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At least 145 records · Page 8Linked to original sources
PubMed1983

Cryopreservation of the microfilariae of Brugia malayi, Dirofilaria corynodes, and Wuchereria bancrofti.

Methods are presented for the cryopreservation of a sheathed microfilaria, Brugia malayi, and an unsheathed species, Dirofilaria corynodes. The former survived best when frozen at the rate of -0.8 degree or -0.5 degree C per minute using 9% dimethyl sulfoxide (DMSO) as the cryopreservative. Approximately 52-79% of the thawed microfilariae developed to the third stage in Aedes aegypti mosquitoes versus 79% of the unfrozen specimens. For D. corynodes the optimum freezing rate was -2 degrees or -5 degrees C per minute, and 6% DMSO combined with 0.004 M polyvinylpyrrolidone (PVP) afforded the best cryoprotective effect. The development of thawed microfilariae in mosquitoes ranged from 22-32% versus 29% for unfrozen specimens. In general, the viability of both species of microfilaria was retained best when stored in liquid nitrogen (-196 degrees C). The entire life cycle of B. malayi was completed in the laboratory using cryopreserved microfilariae as the initial source. The cryopreservation of Wuchereria bancrofti also is discussed.

Aedes↗
PubMed1987

Functional and antigenic maturation of Brugia malayi microfilariae.

Brugia malayi microfilariae of specified ages were obtained from gerbils implanted with fertile adult worms. Such microfilariae were tested for their capacity to infect mosquitoes. A strong age dependence was found for the microfilariae's capacity to: penetrate the mosquito midgut, exsheath in response to 20 mM calcium, and develop to third stage larvae in the mosquito. In addition, differences were found between 2-day-old microfilariae and controls (from larva-infected gerbils) in their reactivities with a series of monoclonal antibodies. Thus, defined immunochemical changes occur in microfilariae as they assume functional maturity.

Aedes↗
PubMed2003

The effects of diethylcarbamazine on the ultrastructure of microfilariae of Wuchereria bancrofti.

An ultrastructural study of microfilariae of Wuchereria bancrofti was performed after in vitro treatment with diethylcarbamazine. One of the first morphological alterations produced by treatment with 5, 10 or 50 microg/ml of DEC was the loss of microfilarial sheaths. Drastic effects of DEC were only detected when microfilariae were exsheathed. Microfilariae treated with 5, 10 or 50 microg/ml DEC showed severely affected organelles, formation of several vacuoles mainly in the hypodermis, and cytolysis. Some microfilariae showed extreme cellular disorganization with abundance of electron-dense degenerating organelles, numerous large vacuoles, and nuclear condensation. Lamellar bodies probably related to an assembly of endoplasmic reticulum membranes were observed in some damaged microfilariae. Thus, in vitro treatment with concentrations of DEC similar to therapeutic conditions had direct effect by causing a loss of the microfilarial sheath of W. bancrofti with subsequent damage of organelles and apoptosis.

Animals↗
PubMed1986

Detection of Dirofilaria immitis microfilariae in peripheral blood. A quantitative comparison of the efficiency and sensitivity of four techniques.

Four techniques for the detection and quantification of Dirofilaria immitis microfilariae in peripheral blood were compared, namely the conventional thick smear, thick films prepared by cytocentrifugation, filtration of blood through polycarbonate membranes, and density gradient centrifugation followed by membrane filtration. The efficiency of the methods and their sensitivity was assessed by determining quantitatively the recovery of known numbers of microfilariae from defined volumes of blood. Polycarbonate membrane filtration either alone or in combination with density gradient centrifugation showed an efficiency of 0.9 and 0.8, respectively, and reached 100% sensitivity with microfilariae densities of greater than or equal to 10 microfilariae per ml of blood. Conventional thick smears and cytocentrifugation were of considerably lower efficiency (0.02 and 0.03, respectively) and reached 100% sensitivity with more than 200 microfilariae per ml.

Animals↗
PubMed1987

In vitro study on the effect of the new chemotherapeutic agents CGP 6140 and CGP 20376 on the microfilariae of Onchocerca volvulus.

The effect of two new filaricidal compounds, CGP 6140 and CGP 20376, on the microfilariae of O. volvulus was tested in vitro. Culture medium consisted of a 1:1 mixture of IMDM/NCTC 135 supplemented with 20% heat-inactivated foetal calf serum and gentamycin. For pulse experiments the microfilariae were exposed to the drugs for one or three hours in medium without serum and then replaced to serum supplemented medium. In the continuous cultures the microfilariae were exposed to the drugs fur up to 72 hours without a change of medium. The effect of the drugs was assessed by their ability to reduce the larval motility. A reduction of motility of 98-100% after 24 hours of exposure occurred at levels of 1 micron/ml CGP 20376 or 10 mu mg/ml CGP 6140. After exposure for one hour CGP 20376 immobilized 100% of the microfilariae irreversibly at a drug level of 1 microgram/ml. Whereas no significant immobilization was seen with CGP 6140 after one hour. After exposure for three hours CGP 6140 immobilized up to 100% of the microfilariae at drug levels of 10 and 5 micrograms/ml.

Animals↗
PubMed1985

Resistance against Brugia malayi microfilariae induced by a monoclonal antibody which promotes killing by macrophages and recognizes surface antigen(s).

Several monoclonal antibodies were produced following the immunization of mice with infective larvae of Brugia malayi. One of these gives a positive fluorescence reaction on the surface of B. malayi microfilariae and this particular monoclonal antibody (IgM isotype) was able to mediate mouse peritoneal macrophage adherence to, and killing of, B. malayi microfilariae in vitro. Adherence and killing were enhanced by fresh normal mouse serum, suggesting a role for complement. When the same monoclonal antibody was passively transferred to mice harbouring microfilariae in their circulation, a complete clearance of microfilariae was observed in 70% of the animals. This monoclonal antibody was able to recognize antigenic determinants (of 110,000 MW) present on the surface of B. malayi microfilariae by radioimmunoprecipitation.

Animals↗
PubMed1983

Occurrence of microfilariae in various hollow organs and in the peritoneal cavity after treatment of Litomosoides carinii infected Mastomys natalensis with diethylcarbamazine and haloxon.

Treatment of Litomosoides carinii infected Mastomys natalensis with diethylcarbamazine (DEC: 500 mg/kg p.o.) was followed by increased occurrence of microfilariae in the bronchi of the host after 40 min and lasting at least until 6 h after treatment. After 4 h, increased levels of larvae were observed in the gut. Only a few microfilariae occurred in the bladder and sputum. Accumulations of microfilariae were found furthermore in the Lnn. hepaticae whereas no changes were observed in the inguinal or jejunal and lung and pleura associated lymph nodes. Increased numbers of microfilariae were found in the peritoneal cavity only after 8 and continuing until at least 48 h after treatment. In contrast, after haloxon treatment (100 mg/kg p.o.) an accumulation of microfilariae was found in the peritoneal cavity only, following a time course similar to that after DEC.

Animals↗
PubMed1978

The lethal effects of the cibarial and pharyngeal armatures of mosquitoes on microfilariae.

Microfilariae of Wuchereria bancrofti and Brugia pahangi were killed by the chewing action of the cibarial and pharyngeal armatures and other papillae and spines in the fore-gut of mosquitoes. The proportion of ingested microfilariae that were killed was largely dependent on the presence and shape of the cibarial armature. Anopheles farauti No. 1 and Anopheles gambiae species A and B have well developed cibarial armatures and killed 36 to 96% of the ingested microfilariae. Culex pipiens fatigans has a poorly developed cibarial armature and killed only 6% of the microfilariae. Aedes aegypti and Aedes togoi lack cibarial armatures but have the remaining fore-gut structures. They killed only 2 to 22% of the microfilariae. The significance of these observations in relation to the control of filariasis with diethylcarbamazine is discussed.

Animals↗
PubMed1996

Susceptibility of Brugia malayi and Onchocerca lienalis microfilariae to nitric oxide and hydrogen peroxide in cell-free culture and from IFN gamma-activated macrophages.

The susceptibility of Brugia malayi and Onchocerca lienalis microfilariae to H2O2 and NO either in cell-free culture or from IFN gamma-activated macrophages was examined. In cell-free culture, O. lienalis microfilariae were highly susceptible to H2O2 induced toxicity, exhibiting rapid reductions in motility and viability. The addition of exogenous catalase abrogated H2O2-induced killing. In contrast, B. malayi microfilariae were relatively resistant to H2O2, with concentrations as high as 50 microM having no effect on motility or viability. On exposure to NO, both species showed reductions in motility within 5-30 min, but longer was required to see effects on the viability of microfilariae. Parasites incubated with IFN gamma-activated macrophages also exhibited marked reductions in motility and viability. In cultures with B. malayi and activated macrophages, inhibition of these effects was achieved by the addition of either L-NMMA, to abolish NO production, or neutralizing anti-TNF alpha antibodies. Attempts to inhibit parasite killing by the addition of catalase to macrophage cultures were ineffective. The results of this study show that B. malayi and O. lienalis microfilariae have different susceptibility to H2O2, but are equally affected by exposure to NO. Moreover both species are killed by IFN gamma-activated macrophages and in the case of B. malayi, killing is dependent on the generation of NO via TNF alpha.

Animals↗
PubMed1999

Long-term suppression of Mansonella streptocerca microfilariae after treatment with ivermectin.

The long-term effect of a single oral dose of 150 microg/kg of body weight of ivermectin on Mansonella streptocerca microfilariae was studied in western Uganda. Before treatment, the geometric mean microfilaria density (mf) in 93 infected persons was 2.4 mf/mg of skin (range, 0.1-42.6). One year after treatment, 43 persons (46%) were microfilaria-negative, and the geometric mean in the remaining persons dropped significantly, to 0.7 mf/mg (range, 0.1-6.9). Thus, ivermectin is highly effective against M. streptocerca, and a single dose leads to a sustained suppression of microfilariae in skin. In Africa, ivermectin is used for mass treatment to control Onchocerca volvulus and Wuchereria bancrofti. Because these filarial parasites are often coendemic with M. streptocerca, the treated population may receive the additional benefit of suppression of M. streptocerca microfilariae.

Adolescent↗
PubMed2002

Orientation of Onchocerca lienalis stiles (Filarioidea: Onchocercidae) microfilariae to black fly saliva.

Black flies (Simulium spp.) are intermediate hosts and vectors of parasitic nematodes belonging to the genus Onchocerca (Filarioidea Onchocercidae). Infection and subsequent transmission of infective third-stage larvae occur at the vertebrate host-skin interface. Experimental evidence presented here demonstrates that Onchocerca lienalis Stiles microfilariae orient to one or more components (microfilarial orientation factor [s]; MOF) in black fly saliva. MOFs may serve as a means for microfilariae to find and infect black flies during the act of blood-feeding. Directed movement through the host's skin to the bite site is necessary because Onchocerca spp. microfilariae do not circulate in the blood. The substance directing microfilarial orientation appears to be a salivary protein, but it is not the Simulium vittatum Zetterstedt erythema protein (SVEP) described from New World Simulium spp. These results support earlier field observations that associated increased numbers of cutaneous microfilariae with black fly feeding and indicate that a fundamental molecular mechanism linked to vector saliva may be key for the maintenance of the life cycle of Onchocerca spp. Salivary molecules that induce orientation of microfilariae to the bite site are potential targets for use in transmission-blocking vaccines to uncouple this primary vector infection step.

Animals↗
PubMed1976

Fundus lesions in the rabbit eye following inoculation of onchocerca volvulus microfilariae into the posterior segment. I. The clinical picture.

Live microfilariae of the Cameroon forest and Sudan-savanna strains of Onchocerca volvulus were inoculated into the vitreous or into the subretinal layers of the eyes of rabbits. The lesions produced are described, and are compared with those seen in control animals, which had received inocula of microfilariae-free saline supernate introduced with a similar degree of operative trauma. Control rabbits showed only minor pigment disturbance in the retina and choroid, near the healed operation scars. Infected animals showed evidence of an inflammatory process in the eye, lasting for up to 4 weeks. Fundus lesions developed following inoculation of microfilariae into the vitreous, but they were more frequent and more severe following subretinal inoculation. The lesions produced were: pallor, vascular narrowing, and flattening of the optic disc; subretinal inflammatory exudate, giving rise to a disturbance of pigment in the retinal pigment epithelium; scattered, small choroidoretinal scars, and larger circumscribed areas of choroidoretinitis, sometimes accompanied by optic atrophy. In many eyes inoculated with microfilariae the wincing reflex was lost, indicating some visual impairment. Many of the lesions were similar to those seen in human patients with onchocerciasis, but they developed much more rapidly. Microfilariae inoculated intravenously, or into the periocular tissues, were not observed to penetrate into the eye-ball.

Animals↗
PubMedDate not supplied

Comparison of an immunochromatographic card test with night blood smear examination for detection of Wuchereria bancrofti microfilaria carriers.

BACKGROUND: At present, two diagnostic tests--Og4C3 ELISA and an immunochromatographic card test (ICT)--are available to detect circulating filarial antigens of Wuchereria bancrofti in serum/whole blood samples collected during the day. We aimed to assess the sensitivity of the new format card test 'NOW ICT Filariasis' in detecting microfilaria carriers of W. bancrofti in comparison with conventional microscopic techniques and Og4C3 ELISA. METHODS: A total of 200 persons were selected from two villages following a quota sampling design (100 in each village). The required number of houses was selected using a systematic sampling procedure with a random start of the first household. Blood samples were taken from all the available persons in each selected house until the quota of 100 was reached. The new format ICT test, Og4C3 ELISA and night blood smear examination for microfilaria were carried out following standard procedures. RESULTS: The sensitivity of the new format ICT test was 100% among microfilaria carriers (detected by both early and late readings). The kappa statistic measure of agreement between the two readings of all the samples (n =200) tested was 0.811 (p<0.05). The new format test also reported 25% of microfilaria-negative individuals as being positive for circulating filarial antigens. However, the diagnostic lines were not stable beyond 10 minutes (particularly in the case of amicrofilaraemic persons). Though there was an overall agreement between the results of ICT and Og4C3 tests (kappa =0.612; p< 0.05), the sensitivity of the Og4C3 test was lower than that of ICT. CONCLUSION: The new format ICT test is highly sensitive in detecting microfilaria carriers in endemic communities. Improvement in the format to provide stable diagnostic lines, specificity of the format and cost of the test kit are to be considered before its large-scale use.

Adult↗
PubMedDate not supplied

[Transplacental passage of Wuchereria bancrofti microfilariae in newborns of microfilaremic mothers].

The occurrence of circulating Wuchereria bancrofti microfilariae was investigated in 304 pregnant women from the "Unidade Mista Pof. Barros Lima" and "Hospital das Clínicas/UFPE". The filtration technique was employed to detect microfilaraemia during pregnancy, and 13 women were found to be positive (4.2%). The investigation of microfilariae in the cord blood of their children was negative (6/13), and also in venous blood samples collected up to 72 hours after birth and with 6 months of life. Milk samples from these mothers also had no microfilariae. The authors suggest that the occurrence of placentary lesions may be a possible factor involved in the transplacental transfer of microfilariae, and that in utero exposure to microfilariae and/or filarial antigens may influence the response to a filarial infection acquired later, thus being important a clinical and laboratorial follow-up of children exposed previously to filarial antigens during early periods of human development.

Adolescent↗
PubMed1978

Ultrastructural characterization of the cuticle of Onchocerca volvulus microfilaria.

Previous ultrastructural studies on various microfilariae have suggested the presence of a trilaminar membrane at the parasite cuticle. In the present report, the formation of the cuticle of Onchocerca volvulus microfilariae was studied at different developmental stages by transmission electron microscopy of samples obtained from subcutaneous nodules of untreated patients. The cuticle is formed by the layering of surface coat fibrillar components of the hypodermal cells. No plasma membrane is found at the cuticle of the microfilaria. The use of freeze-fracture replication confirmed the absence of a classic plasma membrane at the parasite cuticle. Our results suggest that immunogenic determinants of the microfilaria cellular elements are hidden from the exterior by the acellular cuticle. This may explain the lack of cellular reaction usually found around living O. volvulus microfilariae in the dermis of onchocerciasis patients.

Animals↗
PubMed1981

Electron microscopic studies on microfilariae of Dipetalonema viteae and Litomosoides carinii: the occurrence of intracellular parasites after treatment with metrifonate or diethylcarbamazine.

Microfilariae of Dipetalonema viteae and Litomosoides carinii were studied by means of electron microscopy after oral treatment of their hosts with metrifonate (3 x 100 mg/kg) or diethylcarbamazine (3 x 250 mg/kg). These dosages led to the disappearance of microfilariae from the peripheral venous blood. However, in numerous organs blood capillaries or interstitial spaces contained degenerating microfilariae. In these cases the cytoplasm of the microfilarian cells was completely lysed, whereas the cuticle seemed to be unaffected, at least initially. Microfilariae of both species were also often found intracellularly especially in liver and muscle cells after application of both drugs. The intracellular microfilariae, however, had fewer or even no lesions, suggesting that they might escape the activity of the drug.

Animals↗
PubMed1981

The effect of drug treatment on the pattern of emergence of Onchocerca volvulus microfilariae from skin snips.

A controlled study was carried out to determine the effect of some known anti-filarial drugs on the pattern of emergence of Onchocerca volvulus microfilariae from skin snips into saline. The results show that before treatment, 81.7 to 92.1% of microfilariae emerge in all the groups within 24 hours. The differences between the groups were not significant. After treatment with oral diethylcarbamazine, metrifonate and topical diethylcarbamazine (DEC) the percentage of microfilariae emerging from the snips dropped significantly to 48.4, 56.0 and 60.1 respectively, whereas no significant change occurred following treatment with levamisole (88.1%) and yeast tablets (89.1%). A pair-wise comparison of the post-treatment microfilarial emergence in all the groups showed statistically significant differences when (i) oral DEC is compared to levamisole, topical DEC and yeast, (ii) metrifonate is compared to levamisole and yeast and (iii) topical DEC is compared to yeast. It is suggested that microfilariae which fail to emerge from snips after treatment are those that have been killed or paralysed by the action of the drugs. The study has thus established that drug action in vivo is one of the factors which affects the proportion of microfilariae which emerge from skin snips and provides an additional parameter for measuring the antimicrofilarial potential of drugs in clinical chemotherapeutic trials.

Animals↗
PubMed1978

Histochemical enzyme-staining patterns of onchocerca volvulus microfilariae and their occurrence in different onchocerciasis areas.

Histochemical differentiation of Onchocerca volvulus microfilariae from 164 patients in West African rain-forest (Liberia), Sudan-savanna (Upper Volta), Guatemala and the Yemen has been carried out using a staining method for the demonstration of acid phosphatase. Intrauterine microfilariae showed considerable changes in their enzyme activity during embryonic development which are probably associated with the maturation of the parasite before migration to the tissues. Five distinct types of staining patterns could be distinguished among microfilariae from the skin according to the localization of the enzyme in specific structures of the microfilaria. Two or more types of staining patterns were found in most persons in the different geographic regions. There were significant differences in the overall distribution of the various staining patterns in persons from the different areas. At the present state of our knowledge, little is known about the nature and significance of these differences in the staining patterns of microfilariae. The question of whether they can be ascribed to an ageing process, strain differences or other factors is discussed.

Acid Phosphatase↗