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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Onchocerciasis--infection by Onchocerca volvulus--has four cardinal manifestations: dermatitis, subcutaneous nodules, sclerosing lymphadenitis, and eye disease. The first three are discussed here. The dermatitis begins when microfilariae degenerate in the dermis. This process is accompanied by inflammation, with degranulation of eosinophils and deposition of the major basic protein of the eosinophil granules on the cuticle of the microfilariae. So far as is known, the chronic effects of onchocerciasis are all a consequence of the degeneration of microfilariae. Subcutaneous nodules contain coiled adult worms and have an outer layer of fibrous scar and a central inflammatory cell exudate, which may cavitate. Perfusion of India ink reveals arborization of capillaries around adult worms, which derive nutrition from these networks. Onchocercal lymphadenitis is characterized initially by histiocytic hyperplasia and follicular atrophy and later by fibrosis and obstruction of lymph flow, a condition causing adenolymphocele ("hanging groin") and elephantiasis of the genitalia. Some patients appear to have immune tolerance to degenerating microfilariae, perhaps as a result of exposure in utero to microfilarial antigens in the maternal circulation. In contrast, other patients (Yemenites, for example) have a localized but intense response to a few microfilariae; these patients are hypersensitive--perhaps because they were not exposed to microfilarial antigens in utero. Autopsy data on infection of deep organs are limited.
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PMID:Pathologic changes of human onchocerciasis: implications for future research. 407 Sep 19

Onchocerciasis is one of the major filarial diseases affecting humans and a leading cause of blindness. Control of the disease by chemotherapy and by elimination of the vector is not feasible in most areas of endemicity. The host immune response is thought to play a major role in the pathogenesis of complications. However, there is no clear evidence of protective immunity to reinfection in individuals who continue to be exposed to infective larvae. Antigens of Onchocerca volvulus are complex and show extensive cross-reactivity with other filarial parasites of humans and animals. Infection in humans results in the production of precipitating and reaginic antibodies to the parasite and in increases in levels of immunoglobulins that have no apparent specificity for parasitic antigens. Chronic antigenic stimulation in the presence of an antibody response leads to increased levels of circulating immune complexes. Cell-mediated immunity to parasite-derived antigens, as measured by migration inhibition, lymphocyte blastogenesis, and delayed skin-test reactivity, is decreased during infection. In addition, there is a decrease in delayed skin-test reactivity and in lymphocyte blastogenesis in response to unrelated antigens.
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PMID:Humoral and cellular immune responses to Onchocerca volvulus infection in humans. 407 Sep 16

Simulium damnosum is known to be a sibling species complex with at least 24 cytotaxonomically distinct forms in Africa. Of these, six occur in the area of West Africa covered by the World Health Organization Onchocerciasis Control Programme. They are all vectors of Onchocerca volvulus, and several are capable of migrating great distances. We report here a comparatively simple chemical method of species identification using individual adult females of pooled samples that have been collected and stored dry in glass vials. Females of two species, S. sirbanum and S. squamosum, were identified by extraction and analysis of cuticular components using gas chromatography. Statistically significant differences were seen between these two species for each of five sets of consistently appearing peaks that were quantitated and compared. The technique has considerable potential for use in the field since extracts or specimens may be stored indefinitely at ambient temperature before analysis.
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PMID:Identification of two West African black flies (Diptera: Simuliidae) of the Simulium damnosum species complex by analysis of cuticular paraffins. 611 31

Initial clinical studies in 32 Senegalese subjects have demonstrated the efficacy of ivermectin in Onchocerca volvulus infection (river blindness). Although O. volvulus microfilariae in skin snips were not reduced in number after single oral doses of 5 micrograms or 10 micrograms/kg body-weight, they were greatly reduced in all subjects after single oral doses of 30 micrograms or 50 micrograms/kg and were eliminated completely in 6 of th 8 subjects who received the 50 micrograms/kg dose. All subjects tolerated the drug well. Transient pruritus which did not require treatment was observed on the day the dose was given in 2 of the 8 subjects after the 30 micrograms/kg dose and in 4 of the 8 who received the 50 micrograms/kg dose. Ivermectin produced no abnormal laboratory results.
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PMID:Efficacy and tolerance of ivermectin in human onchocerciasis. 612 84

The azo-dye method for the histochemical demonstration of acid phosphatase activity was used to differentiate filarial larvae within and outside th area of the Onchocerciasis Control Programme (OCP) in natural infections of female S. damnosum s.l. caught in West Africa. The histochemical patterns of 1263 larvae (all stages) dissected from 556 positive files caught at 35 catching sites during the period of reinvasion in 1978 and 1979 were determined and compared with those of O. volvulus known from experimental infections. In Mali, Ivory Coast and Upper Volta, about 16% of 3rd-stage larvae in 17.3% of invading female S. damnosum s.l. (savanna cytospecies) could be separated from those of O. volvulus-like larvae, on account of their different enzyme staining patterns. The percentage of larvae enzymatically distinguishable from O. volvulus and the flies carrying them showed a distinct geographical distribution; the highest percentages (36.4/38.4) were found in the north-west (Mali) and the lowest percentages (4.4/8.2%) were found in the interior (east-central) of the Programme area (Upper Volta). By contrast, all larvae found in S. damnosum s.l. females caught in Ghana and in Togo were morphologically as well as enzymatically similar to those of O. volvulus. Third-stage larvae of the enzymatically distinguishable "species" were found to be somewhat longer than those of O. volvulus-like larvae. Morphologically, the larvae concerned probably belong to the genus Onchocerca, but their specific identity and vertebrate host remain unknown.
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PMID:Histochemical differentiation of filarial larvae found in Simulium damnosum s.l. in West Africa. 617 76

Simulium quadrivittatum Loew (Diptera: Simuliidae), a man-biting black fly, was shown, for the first time, to be capable of supporting development of Onchocerca volvulus Leuckart (Nematoda: Filarioidea) from microfilariae to third-stage (infective) larvae. The black flies were collected in Chiriqui Province, Panama and transported alive to Guatemala, where they were allowed to feed on a human subject infected with O. volvulus. Samples of these flies were dissected over an 11-day period to assess morphogenesis of the parasite. Vigorously motile microfilariae were recovered from the mid-gut during the first 24 hours postfeeding; second-stage larvae were found in the thoracic musculature on day 4; and fully developed third-stage larvae were obtained from the cephalic capsule by day 10. This rate of larval development is similar to that observed in Guatemalan S. ochraceum. Onchocerciasis is not known to occur in Panama. The results of the present study direct attention to a potential public health hazard there and possibly elsewhere in Central America.
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PMID:Morphogenesis of larval Onchocerca volvulus in the Panamanian black fly, Simulium quadrivittatum. 673 72

Diethylcarbamazine (DEC) therapy for Onchocerca volvulus infection results in frequent ocular and systemic complications, but the pathogenesis of these complications is unclear. Twenty men with O. volvulus infection were treated over a period of six months with DEC given daily for one week and weekly thereafter. Major systemic and ocular complications included proteinuria, severe pruritus, visual field constriction, optic nerve pallor, chorioretinitis, anterior uveitis, and punctate keratitis. Levels of circulating immune complexes (CICs) were increased (greater than 11% [125I]C1q binding) in 14 of the 20 men prior to treatment. Persons with pretreatment C1q binding activity of greater than 30% were at increased risk to develop constriction of visual fields (P less than 0.05) and proteinuria (P less than 0.015). Linear regression analysis revealed a striking correlation between pretreatment levels of CICs and the total number of both systemic and ocular complications (P less than 0.001) and ocular complications alone (P less than 0.005). These results suggest that CICs may be important in the pathogenesis of the delayed systemic and ocular complications following DEC therapy for O. volvulus infection.
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PMID:Ocular and systemic complications of diethylcarbamazine therapy for onchocerciasis: association with circulating immune complexes. 684 23

The microtest ELISA has been used for human Onchocerciasis serological study. The antigens employed were adult Onchocerca volvulus extracts, collected from dissected nodules, delipidized and cleared from human proteins by affinity Chromatography. Under the circumstances, the positivity limit of the test seems excellent (maximum )D: 0,23) defined with 171 negative sera, 66 of them taken from Africans. Specificity controls were studied with 56 heterologous sera; cross-reactions occurred with hydatidosis and especially wit various nematode infections, in particular loasis. With reagents and technical conditions used, the specificity limit of the test corresponds to an OD of 0,4 (measured with a 3 mm optical course). The diagnosis value of the test was verified by studying sera from 90 individuals wit a positive skin biopsy and with sera from 233 adults living in endemic areas. For all the infected people, the global percentage of positivity with ELISA is not greater than that with indirect immunofluorescent antibody test (85%). On the other hand, the micro-test ELISA seems slightly more sensitive in detection of high serological positivities. We did not find any statistically relationship presence and quantity of microfilarial worms in skin biopsy and positivity with the microtest ELISA. Likewise, in some polyinfested patients (with Onchocerca volvulus and Dipetalonema perstans or Wuchereria bancrofti), we did not observe any correlation between the results given the microtest ELISA and the quantity of microfilariae in the blood stream.
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PMID:[Serodiagnosis of onchocerciasis using micro-ELISA. Study of 450 sera and comparison with indirect immunofluorescence]. 700 42

The data collected by the Onchocerciasis Research and Control Project in Guatemala were theoretically analyzed. First, Muench's simple catalytic model was applied to the age distribution of the microfilaria-positive rate in each village to obtain the force of infection. The intensity of infection, expressed by force of infection, with Onchocerca volvulus in humans of individual villages was found to be clearly associated with the distribution and abundance of the vector, Simulium ochraceum. By comparing the values of the force of infection between males and females in a village, it can be decided whether humans were infected mainly outside the village or inside. The greater force of infection found in males was considered to be attributable to the more frequent visit of males than females to the mountainous areas where the density of S. ochraceum is higher. On the other hand, the force of infection of males was nearly equal to that of females when the S. ochraceum density was high inside the villages, suggesting the occurrence of within-village infection. Through further theoretical considerations, a mathematical model for the relation between the biting density of vectors and the microfilaria-positive rate of humans in a village was proposed, and the critical density of vectors for maintaining the endemic of onchocerciasis was estimated.
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PMID:Theoretical approach to the epidemiology of onchocerciasis in Guatemala. 715 8

Lactate dehydrogenase and malate dehydrogenases were partially purified and characterized from adult O. volvulus. The molecular weight of lactate dehydrogenase was determined to be 130 000, those of malate dehydrogenase I and II to be 120 000 and 65 000, respectively. The activities of both malate dehydrogenases and of the lactate dehydrogenase were strongly inhibited by suramin. The inhibition constants were determined to be in the range of 2 microM to 5 microM. The type of inhibition was found to be competitive with respect to the coenzyme NADH and to be non-competitive to the substrates. It is suggested that the mode of action of suramin in the therapy of Onchocerciasis might depend on the blokkade of reoxidation of NADH produced within the glycolytic pathway.
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PMID:Onchocerca volvulus: effect of suramin on lactate dehydrogenase and malate dehydrogenase. 737 52


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