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At least 343 records · Page 19Linked to original sources
PubMed2000

Longitudinal studies of skin microfilaria and antibody conversion rates in children living in an endemic focus of onchocerciasis in Nigeria.

We monitored skin microfilarial conversion and antibody (serum) conversion rates to Onchocerca volvulus recombinant antigens (OC3.6 and OC9.3) over a 2-year period, in a cohort of 208 children aged 9-11 years and living in a mesoendemic focus of savannah-type onchocerciasis in Nigeria in order to detect prepatent onchocerciasis in children. Between time point A and time point B (9 months apart) the seroconversion rate was 19.4 per cent, and between time points B and C (15 months apart), a further 31.4 per cent of seronegative children had seroconverted. However, only a third of the seroconverted children became microfilaria-positive. From the time-lag between antibody conversion and skin snip conversion, we estimated that a 9-12 month interval was required for the detection of O. volvulus microfilariae following infection with viable third stage larva (L3s). The predictive value of antibody detection as a measure of skin microfilarial conversion was >90 per cent when the optical density (OD) at 490 nm was >0.80. We therefore propose a strategy for monitoring changes in transmission of onchocerciasis following vector control or chemotherapy through an evaluation of annual antibody seroconversion rates in a standardized sentinel population of children.

Animals↗
PubMed1984

Immunoglobulin interactions with surfaces of sheathed and unsheathed microfilariae.

The sheath surface of Brugia pahangi microfilariae (mf) and the cuticle surface of Dirofilaria immitis mf were compared with regard to the ultrastructural arrangement of neutral and charged polysaccharides and binding of immunoglobulins from dog sera. Brugia pahangi: mf demonstrated large amounts of neutral sugar and negatively charged sugars just above the sheath surface, projecting some distance from the surface, in addition to a dense layer of sulphated material on the sheath surface. Microfilariae from high microfilaremic dogs showed no innately bound IgG or IgM when examined fresh from serum nor did they bind IgG or IgM from normal (NDS) or infected (IDS) dog sera after 48 h maintenance in RPMI 1640. Many of these mf did bind IgG and IgM from hyperimmune dog serum (ImDS) and these immunoglobulins were found binding at a distance from the sheath similar to that of the sugars. Dirofilaria immitis mf demonstrated much less neutral sugar at the cuticle surface, no negatively charged sugars and a diffuse, rather than dense, distribution of sulfated material extending from the cuticle. The majority of these mf showed innately bound IgG and IgM. After 48 h maintenance in RPMI 1640 D. immitis mf bound and shed IgG and IgM from NDS, high microfilaremia D. immitis IDS and D. immitis mf ImDS at distinctly different rates.

Animals↗
PubMed1994

Bancroftian filariasis-differential reactivity of anti-sheath antibodies in microfilariae carriers.

Anti-sheath antibodies have been detected using an immunofluorescent assay (IFAT) in the sera of microfilariae carriers (AS cases) residing in areas endemic for Bancroftian filariasis. Microfilariae (mf) of Wuchereria bancrofti purified from five different mf carriers were used separately as antigen to identify anti-sheath antibodies. The reactivity of sera from AS cases to mf sheath was found to be variable to the five different mf preparations. While as high as 25% of the sera reacted with mf purified from one individual, none of them reacted with mf purified from two other individuals. Such a differential reactivity to the sheath was found to be a feature of antibodies in AS cases only. Sera of seven amicrofilaraemic patients with elephantiasis reacted uniformly with all five mf preparations. The possible existence of polymorphic antigen(s) on the sheath of W. bancrofti mf has been proposed.

Animals↗
PubMed1995

Accelerated clearance of Onchocerca microfilariae and resistance to reinfection in interleukin-4 gene knockout mice.

Immunity to Onchocerca microfilariae (mf) in mice is associated with CD4+ Th2 cells and is dependent on IL-5. In view of the role of IL-4 in the development of Th2 cells, we have utilized IL-4 gene knockout mice (IL-4-/-) to investigate microfilarial clearance and resistance to reinfection. Paradoxically, in the absence of IL-4 there is accelerated clearance of microfilariae during a primary infection and unimpeded expression of resistance to reinfection. IL-4-/- mice showed a lack of an IgE response although peripheral eosinophilia was equivalent to wildtype controls. The data presented here suggest that elimination of mf can occur independent of IL-4 and that in this model it may even be detrimental to the host.

Animals↗
PubMed1996

Studies on the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae in paired samples of capillary and venous blood from Recife, Brazil.

We examined the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae (mf) and determined the effect of these parasite properties on the accuracy of blood filming and filtration methods for diagnosis of bancroftian filariasis in the endemic area of Recife, Brazil. Microfilariae in both venous and capillary blood exhibited a nocturnal periodicity pattern with a relatively high amplitude. Overall, capillary blood contained approximately 1.25 times the number of mf present at the same time in the same volume of venous blood. However, the ratio of mf present in capillary and venous blood varied over a 24-hour period, so that the fewest mf were present in the capillary bed of the skin at the time when biting activity of the local Culex vector is the lowest. Twenty or 60 microliters blood films did not reliably detect carriers with fewer than 100 or 60 mf/ml venous blood, respectively, and were thus inadequate for the identification of low density mf carriers. In contrast, all carriers with > 1 mf/20 or 60 microliters blood smear at night could be identified during daytime hours by filtration of 1 micromilligram venous blood.

Animals↗
PubMed2003

Dermatitis associated with Dirofilaria repens microfilariae in three dogs in Saudi Arabia.

The presence of microfilariae of the zoonotic nematode Dirofilaria repens is reported in three dogs from Saudi Arabia, manifesting as pruritic dermatitis with signs including erythema, alopecia, papules, crusting and hyperkeratosis. All dogs were found to have concurrent babesiosis. Specific treatments against the two conditions led to complete clinical recovery and disappearance of microfilariae from the blood one month later.

Animals↗
PubMed1994

Microfilariae in the mammary gland of a bitch.

A microfilarial infection of the mammary gland of a bitch with Dirofilaria immitis was diagnosed by fine needle aspiration biopsy. The animal had had a progressively enlarging, painful, pendulous, cystic swelling, measuring 12 x 18 cm, in the second left abdominal mammary gland for four to five months. Two separate biopsies revealed microfilariae and mammary duct epithelial cells, but no inflammatory cells. A histological examination revealed atrophic and necrotic mammary lobules with dilated and cystic ducts. Solid carcinoma was also observed in a small area of the mammary mass. The interlobular connective tissue was oedematous and the lymphatic and vascular channels were dilated. Microfilariae were observed within both the small blood vessels and capillaries and in the interlobular stroma of the mammary tissue, but there was no evidence of an inflammatory response.

Animals↗
PubMed1994

Efficacy of ivermectin against Setaria microfilariae in calves and cerebrospinal setariosis in sheep and goats.

Ten calves harboring microfilariae (Mf) were injected with ivermectin at a single dose of 200 micrograms/kg body weight. Thereafter, the number of calves harboring Mf was gradually reduced to 7, 2 and 0 by 1, 4 and 12 weeks, respectively and remained negative for microfilariae by 16 weeks after injection. Furthermore, none of 221 goats and sheep injected twice with ivermectin at a dose of 200 micrograms/kg body weight developed setariosis while 17 out of 303 non-injected animals suffered from that disease. Therefore, ivermectin was much effective for the eradication of Mf in calves and the prevention of setariosis in sheep and goats.

Animals↗
PubMedDate not supplied

Bloodmeal microfilariae density and the uptake and establishment of Wuchereria bancrofti infections in Culex quinquefasciatus and Aedes aegypti.

The relationship between ingestion of microfilariae (mf), production of infective larvae (L3) and mf density in human blood has been suggested as an important determinant in the transmission dynamics of lymphatic filariasis. Here we assess the role of these factors in determining the competence of a natural vector Culex quinquefasciatus and a non vector Aedes aegypti to transmit Wuchereria bancrofti. Mosquitoes were infected via a membrane feeding procedure. Both mosquito species ingested more than the expected number of microfilariae (concentrating factor was 1.28 and 1.81 for Cx. quinquefasciatus and Ae. aegypti, respectively) but Cx. quinquefasciatus ingested around twice as many mf as Ae. aegypti because its larger blood meal size. Ae. aegypti showed a faster mf migration capacity compared to Cx. quinquefasciatus but did not allow parasite maturation under our experimental conditions. Similar proportions of melanized parasites were observed in Ae. aegypti (2. 4%) and Cx. quinquefasciatus (2.1%). However, no relationship between rate of infection and melanization was observed. We conclude that in these conditions physiological factors governing parasite development in the thorax may be more important in limiting vectorial competence than the density of mf ingested.

Aedes↗
PubMed1993

Ophthalmological study of the lesions induced by the filarial worm with dermal microfilariae, Monanema martini, in its murid hosts.

The filaria Monanema martini with skin-dwelling microfilariae induces in its natural murid hosts lesions similar to those in human onchocerciasis. This was demonstrated by histo-pathological studies but it appeared useful to evaluate the model by a clinical investigation. An ophthalmological analysis was performed on the two species of hosts, inoculated by one, two, or multiple doses of larvae, and with infections of at least one year duration. A total of 140 eyes was examined (anterior and posterior segments). We established a system for enumerating the different types and severities of lesions. We prepared a file for each eye and attempted to quantify our observations. The significant lesions were different in the two host species. In Arvicanthis niloticus, in which motile microfilariae were seen in the anterior segment, punctate keratitis was predominant. In Lemniscomys striatus, the posterior segment showed complete chorioretinal atrophy, similar to the final stage of onchocercal chorioretinitis in humans. M. martini represents in its natural hosts two complementary models for the study of the pathogenesis and treatment of human onchocerciasis.

Animals↗
PubMed1980

Uptake of amino acids and glucose by microfilariae of Dirofilaria immitis in vitro.

The uptake of amino acids and glucose by microfilariae of Dirofilaria immitis maintained for 8 days in vitro was studied. The quantity of glutamic acid, histidine, lysine, alanine, tryptophan, and cystine in the medium did not change. Isoleucine, serine, valine, phenylalanine, tyrosine, methionine, and cystathionine decreased slightly; both asparatic acid and leucine decreased considerably. Glutamine, threonine, and proline decreased markedly, while glycine increased to some extent. Ornithine increased and arginine decreased; however, their changes were smaller than the changes of respective amino acids in the control medium free of microfilariae. Glucose decreased markedly.

Amino Acids↗
PubMed1980

Microfilaria bolivarensis: a new species of filaria from man in Venezuela.

An unsheathed microfilaria, unlike any other already described from man, was found in thick blood smears and Knott samples taken from Amerinds living along the upper Caura River in Bolivar State, Venezuela. The mirofilaria, which measures 256 x 7-8 micrometers in thick blood smears and 300 x 8 micrometers in Knott samples, is easily differentiated morphologically from Mansonella ozzardi with which it often occurs concomitantly. It is readily differentiated, on morphological criteria, from all other species of filariae which infect man, as well. The parasite has been named Microfilaria bolivarensis after the geographical locality in which it was discovered.

Filariasis↗
PubMed1982

Complement-mediated adherence of cells to microfilariae of Brugia malayi.

Immune sera promote the adherence of human buffy coat cells to microfilariae of Brugia malayi. This effect is augmented by the simultaneous addition of fresh human or guinea pig serum. The heat-labile, adherence-promoting factor present in nonimmune sera appears to be complement. In the absence of antibody, microfilariae activate complement via the alternative pathway and C3 is deposited on the microfilarial sheath.

Animals↗
PubMed1987

The paralyzing effect of midazolam on Onchocerca volvulus microfilariae in vitro.

Midazolam, a water soluble benzodiazepine derivative, inhibited the motility of Onchocerca volvulus microfilariae in vitro at concentrations of 25, 50, and 100 micrograms/ml. The effect was proportional to the concentrations used. Microfilariae regained motility after elimination of midazolam by washing. Diethylcarbamazine did not alter the midazolam effect. It is suggested that the Mazzotti reaction as the sequelae of diethylcarbamazine is caused by transient increased microfilarial migration. Combining midazolam with the diethylcarbamazine medication may prevent the Mazzotti reaction.

Animals↗
PubMed1989

Reliability of detection of microfilariae in skin snips in the diagnosis of onchocerciasis.

To quantify the sensitivity of skin snips for the diagnosis of onchocerciasis, data collected over a 2 year period from 261 Liberians, 12-60 years of age, were examined. The overall sensitivity of 6 snips per person was estimated to be 91.6%. When the microfilariae density was greater than or equal to 3.5 microfilariae/mg skin, there were no false negatives. At lower microfilaria densities, the sensitivity declined markedly. Furthermore, it was found that smaller and lighter snips were more likely to be classified as being falsely negative. The load of infection at the community level may be reduced after intervention strategies, such as vector control or community-based chemotherapy. Interpretation of the impact of these programs on the prevalence of infection should take into account the lower sensitivity of the skin snips at lower levels of infection.

Adult↗
PubMed1993

Trypanosomes and microfilariae in feral owl and squirrel monkeys maintained in research colonies.

A group of 358 owl and squirrel monkeys imported from Colombia, Peru, and Bolivia for the U.S. Agency for International Development Malaria Vaccine Development Program was examined for trypanosomes and microfilariae. Trypanosoma rangeli, isolated by hemoculture from Aotus nancymai, Saimiri b. boliviensis, and S. b. peruviensis, accounted for 76.6% of all trypanosome infections. Trypanosoma cruzi was isolated from 25 of 194 S. b. boliviensis, including two mixed infections with T. rangeli. Identifications of trypanosomes were confirmed by blinded tests with a panel of five rRNA probes on a subsample of cultures identified morphologically. Although no trypanosomes were isolated from Aotus vociferans or A. lemurinus griseimembra, positive serologic responses to T. cruzi were observed by indirect immunofluorescence assay in all species of monkeys examined and ranged from 42.1% among S. b. peruviensis to 92.3% among A. vociferans. Among T. rangeli-infected monkeys, 43.7% were seronegative for T. cruzi. No microfilariae were found in S. b. boliviensis or A. l. griseimembra. Mansonella barbascalensis and Dipetalonema caudispina were observed in A. vociferans, M. panamensis in A. nancymai, and M. saimiri and D. caudispina in S. b. peruviensis. Such naturally occurring infections in imported animal models are potential sources of accidental transmission to animal handlers and uninfected laboratory animals and can introduce confounding variables into otherwise well-planned and well-executed studies.

Animals↗