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PubMedDate not supplied

Estimation of the fecund life span of Wuchereria bancrofti in an endemic area.

A stochastic approach appropriate for general use in endemic communities was applied to estimate the average yearly instantaneous rate of loss of Wuchereria bancrofti microfilaraemia from infected individuals, and gain by uninfected individuals, from longitudinal data. This method was shown to give similar results (i.e., the rate of loss was independent of age, while the rate of gain differed significantly between age classes) to a previously used method based on transmision interruption, provided that the intersurvey interval was > 5 years. The method was used to estimate the fecund life span of W. bancrofti in an endemic area at 5 years. The results suggest that the life span is at the lower end of previous estimates.

Adolescent↗
PubMedDate not supplied

A polymerase chain reaction assay to determine infection of Aedes polynesiensis by Wuchereria bancrofti.

The sensitivity of a previously described polymerase chain reaction (PCR) assay was improved to detect a single mosquito, infected by as few as 1-2 microfilariae of Wuchereria bancrofti, among 20-50 uninfected mosquitoes. Wild-caught Aedes polynesiensis were used to compare assessment of infection by dissection of individuals with the PCR assay of pools of mosquitoes. The PCR assay was at least as sensitive as dissection for detection of mosquitoes infected with W. bancrofti.

Aedes↗
PubMedDate not supplied

Amicrofilaraemic carriers of adult Wuchereria bancrofti.

To determine the extent to which Wuchereria bancrofti infections can be detected in asymptomatic amicrofilaraemic men in Greater Recife, Brazil, we studied 100 asymptomatic men who were long-term residents (> or = 15 years) of this filariasis-endemic area and who were amicrofilaraemic in 60 microL of capillary blood collected at night. Increasing amounts (1, 5, and 10 mL) of venous blood were collected in consecutive weeks, filtered, and examined for microfilariae; 27 men were eventually found to be microfilariaemic and 10 remained amicrofilaraemic but were found to be carriers of living adult W. bancrofti by ultrasound examination of the scrotal area. Thus, 37% of 'amicrofilaraemic' men (in 60 microL of blood) were found to be infected by more thorough investigation. Ultrasound is a valuable tool to identify adult worm infections in amicrofilaraemic persons, particularly for evaluation of serological assays and immunological studies in which the distinction between 'amicrofilaraemic adult worm carriers' and 'endemic normal subjects' is critical.

Adolescent↗
PubMedDate not supplied

Epidemiology of acute filarial episodes caused by Wuchereria bancrofti infection in two rural villages in Tamil, Nadu, south India.

This year-long study investigated the epidemiology of acute filarial episodes due to Wuchereria bancrofti in 2 rural villages in south India. The annual incidence of 96.5 episodes/1000 population was significantly higher in males (108.5) than females (84.1) an strongly age dependent. First occurrence of acute disease was observed in 0.86% of the population, and the average duration of each episode was 3.6 +/- 2.0 d. Although more than half (63.5%) of the affected individuals suffered only 1 episode, a few experienced as many as 8 over the one-year period. Individuals with chronic disease were more prone to acute attacks, with 82.9% of the total episodes occurring in this group. No seasonal pattern was observed in the frequency of episodes. Probit analysis showed that the number of episodes per affected person was dependent on sex and chronic condition. Swelling of lymph nodes in the inguinal region and fever were the most common symptoms of acute disease. The high incidence and resulting debility observed in this study suggest that acute episodes are a significant health problem associated with lymphatic filariasis. There is clearly a need for more studies on this acute form of filarial disease to aid the understanding of the aetiology and epidemiology of acute episodes, in planning appropriate control interventions, and in evaluating the resulting health burden.

Acute Disease↗
PubMedDate not supplied

Occurrence of living adult Wuchereria bancrofti in the scrotal area of men with microfilaraemia.

To determine the frequency with which living adult Wuchereria bancrofti can be detected by ultrasound in the scrotal area of men with filarial infection, we used a 7.5 MHz transducer to perform weekly ultrasound examinations on 100 microfilaraemic men (18-34 years old) from Greater Recife, Brazil. The peculiar pattern of movement that characterizes the adult worm image on ultrasound (the filaria dance sign) was detected in the lymphatic vessels of the spermatic cord in 80 men (bilaterally in 29 men). Among 20 men with no filaria dance sign, the geometric mean microfilarial density was 68/mL, compared with 238/mL and 775/mL among those with unilateral and bilateral filaria dance signs, respectively (P = 0.0001). The lymphatic vessels of the spermatic cord appear to be a common, and perhaps the principal, site of adult W. bancrofti in men with asymptomatic microfilaraemia. Studies are needed to define the relationship between the presence of filarial worms in the scrotal area and the development of filaria-associated morbidity.

Adolescent↗
PubMedDate not supplied

A polymerase chain reaction assay for the detection of Wuchereria bancrofti in blood samples from French Polynesia.

A polymerase chain reaction (PCR) assay based on a highly repeated deoxyribonucleic acid (DNA) sequence found in Wuchereria bancrofti (the SspI repeat) has been developed to address the shortcomings of traditional diagnostic methods. In this field study in a W. bancrofti endemic region of French Polynesia, 373 human blood samples were collected and 100 microL of blood were screened by the SspI PCR assay and 1 microL by membrane filtration. The SspI PCR assay detected 99 of 113 blood samples in which microfilariae had been detected by filtration (sensitivity of 88%) with a specificity of 100%. All the samples missed by the SspI PCR assay had less than 8 microfilariae per mL of blood. To evaluate the efficacy of screening larger blood samples by PCR, both 100 microL and 500 microL samples from 50 patients with very low-level microfilaraemia were screened by the SspI PCR assay; the sensitivity increased from 60% to 84% when using the larger volume of blood. Finally, an enzyme-linked immunosorbent assay-based version of the SspI PCR assay was used to screen blood from 12 patients following treatment with diethylcarbamazine, ivermectin, or both. These results showed that the PCR assay closely paralleled the presence or absence of microfilariae in the blood and that no increase in the DNA level was seen immediately following drug treatment.

Adult↗
PubMedDate not supplied

A polymerase chain reaction-based assay for detection of Wuchereria bancrofti in human blood and Culex pipiens.

Human blood samples and indoor-resting Culex pipiens were collected in 33 randomly selected houses from different sectors of a village in the Nile Delta of Egypt which was endemic for Wuchereria bancrofti. Blood was also collected from subjects with no history of living in filarial endemic areas. Human blood samples were divided and assessed by both membrane filtration and polymerase chain reaction (PCR). Similarly, mosquito samples were assessed by both dissection and PCR. Blood pools representing each household were tested by PCR. If a pool gave a positive result, then individual blood specimens were also tested by PCR. Of the 33 houses tested, both membrane filtration and blood pools assayed by PCR identified 14 (42.4%) 'infected houses'. PCR detected parasite deoxyribonucleic acid (DNA) in blood pools from an additional 3 households that gave negative results by membrane filtration. Of 178 endemic blood samples tested by membrane filtration, 22 (12.3%) had microfilariae and all were individually positive by PCR. Although microfilaria counts were lower in blood collected during the day than in night-collected blood, the PCR results were consistent, regardless of time of collection. All non-endemic blood samples were negative by PCR. Among the 33 houses rested, mosquito pools assayed by PCR identified 17 (51.5%) as 'infected households'. Of these, 8 houses (47%) contained at least one microfilaraemic resident. One 'infected household' was identified by mosquito dissection. We concluded that PCR is a powerful epidemiological tool for screening villages for the prevalence of W. bancrofti. PCR detection of W. bancrofti DNA in blood-fed mosquitoes could be used initially to locate endemic areas with transmission of bancroftian filariasis. PCR detection of W. bancrofti DNA in blood collected during the day could then be used to assess W. bancrofti infection rates.

Animals↗
PubMedDate not supplied

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.

Adult↗
PubMedDate not supplied

Wuchereria bancrofti microfilaraemia in children in relation to parental infection status.

A total of 946 families with 2302 children was surveyed for microfilaraemia due to Wuchereria bancrofti. The prevalence of microfilaraemia among offspring born to microfilaraemic parents was significantly higher than in those born to amicrofilaraemic parents (P = 0.0049; relative risk = 3.40). However, there was no statistically significant difference between the prevalence of microfilaraemia in children born to microfilaraemic mothers or microfilaraemic fathers, suggesting that parental (not only maternal) infection is the important risk factor, and it may be exposure within the household which is important. Logistic regression analyses also confirmed that the risk of infection for offspring born to either microfilaraemic mothers or microfilaraemic fathers was higher than that for offspring born to amicrofilaraemic parents and indicated that infection in children < or = 20 years old was primarily dependent on parental infection status and minimally influenced by factors other than household exposure.

Adolescent↗
PubMedDate not supplied

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.

Adolescent↗
PubMedDate not supplied

The use of whole blood absorbed on filter paper to detect Wuchereria bancrofti circulating antigen.

The Og4C3 enzyme-linked immunosorbent assay (ELISA) to detect circulating Wuchereria bancrofti antigen uses 50 microL of serum. In this study, a whole blood sample absorbed on filter paper was tested as a substitute for serum. Serum samples were obtained from 60 Sri Lankan subjects by venepuncture and finger-prick blood samples from the same individuals were directly absorbed on filter paper. Og4C3 ELISAs using serum and filter paper blood were compared. Despite the fact that the estimated amount of serum available for the ELISA with filter paper blood was only one-fifth of that available when serum was used, the 2 ELISAs gave almost identical results. Of the 39 positive serum samples, 38 were detected using filter paper blood. Employing the ELISA using filter paper blood, 619 people in Matara, Sri Lanka, were examined for antigenaemia. The positivity rate was 22.5%, 3.1 times higher than the rate of microfilaraemia detected by examination of 60 microL blood films.

Animals↗
PubMedDate not supplied

Diagnosis of Wuchereria bancrofti infection by the polymerase chain reaction using urine and day blood samples from amicrofilaraemic patients.

A sensitive and specific polymerase chain reaction (PCR) based on a highly repeated deoxyribonucleic acid (DNA) sequence (188 bp; SspI repeat) was tested for the detection of Wuchereria bancrofti DNA in blood and urine samples collected during the day from individuals in Coque, Recife, Brazil, an endemic area for W. bancrofti. All microfilaraemic individuals were also positive by PCR, irrespective of the samples used. The PCR system was capable of detecting W. bancrofti DNA in amicrofilaraemic individuals: c. 93% were positive by PCR when day blood samples were used and 59.7% when urine samples collected at 07:00 were used. Thus, nocturnally periodic W. bancrofti infection can be detected in blood samples collected during the day, which is convenient for large-scale screening. In addition, non-invasive urine collection provided suitable samples for PCR, which is clearly advantageous for preliminary mass diagnosis.

Animals↗
PubMedDate not supplied

The relationship between infection and disease in Wuchereria bancrofti infection in Ghana.

The relationship between infection and clinical disease in Wuchereria bancrofti infection was investigated in a community-based study in different endemic areas in Ghana. At the individual level, there was no association between acute adenolymphangitis and infection (microfilaraemia) status. There was a negative association between infection status and lymphoedema/elephantiasis, but a positive association with hydrocele; however, the intensity of infection was negatively associated with both elephantiasis and hydrocele. The community prevalence of infection was strongly associated with the prevalence of clinical filariasis (especially hydrocele). There was a strong positive association between the prevalence of infection in males and the odds of a case of hydrocele being microfilaraemic, suggesting that there is no acquired immunity to reinfection in cases of hydrocele. The pathophysiologies of elephantiasis and hydrocele may therefore differ from one another, and require further investigation.

Age Distribution↗
PubMedDate not supplied

A study on the provocative day test effect of ivermectin and albendazole on nocturnal periodic Wuchereria bancrofti microfilaraemia.

We conducted a randomized double-blind placebo-controlled study, in the Ahanta West District of Ghana, on the provocative day test effect of ivermectin and albendazole alone and in combination on nocturnal periodic Wuchereria bancrofti microfilaraemia. Sixty-three individuals with high night-time microfilaria (mf) intensities were identified in 1997 or 1998 and randomized into 4 groups. Blood samples for mf were then collected from the same individuals in the daytime (between 09:00 and 15:00) immediately before and 30-50 min after treatment. Groups 1-4 were treated with ivermectin alone (150-200 micrograms/kg), albendazole alone (400 mg), the combination of ivermectin and albendazole, and placebo, respectively. Intensities of mf in daytime samples were considerably lower than in night-time samples. Neither ivermectin or albendazole alone nor their combination provoked significant liberation of W. bancrofti mf into the peripheral circulation after the daytime treatment.

Adolescent↗
PubMedDate not supplied

Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomised placebo-controlled trial.

BACKGROUND: Wolbachia endosymbionts of filarial nematodes are vital for larval development and adult-worm fertility and viability. This essential dependency on the bacterium for survival of the parasites has provided a new approach to treat filariasis with antibiotics. We used this strategy to investigate the effects of doxycycline treatment on the major cause of lymphatic filariasis, Wuchereria bancrofti. METHODS: We undertook a double-blind, randomised, placebo-controlled field trial of doxycycline (200 mg per day) for 8 weeks in 72 individuals infected with W bancrofti from Kimang'a village, Pangani, Tanzania. Participants were randomly assigned by block randomisation to receive capsules of doxycycline (n=34) or placebo (n=38). We assessed treatment efficacy by monitoring microfilaraemia, antigenaemia, and ultrasound detection of adult worms. Follow-up assessments were done at 5, 8, 11, and 14 months after the start of treatment. Analysis was per protocol. FINDINGS: One person from the doxycycline group died from HIV infection. Five (doxycycline) and 11 (placebo) individuals were absent at the time of ultrasound analysis. Doxycycline treatment almost completely eliminated microfilaraemia at 8-14 months' follow-up (for all timepoints p<0.001). Ultrasonography detected adult worms in only six (22%) of 27 individuals treated with doxycycline compared with 24 (88%) of 27 with placebo at 14 months after the start of treatment (p<0.0001). At the same timepoint, filarial antigenaemia in the doxycycline group fell to about half of that before treatment (p=0.015). Adverse events were few and mild. INTERPRETATION: An 8-week course of doxycycline is a safe and well-tolerated treatment for lymphatic filariasis with significant activity against adult worms and microfilaraemia.

Adolescent↗
PubMed1997

Randomised placebo-controlled comparison of ivermectin and albendazole alone and in combination for Wuchereria bancrofti microfilaraemia in Haitian children.

BACKGROUND: Lymphatic filariasis and intestinal helminth infections are important disorders in tropical areas. Periodic treatment with albendazole is now used in many school-based intestinal helminth-control programmes. However, few such programmes exist for lymphatic filariasis, despite evidence that single-dose treatment with ivermectin can greatly reduce the concentration of Wuchereria bancrofti microfilariae in the blood for months to years. We aimed to assess the potential for school-based control of lymphatic filariasis by investigating the efficacy and tolerability or combined ivermectin and albendazole in Haitian schoolchildren. METHODS: In January, 1996, we collected 832 20 microL capillary blood samples for inclusion in a randomised controlled study from children aged 5-11 years, and examined them by microscopy for W bancrofti microfilariae. Infected children were randomly assigned treatment with placebo (n = 29), a single 200-400 micrograms/kg dose of ivermectin (mean, 273 micrograms/kg, n = 28), 400 mg albendazole (n = 29), or a combination of 200-400 micrograms/kg ivermectin and 400 mg albendazole (n = 24). Children with high concentrations of microfilariae in the blood were admitted to hospital and adverse reactions were monitored for 3-5 days, otherwise children were examined at school or during a visit to their home. 4 months after treatment, we examined blood samples again for microfilariae. FINDINGS: 113 microfilaraemic children were enrolled (mean age 7.8 years). 4 months after treatment, the proportion of children who remained positive for microfilariae was significantly lower in the ivermectin plus albendazole group (four [17%]), but there were no significant changes in the other three groups (20 [69%] placebo, 22 [76%] albendazole alone, 17 [61%] ivermectin alone remained positive; p = 0.004). Geometric mean microfilarial concentration decreased from 9.3 to 5.3 per 20 microL blood among children who received placebo; from 15.5 to 1.5 per 20 microL blood among those who received ivermectin only (p = 0.032); from 14.1 to 5.1 per 20 microL blood among those who received albendazole alone; and from 13.7 to 0.3 per 20 microL blood among those who received both ivermectin and albendazole (p = 0.0001). Systemic adverse reactions did not differ significantly between children who received ivermectin alone and those who were treated with ivermectin and albendazole [corrected]. INTERPRETATION: For children with W bancrofti microfilaraemia, combined treatment with ivermectin and albendazole was more effective than treatment with ivermectin only, with no measurable increase in severity of adverse reactions.

Albendazole↗
PubMed1998

Randomised community-based trial of annual single-dose diethylcarbamazine with or without ivermectin against Wuchereria bancrofti infection in human beings and mosquitoes.

BACKGROUND: WHO has targeted lymphatic filariasis for elimination. Studies of vector-parasite relations of Wuchereria bancrofti suggest that a reduction in the microfilarial reservoir by mass chemotherapy may interrupt transmission and thereby eliminate infection. However, no field data exist on the impact of chemotherapy alone on vector efficiency and transmission intensity of W bancrofti. We compared the impact of an annual community-wide single-dose treatment with diethylcarbamazine alone or with ivermectin on rate and intensity of microfilaraemia, and transmission intensity in an area of Papua New Guinea endemic for intense W bancrofti transmission. METHODS: We carried out clinical and parasitological surveys in 14 communities in matched pairs. People aged 5 years or older in seven communities received randomly assigned diethylcarbamazine 6 mg/kg and people in the other seven communities received diethylcarbamazine 6 mg/kg plus ivermectin 400 micrograms/kg. We made physical examinations for hydroceles and leg oedema and investigated microfilarial densities by membrane filtration before and after treatment. We selected five communities for monthly entomological surveys between September, 1993, and September, 1995. Mosquitoes were collected in these communities by the all-night landing catch method and were individually dissected to identify rates of infection and infectiveness. FINDINGS: 2219 (87.6%) of 2534 eligible people received treatment. Microfilarial rate and density had decreased 1 year after treatment in all 14 communities; this decrease was significantly higher in communities given combined therapy than in those given diethylcarbamazine alone (mean decreases 57.5% and 30.6%, respectively; p = 0.0013). Greater decreases were also seen in community-specific microfilarial intensity with combined therapy (mean reductions 91.1% and 69.8%, respectively; p = 0.0047). The rate of leg oedema was not altered, but the frequency of advanced hydroceles decreased by 47% with combined therapy and 56% with diethylcarbamazine alone. 26,641 Anopheles punctulatus mosquitoes were caught during 499 person-nights of landing catches. Exposure to infective third-stage larvae decreased in all monitored five communities. Annual transmission potential decreased by between 75.7% and 98.8% in combined-therapy communities and between 75.6% and 79.4% in communities given diethylcarbamazine alone. Transmission was almost interrupted in two communities treated with combined therapy. INTERPRETATION: Annual single-dose community-wide treatment with diethylcarbamazine alone or with ivermectin is effective for the control of lymphatic filariasis in highly endemic areas, but combination therapy brings about greater decreases in rates and intensity of microfilaraemia.

Adolescent↗
PubMed2002

Molecular characterization of a calcium binding translationally controlled tumor protein homologue from the filarial parasites Brugia malayi and Wuchereria bancrofti.

We have cloned homologues of the mammalian translationally controlled tumor protein (TCTP) from the human filarial parasites Wuchereria bancrofti and Brugia malayi. TCTP genes from B. malayi and W. bancrofti were expressed in a T7 promoter vector as histidine tagged fusion proteins. Both the recombinant B. malayi TCTP (rBm-TCTP) and recombinant W. bancrofti TCTP (rWb-TCTP) have a molecular mass of approximately 28 kDa with the histidine tag. Sequence analyses showed that there is a 98% similarity between the two filarial TCTPs at amino acid levels and are immunologically cross-reactive. Analysis of soluble proteins from various lifecycle stages of B. malayi suggested that the expression of Bm-TCTP might be differentially regulated and occurs in multimeric form. Recombinant TCTP were found to form multimers in solution under non-reducing conditions. The tendency for filarial TCTPs to become multimers was predicted by the presence of the Lupas coiled coil structure in their sequence. Despite the absence of a signal sequence, Bm-TCTP is present abundantly in the excretory/secretions (ES) of microfilariae. Characterization studies showed that both Bm- and Wb-TCTPs are calcium-binding proteins and have histamine-releasing function in vitro. When injected intraperitoneally both the filarial TCTPs induced inflammatory infiltration of eosinophils into the peritoneal cavity of mice suggesting that the filarial TCTPs may have a role in the allergic inflammatory responses associated with filarial infections.

Amino Acid Sequence↗