Ultrastructural analysis of Wuchereria bancrofti (Nematoda: Filarioidea) body wall.

Bancroftian filariasis constitutes the principal mosquito-borne nematode infection of humans and the surface of adult of Wuchereria bancrofti seems to be especially important in the intricate interplay between host and parasite. The study of the parasite's surface structure might help to understand the localization and function of various organelles. W. bancrofti adult worms were recovered from untreated patients during hydrocele repair surgery and studied by transmission electron microscopy. The body wall of adult parasite is composed of cuticle, hypodermis and muscular layer. Cuticle is the external layer and shows transverse cuticular striation. It is composed by an epicuticle, cortical layers, median layer, fibrous layers and basal layer. The epicuticle is the most external cuticular layer and appears as a single laminar electron-dense layer. The cortical external region is more electron-dense and granular in appearance than the inner cortical layer. Electron-dense structures, called bosses are randomly distributed filling the cuticular striation. The median layer is formed by an electron-dense and continuous thick line. The fibrous layer is subdivided in inner and external layers connected by projections. The basal layer includes a large quantity of membranous projections directed toward the hypodermis. The hypodermis is a syncytium where some cellular organelles are observed. The somatic musculature is meromyarian. The muscle fibers consist of contractile and non-contractile regions and the contractile region is composed of myofilaments separated by dense body. This is the first study of W. bancrofti adult worms obtained from untreated patients and studied by transmission electron microscopy.

Sex ratio of Wuchereria bancrofti in surgical specimens from an endemic area of Brazil.

The sex ratio of adult Wuchereria bancrofti from 172 histologically diagnosed cases of lymphatic filariasis, all from an endemic area of Recife, in north-eastern Brazil, was investigated. Of 172 tissue specimens examined, 74 (43%) were lymph nodes and 98 (57%) lymphatic-vessel segments. The morphology of the worms was generally disrupted, in some cases to the point where the worms were almost completely absorbed by the granulomatous inflammatory response. Parasite gender was clearly determined in only 110 (64%) specimens, 61 (55.5 %) of which were lymph nodes and 49 (44.5%) lymphatic vessels. Eighty-seven (79.1%) of these tissue specimens contained only female worms, 17 (14.5%) both males and females, and six only males, giving an overall female:male 'specimen' ratio of 4.5:1. Of the 63 tissue specimens in which dead or degenerating worms were noted, 60 (92.2%) contained only females. All the female worms detected were gravid, regardless of whether male worms were present in the specimen. The implications of these findings for parasite dynamics, the pathogenesis of bancroftian filariasis and the interpretation of ultrasound images of living adult worms are discussed.

Comparative analysis of a chemotherapy effect on the cuticular surface of Wuchereria bancrofti adult worms in vivo.

Wuchereria bancrofti is the main species responsible for human lymphatic filariasis and remains a major public health problem in tropical countries around the world. Diethylcarbamazine (DEC) has been used for decades in control programs as an effective microfilaricide, although its efficacy in killing adult worms is only around 50% and its direct mode of action is unclear. Recently, in an attempt to control and eliminate lymphatic filariasis, WHO has recommended albendazole (ALB), a broad-spectrum anthelminthic combined with DEC or ivermectin for mass treatment. Some studies have shown that DEC alone blocks oogenesis, fertilization in adult worms, and loss of the microfilarial sheath of several filarial species, whereas ALB is thought to target nematode tubulin. So far, the direct effect of ALB in combination with DEC has not been described in W. bancrofti adult worms. Therefore, the purpose of this study is to investigate by scanning electron microscopy if DEC coadministered with ALB can induce in vivo morphological alterations of the W. bancrofti adult worm surface obtained from a patient in whom the adult worm remained alive, checked serially by ultrasonography for 2 months after antifilarial treatment. Our analysis demonstrates that worms presented morphologic alterations in some regions suggesting cuticular surface damage. On the other hand, adult worms that were recovered from a patient treated with DEC alone after a single dose did not show such any abnormalities.

Children and adolescents infected with Wuchereria bancrofti in Greater Recife, Brazil: a randomized, year-long clinical trial of single treatments with diethylcarbamazine or diethylcarbamazine-albendazole.

In filariasis-endemic areas beyond sub-Saharan Africa, the World Health Organization's recommended strategy for interrupting transmission of the causative parasites is annual, single-dose, mass treatment with a combination of diethylcarbamazine (DEC; given at 6 mg/kg) and albendazole (ALB; given at 400 mg) for 4-6 years (the minimum estimated life-span of the adult parasites). In an open, hospital-based, randomized and controlled trial, with a blinded evaluation of outcome, 82 children and adolescents from Recife, all with Wuchereria bancrofti microfilaraemias, were given either DEC alone (6 mg/kg) or the same dose of DEC combined with ALB (at 400 mg/patient). Every 90 days for 1 year after the single treatment, each patient was checked for microfilaraemia by the filtration of up to 5 ml of venous blood collected at night. One year post-treatment, 16 (39%) of the 41 patients given DEC alone and 20 (49%) of the 41 given DEC-ALB were found microfilaraemic (relative risk=0.8, with a 95% confidence interval of 0.49-1.31) and the corresponding geometric mean levels of microfilaraemia were 2.0% and 1.8% of the levels recorded immediately pre-treatment, respectively (P>0.05). In terms of the prevalences and intensities of microfilaraemia, therefore, the addition of ALB to the DEC appeared to offer no significant benefit.

Bancroftian filariasis in children and adolescents: clinical-pathological observations in 22 cases from an endemic area.

In areas where bancroftian filariasis is endemic, the clinical manifestations of the disease, which are often very varied, appear most frequently during early adulthood or later. In consequence, very little attention, if any, has been given to the signs and symptoms of the disease in childhood. In an attempt to fill this gap, clinical and pathological observations were made, in Brazil, on 22 children (aged 2-15 years) who were infected with Wuchereria bancrofti. There was a predominance of lymph-node involvement. In all but three (14%) of the children (who had adult parasites in their intrascrotal lymphatic vessels), the adult worms were located in the afferent or efferent vessels of draining lymph nodes, predominantly in the inguinal region. None of the patients presented with distal lymphoedema, and the adenopathy was characterized by painless, localized, lymph-node enlargement, without signs of inflammation in the overlying skin. Histologically, the alterations in the lymphatic vessels and surrounding structures were similar to those described in adult patients, and depended essentially on adult-parasite viability. The localization of the adult worms in the paediatric cases was peculiar and distinct from that observed in adult patients, in whom the adult parasites are usually found in extra-nodal lymphatic vessels. In areas endemic for bancroftian filariasis, therefore, filarial infection should be considered as a possible cause of adenopathy. For the differential diagnosis of adenopathy in young patients from endemic areas, the authors recommend the use of ultrasound and other non-invasive diagnostic tools, as alternatives to excisional biopsies, which are often unnecessary in bancroftian filariasis.

The histopathology of bancroftian filariasis revisited: the role of the adult worm in the lymphatic-vessel disease.

Although morphology is generally limited to static images, the histopathological features of bancroftian lymphatic disease are presented here in a way that is as dynamic as possible and closely associated with the clinical, ultrasonographic and surgical characteristics. The protean spectrum of alterations seen in the host's lymphatic vessels is discussed, and the changes caused by the live and dead worms are highlighted, as independent events. Evidence of a remodelling process, in which the lymphatic endothelial cells appear to have a key role, is provided for the first time. Despite many new pieces of information, there remain many 'blank pages' in the natural history of bancroftian filariasis.

Lymphatic filariasis in children: adenopathy and its evolution in two young girls.

Lymphatic filariasis is a widespread infectious disease of children in endemic areas, but little is known about the early lymphatic damage in children and its evolution, either with or without treatment. Two girls (ages 6 and 12 years) from a Wuchereria bancrofti endemic region of Brazil presented with chronic inguinal adenopathy. Neither had microfilaremia. By ultrasound both were shown to have living adult worms in their enlarged inguinal nodes and had occult local lymphatic damage (lymphangiectasis). One girl spontaneously developed acute adenitis in the affected node prior to any intervention; this adenitis resolved within 10 days and was associated with the progressive disappearance over 45-90 days of all local abnormalities detectable by ultrasound. In the other child, after treatment with a single dose of diethylcarbamazine (DEC), the same clinical picture of transient adenitis and resolving abnormalities (detectable by ultrasound) occurred. These findings demonstrated filariasis as the cause of adenopathy in children, and also both spontaneous and treatment-induced worm-death, with subsequent reversal of lymphatic abnormalities.

Pathogenesis of lymphatic disease in bancroftian filariasis: a clinical perspective.

The pathogenesis of lymphatic filariasis has been a matter of debate for many decades. Here, Gerusa Dreyer and colleagues propose a dynamic model of bancroftian filariasis, integrating clinical, parasitological, surgical, therapeutic, ultrasonographic and histopathological data. This model has profound implications for filariasis control programs and the management of the individual patient.

[Rational for morbidity management in bancroftian filariasis endemic areas]. / Bases para o tratamento da morbidade em áreas endêmicas de filariose bancroftiana.

Selection of the most appropriate therapy for the patient with bancroftian filariasis requires a knowledge of the diverse clinical characteristics of filarial disease and their pathogenesis. As a result of new diagnostic tests and clinical advances, our understanding of bancroftian filariasis has changed rapidly, as have our ideas about treatment. In the past, it was believed that elephantiasis was caused by an immunologic reaction of the host to the filarial parasite. From this perspective, elephantiasis was seen as the endpoint of an unalterable relationship between the host and the parasite, and given the absence of effective medication or procedures, affected individuals were considered "immunologically predisposed" to this end-stage disease. In the last few years, however, new evidence has suggested that lymphedema and elephantiasis have another etiologic agent. Namely, the principal factor in the evolution of lymphedema and elephantiasis is the involvement of recurrent secondary bacterial infections. Today, it is clear that other forms of supportive therapy (including education and psychological counseling) are necessary and are often more important than antiparasitic drugs.

Extralymphatic disease due to bancroftian filariasis.

Infection with Wuchereria bancrofti, Brugia malayi, or B. timori not only affects the structure and function of lymphatic vessels but is also associated with extralymphatic pathology and disease. Because it is now possible to detect living adult worms by ultrasonography, much emphasis is placed on lymphatic pathology. However, the finding of renal damage in asymptomatic microfilaremic carriers has led to increased recognition of the importance of extralymphatic clinical manifestation in bancroftian filariasis. The authors present a number of clinical syndromes that may be manifestations of extralymphatic filarial disease and discuss possible mechanisms that cause these conditions. The main purpose of this paper is to raise the awareness of students and physicians of the prevalence and the importance of extralymphatic disease in bancroftian filariasis so that it is diagnosed and treated properly and also to alert for the need of additional research in this area.

Extralymphatic disease due to bancroftian filariasis

Infection with Wuchereria bancrofti, Brugia malayi, or B. timori not only affects the structure and function of lymphatic vessels but is also associated with extralymphatic pathology and disease. Because it is now possible to detect living adult worms by ultrasonography, much emphasis is placed on lymphatic pathology. However, the finding of renal damage in asymptomatic microfilaremic carriers has led to increased recognition of the importance of extralymphatic clinical manifestation in bancroftian filariasis. The authors present a number of clinical syndromes that may be manifestations of extralymphatic filarial disease and discuss possible mechanisms that cause these conditions. The main purpose of this paper is to raise the awareness of students and physicians of the prevalence and the importance of extralymphatic disease in bancroftian filariasis so that it is diagnosed and treated properly and also to alert for the need of additional research in this area.

Proposed panel of diagnostic criteria, including the use of ultrasound, to refine the concept of 'endemic normals' in lymphatic filariasis.

Although living adult Wuchereria bancrofti worms can be detected by ultrasound examination of the scrotal area in approximately 80% of men infected with this filarial parasite, the location of the adult worms in the remaining 20% remains unclear. To determine this, 32 individuals who had W. bancrofti microfilaraemia but no adult worms detectable on ultrasound were treated with diethylcarbarmazine (DEC), either with a single 6 mg/kg dose (n = 13) or with a 12-day course of 6 mg/kg per day (n = 19). They were then monitored with serial physical and ultrasound examinations. Thirteen (41%) subjects developed small, single scrotal nodules 12 h to 7 days after treatment; this rate was unaffected by the dose of DEC. No nodules were detected outside the scrotal area. All 5 men with lymphangiectasia suspected on ultrasound before treatment developed scrotal nodules, compared to 8 (29.6%) of 27 men without ultrasonographic evidence (P = 0.006). Thus, using both ultrasound and 'provocative' treatment with DEC, adult W. bancrofti can be detected in the scrotal area of an estimated 88% of infected men. Because no single diagnostic test for W. bancrofti infection is completely sensitive, a panel of tests, including ultrasound, is proposed to identify with greater accuracy 'endemic normals' for immunological and epidemiological studies.

Screening of army soldiers for Wuchereria bancrofti infection in the metropolitan Recife region, Brazil: implications for epidemiological surveillance.

Between 1989 and 1995, blood surveys were performed for Wuchereria bancrofti infection in several barracks of the Brazilian army in the metropolitan Recife region. For initial screening, 60 microliters of capillary blood were examined for microfilaria. All men who tested positive had microfilaria quantified by filtration of venous blood through a polycarbonate membrane. Of 23,773 men screened, 585 (2.5%) had microfilaria (mf). Microfilarial density ranged from < 1-8706 mf/ml of blood. Thirteen individuals had ultra-low microfilarial densities (1 mf/11 ml of blood). Characterization of 174 autochthonous cases made it possible to map 8 new districts in 4 cities within metropolitan Recife region where transmission of W. bancrofti was previously unknown. Routine screening of soldiers in the military may provide important surveillance data for national programmes to eliminate transmission of W. bancrofti.

Immunocytochemical localization and distribution of human albumin in Wuchereria bancrofti adult worms.

To determine whether albumin is present on adult worms of Wuchereria bancrofti, thin sections of resin-embedded parasites were incubated with a specific antiserum to human albumin. With the exception of the epicuticle, all layers of the cuticle and the hypodermis were intensely labeled. Concentration of gold particles was observed within infoldings of the hypodermal membrane. Moderate labeling of the thin basement membrane that lines the pseudocelomic cavity and the gonoduct was also observed. Within the uterus, ovular membranes labeled intensely; groups of organized particles were seen below ovular membranes and also within invaginations of microfilarial embryos. In contrast, few gold particles were seen on the surface of mature intrauterine microfilariae. No labeling was observed in control sections incubated with antiserum preadsorbed with purified human albumin. The findings suggest that human albumin may be essential for the nutrition and development of W bancrofti microfilariae.

Longitudinal evaluation of growth, puberty, and bone maturation in children with Williams syndrome.

OBJECTIVES: To establish syndrome-specific growth curves and growth rate (GR) curves for Williams syndrome (WS) and define the pattern of bone maturation and pubertal development. METHODS: In a prospective longitudinal study between 1990 and 1997, the growth data of 244 children with WS were collected: 295 values for GR were calculated for 74 girls and 331 values for 89 boys. RESULTS: Mean GR of children with WS was below normal by 1 to 2 cm/y in the first few years of life. One group of girls (n = 20) experienced an early pubertal growth spurt at age 9 years (maximal GR, 7.8 +/- 2.1 cm/y; menarcheal age, 10.4 +/- 1.4 years). A second group (n = 5) showed the growth spurt at age 11 years (7.5 +/- 1.1 cm/y; menarcheal age, 12.6 +/- 1.3 years). In boys, peak height velocity (8.7 +/- 2.3 cm/y) occurred at age 11 to 12 years. Bone age was delayed in both sexes during childhood and accelerated markedly during puberty. Final height was 152.4 +/- 5.7 cm in girls (n = 38) and 165.2 +/- 10. 9 cm in boys (n = 43). CONCLUSIONS: The syndrome-specific GR curves for WS showed a premature and abbreviated pubertal growth spurt in both sexes. This growth spurt was directly related to bone age acceleration during puberty. The data from this longitudinal study provide an overview of both the dynamics of growth and its course in children with WS.

Acute attacks in the extremities of persons living in an area endemic for bancroftian filariasis: differentiation of two syndromes.

The natural history of lymphatic disease in human filariasis remains unclear, but recurrent episodes of acute lymphangitis are believed to constitute a major risk factor for the development of chronic lymphoedema and elephantiasis. Prospective analysis of 600 patients referred to the filariasis clinic of the Centro de Pesquisas Aggeu Magalhães/FIOCRUZ in Recife, Brazil, indicated that 2 distinct acute syndromes accompanied by lymphangitis occur in residents of this filariasis-endemic area. One syndrome, which we call acute filarial lymphangitis (AFL), is caused by the death of adult worms. It is relatively uncommon in untreated persons, usually is asymptomatic or has a mild clinical course, and rarely causes residual lymphoedema. The second syndrome, of acute dermatolymphangioadenitis (ADLA), is not caused by filarial worms per se, but probably results from secondary bacterial infections. ADLA is a common cause of chronic lymphoedema and elephantiasis in Recife as well as in other areas of Brazil where lymphatic filariasis is not present. The syndromes of AFL and ADLA can be readily distinguished from each other by simple clinical criteria.

Bancroftian filariasis in a paediatric population: an ultrasonographic study.

Little is known about lymphatic filariasis or the anatomical location of adult Wuchereria bancrofti in children. Seventy-eight children from Greater Recife, 23 microfilaria-positive and 55 microfilaria-negative in approximately 60 microL blood, underwent ultrasound examinations of the major superficial lymphatic vessels of the limbs, scrotal area (boys), and breast area (girls). The characteristic movements of adult worms, known as the filaria dance sign (FDS), were detected in 11 (14.1%) children. In 9 boys, the FDS was detected in lymphatic vessels of the scrotal area (8, ages 14-16) and the inguinal cord (1, age 11). In girls, the FDS was detected in a crural lymphatic vessel and an axillary lymph node. FDS detection was more common in boys (P = 0.06), older children (P = 0.001), and children with microfilaraemia (P = 0.05). Diffuse lymphangiectasia was visualized in 4 boys (ages 14-16) and 2 children had clinical signs of filariasis. These ultrasonographic findings associate W. bancrofti with both infection and disease in children.