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PubMedDate not supplied

Epidemiology of subperiodic Wuchereria bancrofti infection in the Nicobar Islands, India.

Diurnally subperiodic filariasis due to Wuchereria bancrofti has been reported from tribal populations in the Nancowry group of islands in the Andaman and Nicobar Islands, India. This was confirmed in a survey carried out during the monsoon season in 1993. Microfilariae were detected in the peripheral blood throughout a 24 h period with a peak at 18:00. The microfilaria (mf) rate ranged from 1.2% to 18.7%, with a low disease rate (mean = 1.9%). Incidence of mf was low in children less than 10 years old (3.5%), but increased with increasing age. Culex (Culex) quinquefasciatus was present at a very low density. Aedes (Finlaya) niveus and Aedes (Stegomyia) malayensis were the only species commonly biting man. The former was incriminated as a vector, and found naturally infected with W. bancrofti (infection and infectivity rates 1.1% and 0.9% respectively). After experimental feeding on donors, W. bancrofti developed to L3 stage larvae in A. niveus but failed to develop in A. malayensis and A. aegypti.

Adolescent↗
PubMed1988

Antibodies to diethylcarbamazine cross-react with microfilariae of Wuchereria bancrofti.

Antibodies directed against the microfilarial sheath have been instrumental in the immune elimination of circulating microfilariae in human lymphatic filariasis. We report here that antibodies to diethylcarbamazine (DEC, the most commonly used anti-filarial drug) cross-react with the sheath of Wuchereria bancrofti microfilariae. Antibodies with reactivity to DEC were raised in rabbits by immunization with a conjugate of methylpiperazine carboxylic acid (MPCA, an acid hydrolysis product of DEC) coupled to bovine serum albumin. The reactivity of these antibodies with microfilarial sheath of W. bancrofti was demonstrated by indirect immunofluorescent assay and indirect immunoperoxidase assay. This reactivity could be effectively inhibited by pre-incubation of the antisera with different haptens such as DEC, MPCA or piperazine citrate.

Animals↗
PubMed1991

Detection of amplified Wuchereria bancrofti DNA in mosquitoes with a nonradioactive probe.

A technique to identify Wuchereria bancrofti larvae in mosquito vectors with an enzyme-labeled DNA probe is described. To overcome the low sensitivity of nonradioactive detection methods, analyte DNA was amplified by polymerase chain reaction (PCR). Oligonucleotide primers were used to amplify W. bancrofti-specific DNA fragments of 380 and 650 bp, respectively. Parasite DNA in mosquito extracts was isolated free of inhibitors of the PCR by hybridization to a biotinylated DNA fragment (IWb 67), which hybridizes to DNA from most filarial species, followed by absorption of the resulting DNA hybrids onto avidin-coated acrylic beads. PCR-amplified DNA was detected with a biotin-labeled W. bancrofti-specific repeat DNA (IWb 35) coupled to avidin-alkaline phosphatase and the chemiluminescent substrate, AMPPD. The DNA equivalent of less than one larva can be detected by this method in mosquito extracts. The sensitivity of detection was comparable to that of radioactive probes and the assay is suitable for field application in endemic countries.

Animals↗
PubMed1991

A recombinant clone of Wuchereria bancrofti with DNA specificity for human lymphatic filarial parasites.

In order to understand the immune response to Wuchereria bancrofti and to aid in the diagnosis of W. bancrofti infections, recombinant antigens were identified from a W. bancrofti genomic expression library made in lambda gt11 using a pool of sera from infected Indian patients. One of the recombinant clones, lambda WbN1, containing a 2.5-kb insert, reacted strongly to a pool of sera from patients with lymphatic filariasis but not to normal human sera. In addition, this clone showed restricted specificity at the genomic level to the major lymphatic filarial parasites W. bancrofti and Brugia malayi but not to the closely related filarial parasite Brugia pahangi or to other filarial and non-filarial species tested. Nucleotide sequence analysis indicated the cloned DNA to have homology to myosin-like myofibrillar proteins. Polymerase chain reaction amplification initiated by specific synthetic oligomers amplified DNA in a species-specific manner from as little as 16 pg of isolated DNA or from one microfilaria.

Amino Acid Sequence↗
PubMed1992

A cloned antigen for serological diagnosis of Wuchereria bancrofti microfilaremia with daytime blood samples.

By differentially screening an adult Brugia malayi cDNA library with sera from microfilaremic and amicrofilaremic donors infected with Wuchereria bancrofti, we have identified a novel parasite antigen denoted SXP-1. Recombinant SXP-1 filarial antigen is preferentially recognized by sera from microfilaremic persons with bancroftian filariasis and from skin snip-positive patients with onchocerciasis. Antibodies to SXP-1 are restricted to the IgG4 subclass and gradually decline after treatment with diethylcarbamazine. These findings indicate that it may be possible to replace microscopic examination of night blood films with a serological test designed to detect antibodies to a mix of SXP-1 and other suitable antigens for the diagnosis of microfilaremia due to bancroftian filariasis.

Amino Acid Sequence↗
PubMed2005

Combined detection of Brugia malayi and Wuchereria bancrofti using single PCR.

A single step PCR method has been developed for the combined detection of the human filarial parasites, Brugia malayi and Wuchereria bancrofti. Parasites' DNA were isolated from filaria positive blood samples that were collected from endemic areas. The primers used were Hha1 and Ssp I, which amplified the DNA fragments of 322 bp and 188 bp specific to B. malayi and W. bancrofti, respectively. The sensitivity of the assay was tested with blood and mosquito samples having one W. bancrofti in a pool of 10 B. malayi. The assay was further evaluated on field collected blood and mosquito samples. Use of this assay as a diagnostic tool for the detection of filariasis being the most promising aspect of this study, offers scope for detection of both the parasites even at low levels of infection.

Animals↗
PubMed2006

Phylogeography of human lymphatic filarial parasite, Wuchereria bancrofti in India.

Wuchereria bancrofti, a nematode parasite causing human lymphatic filariasis is widely distributed in India. The phylogeography of this parasite was studied by constructing RAPD profiles of parasite populations collected from 71 microfilaria carriers residing in different geoclimatic regions of India. The analysis showed that the phylogeography of W. bancrofti populations is complex, with a high genetic divergence and gene flow among populations. The total genetic diversity (H(T)) and genetic differentiation (G(ST)) estimated for all the parasite populations were 0.0926 and 0.5859, respectively. The gene flow (Nm) between different regions indicated that two strains of W. bancrofti were prevalent in the country, one in the eastern side and the other on the western side of the Western Ghats. A highly significant genetic differentiation (F(ST) [theta] = 0.7978) was estimated between these two strains (chi 2 = 308.2789; P < 0.001). The gene flow between these strains was very low (0.2338). These two strains appear to have drifted genetically because of their geographic isolation by this thickly forested mountain range. The strain in the eastern side was found to be monophyletic in origin and is undergoing genetic divergence as the major parasite population in the country, spanning from eastern peninsular region to the northern plains. The variable geoclimatic factors and the antifilarial chemotherapeutical pressure on the parasite, which is in place for the past half a century, might have contributed for the high genetic heterogeneity its strains/populations in the country. The route of entry of the parasite into Indian sub-continent possibly appeared to be from an ancient origin from the countries of the Southeast Asian archipelago, through the eastern coastal line of the southern peninsula.

Animals↗
PubMedDate not supplied

Wuchereria bancrofti: cloning and characterization of heat shock protein 70 from the human lymphatic filarial parasite.

Heat shock protein 70 (HSP70) was identified as an immunodominant antigen by screening a Wuchereria bancrofti (Wb) microfilarial cDNA library with pooled Wb-infected sera, with 28% of the immunopositive clones coding for Wb-HSP70. The deduced amino acid sequence showed greater than 97 and 85% identity with HSP70 from filarial nematodes and humans, respectively. Recombinant HSP70 (74 kDa) and a recombinant protein from the C-terminal portion (43 kDa) also reacted with pooled Wb-infected sera, suggesting that the C-terminal region of HSP70 contains at least one antibody epitope. Brugia malayi L3 larvae showed increasing levels of HSP70 with increasing temperatures. Further, a polyclonal mouse anti-Wb-HSP70 antibody had reactivity to the HSP70 of cattle filarial parasite Settaria digitata and to human HSP70 derived from a Hep-2 cell line. Immune reactivity to Wb-HSP70 was strong, with uninfected non-endemic normal sera showing significantly greater reactions than sera from filaria-infected individuals. Both immunodominant self-HSP70 and HSP70 from other microbial infections may be primary targets for developing autoantibodies naturally.

Amino Acid Sequence↗
PubMed2005

Detection of lymphatic Wuchereria bancrofti in carriers and long-term storage blood samples using semi-nested PCR.

The semi-nested PCR was conducted for detection of Wuchereria bancrofti in patients' blood. The primers were designed based on the repetitive DNA sequences of the parasite. The results demonstrated that the semi-nested PCR could detect as little as 0.001 fg of parasite DNA. In addition, the primers showed no PCR amplification from human and other hemoparasites such as Brugia malayi, Plasmodium falciparum and P. vivax DNAs. This technique was used for detection of 18 W. bancrofti infected blood samples with a long-term storage, the data revealed that all samples were positive. The results obtained from this study clearly indicated that the semi-nested PCR is specific, sensitive, and suitable for detection of the disease carriers.

Animals↗
PubMed2005

Isolation and analysis of partial cDNA sequence coding for superoxide dismutase in Wuchereria bancrofti.

Molecular characterization of Wuchereria bancrofti is essential to develop suitable anti-filarial drugs and vaccines. We describe here isolation, sequence analysis and cloning of a partial cDNA of an enzyme superoxide dismutase from this parasite. The immunoscreening of a lambda zap W. bancrofti microfilarial (Mf) cDNA library with microfilaremic sera had resulted in the isolation of several seroreactive clones including, WbSOD. This clone contained a 309 bp insert and showed significant nucleotide and deduced amino acid sequence homologies to the superoxide dismutases of other nematode parasites. The antioxidant property of this enzyme may have important contribution in the defense mechanism of the parasite against host immune response.

Amino Acid Sequence↗
PubMed2006

Polymorphism of gp15/400 allergen gene of Wuchereria bancrofti from different regions of India endemic for lymphatic filariasis.

Nematode polyprotein allergens (NPA) are lipid-binding/transport molecules that elicit elevated levels of IgE response in the infected host, leading to Th2 type of immune response. They also transport arachidonic acid and metabolites that is known to be the action of antifilarial drug, diethylcarbamazine, and hence are of great significance to the control of lymphatic filariasis. We investigated the polymorphism of gp15/400 polyprotein of 35 isolates of lymphatic filarial parasite Wuchereria bancrofti collected from different geographic locations of India. The repeat subunit of the gene was found to be highly conserved in all the isolates with only two nucleotide synonymous changes at positions 369 (A-G) and 375 (C-T). As this molecule is highly conserved and has multifarious roles in the survival and pathogenesis of the parasite, it has good potential as a target for drug, immunodulation tools and immunotherapy development.

Allergens↗
PubMed2005

The ultrastructure of infective larvae (L3) of Wuchereria bancrofti after treatment with diethylcarbamazine.

Although the large use of diethylcarbamazine (DEC), as the major anti-filaricide drug, its mechanism of action remains a matter of controversy. Several authors defend the hypothesis that DEC has no direct effect on nematodes. This study demonstrated that infective larvae (L3) of Wuchereria bancrofti treated in vitro with DEC presented several behaviour and morphological changes. The first alteration produced by treatment for 2 h with 3, 5, 10 microg/ml of DEC was the reduction of motility. Larvae treated with 5, 10 microg/ml DEC showed severely affected organelles, formation of several vacuoles, mainly in neurocytes and in the muscle cells, and dissolution of cytoplasm. Some larvae showed extreme cellular disorganization with abundance of large and dense mitochondria and numerous large vacuoles containing residual organelles. Lamellar bodies, probably related to an assembly of hipodermal membranes, were also observed in some damaged larvae. Thus, undoubtedly in vitro treatment with concentrations of DEC similar to therapeutic conditions, which are 1-5 microg/ml (Hawking, 1979), had a direct effect on infective larvae of W. bancrofti by causing, primarily neuromuscular alterations with subsequent damage to organelles.

Animals↗
PubMed2005

Some morphological aspects of Wuchereria bancrofti uterus after treatment with diethylcarbamazine.

Confocal and EM analyses revealed that some female Wuchereria bancrofti, obtained from volunteers that received recommended diethylcarbamazine dose regimens, showed few or no embryos. Furthermore, inside the gravid uterus of female W. bancrofti treated with DEC we observed a finely granular, electron-dense material organised as strings of pearls, approximately 70 nm in maximal length surrounding intra-uterine microfilariae and apparently secreted by the embryo. Over the eggshells a similar material was also observed, possibly secreted by the uterine wall. The surface of intra-uterine microfilariae presented a material with identical electron-density to the scattered structures observed inside the egg. Similarly, the sheath of blood microfilariae of W. bancrofti also showed electron-dense projections, with shape and size similar to that observed inside the uterus.

Animals↗
PubMed2004

The effect of single dose ivermectin alone or in combination with albendazole on Wuchereria bancrofti infection in primary school children in Tanzania.

Examination of 1829 children from 6 primary schools in coastal Tanzania revealed overall Wuchereria bancrofti microfilaria (mf) and circulating filarial antigen (CFA) prevalences of 17.3% and 43.7%, respectively. A randomized double-blind field trial with a single dose of ivermectin (150-200 microg/kg body weight) alone or in combination with albendazole (400 mg) was subsequently carried out among these children. Both treatment regimens resulted in a considerable decrease in mean mf intensities, with overall reductions being slightly but statistically significantly higher for the combination than for ivermectin alone. The difference in effect between the two treatment regimens was most pronounced at 6 months, whereas it was minor at 12 months after treatment. The relative effect of treatment on mean CFA units was less pronounced than on mf. For both treatment regimens, reductions in CFA intensity appeared to be higher in children who were both CFA and mf positive before treatment, which may suggest that treatment mainly affected the survival and/or production of mf, rather than the survival of adult worms. New cases of infection appeared after treatment with both regimens among the pre-treatment mf and CFA negative children. Adverse reactions were few and mild in both groups, and mainly reported from pre-treatment mf and CFA positive children. The alarmingly high prevalence of W. bancrofti infection in primary school children highlights the importance of also determining the reversibility of already acquired early lesions, and the development of new measures and strategies to specifically protect children from later developing clinical disease.

Adolescent↗
PubMed2005

The effect of eight half-yearly single-dose treatments with DEC on Wuchereria bancrofti circulating antigenaemia.

The effect of eight half-yearly treatment rounds with diethylcarbamazine (DEC; 6mg/kg bodyweight) on Wuchereria bancrofti-specific circulating filarial antigen (CFA), a marker of adult worm infection, was followed in 79 individuals who were CFA-positive before start of treatment. Half of these were also microfilariae (mf)-positive. Microfilaraemia decreased rapidly after onset of treatment and became undetectable after four treatments. Circulating antigenaemia also decreased progressively, but at a much slower rate. After two, four and eight treatment rounds, the mean CFA intensity was reduced by 81, 94 and 98%, and the prevalence of CFA positivity was 85, 66 and 57%, compared with pre-treatment, respectively. CFA clearance rates were negatively related to pre-treatment CFA intensities, and were higher among pre-treatment mf-negative individuals than among pre-treatment mf-positive individuals. Even among patients who had pre-treatment CFA intensities above the upper measuring level (32000antigen units), and who continued to have intensities above this level after treatment, a decrease in post-treatment CFA intensities was obvious from a continuous decrease in ELISA optical density values. Repeated DEC therapy thus appears to have a slow but profound and persistent macrofilaricidal effect, which in the long run may be beneficial to populations undergoing DEC-based control interventions by reducing the probability of future morbidity development.

Administration, Oral↗
PubMed2005

Does longevity of adult Wuchereria bancrofti increase with decreasing intensity of parasite transmission? Insights from clinical observations.

To interrupt transmission of Wuchereria bancrofti, a parasite that causes lymphatic filariasis, mass treatment of at-risk populations with antifilarial drugs is recommended for 4-6 years, the minimum estimated adult worm lifespan. Factors associated with adult worm longevity are unknown. In Recife, Brazil, we conducted a retrospective cohort study of 57 men whose adult W. bancrofti were not sensitive to diethylcarbamazine and who were followed with semi-annual physical examinations (to detect intrascrotal nodules, indicative of adult worm death) and ultrasound examinations (to detect the 'filaria dance sign' (FDS), indicative of living adult worms). After 5 years, the FDS remained detectable in 10 (24.4%) of 41 adult worm nests in 25 men from areas of high filariasis transmission intensity and in 30 (90.9%) of 33 nests in 32 men from areas of low transmission (P<0.001). New nodules and adult worm nests were detected only in men from high-transmission areas. Of 30 men who were microfilaria-positive initially and whose FDS remained detectable after 5 years of follow-up, 19 (63.3%) remained microfilaria-positive in 5 ml blood (mean density, 0.4 per ml). In conclusion, survival of adult W. bancrofti is inversely associated with transmission intensity. These findings have implications for filariasis elimination and research.

Adolescent↗
PubMed2006

Efficacy of co-administered diethylcarbamazine and albendazole against adult Wuchereria bancrofti.

Although diethylcarbamazine (DEC) and albendazole are recommended to interrupt transmission of Wuchereria bancrofti, little is known about the macrofilaricidal effect of this drug combination. Forty-seven men with W. bancrofti infection were randomly assigned to receive a single dose of either DEC alone (6 mg/kg) (n=25) or a combination of DEC (6 mg/kg) and albendazole (400 mg) (n=22). Physical examinations for scrotal nodules (resulting from worm death) and ultrasound examinations (to detect living adult worms) were performed before treatment and 7, 14, 30, 45, 60, 90, 180, 270 and 360 days after treatment. Blood was examined for microfilariae before and 30 days and 360 days after treatment. Seven days post treatment, intrascrotal nodules were detected at the site of 21 (46.7%) adult worm nests in men who received DEC alone compared with 2 (6.1%) sites in men who received DEC and albendazole (P=0.002). One year after treatment, 10 (22.2%) original adult worm nests remained detectable by ultrasound among men who received DEC alone compared with 18/32 (56.3%) nests among men who received both drugs (P=0.016). Microfilaraemia prevalence and density decreased to a similar extent in both groups. Addition of albendazole appeared to decrease the macrofilaricidal effect of DEC against W. bancrofti, with no detectable enhancement in microfilarial suppression.

Adolescent↗
PubMed2006

Changes in Wuchereria bancrofti infection in a highly endemic community following 10 rounds of mass administration of diethylcarbamazine.

Mass drug administration (MDA) is the principal strategy of the programme to eliminate lymphatic filariasis (LF). Evaluation of MDA in highly endemic 'sentinel' communities is necessary to understand its impact on LF infection. This study examined the changes in Wuchereria bancrofti infection following 10 rounds of annual mass administration of diethylcarbamazine (DEC) in a highly endemic community. The mean number of DEC treatments received per adult in the community was 7.4+/-2.0. Following 10 rounds of DEC administration, the number of microfilaria (mf) carriers fell from 565 to 55. None of the pre-MDA amicrofilaraemic individuals showed circulating filarial antigen (CFA). However, 54.5% of the pre-MDA microfilaraemic individuals were positive for CFA. All the pre-MDA high intensity mf carriers continued to be positive for CFA, and some of them also showed blood mf. These patients are the most difficult to be cured by MDA and were distributed in 8.2% of the households. All the children born during the last 7 years of the MDA programme were negative for CFA. The study suggests that six to seven DEC treatments per individual suppresses microfilaraemia, except in some people with heavy infection, and repeated MDA has very good potential to prevent infection in children.

Adult↗