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PubMed1995

Efficacy of moxidectin oral gel against Onchocerca cervicalis microfilariae.

During a series of dose-titration experiments designed to evaluate the efficacy of moxidectin oral gel against equine gastrointestinal parasites, infection with Onchocerca cervicalis was diagnosed in 25 of 82 ponies prior to treatment. Microfilariae were identified in full-thickness skin biopsies taken from the ventral midline. Treatment with moxidectin in single doses of 300, 400, or 500 micrograms/kg of body weight was 100% effective in eliminating microfilariae from 20 skin biopsies taken 14 days posttreatment, whereas 5 microfilaria-positive ponies in 2 control groups remained positive following placebo treatment. No adverse reaction was seen in any pony following treatment with moxidectin or the vehicle control.

Administration, Oral↗

PubMed1975

[The mechanism controlling the crossing of the vector's stomach wall by microfilariae (Dipetalonema dessetae-Aedes aegypti)].

In some of the human filariasis, the number of microfiliariae which succeed in crossing the vector's stomach wall is smaller when the number of ingested microfilariae is larger (limitation). In the couple Dipetalonema dessetae-Aedes aegypti, this phenomenon appears to be due to a specific lysis of the stomach cells invaded by the microfilariae. This reaction is started when the microfilariae are very numberous. There is "information" transmitted to the whole of the vector's stomach.

Aedes↗

PubMed1993

Characterization of the N-linked oligosaccharides in glycoproteins synthesized by microfilariae of Dirofilaria immitis.

In this report, we describe studies on the structures of the N-linked oligosaccharides contained in glycoproteins synthesized by microfilariae of the canine heartworm, Dirofilaria immitis. Microfilariae were incubated in media containing either 2-[3H]mannose, 6-[3H]glucosamine, or 6-[3H]galactose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorographic analyses indicated that many glycoproteins were radiolabeled by both the mannose and glucosamine, whereas glycoproteins were not radiolabeled by the galactose. Glycopeptides from these total glycoproteins were fractionated and purified by serial lectin affinity chromatography, and the structures of the oligosaccharides in the isolated glycopeptides were analyzed by a variety of techniques. The N-linked oligosaccharides were shown to contain mannose (Man), fucose, N-acetylglucosamine (GlcNAc), and N-acetylgalactosamine (GalNAc). However, they lacked sialic acid and galactose, which are commonly found in mammalian glycoproteins. GalNAc was shown to be in an unusual terminal position and beta-linked in the sequence GalNAc beta GlcNAc beta Man-R, where R is the typical branch of complex-type N-linked oligosaccharides. Similar structures were recently found by us to be synthesized by the helminthic parasite Schistosoma mansoni. These results demonstrate that glycoproteins synthesized by microfilariae of D. immitis have unusual carbohydrate moieties and may lead to a better understanding of the specific roles of glycoprotein oligosaccharides in host-parasite interactions.

Animals↗

PubMed1995

A simple field method for the purification of Onchocerca ochengi microfilariae from a mixed Onchocerca infection in cattle.

Onchocerca ochengi, a bovine parasite, is a suitable model for research on human River Blindness. However, the microfilariae are normally found concomitantly with at least one of the other three bovine Onchocerca species O. dukei, O. gutturosa and O. armillata causing difficulties for the work on the microfilariae. We describe a simple and field applicable method for the separation of living O. ochengi microfilariae from the other Onchocerca species using Sephadex G-25 columns. Elution of mixed populations resulted in the passage of O. gutturosa and/or O. dukei in the initial 1 ml fraction with O. ochengi eluting as an almost 100% pure species in the 4th and 5th fractions.

Animals↗

PubMed1997

Scanning electron microscopic study of microfilaria and the third stage larva of Wuchereria bancrofti.

The surface structures of microfilaria and of the third stage larva of Wuchereria bancrofti were studied by scanning electron microscopy. Distinct features were observed that could be used for differentiating species of this parasite. Specifically, the sheath of microfilariae of W. bancrofti projected beyond the head. The head region of the microfilaria was composed of a cephalic cap with hook, mouth and amphidial opening, and its cuticle showed annulation. Spines were absent at the first transverse annulation, and the tail end showed a slight constriction. In the infective stage larva, characters which are used for differentiating species, such as the two bubble-like ventro-lateral papillae and one dorso-terminal papilla were rather similar to each other in size, but the grooves seen around the base were absent. A previously unreported feature of the third stage larva of W. bancrofti that was discovered in this study is a papilliform process on the left side of the posterior region, between the anus and the tail end.

Animals↗

PubMed1995

Brugia pahangi: effects of melanization on the uptake of nutrients by microfilariae in vitro.

The effects of melanization on nutrient uptake by the microfilariae of Brugia pahangi were investigated by using in vitro melanization and autoradiographic techniques. It was found that the melanotic capsules which formed around the microfilariae in vitro completely inhibited the uptake of the following radiolabeled nutrients into microfilarial tissues: D-[6-3H]glucose, L-[4,5-3H]leucine, [2-3H]glycine, [1-14C]linoleic acid, [5,6,8,9,11,12,14,15-3H]arachidonic acid, [2,8-3H]adenine, [8-14C]guanine HCl, and [5,6-3H]uracil. These results provide strong evidence that melanization may kill the microfilariae by starvation.

Adenine↗

PubMed1998

Onchocerca volvulus: microfilariae secrete elastinolytic and males nonelastinolytic matrix-degrading serine and metalloproteases.

Host tissue penetration by parasitic nematodes may be mediated by both mechanical processes and proteolytic enzymes released by the parasites. Analysis of excretory-secretory (ES) products of Onchocerca volvulus microfilariae and adult stages on substrate gels demonstrated that they contain several distinct proteolytic enzymes. The analysis of the ES products of the microfilariae revealed one low and two high molecular weight proteolytic bands that degraded gelatin in substrate gels. The low molecular weight protein was found to be an elastinolytic protease cleaving soluble and insoluble elastin. ES products of males contained several high molecular weight proteases in the range of >/= 100-kDa degrading gelatin but lacked the low elastinolytic protease. The ES proteases of both developmental stages degraded the extracellular matrix proteins fibronectin, laminin, and collagen type IV, but not intact immunoglobulin G. The optimal protease activity for each of the proteases was found to be at a neutral pH. Inhibitor studies demonstrated their classification as serine and metalloproteases. Female and male extracts were able to hydrolyze azocasein but not gelatin in substrate gels. Protease activity could not be detected in ES products of females and microfilariae extract.

Animals↗

PubMed1994

An ultrastructural, cytochemical and freeze-fracture study of the surface structures of Brugia malayi microfilariae.

Ultrastructural analysis of the cuticle of Brugia malayi microfilariae indicated that it is composed of 2 regions: the inner one 15-20 nm thick with a homogeneous aspect and the outer one, designated as epicuticle, which is 15-20 nm thick. Three laminae separated by electron-lucent regions were seen in the epicuticle. Labeling of the cuticle and epicuticle of B. malayi and Wuchereria bancrofti microfilariae was observed when thin sections of Lowicryl-embedded parasites were incubated in the presence of gold-labeled phospholipase-C. Replicas of freeze-fractured microfilariae showed the presence of 2 fracture planes in the epicuticle and no fracture plane in the inner region of the cuticle. The P face of the epicuticle outer fracture plane presented few particles similar to intramembranous particles (IMPs). The epicuticle inner fracture plane P and E faces presented large numbers of densely-packed small particles and many protuberances. Also, fracture faces of hypodermal and muscle cell plasma membranes were analyzed. Faces P and E of fractured membranes showed the presence of typical IMPs. P faces of both membranes showed larger amounts of particles than E faces. Fracture of muscle plasma membrane revealed a linear array of particles disposed in parallel rows on its P face.

Animals↗

PubMed1985

Chitin synthesis and sheath morphogenesis in Brugia malayi microfilariae.

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.

Acetylglucosamine↗

PubMed1989

A stage-specific calcium-binding protein from microfilariae of Brugia malayi (Filariidae).

The monoclonal antibody MF1 has been shown to cause transient clearance of blood-borne microfilariae in gerbils infected with Brugia malayi. The present study demonstrates that the MF1 antibody recognizes a proteinaceous determinant on two polypeptides of 70 and 75 kDa. Both the monoclonal antibody and antisera raised to the gel-purified antigen show binding restricted to mature microfilariae. Intrauterine and recently shed microfilariae apparently lack the MF1 molecules. Prominent 45Ca-binding molecules comigrate with the MF1 antigens in one-dimensional electrophoresis (under both reducing and non-reducing conditions), and co-purify through ion exchange chromatography. The MF1 antigen thus appears to be a developmentally regulated calcium-binding protein(s).

Animals↗

PubMed1999

Effects of an Onchocerca-derived cysteine protease inhibitor on microfilariae in their simuliid vector.

A recombinant cysteine protease inhibitor, onchocystatin of the parasitic nematode Onchocerca volvulus, was tested for its role in microfilarial development in the simuliid vector. Onchocystatin was found to be present in female adults and skin microfilariae of the bovine parasite O. ochengi, the closest relative of O. volvulus. In addition the inhibitor could be detected as an excretory-secretory (E-S) product of the microfilariae. Co-injection of onchocystatin and the O. ochengi microfilariae into the surrogate vector Simulium ornatum s.l. significantly enhanced the recovery rates of the parasite within 24 h into the infection (P > 0.001). The findings suggest a possible role of onchocystatin in the evasion by the parasite of the immune response of its vector.

Animals↗

PubMed1999

Interleukin-12 modulates T-cell responses to microfilariae but fails to abrogate interleukin-5-dependent immunity in a mouse model of onchocerciasis.

Infection of mice with microfilariae of Onchocerca lienalis induces high levels of protective immunity to reinfection, which is dependent on interleukin (IL)-5 but not IL-4. Here, we have investigated the effect of exogenous IL-12 administration during either the priming or effector phases of the immune response. When administered during priming, IL-12 induced down-regulation of parasite-specific serum immunoglobulin (Ig)E and up-regulation of IgG2a. Antigen-specific IL-4 responses were strongly suppressed, whilst blood eosinophil levels were partially reduced. When administered during a challenge infection, IL-12 did not significantly influence the balance of antibody isotypes, but partially reduced eosinophil production. Antigen-specific IL-4 responses were again completely ablated. Unusually, interferon-gamma (IFN-gamma) responses were not significantly affected following IL-12 administration, either during priming or after challenge infections. Moreover, despite a fall in antigen-specific IL-5 production, the expression of IL-5-dependent immunity, as determined by reduction in worm recoveries, was fully maintained. These data demonstrate that parasite-induced IL-4 can be abrogated without affecting protective immunity to Onchocerca microfilariae in mice. In view of the established role of IL-4 in pathogenesis, this may have important implications for the development of immunoprophylaxis aimed at microfilariae and the alleviation of pathology in onchocerciasis.

Animals↗

PubMed1979

Bancroftian filariasis: a comparison of microfilariae counting techniques using counting chamber, standard slide and membrane (nuclepore) filtration.

Three techniques were compared for counting microfilariae of Wuchereria bancrofti in blood specimens--a standard slide method, the counting chamber technique (CCT) and a membrane filtration technique (MFCT). The CCT was much more sensitive than the slide method, the difference in sensitivity between these two methods probably being due mainly to the loss of microfilariae during the dehaemoglobinizing process prior to staining in the standard slide method. There was good correlation between the techniques when 0.1 ml of finger-prick blood was examined by the CCT and 1 ml of venous blood by the MFCT. The number of additional positives revealed by the MFCT was ten of 275 (3.6%) subjects examined. The use of venepuncture for MFCT is impractical for field surveys in East Africa whereas a microfilarial count on 0.1 ml of finger-prick blood meets most of the criteria required of a field technique. The method is simple, quantitative and acceptable to the population. The results are reproducible, can be readily checked, the technique provides a useful and practical method for obtaining prevalence information following control schemes. The finding of a relatively low prevalence of microfilariae seen by both MFCT and CCT in children aged five to nine years from a highly endemic filariasis area agrees with the results of previous East African surveys carried out by blood smear and CCT.

Adolescent↗

PubMed1994

Salivarectomy effects on the ingestion of Brugia pahangi (Nematoda: Filarioidea) microfilariae by susceptible and refractory strains of Aedes aegypti (Diptera: Culicidae).

Ingestion of Brugia pahangi Buckley & Edeson microfilariae by susceptible (Liverpool) and refractory (Bora-Bora) strains of salivary duct-severed Aedes aegypti (L.) was investigated. The transection at either the salivary common duct or the two lateral ducts of mosquitoes did not affect the mean number of microfilariae nor the mean amount of blood ingested per mosquito. These results indicated that mosquito salivary secretion did not have a chemotropic effect on microfilariae.

Aedes↗

PubMedDate not supplied

Diagnosis of microfilaria in gastric brush cytology. A case report.

BACKGROUND: Filariasis due to Wuchereria bancrofti is endemic to southern Asia. While the laboratory diagnosis has been conventionally made by demonstrating microfilariae in peripheral blood smears, these have also been occasionally diagnosed on aspiration cytology of various organs. CASE: A 54-year-old male presented with a burning sensation in the epigastrium of five months' duration. Endoscopic brush biopsy revealed numerous sheathed microfilariae of W bancrofti. The patient had had no symptoms suggestive of filarial infection in the past. Cytology revealed numerous microfilariae among lymphocytes and neutrophils. CONCLUSION: This case illustrates that a thorough examination of gastric brushings can at times reveal unexpected findings and may prove to be a useful supplement to endoscopic biopsy.

Animals↗

PubMed1976

Morphology of the microfilaria of Brugia malayi in Cheju-Do, Korea.

The morphological characters of the microfilaria of Brugia malayi collected in Cheju-Do, Korea were described and compared with those or other local strains, already reported from the Malay Archipelago(Brug, 1927), Huchow, South China (Feng, 1933), Hachijo Kojima, Japan (Hayashi, 1951) etc. And it was found that there are no marked difference among these kinds of Microfilaria malayi. The percentage measurements of the fixed points in the Microfilaria malayi from Korea are summarized as follows; B.N.C.: 3.38%(2.90-3.72%), N.R.: 22.64% (17.36-25.81%), E.P.: 32.26% (27.49-36.60%), E.C.: 38.78% (34.90-41.72%), Inn. K. begin: 53.95% (49.50-58.84%) end: 67.87%(63.02-72.97%), G-1: 70.42% (60.22-75.23%), G-2:76.70% (75.10-78.32%), G-3:78.84% (77.81-79.59%), G-4:80.84%(79.82-81.35%), A.P.:82.94%(77.32-89.72%), Length: 193.39(+/-12.3 micrometer)(170.77-233.08 micrometer), Width: 7.04+/-0.37 micrometer(5.99-7.99 micrometer), Sheath: 268.48+/-17.07 micrometer(218.72-286.47 micrometer), Ratio(Cephalic space): 1: 0.78

Journal Article↗

PubMed1998

Periodicity exhibited by Dirofilaria immitis microfilariae identified in dogs of Korea.

Microfilarial periodicity of Dirofilaria immitis (the dog heartworm) was determined at two hr intervals for 72 consecutive hrs in 10 naturally infected war dogs, 3-9 years old, in Korea to facilitate harvest of the microfilariae for possible use in laboratory works and to elucidate further the periodicity of the microfilaria depending on geographic location. Although the periodicity had been observed as being low-grade nocturnal, maximal microfilarial counts were found at 21:00 hr and minimal at 11:00 hr, giving rise to an evident peak in fluctuation of the larval counts. This is the first record of the periodicity of the microfilariae identified as D. immitis in Korea.

Animals↗

PubMed1978

Circulating non-human microfilaria in a patient with systemic lupus erythematosus.

A 12-yr-old girl with systemic lupus erythematosus requiring steroid therapy was found to have a circulating microfilaria during an exacerbation of her illness. Morphologically, the microfilaria does not correspond precisely with any previously described species, though similarities exist between the patient's microfilaria and those of Dipetalonema reconditum of the dog and D. interstitium of the grey squirrel. The organism reported here is probably an undescribed species from a wild mammal. Although the association may be merely coincidental, this case suggests that compromised immunity might have led to this unusual infection with a non-human filaria.

Animals↗