Efficacy of three formulations of diflubenzuron, an insect growth regulator, against Culex quinquefasciatus Say, the vector of Bancroftian filariasis in India.

Background & objectives: Insect growth regulators (IGRs) offer alternatives to conventional chemical larvicides that pose problem of resistance and environmental safety. However, only a limited number of IGRs have been approved for use in mosquito control. In the present study, two new formulations of the IGR diflubenzuron, 2 per cent granular (GR) and 2 per cent tablet (DT) were tested for its efficacy against Culex quinquefasciatus, in comparison to its 25 per cent wettable powder (WP) formulation. Methods: The WP, GR and DT formulations were tested in cesspits, street drains and abandoned wells each at four dosages, 25, 50, 75 and 100 g ai/ha. Additionally, the DT formulation was tested at a higher dosage of 1 tablet/m2 (equal to 400 g ai/ha). Results: The WP and GR formulations yielded >80 per cent inhibition of adult emergence (IE) for 7-10 days in cesspits, 4-7 days in street drains and 7-21 days in abandoned wells at all dosages tested. The DT formulation was effective only at higher dosage 100 g ai/ha and or 1 tablet/m2 for 7-15 days at all habitats. Interpretation & conclusions: The trial showed that the dosage 25 g ai/ha of 25 per cent WP could be the field dosage for cesspits and wells, and 50 g ai/ha for drains, to be applied at weekly intervals. The dosages 25, 50 and 100 g ai/ha of 2 per cent GR could be the field dosages for application in cesspits at weekly intervals, in abandoned wells every three weeks and in drains at weekly intervals, respectively. Diflubenzuron 25 per cent WP and 2 per cent GR could be used for larval control of Cx. quinquefasciatus under integrated vector management programme.

Evaluation of toxicity of plant extracts against vector of lymphatic filariasis, Culex quinquefasciatus.

Background & objectives: Conventional insecticides are generally used as larvicides to control Culex quinquefasciatus, vector of lymphatic filariasis. This study was undertaken to evaluate the larvicidal activity of some potential larvicidal plants leaf extracts against Cx. quinquefasciatus larvae. Methods: The toxic effects of petroleum ether leaf extracts of plants viz., Argemone mexicana (Mexican prickly poppy), Clausena dentata (Dentate), Cipadessa baccifera (Rana bili), Dodonaea angustifolia (Hop bush) and Melia dubia (Pride of India) were evaluated under laboratory conditions in individual and in combination against 3rd - 4th instar larvae of Cx. quinquefasciatus. Results: The results indicated that among the selected plants, A. mexicana showed maximum larvicidal activity with an LC50 value of 48.89 ppm. Its toxicity was enhanced when the extract was mixed (1:1) with that of C. dentata as the LC50 value became 28.60 ppm indicating synergistic action of A. mexicana. Interpretation & conclusions: Our results showed high larvicidal potential in A. mexicana leaf extract, and it also showed additive effect when mixed with C. dentata extract.

Perfil epidemiológico e antigênico da população não aderente ao tratamento em massa para filariose linfática no município de Olinda - PE / Antigenic and epidemiological profile of the population adheres to mass treatment for lymphatic filariasis in the city of Olinda-PE

A Organização Mundial de Saúde aponta a Filariose Linfática como endemia potencialmente eliminável. Para isso, foi criado o Programa Global de Eliminação da Filariose Linfática, que possui como uma de suas estratégias o tratamento em massa da população endêmica. A baixa adesão ao tratamento representa um sério obstáculo ao sucesso do programa. Assim, o objetivo deste estudo é descrever o perfil epidemiológico e antigênico e os fatores relacionados a não adesão ao tratamento em massa para filariose linfática no município de Olinda-PE. Trata-se de um estudo de corte transversal, cuja população foi constituída por pessoas que se recusaram a participar do tratamento em massa nos bairros Alto da Bondade e Alto da Conquista, nos anos de 2009 e 2010. Os dados foram coletados através da aplicação de questionários e do teste antigênico (ICT card test). Os indivíduos positivos pelo ICT card test foram avaliados através da filtração (teste parasitológico padrão-ouro). Para o processamento e a análise de dados foi utilizado o programa Epi-Info. Foram pesquisados 102 indivíduos, sendo 51 (50,00 por cento) moradores do Alto da Bondade e 51 (50,00 por cento) do Alto da Conquista. A maioria era do sexo feminino (63,73 por cento) com média de idade de 49,39 anos, e possuía o ensino médio (17,6 por cento). Sobre as características socioambientais, verificou-se que todos os domicílios visitados eram de alvenaria. Cerca de 90por cento possuía abastecimento de água ligado à rede geral e coleta de lixo por serviço de limpeza urbana, porém o esgotamento sanitário era feito através de fossas rudimentares. Do total de pesquisados, quatro (3,92 por cento) apresentaram-se antígeno-positivos para Wuchereria bancrofti através do teste ICT card test), porém não apresentaram positividade na filtração. Os principais motivos encontrados para a não adesão ao tratamento em massa foram o não recebimento da medicação e relacionados às reações adversas, porém tais razões não foram completamente esclarecidas. Novas estratégias são necessárias para o aumento da adesão ao tratamento em massa, dentre as quais ações de educação em saúde e campanhas de sensibilização.

An allele specific PCR assay for screening for drug resistance among Wuchereria bancrofti populations in India.

Background & objectives: Albendazole, a commonly used anthelminthic drug that targets the polymerization of α- and β-tubulin dimer is currently co-administered with the antifilarial drug, diethylcarbamazine citrate (DEC) in the ongoing Global Programme for Elimination of Lymphatic Filariasis (GPELF). The experience in veterinary field has shown that there can be a rapid development of resistance to this drug, which therefore, needs to be monitored regularly in GPELF. Hence, we investigated the nucleotide polymorphism in the albendazole-binding domain of the isotype 1 β-tubulin gene from several populations of Wuchereria bancrofti and developed an AS-PCR assay useful in screening for sensitive/resistance alleles among parasite populations and also evaluated its utility. Methods: For studying the polymorphism of isotype 1 β-tubulin gene, a 475 bp fragment spanning exon 5 and 6 of the gene was amplified and sequenced from the genomic DNA of W. bancrofti collected from six geographic regions of India. An allele specific (AS) PCR for screening albendazole sensitivity/resistance was developed and a total of 55 mf samples from blood smears on slides collected from Thiruvannamalai, Thanjavur and Puducherry were screened. Selective therapy with DEC was in place in three areas, mass drug administration (MDA) with DEC alone was implemented in four areas, while DEC plus albendazole was administered in one district. Results: The analysis of the nucleotide sequence of the fragment from 20 W. bancrofti populations showed the domain to be highly conserved. An allele-specific PCR assay developed was used to detect sensitive/ resistance alleles among 55 isolates of W. bancrofti and no albendazole resistance alleles were detected among the populations tested. Interpretation & conclusion: The drug-binding domain of isotype 1 β-tubulin gene of W. bancrofti from different geographical locations was highly conserved. The AS-PCR developed showed potential application as a tool for monitoring albendazole sensitivity/resistance alleles among W. bancrofti populations, in areas where combination therapy of DEC-albendazole is being mass administered in the LF elimination programme.

Mudanças de paradigmas na filariose bancroftiana / Paradigm shift in bancroftian filariasis

Ao longo do tempo, a maneira como se entende um determinado assunto passa por modificações através da pesquisa científica. Na maioria das vezes, essas mudanças causam pequenas diferenças na estrutura total do tópico em questão. Outras vezes, entretanto, ocorrem mudanças revolucionárias que não só alteram a compreensão do assunto em si, mas promovem a abertura de diferentes perspectivas que podem desencadear o início de novas etapas de interpretações e de novos caminhos de conhecimento. Exemplo disso foram os estudos de Gregor Johann Mendel que levaram à descoberta de leis da hereditariedade que, por sua vez, revolucionaram a biologia e traçaram as bases da genética. Em algumas situações, as mudanças não só modificam a forma de pensar, mas também têm implicações práticas ao melhorar a qualidade de vida de muitos seres humanos. No seu livro A Estrutura de Revoluções Científicas, Thomas Kuhn se refere às ruturas nessa evolução científica como "mudanças de paradigma", um termo que hoje é usado de uma forma genérica para descrever uma modificação profunda em nossos pontos de referência. O paradigma de que o estágio adulto da Wuchereria bancrofti causava a obstrução do vaso linfático e desencadeava uma reação imunológica inevitável em indivíduos predispostos, provocando a elefantíase, foi substituído pela esperança de que ser infectado não mais significa, necessariamente, ser um potencial portador da forma mais deformante da disfunção linfática. A infecção bacteriana secundária de repetição (semelhante clinicamente à erisipela) é hoje reconhecida como o fator mais importante para a instalação e a progressão do linfedema crônico, nos indivíduos que vivem em áreas endêmicas de filariose linfática. Evitar ou minimizar os episódios agudos bacterianos é um processo factível para a maioria dos habitantes das comunidades endêmicas, através do uso regular de água e sabão: a forma mais simples de higiene já conhecida pelo ser humano.

The way a particular subject is understood changes over time as a result of scientific research. In most cases, these changes are minor, with limited effect on the overall knowledge on the subject. Sometimes, however, revolutionary changes occur and not only modify the understanding of the subject but open perspectives that can trigger new interpretations and new ways for expansion of scientific knowledge. The studies of Gregor Johann Mendel were a good example. They led to discovery of the laws of inheritance which, in turn, have revolutionized biology and provided the foundation for genetics. In certain situations, changes not only alter ways of thinking, but have practical implications, also improving the quality of life for many people. In his book The Structure of Scientific Revolutions, Thomas Kuhn refers to discontinuities in scientific development as a "change of paradigm", a term now used in a generic manner to describe a profound changes in our reference points. For lymphatic filariasis the old paradigm stated that Wuchereria bancrofti at the adult stage causes lymphatic vessel obstruction, triggering an inevitable immune response in predisposed individuals and leading to elephantiasis. This has been replaced by a new paradigm, which offers hope that W. bancrofti infection does not necessarily predispose to the disfiguring outward manifestation of lymphatic dysfunction. Repeated secondary bacterial infections (erysipela-like) are now recognized as the most important factor for initiation and progression of chronic lymphedema in individuals living in filariasis-endemic areas. Most inhabitants of endemic communities can prevent and minimize the acute bacterial episodes by regular use of soap and water, the simplest form of hygiene already well known to human beings.

Disseminated Microfilaremia Associated with Lung Cyst and Empyema: An Autopsy Report

Clinical manifestations of extralymphatic disease caused by filariasis are varied and range from symptoms due to tropical pulmonary eosinophilia to hematuria, proteinuria, splenomegaly, and rarely arthritis. Disseminated microfilaremia in association with loculated lung cyst and empyema is of rare occurrence and to the best of our knowledge has not been documented in the literature so far. We report here a case of disseminated microfilaremia due to Wuchereria bancrofti infection accompanied by a lung cyst and empyema in a 21-year-old Indian man.

Lymphoscintigraphic evidence of lymph vessel dilation in the limbs of children with Brugia malayi infection.

Lymphatic filariasis (LF) is targeted for global elimination by the year 2020. It was earlier believed that LF is mostly a disease of adults. Recent studies indicate that in endemic countries filarial infection starts mostly in childhood even though the disease manifestations occur much later in life. The initial damage to the lymph vessels where the adult worms are lodged is dilation, thought to be irreversible even with treatment. Most of these studies relate to bancroftian filariasis. Studies that address this early pathology in brugian filariasis in humans are scarce. We report here for the first time, the lymphatic abnormalities seen on lymphoscintigraphy (LSG) in children with Brugia malayi filariasis. LSG was performed in 100 children aged between 3-15 years, who were enrolled in the study either because they were microfilaremic; had present or past filarial disease or were positive for antifilarial IgG4 antibodies. Inguinal and axillary lymph nodes were imaged in most children. Dilated lymph vessels were visualized in 80 children and this pathology was evenly distributed in all the three study groups. Lymph vessels dilation was seen even in three year old children. The implications of these findings for management of LF and control programmes are discussed.

Susceptibility of Mansonia uniformis to Brugia malayi microfilariae from infected domestic cat.

Microfilariae of Brugia malayi is transmitted to man and other susceptible hosts via mosquito. The transmission of B. malayi from cat to man by Ma. uniformis bite has never been reported. The Ma. uniformis mosquito is the normal vector for Wuchereria bancrofti but has never been reported as a vector for B. malayi, or a susceptible host for the growth and development of the microfilariae of B. malayi. The purpose of this study was to examine the development of B. malayi in Mansonia uniformis after feeding on the blood of an infected cat in the laboratory. The B. malayi infected cat was identified using PCR with the primers Bm-1/Bm-2 on DNA (at 10 ng/50 microl) extracted from the WBC of the cat. W. bancrofti was employed as a negative control. The sensitivity of the B. malayi DNA detection by PCR was 0.0001 ng. Adult Ma. uniformis mosquitos at the ages of 5, 10, and 15 days, 100 mosquitos in each group, were fed on the infected cat blood. Recovery of third stage microfilariae was found to be the highest in the 5-day old mosquito group (48%), followed by the 10- and 15-day old mosquito groups (32% and 18%, respectively). The mean number of B. malayi microfilariae found in thorax, head, and abdomen of the mosquitos were composed. The 5-day old (40.3%) and 10-day old (41.9%) mosquitos were significantly more susceptible to microfilariae than the 15-day old mosquitos (17.8%) (p-values using the Scheffe method: 0.027 and 0.039, respectively). There was no significant difference in the mean number of microfilariae in the thorax (p = 0.482) by age, but the mean numbers of microfilariae in the heads, and abdomens were significantly different by age between the 5- and10-, and the 15-day old mosquitos (p < 0.001 and p = 0.004, respectively).

Impact of different housing structures on filarial transmission in rural areas of southern India.

The aim of the present investigation was to assess the filarial transmission levels in houses of different structure in rural areas of Andhra Pradesh, India. During this study, ecologically-similar households were selected for entomological study. The per-man-hour density (PMHD), infection and infectivity rates, were recorded in different ranges ie, 16.1 to 77.6, 0-31.2% and 0-5.6%, respectively.

W. bancrofti as a causal agent of polymyositis.

A case of polymyositis associated with Bancroftian filariasis in an adult male who presented with generalised painful swelling and weakness of muscles is presented. He had elevated muscle enzymes, a myopathic EMG pattern, focal vasculitis on gastrocnemius muscle biopsy and W. bancrofti in the peripheral blood. There was clinical, biochemical and histopathological evidence of resolution of the disorder and total clearance of microfilaremia with diethyl carbamazine (DEC) therapy.

The resting and house frequenting behavior of Mansonia annulifera, Ma. uniformis and Ma. indiana, the vectors of Malayan filariasis in Kerala State, India.

Mansonia annulifera, was recorded to be an endophilic species, preferring to rest indoors, while Ma. uniformis was exophilic, having a predilection for outdoor resting habitats, eg bushes and shrubs. Ma. indiana did not show a clear preference to either of these biotopes. In indoor resting collections, the unfed proportion of Ma. uniformis was significantly higher during post-dusk compared to day hours (p < 0.05), indicating that this exophilic species enters houses during dusk hours for feeding. The full fed proportion was higher during day hours compared to dusk/night hours. The semigravid proportion showed a significant reduction during post-dusk hours (p < 0.05). These findings suggest that after having a blood-meal this species rest indoors and leave the houses for outdoor resting sites during the dusk hours on the subsequent night.

A simple deterministic model for host-parasite relationship in Wuchereria bancrofti infection & its relevance to parasite regulation in human host.

A deterministic immigration-death model, which reflects the population dynamics of W. bancrofti in human host has been applied to study the relationship between vector and human infections. Application of the model showed that the rate of acquisition and loss of human infection were approximately equal (L = 0.130 and M = 0.129). The relationship of infective resting density (IRD) in vector population with maximum intensity (Imax) of infections and microfilaria prevalence (MFP) in human population were examined by using the least squares polynomial regressions. The fifth order polynomial regressions were found to be adequate to describe the observed pattern (Imax vs IRD: R2 = 0.8464, P = 0.0015; MFP vs IRD: R2 = 0.7246, P = 0.019). The observed relationships indicated that at an infective resting density of 0.26 per man hour or above, the density-dependent factors start regulating the human infections, which showed a declining trend, following this level.

Filariasis in Tak Province, northwest Thailand: the presence of subperiodic variant Wuchereria bancrofti.

The microfilariae found in carriers at Tak Province, Northwestern Thailand were morphologically and morphometrically studied. It was found that the parasites conformed to that of W. bancrofti microfilaria. The microfilarial periodicity as determined from four carriers was found to be nocturnally (early evening) subperiodic type showing a distinct peak at 1800 hours.