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.

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.

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.

Evaluation of PCR-based methods for the diagnosis of infection in bancroftian filariasis.

The value of the polymerase chain reaction (PCR) in the diagnosis of Wuchereria bancrofti infection was evaluated in comparison to microscopical examination of night blood smears, Nuclepore filtration, serology and ultrasonography. No correlation was found between PCR-based deoxyribonucleic acid (DNA) probing and serology. We did not find any evidence of free filarial DNA in either blood plasma or chylocoele fluid. We conclude that the 2 PCR-based techniques evaluated are not more sensitive than Nuclepore filtration for detection of W. bancrofti microfilaraemia, need at least 1 intact microfilaria in the volume of blood used for DNA extraction, and were much inferior to ultrasonography for detection of amicrofilaraemic adult worm carriers.

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.

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.

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.

Direct assessment in vivo of the efficacy of combined single-dose ivermectin and diethylcarbamazine against adult Wuchereria bancrofti.

When ivermectin and diethylcarbamazine (DEC) are given simultaneously in a single dose to persons with Wuchereria bancrofti infection, the resulting suppression of microfilaraemia is more profound and sustained than when either drug is given alone. To assess whether this effect is a result of enhanced macrofilaricidal efficacy, we used ultrasound to monitor the adult worms in the scrotal area of men with W. bancrofti microfilaraemia. Twenty-one men were treated simultaneously with DEC (6 mg/kg) and either 200 micrograms/kg or 400 micrograms/kg of ivermectin (11 and 10 men, respectively). Ten other men received a single 200 micrograms/kg dose of ivermectin followed 5 d later by a 6 mg/kg dose of DEC (sequential treatment). All men became amicrofilaraemic after treatment and all except one remained so for one year. Cessation of adult worm movement, indicative of death of all the adult worms in a given 'nest', was observed in none of 30 nests in men who received simultaneous treatment and in 3 of the 19 nests (16%) in the men who received sequential treatment (P = 0.05). Scrotal nodules were detected in 5 of 21 men (24%) who received simultaneous treatment and in 8 men (80%) who received sequential treatment (P < 0.01). Thus, co-administration of ivermectin with DEC seems to interfere with the macrofilaricidal action of DEC. These findings have implications both for treatment of the individual patient and for community-based drug distribution programmes designed to interrupt transmission of W. bancrofti.

Ultrasonographic detection of living adult Wuchereria bancrofti using a 3.5-MHz transducer.

Adult Wuchereria bancrofti can be readily detected by ultrasound in the lymphatic vessels of the spermatic cord with a 7.5-MHz transducer, but most ultrasound machines in developing countries are equipped with 3.5-MHz transducers. To assess the potential for ultrasound as a tool for diagnosis and epidemiologic assessment in lymphatic filariasis, we compared the performance of 3.5-MHz and 7.5-MHz transducers in 61 men in Recife, Brazil. All men had three ultrasound examinations using a 3.5 MHz transducer and an examination with a 7.5-MHz probe. Using the 7.5-MHz transducer, adult W. bancrofti were detected in 41 men; 81 adult worm nests were detected. Sixty-four (79%) nests were detected with the 3.5-MHz probe, each on all three examinations. The 3.5-MHz probe correctly identified 35 (85.4%) of 41 men as infected; sensitivity increased with lymphatic vessel diameter. Ultrasonographic examination with a 3.5-MHz transducer is a sensitive method for detection of adult W. bancrofti in men and merits consideration as a tool for rapid epidemiologic assessment.

Dietilcarbamazina no tratamento da filariose bancroftiana / Diethylcarbamazine in the treatment of Bancroft's filariasis

Os autores realizaram uma ampla revisão sobre o tratamento da filariose bancroftiana com a droga dietilcarbamazina. Os aspectos interessantes sobre o histórico de sua descoberta e os conceitos básicos de sua farmacologia foram relatados de forma resumida. Ênfase especial, por outro lado, foi dada às especulações feitas pelos diversos autores sobre os achados intrigantes descritos na literatura. Foram trazidos os novos avanços sobre o conhecimento da doença, como por exemplo, a visualização pela ultra-sonografia do verme vivo de Wuchereria bancrofti, no seu hospedeiro natural, o homem. Isso possibilitou a compreensão de muitos dos achados aparentemente paradoxais encontrados na literatura sobre o tratamento da infeção com a DEC. Assim, devido à inexistência de uma droga sucessora que reunisse efeitos micro e macrofilaricidas ideais e aos novos conhecimentos sobre a bancroftose e sobre a própria dietilcarbamazina, foi-lhe conferido um novo realce. Esses aspectos a colocaram numa posição de destaque no cenário da infecção, à época do seu quase cinqüentenário de existência.

The authors presented a detailed review about the treatment of bancroftian filariasis with diethylcarbamazine. The interesting aspects about the drug discovery and the basic concepts about its pharmacology were reported in a summarised form. On the other hand, emphasis was made about the speculation done by several authors about the intriguing findings regarding its efficacy reported in the literature. Latter, it was brought the new advances about the disease, as for example, the visualization by ultrasound of living Wuchereria bancrofti adult worm on its natural host--the human being. This made possible the comprehension of several paradoxical issues reported, focusing the treatment of infection using diethylcarbamazine. So far, because of the lack of ideal drug with micro and macrofilaricidal properties, together with the new understand about the disease and the new parameters for monitoring the efficacy of the drug, diethylcarbamazine has back its importance conquered at the begin of its discovery, almost fifth years ago.

[Diethylcarbamazine in the treatment of Bancroft's filariasis]. / Dietilcarbamazina no tratamento da filariose bancroftiana.

The authors presented a detailed review about the treatment of bancroftian filariasis with diethylcarbamazine. The interesting aspects about the drug discovery and the basic concepts about its pharmacology were reported in a summarised form. On the other hand, emphasis was made about the speculation done by several authors about the intriguing findings regarding its efficacy reported in the literature. Latter, it was brought the new advances about the disease, as for example, the visualization by ultrasound of living Wuchereria bancrofti adult worm on its natural host--the human being. This made possible the comprehension of several paradoxical issues reported, focusing the treatment of infection using diethylcarbamazine. So far, because of the lack of ideal drug with micro and macrofilaricidal properties, together with the new understand about the disease and the new parameters for monitoring the efficacy of the drug, diethylcarbamazine has back its importance conquered at the begin of its discovery, almost fifth years ago.

Assessment of the efficacy of diethylcarbamazine on adult Wuchereria bancrofti in vivo.

To assess directly the effect of various doses of diethylcarbamazine (DEC) on adult Wuchereria bancrofti, 31 infected men were randomly assigned to receive an initial single DEC dose of 1 mg/kg (n = 7), 6 mg/kg (n = 10), or 12 mg/kg (n = 14). Beginning 7 d later, the dosage of DEC and duration of treatment were progressively increased for 7-10 weeks. Physical examinations were performed to detect scrotal nodules and the scrotal area was examined by ultrasound (7.5 MHz transducer) to monitor the 'filaria dance sign' (FDS), the characteristic pattern of adult worm movement. Of 53 adult worm 'nests' that were detected by ultrasound, 22 (41.5%) were DEC-sensitive (FDS became non-detectable and a nodule became palpable at the site); 20 (37.7%) were not sensitive (FDS remained unchanged and detectable and no nodule developed), and 11 (20.8%) showed mixed responses (FDS remained detectable but a palpable nodule developed). All but one sensitive or mixed response occurred within 1 week after the initial single dose. Of 39 'nests' in men who initially received a single 6 or 12 mg/kg dose of DEC, 20 (51.3%) had sensitive responses compared to 2 (14.3%) of 14 'nests' in men who received a single 1 mg/kg dose (P = 0.04). Above 6 mg/kg, the macrofilaricidal effect of DEC did not increase with dose; a significant proportion of adult W. bancrofti were not susceptible to DEC during the study period.

Evaluation of the Og4C3 ELISA in Wuchereria bancrofti infection: infected persons with undetectable or ultra-low microfilarial densities.

The recently developed Og4C3 ELISA, which detects circulating Wuchereria bancrofti antigen, appears promising for use in epidemiological surveys, but its sensitivity is unknown in persons with ultra-low microfilarial densities. We used the Og4C3 to test the sera of 282 persons who were microfilaria-positive in 1-16 ml of blood, 18 persons who were microfilaria-negative but who had ultrasonographic or biopsy evidence of adult W. bancrofti infection, and 63 lifelong residents of a non-endemic area of Brazil. A total of 276 (97.9%) persons with detectable microfilaraemia tested positive (optical density > 0.033). At microfilarial densities of < 1, 1-30, and > 30 microfilariae per ml of blood, the sensitivity of the Og4C3 was 72.2, 97.6 and 100%, respectively (chi 2-test for trend, P < 10(-6)). The assay was positive in 66.7% of amicrofilaraemic persons with evidence of adult worm infection and in one (1.6%) of 63 residents of the non-endemic area (specificity, 98.4%). Our findings support the increasingly widespread use of the Og4C3 for field investigations and epidemiological assessments. However, the sensitivity of the assay may be low in persons who are microfilaria-negative or with densities of < 1 microfilaria per ml.

Ultrasonographic evidence of abnormal lymphatic vessels in young men with adult Wuchereria bancrofti infection in the scrotal area.

PURPOSE: We determined the prevalence and magnitude of dilatation of the lymphatic vessels of the spermatic cord in men infected with Wuchereria bancrofti, which is known major cause of hydrocele in the tropics. MATERIALS AND METHODS: Scrotal ultrasound was performed with a 7.5 MHz, transducer in 78 men from Recife, Brazil (endemic for filariasis) and in 15 from a nonendemic area. RESULTS: Among men from Recife the lymphatic vessels were dilated (1.3 to 15.0 mm., mean 3.8) at the location of the adult worm. Vessel diameter was not associated with hydrocele. CONCLUSIONS: Lymphatic dilation was observed in all men with ultrasonographically detectable W. bancrofti infection, even those who were asymptomatic.

Ultrasonographic assessment of the adulticidal efficacy of repeat high-dose ivermectin in bancroftian filariasis.

Since diethylcarbamazine, the drug recommended for treatment of lymphatic filariasis, seems only partially effective against the adult worm, intense interest persists in identifying a macrofilaricidal drug for this infection. To evaluate directly in vivo the macrofilaricidal activity of repeat high-dose ivermectin, 15 men who had living adult Wuchereria bancrofti detected in the scrotal area by ultrasound were treated with 400 micrograms/kg of ivermectin at 2-week intervals for 6 months (total dose, 4.8 mg/kg). Serial ultrasound examinations were performed before, during, and for 6 months after treatment. Profound suppression of microfilaraemia followed the first dose of ivermectin, but movements characteristic of the adult worm on ultrasound remained unchanged both in location and pattern. Even when given in total doses of 4.8 mg/kg, ivermectin appears to have no observable activity against adult W. bancrofti, although its ability to suppress microfilaraemia makes it potentially useful for the control of lymphatic filariasis.

Detection of living adult Wuchereria bancrofti in a patient with tropical pulmonary eosinophilia.

Tropical pulmonary eosinophilia (TPE) is a relatively unusual and diagnostically challenging manifestation of infection with Wuchereria bancrofti. The pathogenesis of TPE remains unclear, although immune hyperresponsiveness to the microfilarial stage of the parasite is thought to play an essential role. Microfilariae are almost never detected in the peripheral blood of persons with TPE and living adult worms have not been reported. Thus, no parasitologic marker has existed with which to assess the effectiveness of antifilarial treatment. In 1986, a 74-year old man from Olinda, Pernambuco, Brazil, developed classic signs and symptoms of filarial TPE. Within 48 h after beginning treatment with diethylcarbamazine (DEC), the drug of choice for TPE, his symptoms dramatically improved. He remained symptom-free until June 1994, when he again developed signs and symptoms of TPE. To visualize the adult worm and monitor the macrofilaricidal effectiveness of DEC treatment, ultrasound examinations of the scrotal area were performed before, during, and for 6 months after treatment. These examinations revealed diffuse dilatation of the lymphatic vessels of the spermatic cord and movements characteristic of living adult W. bancrofti known as the "filaria dance sign". Although the patient responded clinically to treatment, no change was noted in the filaria dance sign throughout the observation period. Visualization of adult W. bancrofti by ultrasound can be used to monitor the parasitologic effectiveness of treatment for TPE and to explore the relationship between death of the adult worm and recurrence of symptoms.