Survey of Bancroftian filariasis infection in humans and Culex mosquitoes in the western Brazilian Amazon region: implications for transmission and control

Introduction The aim of this work was to identify possible lymphatic filariasis foci in the western Brazilian Amazonian that could be established from the reports of Rachou in the 1950s. The study was conducted in three cities of the western Brazilian Amazon region - Porto Velho and Guajará-Mirim (State of Rondônia) and Humaitá (State of Amazonas). Methods For human infection evaluation thick blood smear stained with Giemsa was used to analyze samples collected from 10pm to 1am. Polymerase chain reaction (PCR) was used to examine mosquito vectors for the presence of Wuchereria bancrofti DNA. Humans were randomly sampled from night schools students and from inhabitants in neighborhoods lacking sanitation. Mosquitoes were collected from residences only. Results A total 2,709 night students enrolled in the Program for Education of Young Adults (EJA), and 935 people registered in the residences near the schools were examined, being 641 from Porto Velho, 214 from Guajará-Mirim and 80 from Humaitá. No individual examined was positive for the presence of microfilariae in the blood stream. A total of 7,860 female Culex quinquefasciatus specimens examined were negative by PCR. Conclusions This survey including human and mosquito examinations indicates that the western Amazon region of Brazil is not a focus of Bancroftian filariasis infection or transmission. Therefore, there is no need to be included in the Brazilian lymphatic filariasis control program. .

Prevalence of Bancroftian Filariasis among Edim Otop sub-urban dwellers in Calabar Municipality of cross river state, Nigeria.

Study on the prevalence of brancroftian filariasis among sub-urban dwellers of Edim Otop Community in Calabar, Nigeria was carried out between April and November, 2009. Two hundred and twenty two willing participants within the age range of 15-55 years, from 5 designated zones were randomly selected for the collection of day and night blood samples for screening by ICT card test and Knott’s concentration methods respectively for Wuchereria bancroftian antigen and microfilaria. The participants were made up of 129 males (56.31%) and 92 females (43.69%). The numbers of positive cases obtained by the highly sensitive ICT card test were 38 (17.20%). There was no positive case by the conventional Knott’s concentration method. The highest number of positive cases (4.5%) was obtained from Edim Otop Close and Bassey Oqua zones with 40 and 38 participants, while the least number of positive cases (2.2%) were obtained from Edim Otop Crescent and University of Calabar Satellite town as compared to other zones of the study. . The highest (15.85%) antigenaemia were observed within the ages of 37-47 and the least (0.9%) within 15-25 years old participants. A higher percentage of positive cases were recorded among male participants (57.89%) than females (42.11%). There was no significant difference (P>0.05) in the distribution of parasites according to age and gender in the study area using Chi square methods. Edim Otop Community in Calabar, Cross River State is presented in this study as having shown positive cases of antigenaemia due to Wuchereria bancrofti.

Spatio-temporal variations in adult density, abdominal status & indoor resting pattern of Culex quinquefasciatus Say in Panaji, Goa, India.

Background & objectives: Goa is one of the filariasis endemic states of India. However, information on density pattern and resting behavior of Culex quinquefasciatus Say, the principal vector of filariasis in Goa is lacking. Therefore, current longitudinal study was undertaken to investigate these aspects. Methods: Panaji was divided into six zones and a total of 240 man hours were spent in 60 fixed catching sites to collect the adult Cx. quinquefasciatus mosquitoes on fortnightly basis from indoor resting sites during 2005-06. The female mosquitoes were classified as unfed, fed, semi-gravid and gravid to ascertain the resting behavior of Cx. quinquefasciatus adults. The data were analysed to evaluate the spatio-temporal variations in adult density, abdominal status and indoor resting sites and linked to meteorological variables like temperature, relative humidity, rainfall and number of rainy days. Results: Cx. quinquefasciatus adults were prevalent perennially in Panaji with highest per man hour density of females (48.6) in February and the lowest density (6.6) in September. Monthly variations in the densities between different months was significant (F=15.3; P<0.05). Rainfall significantly influenced the population of Cx. quinquefasciatus (t=2.63; P<0.05). Fed group and semi-gravid group showed a strong correlation with the relative humidity (P<0.05), rain fall (P<0.05) and number of rainy days (P<0.05). 62.4 per cent of females and 65.1 per cent of males preferred to rest on hanging objects. Spatio-temporal variations in the number of Cx. quinquefasciatus females and males resting on different sites and also the variations in different sites (P<0.05) were significant. Interpretation & conclusion: The density of female Cx. quinquefasciatus encountered in all the months was higher than the estimated tolerated level of density of 34 per ten man hours up to which there is no risk of filariasis transmission. The strong correlation between the abdominal conditions and relative humidity, rainfall and number of rainy days imply that these meteorological variables significantly influenced the feeding and fecundity of the species. 85.3 per cent of the indoor resting population comprising of fed, semi-gravid and gravid females confirmed the endophilic nature of the species. The preferential resting behavior of both females and males on hanging objects suggest that use of insecticide treated long-lasting bed nets as personal protective measure can be exploited to reduce the density of the vector species.

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.

A complexidade do custo socioeconômico da filariose linfática / The complexity of the socioeconomic costs of lymphatic filariasis

A falta de conhecimento do impacto socioeconômico das diversas doenças é, geralmente, um dos maiores obstáculos para a obtenção de verbas para investimentos em pesquisa aplicada, assim como para iniciar a implementação de programas de controle necessários aos países em desenvolvimento. Os autores analisam e ressaltam aspectos relevantes da complexidade de quantificação do impacto socioeconômico da filariose linfática e enfatizam as lacunas existentes em algumas áreas do conhecimento, que ainda não foram devidamente exploradas para os portadores da doença. Aos dados de literatura aliam os ecos do aprendizado adquirido através do atendimento de pacientes portadores de infecção e doença bancroftiana em serviço terciário de referência do Núcleo de Ensino Pesquisa e Assistência em Filariose (NEPAF), Recife, Brasil. O impacto social, no seu sentido mais abrangente, mostra indícios fortes de perdas na qualidade de vida dos pacientes, infelizmente ainda pouco documentadas e, até certo ponto, de muito difícil contabilização, pelo tão peculiar abandono social das comunidades endêmicas.

Lack of knowledge of the socioeconomic impact of various diseases is generally one of the biggest obstacles to obtaining funds for investment in applied research and for starting to implement control programs that are needed in developing countries. The authors analyze and emphasize important aspects of the complexity of quantifying the socioeconomic impact of lymphatic filariasis. They highlight the gaps that exist within some fields of knowledge and that these gaps have still not been properly explored with regard to individuals with this disease. They bring together the data in the literature and echoes from their own experience gained through caring for patients with Bancroftian infection and disease at a tertiary referral service (NEPAF - Filariasis Care, Research and Teaching Center, Recife, Brazil). The social impact, in its broadest sense, consists of strong indications of losses of quality of life among patients. Unfortunately, this is still poorly documented and, up to a certain point, very difficult to quantify because of the very particular social abandonment of the endemic communities.

Aspectos da realidade social de crianças e adolescentes atendidos em serviço de referência para filariose bancroftiana, Recife, estado de Pernambuco / Aspects of the social realities of children and adolescents seen at a reference service for bancroftian filariasis in Recife, state of Pernambuco

Os autores abordam aspectos da realidade social de crianças e adolescentes residentes em Jaboatão dos Guararapes/PE, diagnosticados como portadores de infecção filarial bancroftiana e tratados no Núcleo de Ensino, Pesquisa e Assistência em Filariose da Universidade Federal de Pernambuco (Centro de Ciências da Saúde), um serviço terciário de referência para filariose. Quantificam e classificam as condições de moradia como subumanas, estando em relação direta com a manutenção da transmissão da bancroftose, e alertam para a necessidade de decisão política quanto à implementação de obras de saneamento básico.

The authors report on aspects of the social realities of children and adolescents living in Jaboatão dos Guararapes, State of Pernambuco, who were diagnosed with Bancroftian filariasis infection and were treated at the Filariasis Teaching, Research and Care Center of the Federal University of Pernambuco (Health Sciences Center), which is a tertiary-level reference service for filariasis. The patients’ housing conditions were quantified and classified as subhuman, with a direct relationship with the maintenance of Bancroftian filariasis transmission, and the authors highlight the need for political decisions regarding the implementation of basic sanitation projects.

Diagnostic utility of monoclonal antibodies raised against microfilarial excretory-secretory antigens in bancroftian filariasis.

Two monoclonal antibodies Wuchereria bancrofti Ε 33 and Wuchereria bancrofli Ε 34 raised against Wuchereria bancrofti microfilarial excretory-secretory antigens were studied for their diagnostic utility. Wuchereria bancrofti Ε 34 monoclonal antibody was found to be relatively specific and sensitive in detection of circulating filarial antigen. When Wuchereria bancrofti Ε 34 monoclonal antibody was used alongwith immunoglobulin G fraction of human filarial serum immunoglobulins in double antibody sandwich enzyme linked immunosorbent assay. 68% of microfilaraemic sera (26 out of 38). 12% of clinical filarial sera (3 out of 25), 13% endemic normal sera (2 out of 15) and none of the 20 non-endemic normal sera showed the presence of filarial antigen. The filarial antigen detected by Wuchereria bancrofti Ε 34 monoclonal antibody in double antibody sandwich enzyme linked immunosorbent assay is possibly associated with the active stage (microfilaraemia) of infection.

Immunodiagnosis of bancroftian filariasis—Problems and progress.

The immunodiagnosis of bancroftian filariasis is a major challenge to the immunoparasitologist. Significant progress is yet to be made in developing convenient laboratory animal model and in in vitro cultivation of filarial parasites making it very difficult to obtain required amount of parasite material for research. Parasitological examination techniques are not useful in low microfilaraemia, occult or chronic .filarial infections. A precise and accurate immunodiagnostic technique is very much needed for successful filaria control programmes. Such a test will also avoid the need for laborious night blood examination in bancroftian filariasis. Due to comparatively easy availability, a good amount of work has been done to explore immunodiagnostic potential of heterologous filarial antigens isolated from Litomosoide carinii, Dirofilaria immitis, Brugia malayi, Setaria digitata, Setaria cervi and number of other filarial species. However, there has been limited or no significant success due to number of false negative and false positive reactions. Extensive study has also been made with antigens isolated from Wuchereria bancrofti microfilariae. Soluble antigens of microfilariae have been used in different immunological techniques such as skin test, counter immuno electrophoresis, indirect haemagglutination test, indirect fluorescent antibody test and enzyme linked immunosorbent assay. Fractionation of Wuchereria bancrofti microfilarial soluble antigens yielded mfS3e antigen fraction which was found to be highly reactive in microfilaraemia by enzyme linked immunosorbent assay, but the yield of the purified antigen was not sufficient enough to make it a practical proposition for large scale isolation of antigen. Wuchereria bancrofti microfilarial excretory-secretory antigens were found to be specific and highly sensitive requiring as little as 0·35 ng antigen protein per well in penicillinase enzyme linked immunosorbent assay for detection of filarial antibody. One ml of culture fluid was found to be sufficient for 400,000 tests. Field evaluation of this test showed that it can replace laborious night blood examination. Assay systems have been developed for detection of filarial antigen in serum, urine, hydrocele fluid and immune complexes using immunoglobulins from chronic filarial sera and antisera to excretory filarial antigens. Further purification of excretory-secretory antigens by affinity chromatography and production of monoclonal antibodies should hopefully give suitable reagents for use in sensitive assays such as enzyme immuno assay and immuno radiometric assay, providing an ideal assay system for detection of active filarial infection in the not too distant future.