquitoes collected from southern and northern communities. Validation revealed similar numbers of mosquitoes sampled by CVCs and the research team, both in the wet (F(1,4) = 1.875, P = 0.309) and dry (F(1,4) = 2.276, P = 0.258) seasons in the southern communities, but was significantly different for both wet (F(1,4) = 0.022, P = 0.005) and dry (F(1,4 ) = 0.079, P = 0.033) seasons in the north. The cost of sampling mosquitoes per season was considerably lower by CVCs compared to the research team (15.170 vs 53.739 USD). CONCLUSIONS: This study revealed the feasibility of using CVCs to sample large numbers of mosquitoes with minimal supervision from a research team at considerably lower cost than a research team for lymphatic filariasis xenomonitoring. However, evaluation of the selection and motivation of CVCs, acceptability of CVCs strategy and its epidemiological relevance for lymphatic filariasis xenomonitoring programmes need to be assessed in greater detail.

Socio-environmental variables and transmission risk of lymphatic filariasis in central and northern Mozambique.

Lymphatic filariasis (LF) is endemic in Mozambique, where it is caused by Wuchereria bancrofti with Culex quinquefasciatus as the main vector. It affects approximately 10% of the population (2 million) with about 16 million at risk. Prevalence rates in 40 out of 65 districts that together comprise the four endemic provinces Niassa, Cabo Delgado, Nampula and Zambezia were analysed with the aim of elucidating the socio-environmental variables influencing the transmission. The levels of prevalence were divided into six ranks and certain climatic, environmental and social factors were considered independent variables. A climadiagram was created and the LF risk and the water budget-based index were calculated for each district. Factors influencing the risk of the overall transmission and that of the provincial levels were established by discriminant analysis. The results show that LF transmission increased with mean maximum temperature and decreased with altitude. The almost constant annual temperature (especially in the tropical area), altitude, general economic conditions and predominant crop production (rice) were found to be responsible for the abundance and presence of the vector. However, despite the presence of the vector in the hinterland, presence and survival of the parasite were not found to be favoured there. The transmission risk was found to be highest in Zambezia, and consequently also the prevalence, while the situation in Niassa was the opposite. The conclusion is that temperature, altitude and the development/poverty index (particularly in the urban areas) have to be considered as transmission risk factors for LF in Mozambique. The extent of rice culturing probably also plays a role with respect to this infection.

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.

Programa de controle e eliminação da filariose linfática: uma parceria da Secretaria de Saúde de Olinda-PE, Brasil, com o serviço de referência nacional em filarioses / Elimination and control of lymphatic filariasis program: a partnership between the Department of Health in Olinda, Pernambuco state, Brazil and the national center of lymphatic filariasis

Ante o conhecimento técnico-científico sobre a bancroftose acumulado ao longo dos anos, somado ao conhecimento da biologia do parasito, sabe-se que somente o ser humano funciona como seu reservatório, que este parasito é transmitido por culicídeo, não se multiplica no hospedeiro, não é causador de uma doença infectocontagiosa e há disponibilidade de medicação eficaz. Segundo a Organização Mundial da Saúde, a doença é potencialmente eliminável até 2020. Este relatório descreve, pioneiramente, as ações do Programa de Eliminação da Filariose Linfática do município de Olinda, Pernambuco, Brasil, particularmente o tratamento coletivo efetuado pela equipe do Programa de Saúde da Família, a seleção de grupos sentinelas e o diagnóstico situacional da morbidade. São feitas, neste trabalho, recomendações para a avaliação e o acompanhamento do impacto dessas ações, com as diversas opções de diagnóstico integrado à avaliação vetorial, e também é ressaltada a importância da articulação entre o Serviço de Referência Nacional em Filarioses e a Secretaria de Saúde de Olinda, associando pesquisa e serviço, com o objetivo de assegurar o êxito do programa.

Isolation of an antigen fraction from Setaria cervi adults having potential for immunodiagnosis of human filariasis.

Crude antigenic preparations from heterologous filarial parasites gave false positive results because of complex nature of these antigens and their cross-reactivity with other helminth parasites. In the present study, efforts have been made to isolate and characterize the antigens from Setaria cervi important for diagnostic purposes. The fractionation of S. cervi somatic antigenic preparation on Sephacryl S-200 resulted in separation of three major antigenic peak fractions. Crossed immunoelectrophoretic analysis, using immune rabbit serum, revealed 13-14 antigens in SFP-I pool fraction, which showed high reactivity with filarial patients sera as compared to other two pool fractions. This SFP-I fraction was further purified by DEAE-Cellulose column chromatography. Out of the 4 antigen pool fractions, DFP-IV fraction showed high ELISA reactivity with filarial patient serum pool (Wuchereria bancrofti and Brugia malayi) as compared to other fractions. The SDS-PAGE analysis of DFP-IV fraction revealed 2 major and 1 minor protein bands (mol. wt. range 65-70 kDa). Crossed immunoelectrophoresis also showed the presence of 3 antigenic peaks in DFP-IV fraction. The purified DFP-IV fraction showed high reactivity with filarial patients sera but did not cross-react with sera from ascaris and hookworm infections thereby suggesting the filaria-specificity and potential for immunodiagnosis of human filariasis.

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

Lymphatic filariasis is endemic in the coastal areas of Kenya, with four major foci identified in the early 1970s. The prevalence and intensity of Wuchereria bancrofti infection, together with antifilarial antibody responses, were assessed in a historically highly endemic focus along the River Sabaki, in Malindi district. The prevalences of microfilaraemia and antigenaemia (detected by Og4C3 ELISA) were >20% and >40%, respectively, and both increased steadily with age. The high prevalences of antifilarial IgG1 (86%) and IgG4 (91%) responses indicate that most people living in this setting are exposed to W. bancrofti infection. The children investigated had higher levels of antifilarial IgG1 than the adults. The results of this study, based on a battery of currently available parasitological and immunological methods, provide an epidemiological update on lymphatic filariasis on the northern Kenyan coast. They show that the River Sabaki area is still an important focus for bancroftian filariasis and highlight the importance of implementing an elimination programme, to interrupt the transmission of W. bancrofti in all areas of endemicity in Kenya. The detailed baseline data collected in the River Sabaki area make the communities studied ideal as sentinel sites for epidemiological monitoring and the evaluation of the impact of mass drug administrations to eliminate lymphatic filariasis.

Residual spatial correlation between geographically referenced observations: a Bayesian hierarchical modeling approach.

BACKGROUND: Analytic methods commonly used in epidemiology do not account for spatial correlation between observations. In regression analyses, this omission can bias parameter estimates and yield incorrect standard error estimates. We present a Bayesian hierarchical model (BHM) approach that accounts for spatial correlation, and illustrate its strengths and weaknesses by applying this modeling approach to data on Wuchereria bancrofti infection in Haiti. METHODS: A program to eliminate lymphatic filariasis in Haiti assessed prevalence of W. bancrofti infection in 57 schools across Leogane Commune. We analyzed the spatial pattern in the prevalence data using semi-variograms and correlograms. We then modeled the data using (1) standard logistic regression (GLM); (2) non-Bayesian logistic generalized linear mixed models (GLMMs) with school-specific nonspatial random effects; (3) BHMs with school-specific nonspatial random effects; and (4) BHMs with spatial random effects. RESULTS: An exponential semi-variogram with an effective range of 2.15 km best fit the data. GLMM and nonspatial BHM point estimates were comparable and also were generally similar with the marginal GLM point estimates. In contrast, compared with the nonspatial mixed model results, spatial BHM point estimates were markedly attenuated. DISCUSSION: The clear spatial pattern evident in the Haitian W. bancrofti prevalence data and the observation that point estimates and standard errors differed depending on the modeling approach indicate that it is important to account for residual spatial correlation in analyses of W. bancrofti infection data. Bayesian hierarchical models provide a flexible, readily implementable approach to modeling spatially correlated data. However, our results also illustrate that spatial smoothing must be applied with care.

The eye does not see what the mind does not know: the bacterium in the worm.

Symbiotic relationships underlie the evolutionary success of many different life forms. The filarial worms are long, slender nematode parasites that cause considerable pathology in large segments of the world's population. About 25 years ago, investigators first reported the presence of bacterial organisms living inside these parasitic worms. Recent molecular biological studies have indicated that these bacteria belong to the genus Wolbachia, members of which have been known to be associated with numerous species of insects. Elimination of the Wolbachia from the nematodes (by, for instance, treatment with broad spectrum antibiotics) results in profound disturbances in the physiology of the latter, including a complete block in reproduction. This observation, taken together with the fact that every individual worm examined to date contains Wolbachia, validates the classification of the latter as "endosymbionts." Many studies indicate that the Wolbachia may also play an important role in the pathology caused by the nematode worms, and that it might be possible to target therapy against the Wolbachia to treat the filarial disease. Intriguingly, the intense recent interest in Wolbachia is in complete contrast with the virtually complete indifference evoked by the original discovery of these organisms.

A juvenile filarial worm, Wuchereria bancrofti, extracted from the vitreous of the eye: the first report in the world literature.

A live worm was extracted from the vitreous of the eye of a patient in Sri Lanka. Based on the details of its length, width, oesophagus and vulva it was identified as Ajuvenile female Wuchereria bancrofti.

Evaluation of a single oral dose of diethylcarbamazine 300 mg as provocative test and simultaneous treatment in Myanmar migrant workers with Wuchereria bancrofti infection in Thailand.

We assessed the efficiency of oral diethylcarbamazine (DEC) 300 mg as a provocative test on blood examination 30 minutes after administration, while gauging the overall infection rate in Myanmar migrant workers with Wuchereria bancrofti infection who enrolled for work permits in Thailand in 2002, using circulating filarial antigens (CFA) assays, the NOW ICT Filariasis card test and the Og4C3 ELISA as reference. Overall infection rates of 0.3% (95% CI=0-0.7%), 4.2% (95% CI=1.8-6.5%) and 5.9% (95% CI=3.2-8.7%) by three diagnostic tests, respectively, were observed. Among three different location groups of Myanmar population sample tested, there were no statistically significant differences in the overall infection detection rates. When either the ICT card test or the Og4C3 ELISA was used as a reference, the specificity and positive predictive value of the DEC-provocative day test was the same, 100%. The sensitivities were 25.0% (95% CI = 0.5-49.5%) and 17.6% (95% CI = 0-35.8%) on the ICT and ELISA tests, respectively. The negative predictive values were 96.8% (95% CI = 94.8-98.9%) and 95.1% (95% CI = 92.6-97.6%), respectively. In three microfilaremic persons followed-up monitored at 8-weeks DEC post-provocation, there were 6 x 10(-1) and 7 x 10(-1) decreases in microfilaremia and antigenemia. These findings suggested that, unlike the CFA assays, the DEC-provocative day test is unsuitable for the diagnosis of active W. bancrofti infection in the population tested, and for gauging current infection prevalence. The treatment would likely be beneficial to reduce microfilaremia and antigenemia.

Filariasis elimination in Egypt: impact of low microfilaraemics as sources of infection for mosquitoes.

The elimination strategy for lymphatic filariasis aims at reducing blood microfilaraemia to levels at which vector transmission cannot be sustained. We aimed to determine whether patients with pre-treatment low or ultra-low microfilaria (MF) counts could be a reservoir of infection after mass drug administration (MDA) with a combined regimen. Laboratory-reared mosquitoes were fed on 30 volunteers after 2 rounds of MDA. Microfilaria uptake, infectivity rates and number of Wuchereria bancrofti L3 per mosquito were assessed. One year after MDA-1, 6 subjects transmitted MF, but up to 9 months after MDA-2 transmission failed. Six months after MDA-2 > 90% had clear MF smears and either failed to transmit MF or transmitted MF that did not develop to L3. We conclude that the transmission cycle is seriously weakened after MDA-2.

A morfologia do intestino médio de Culex quinquefasciatus Say, 1823 e sua interação experimental com microfilárias de Litomosoides chagasfilhoi Moraes Neto, Lanfredi e De Souza, 1997 e Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921

Analisamos a morfologia do intestino médio do mosquito Culex quiquefasciatus de região endêmica e a sua interação com as microfilárias de Wuchereria bancrofti (agente da filariose humana) e de Litomosoides chagasfilhoi (agente de filariose de roedores). O intestino médio está dividido em regiões torácica e abdominal como visto em outras espécies de mosquitos. Porém, o intestino médio torácico é formado por dois tipos celulares: células principais e basais; e o intestino médio abdominal por três tipos: células principais clara e basais. Existe uma rede muscular organizar revestindo externamente o órgão, a qual sofre mudanças irreversíveis no intestino médio abdominal após o repasto sangüíneo. A estrutura da matriz peritrófica e a sua formação induzida pela alimentação sangüínea são distintas das demais espécies de mosquitos. O L. chagasfilhoi invade o intestino médio entre 1h e 3h após o repasto infectivo, enquanto que a W. bancrofti entre 30 minutos e 5 horas com o maior número de invasão nas primeiras 2 horas. O L. chagasfilhoi preferencialmente invade o intestino médio abdominal enquanto que a W. bancrofti invade o intestino médio torácico, principalmente perto da região abdominal. Ambas espécies de microfilárias cruzam o intestino médio através do espaço intercelular, causando hipertrofia e extrusão de uma a duas células epiteliais. A perda da bainha pelas microfilárias de ambas espécies não é um pré-requisito para a evasão do intestino. Etapas subseqüentes do ciclo da W. bancrofti, tais como, a melanização na hemocele e a invasão precoce da musculatura de vôo foram também observadas. Não foi possível observar tais etapas nos mosquitos infectados com L. chagasfilhoi porque eles morreram poucas horas após a invasão do intestino médio. Estas diferenças no processo de interação das espécies de microfilárias provavelmente estão relacionados com a capacidade vetorial do mosquito

A morfologia do intestino médio de Culex quinquefasciatus Say, 1823 e sua interação experimental com microfilárias de Litomosoides chagasfilhoi Moraes Neto, Lanfredi e De Souza, 1997 e Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921 / The morphology of the midgut of Culex quinquefasciatus Say, 1823 and its interaction with experimental microfilariae of Litomosoides chagasfilhoi Moraes Neto, Lanfredi and De Souza, 1997 and Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921

Analisamos a morfologia do intestino médio do mosquito Culex quiquefasciatus de região endêmica e a sua interação com as microfilárias de Wuchereria bancrofti (agente da filariose humana) e de Litomosoides chagasfilhoi (agente de filariose de roedores). O intestino médio está dividido em regiões torácica e abdominal como visto em outras espécies de mosquitos. Porém, o intestino médio torácico é formado por dois tipos celulares: células principais e basais; e o intestino médio abdominal por três tipos: células principais clara e basais. Existe uma rede muscular organizada revestindo externamente o órgão, a qual sofre mudanças irreversíveis no intestino médio abdominal após o repasto sangüíneo. A estrutura da matriz peritrófica e a sua formação induzida pela alimentação sangüínea são distintas das demais espécies de mosquitos. O L. chagasfilhoi invade o intestino médio entre 1h e 3h após o repasto infectivo, enquanto que a W. bancrofti entre 30 minutos e 5 horas com o maior número de invasão nas primeiras 2 horas. O L. chagasfilhoi preferencialmente invade o intestino médio abdominal enquanto que a W. bancrofti invade o intestino médio torácico, principalmente perto da região abdominal. Ambas espécies de microfilárias cruzam o intestino médio através do espaço intercelular, causando hipertrofia e extrusão de uma a duas células epiteliais. A perda da bainha pelas microfilárias de ambas espécies não é um pré-requisito para a evasão do intestino. Etapas subseqüentes do ciclo da W. bancrofti, tais como, a melanização na hemocele e a invasão precoce da musculatura de vôo foram também observadas. Não foi possível observar tais etapas nos mosquitos infectados com L. chagasfilhoi porque eles morreram poucas horas após a invasão do intestino médio. Estas diferenças no processo de interação das espécies de microfilárias provavelmente estão relacionados com a capacidade vetorial do mosquito.

Wuchereria bancrofti infection and disease in a rural area of Papua New Guinea.

The relation between infection and disease in lymphatic filariasis is still imperfectly understood. This paper presents baseline data on microfilaraemia, oedema and acute episodes from a drug trial against bancroftian filariasis in Papua New Guinea. Among 2,187 people with data on these manifestations, 1,144 were microfilaraemic, 78 had leg oedema, 356 had acute episodes and 919 were negative for all three. All possible combinations of the three manifestations were observed. The relationships between microfilaraemia and disease are found to be time-dependent. Microfilaraemia is a positive risk factor for leg oedema at lower ages, but a negative one at higher ages. Acute disease over a whole year is found to be positively associated with a point estimate of microfilaraemia. However, when considering incidence within a month of the time of the blood sample, a curvilinear relationship is found and people with low but positive microfilarial counts have the lowest incidence. Possible explanations for these findings are discussed.

Human immune responses to lymphatic filariasis in Papua New Guinea.

The following review highlights our current knowledge about the host immune response to lymphatic filariasis. Our understanding of how the host immune response influences the risk of developing disease has changed dramatically over the past decade. Previously the spectrum of disease associated with lymphatic filariasis was largely attributed to the nature of the host immune response. Now we appreciate that the duration and intensity of infection and possibly the direct influence of parasite-derived molecules also determine the risk of disease. The review highlights recent studies examining the influence of transmission intensity on the host immune response, and how this might be mediated by defects in antigen-presenting cell function, and also the role of basophils and mast cells.

Métodos laboratoriais disponíveis para o diagnóstico da filariose linfática / Available laboratorial diagnostic methods of the lymphatic filariasis

O presente trabalho tem como objetivo revisar os métodos laboratoriais disponíveis para se diagnosticar a filariose linfática bancroftiana. Doença transmitida pelo vetor Culex quinquesfasciatus, e que é encontrada no Brasil, na Regiäo Metropolitana de Recife - PE, Maceió - AL, e Belém - PA. Apesar de existir uma variedade de testes utilizando a pesquisa do parasito, anticorpo, antígeno e DNA, na rotina diagnóstica, um cuidado deve ser tomado pelo profissional de saúde na interpretaçäo dos resultados, quer para diagnóstico ou descarte de infecçäo filarial, quer principalmente para atribuir ou näo à filariose, um quadro de adenopatia, linfedema ou hidrocele de que o paciente seja portador