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At least 307 records · Page 17Linked to original sources
PubMed1986

A rapid, simple method for isolation of viable microfilariae.

We describe a rapid, efficient method for purifying Loa loa microfilariae from blood that does not affect their longterm motility. It is based on the separation of microfilariae on a performed discontinuous Percoll gradient, followed by filtration on cellulose ester membranes. The parasite population, after isolation, is close to 100% pure, 100% viable and remains motile for at least 20 days. Recovery from original blood samples is typically around 90%. The method, because of its simplicity and minimal material requirements, could be used with up to 210 ml of blood. It also allows the isolation of Mansonella perstans microfilariae.

Animals↗
PubMed2001

Short report: A practical technique for the cryopreservation of Dirofilaria immitis, Brugia malayi, and Wuchereria bancrofti microfilariae.

A technique to cryopreserve microfilariae has been developed. This method was used to cryopreserve microfilariae of Dirofilaria immitis, Brugia malayi, and Wuchereria bancrofti at a controlled rate of 1 degree C/min by use of a freezing tank. Microfilariae of each of these species retained their ability to infect susceptible mosquito species and develop to the infective stage after cryopreservation. The method presented here is quickly and easily carried out with inexpensive equipment.

Animals↗
PubMed1976

Fundus lesions in the rabbit eye following inoculation of onchocerca volvulus microfilariae into the posterior segment. II. Pathology.

The injection of living microfilariae of Onchocerca volvulus into the vitreous or immediately beneath the retina of rabbits gave rise to a variable degree of choroiditis. Uveal inflammation was most marked in eyes inoculated directly into the retina and subretinal tissue. The choroiditis was characterised by lymphocytic, plasma cell and eosinophil infiltration and was associated in many instances with degeneration of the overlying retina and pigment epithelium. In the eyes of animals killed more than 40 days after inoculation with microfilariae the leucocytic infiltration was usually mild or even absent, and the predominant finding was circumscribed atrophy and degeneration of the retina. It is concluded that the pathogenesis of the lesions in posterior segment onchocerciasis is basically inflammatory with, possibly, a direct toxic action of the microfilariae on the retina.

Animals↗
PubMedDate not supplied

Daily diethylcarbamazine for the treatment of Brugia malayi microfilaria carriers.

BACKGROUND: Diethylcarbamazine is effective for the treatment of brugian filaria carriers. However, the 12-day course with a daily dose of 6 mg per kg body weight is rarely completed. The World Health Organization has indicated the need for better regimes to control filariasis. METHODS: We evaluated the long term effects of three different dosage regimes of diethylcarbamazine--6, 9 and 12 mg per kg body weight--to a total of 72 mg on 93 microfilaria carriers of Brugia malayi. RESULTS: All cases treated with the 6 mg daily dose showed complete clearance of microfilaria immediately after the treatment. However, at the 9 and 12 mg daily doses only 91% and 85% of cases respectively showed complete clearance. There was a close association between the daily dose and the proportion of cases developing side-effects. The mean initial microfilaria counts were significantly higher in those who had side-effects than in those who did not. An 11-month follow up showed that with the 6 mg daily dose the recurrence rate of microfilaraemia was 29% while with the 12 mg daily dose it was 67%. Four per cent of patients on a daily dose of 6 and 9 mg discontinued treatment while 21% of those on the 12 mg daily dose did so. CONCLUSION: The 6 mg daily dose of diethylcarbamazine was the most effective and best accepted regime.

Adolescent↗
PubMed1978

[Ultrastructural aspects of the degeneration of the dermal microfilaria O. volvulus under the effect of diethylcarbamazine in human onchocerciasis].

Early modifications observed by previous authors are confirmed. More over, some later modifications are described where microfilariae are completely destroyed and removed by phagocytic cells. The theory concerning the mode of action of DEC on microfilariae in vivo is not confirmed (absence of extracellular "coarse particulate material", which is actually the unique morphological finding which leads the previous authors to assess the presence of immune complexes at the surface of microfilariae).

Adolescent↗
PubMed1991

Biting periodicity index of Culex quinquefasciatus & its relationship with microfilaria periodicity in Pondicherry.

The biting periodicity index of the bancroftian filariasis vector, C. quinquefasciatus, was calculated on the basis of a large longitudinal data base and compared with the periodicity index of microfilariae of Wuchereria bancrofti. The biting periodicity index of the vector population was 29.78 and found to be close to the periodicity index of the microfilariae. The peak biting activity of the vector and peak appearance of microfilariae in the peripheral blood occurred at about 01.00 h, which accounts for the optimum infection of the vector population. The early night biting density of the vector population showed a highly significant (P less than 0.0005) linear relationship with all night biting density.

Animals↗
PubMed1977

The carbohydrate metabolism of Brugia pahangi microfilariae.

Evidence is presented that the microfilariae of Litomosoides carinii, Dipetalonema viteae and Brugia pahangi have an aerobic requirement for motility, but possibly not for survival. In addition, the data suggest that in an in vitro anaerobic environment, B. pahangi microfilariae ferment glucose only as far as lactate. In an aerobic environment, however, the data are consistent with a portion of glucose being dissimilated via a one step oxidative decarboxylation of pyruvate formed from glycolysis to acetate and CO2. In addition, a low level of complete oxidation, possibly via a tricarboxylic acid cycle pathway, may be occurring. Finally, if B. pahangi microfilariae are immobilized with levamisole in an aerobic atmosphere, the drug appears to alter the aerobic glucose metabolism of the parasite both qualitatively and quantitatively. A decreased glucose utilization occurs, together with a shift to a more nearly homolactate fermentation. It is suggested that the effects of levamisole on the metabolism of the microfilariid are secondary to the observed paralysis.

Aerobiosis↗
PubMed1989

Fine structure and localization of anionic sites on the surface of microfilaria of Wuchereria bancrofti.

The fine structure of the sheath and the cuticle of microfilaria of Wuchereria bancrofti was analysed and the results obtained were compared with those from other filarial parasites. Cationized ferritin particles bind to the surface of the sheath and the epicuticle. No binding of colloidal iron hydroxyde particles to the microfilaria surface was observed. Reaction product indicative of carbohydrates containing vic-glycol groups was not observed in thin sections of microfilaria submitted to the periodic acid-thiosemicarbazide-silver proteinate technique. The results obtained are discussed in relation to previous studies using lectins.

Animals↗
PubMedDate not supplied

Microfilariae in fine needle aspirates from epididymal lesions.

Microfilariae of Wuchereria bancrofti were observed in fine needle aspiration smears from three epididymal nodules, and degenerating microfilariae suggestive of Brugia malayi were found in the smears from a fourth case. The smears in all four cases showed a polymorphonuclear inflammatory cell component as well as epithelioid cell granulomata. While blood eosinophilia was present in all four cases, eosinophilia was present in the aspiration smears in only one case. Microfilariae could be demonstrated in the peripheral blood in only one case.

Adolescent↗
PubMed1978

Electron microscopical studies on onchocerciasis. I. Mesenchyme reaction in untreated onchocercal dermatitis and ultrastructure of the microfilariae.

Skin biopsies of 22 untreated Liberian patients suffering from onchocercal dermatitis were studied by electron microscopy. The microfilariae tend to accumulate in the upper dermis, without eliciting a cellular reaction. Occasionally macrophages or mast cells are found in the neighbourhood of the microfilariae. The most conspicuous changes concern the presence of perivascular infiltrates, comprised of lymphocytes and macrophages, with a varying admixture of plasma cells. Only exceptionally the macrophages show an increase in number and size of their lysosomes and pseudopodia as well as prominent strands of ergastoplasm indicating an activation. The endothelial walls of the dermal vessels are swollen. The amount of mast cells in the upper dermis is increased. Ultrastructural features of the microfilariae are described, especially the cuticle, muscles, central undifferentiated cells and cephalic region. When comparing these findings with the literature on the fine structural morphology of the Latinamerican form, no differences can be found.

Adolescent↗
PubMed2002

Infection with Brugia microfilariae induces apoptosis of CD4(+) T lymphocytes: a mechanism of immune unresponsiveness in filariasis.

In humans infected with lymphatic filariasis, microfilaraemia [the presence of microfilariae (Mf) in the blood] is generally associated with both poor antigen (Ag)-specific proliferative responses and with protection from severe disease. Clonal deletion has been suggested as one possible mechanism by which parasite-reactive lymphocytes, that may be capable of mediating resistance and/or immunopathology, are silenced in asymptomatic carriers. In this study we demonstrate that splenic lymphocytes from mice infected with microfilariae of Brugia pahangi display an Ag-specific proliferative defect. However, these cells were not completely unresponsive since they produced high levels of Ag-specific IFN-gamma. Using TdT-mediated dUTP-biotin nick end labeling for flow cytometry, CD4(+) lymphocytes from Mf-infected mice cultured with Ag showed high levels of apoptosis when compared to those from L3-infected mice which proliferated well in response to Ag. Treatment of Ag-stimulated cultures with aminoguanidine (AMG), an inhibitor of inducible nitric oxide synthase, rescued the CD4(+) T cells from apoptosis and reversed the proliferative defect. Furthermore, carboxyfluorescein diacetate succinimidyl ester labeling allowed the visualization of dividing CD4(+) T cells in cultures from Mf-infected animals only in the presence of AMG. We hypothesize that CD4(+) T cells indirectly trigger their own apoptosis by secreting significant quantities of IFN-gamma resulting in the induction of high levels of nitric oxide, and the subsequent elimination of effector T cells. Our findings are the first direct evidence that infection with Brugia Mf can selectively induce lymphocyte apoptosis, a phenomenon that could contribute to the proliferative defect and parasite persistence associated with the microfilaraemic state in the infected human.

Aedes↗
PubMed1994

Onchocerca lienalis: rapid clearance of microfilariae within the black fly, Simulium vittatum.

A rapid decrease of about a third of the number of Onchocerca lienalis microfilariae (mf) parenterally inoculated into Simulium vittatum black flies occurred within 5 hr postinoculation (pi). The change of mf counts over time was modeled by a segmented linear regression. During 2 hr pi the slope was -3.5 mf/hr (P < or = 0.001) and between 2 and 24 hr pi the slope was -0.1 mf/hr. Although significantly different from the former slope (P < 0.001), the latter was not significantly different from zero (P > 0.2). The decrease could not be attributed to excretion of mf. Microfilariae (especially those heat-killed prior to inoculation) in intermediate stages of destruction were observed in flies dissected 5 hr pi but not immediately after injection. No short- or long-term (24 hr pi) effects of the injection procedure alone on mf survival were evident. A constant proportion of mf was eliminated regardless of dose within a range of 5 to 100 mf/fly during 24 hr pi. However, a second injection of 50 mf/fly 2.5 hr following an injection of the same dose resulted in a significantly lower proportion of mf eliminated. These results suggest that the availability of an active factor(s) in the fly was reduced 2.5 hr after the first inoculation. The change in the availability of this factor(s) may partly explain the change in clearance rate occurring 2 hr pi. Soluble factor(s), rather than a sequence of cellular responses, seems to be involved in the rapid clearance because it occurred in freshly killed flies at a similar rate to that observed in live flies. The hypothesis that mf differ in their innate susceptibility to rapid clearance was rejected as mf that were recovered 2 hr pi and reinoculated into other flies were eliminated faster than unexposed controls. It is concluded that the rapid clearance of mf represents an as yet undescribed immune response to macroparasites of the fly host.

Animals↗
PubMed1987

Formation by the uterus of a peripheral layer of the sheath in microfilariae of Litomosoides carinii and Brugia malayi.

The eggshells of young developmental stages in the uterus are rather thin and homogenous. In the brezel stage of Brugia malayi they are 35 nm thick and 20 nm in Litomosoides carinii. In young developmental stages up to brezel stages the eggshells bind the lectins WGA, DBA and PNA labelled with colloidal gold. This shows that GlcNAc, GalNAc and Gal residues are present at the surface of the sheath. In intrauterine microfilariae of B. malayi the original sheath is reduced to a thickness of 7 nm. It is reinforced by secretions from a specialized area of the epithelium of the uterus which do not appear as a homogeneous layer but look like a string of pearls. This layer may be called the "uterine layer". It has a thickness of 40-80 nm. In the microfilaria of L. carinii, the thickness of the original sheath is reduced to 2-3 nm and the uterine layer has a thickness of 7 nm. The uterine layer does not react with any of the lectins, which shows that the surface lacks N-acetylglucosamine, N-acetylgalactosamine and galactose residues. The uterine layer appears to be an ancestral (plesiomorphic) feature which is present in free-living nematodes and the highly specialized bloodforms of filariae. The uterine layer seems to protect and disguise the original sheath against the immune reactions of the host.

Animals↗
PubMed1991

Surface antigens of male worms and microfilariae of Onchocerca gibsoni.

Living adult males and microfilariae of the cattle filarial parasite Onchocerca gibsoni were externally labelled with radioactive iodine using the iodogen and Bolton-Hunter procedures. Characterization of labelled surface proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis revealed clear cut differences in the two life cycle stages. In addition, the two radiolabelling procedures yielded some differences in the profiles of radiolabelled surface proteins for both adults and microfilariae. Immunoprecipitation analysis revealed a number of labelled antigens recognized by antibodies in human onchocerciasis serum pools, thereby demonstrating the usefulness of O. gibsoni as a model in Onchocerca volvulus vaccine studies. The reactivity of microfilarial antigens extended to antibodies from other human nematode infections, whereas male surface antigens, particularly those of low molecular weight, were Onchocerca specific. This indicates that O. gibsoni can provide a convenient source of specific diagnostic antigen.

Animals↗
PubMed1992

Millardia meltada, a new host for Acanthocheilonema viteae and a simple technique for separation of microfilariae from peripheral blood.

Millardia meltada were infected with Acanthocheilonema viteae and examined for their susceptibility. The morbidity of infected M. meltada was low compared with that of jirds. On day 47 post-infection (p.i.), 13 of 14 M. meltada developed microfilaremia. Male M. meltada then showed gradually increasing microfilaremia with a peak level of 7000 per 30 microliters blood at week 20 p.i., which was much higher than that (3000) of male jirds. In contrast, microfilarial densities of female M. meltada were markedly low with a peak level of 200 during weeks 10-12 p.i. A simple centrifugation technique with Lympholyte-M was devised for microfilarial separation from the peripheral blood of infected M. meltada and yielded approximately 17 x 10(5) viable microfilariae from 1 ml of blood. This method also makes it possible to collect microfilariae from the same individuals repeatedly. M. meltada, coupled with this microfilarial separation technique, serves as a useful animal model for microfilarial studies of A. viteae.

Animals↗
PubMed1975

A technique for isolating and concentrating microfilariae from peripheral blood by gradient centrifugation.

A method for isolating microfilariae from blood cells by Ficoll-Hypaque centrifugation, followed by concentration by conventional centrifugation, is described. A 30 fold concentration and quantitative recovery of parasites was achieved. This technique should be of value for documenting low levels of parasitaemia, and for obtaining relatively pure suspensions of microfilariae for metabolic studies and antigen analysis.

Blood↗
PubMed1983

The distribution of the microfilariae of Onchocerca volvulus in the different body regions in relation to the attacking behaviour of Simulium damnosum s.l. in the Sudan savanna of northern Cameroon.

Densities of Onchocerca volvulus microfilariae in four volunteers with low to moderate infections were estimated at five body sites by paired skin snips. The landing of Simulium damnosum s.1. females on the body of these volunteers was recorded during 12 hours for six days. Most flies fed at the ankles (53% and 51%) and calves (28% and 27% respectively) in both the standing and sitting positions. The density of microfilariae in the skin was highest in the pelvic region (24.1 mf/mg) and relatively low in the calf (14.8 mf/mg) and ankle (1.0 mf/mg) regions. From the biting rate (females/body part) and the microfilarial density (mf/mg) a transmission index was calculated for the different body regions. This was highest for the calves showing that this part of the leg, if unclothed, accounts for the highest rate of contact (50 to 60% of total) between vector and parasite.

Animals↗