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

A Sudan-savanna and a rain forest onchocerciasis have been described in West Africa. These two patterns of onchocerciasis have in common many epidemiological features but in hyperendemic areas there is a very essential difference between the two. In savanna the prevalence of serious ocular lesions and blindness due to onchocerciasis are much higher than in forest. Therefore attempting to explain these differences five groups of factors (or working hypothesis) are reviewed: --factors related to the vectors; --onchocerca-simulium couples; --different Onchocerca volvulus strains; --factors related to the human-host; --other varied factors: nutritional factors, concomitant ocular infections, luminousness of savanna, periods of transmission... A critical examination of these hypothesis brings to the conclusion that according to our present knowledge the main difference between savanna and rain-forest onchocerciasis may be due to degrees in pathogenicity of different strains of O. volvulus but these hypothesis have not been proved formally. More the part of concomitant factors (co-factors), themselves related to bioclimactic zones must not be ruled out.
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PMID:[Sudan-savanna and rain-forest onchocerciasis in West Africa: an epidemiological problem (author's transl)]. 55 94

Between April 1977 and June 1978, 214 babies born of 210 mothers infected with Onchocerciasis, were examined at the maternity of Po Hospital (Upper Volta). In four of them (1.9%) dermal microfilariae of Onchocerca volvulus were found during the first week after birth. In two other cases microfilariae were seen in the tissue of the umbilical cord. All specimens from placentas and amniotic fluid gave negative results. The infected babies were reexamined monthly monthly from 2 to 18 months, depending on the cases. One child remained positive until the 6th month follow-up. The base-line examination of 5.757 children less than 2 years old from different villages in the WHO Onchocerciasis Control Programme in the Volta River Basin Area showed that 1% of children less than one year old and 2% of children of 12 to 23 months old were carriers of dermal microfilariae. These results indicate that in meso- or hyperendemic areas children less than one year old and carriers of microfilariae of Onchocerca volbulus may have been infected in utero. The existence of such cases, in an area of vector control, does not prove a residual vector borne transmission.
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PMID:[The epidemiological significance of neo-natal parasitism with microfilariae of Onchocerca volvulus (author's transl)]. 57 49

The aerial larvicidng operation of the Onchocerciasis Control Programme of the World Health Organization which began in February 1975 resulted in a sharp reduction in Simulium damnosum numbers. However, at the onset of the rainy season the fly population increased in certain areas. Detailed surveys both on the ground and by helicopter did not reveal any significant failures of treatments that could account for the fly densities observed, and it was concluded that the flies must originate from sources outside the controlled zone. This reinvasion proved to be an annual occurrence which has been studied in detail between 1975 and 1978 in the south-western parts of the control zone. The methods used included full day catches by vector collectors carried out every day throughout the season, cytotaxonomic determination of larvae, detailed morphological examination of reared and biting adults and treatment of suspected source rivers with insecticide. The results indicate that the invasion takes place in a SW-NE direction across country for distances of 300 km or more along the track of the monsoon winds. It involves mainly the savanna cytospecies S. damnosum s. str. and S. sirbanum. The invading populations are composed of older parous flies, many of which carry infective 3rd stage larvae indistinguishable from those of Onchocerca volvulus. These females tend to bite close to the rivers and do not disperse as far as normal populations with a higher proportion of younger flies.
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PMID:Studies on the reinvasion of the Onchocerciasis Control Programme in the Volta River Basin by Simulium damnosum s.I. with emphasis on the south-western areas. 57 81

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.
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PMID:Ultrastructural characterization of the cuticle of Onchocerca volvulus microfilaria. 62 51

Adult Onchocerca volvulus worms were extracted sequentially with buffers of various ionic strengths. The extract was incubated with purified human onchocerciasis immunoglobulin-G (IgG) convalently coupled to Sepharose. Antigens were then eluted with 8 M urea and 7.5 M guanidine-HCl. IgG contained in the eluates was removed by incubating the eluates with rabbit anti-human IgG covalently coupled to Sepharose. As demonstrated by double immunodiffusion and "double" crossed immunoelectrophoresis at least three antigens were isolated. Most of the antigens were totally excluded from Sephadex G-200 but entered the included volume of Sepharose 6B. In electrofocusing they focused in acid regions. Antibodies were generated in rabbits against the three antigens isolated together. The antibodies were covalently coupled to Sepharose, which was subsequently used as a new affinity medium for the isolation of antigens. Such isolated antigens appeared to be identical with those with human onchocerciasis IgG. The isolated antigens and their corresponding artificial antibodies generated in rabbits were successfully applied in the enzyme linked immunoadsorbent assay. Host material and onchocerciasis IgG left behind during the purification procedure interfered in the assay system.
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PMID:Sequential affinity chromatography for the purification of antigens extracted from Onchocerca volvulus adult worms. 64 58

Systematic lymphographic studies in 13 cases of infection with Onchocerca volvulus have enabled a "lymphographic diagram" to be made for each infected patient. The images obtained are similar to those observed in wuchereriasis. The microfilariae in onchocerciasis, however, are not transmitted in the lymphatic system, and the lesions, which vary according to the degree of infestation, show little progression. They are found mainly in the inguino-crural ganglia which are the first main ganglionic relay system for the lower limbs.
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PMID:[Results of lymphography in 13 cases of onchocerciasis]. 65 Jun 32

Clinicopathological studies on lymph nodes of 32 Africans with onchocerciasis--some complicated by hanging groin and elephantiasis of the genitalia--revealed atrophic lymphoid tissue, lymphoedema, chronic inflammation and fibrosis. We identified microfilariae of Onchocerca volvulus in nodes of 24 of 32 Africans (75%). There microfilariae were most numerous in the capsule and in the fibrous tissue of the medulla, but smaller numbers were also found within lymphoid tissue, in dilated lymphatics and in blood vessels. We believe that in Africians, antigens released from microfilariae of O. volvulus lead to the deposition of immune complex in tissues, which in turn causes inflammation and fibrosis and eventually obstructive lymphadenitis. This causes hanging groin and, possibly, also elephantiasis. A distinctive pattern of perivascular fibrosis contains "fibrinoid material" that we interpret as immune complexes involving microfilarial antigens. In contrast, nodes from two Yemenites with severe onchocercal dermatitis of the lower limbs (sowda) had hyperplastic follicles, minimal fibrosis and no microfilariae.
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PMID:Onchocercal lymphadenitis: Clinicopathologic study of 34 patients. 65 85

Counts of microfilariae in the skin, and histological and electronmicroscopic procedures have been used to analyze the response of onchocerciasis patients to diethylcarbamazine citrate (DEC) given either orally or topically. Oral administration of DRC failed to eliminate all microfilariae. Transepidermal DEC resulted in rapid degeneration of microfilariae, and daily single applications of the drug greatly reduced or apparently eliminated microfilariae from the skin. Following weekly topical applications of a DEC emulsion, effective suppression of O. volvulus microfilariae in patients living in a hyperendemic area was maintained for many months; and the dermal pathology resolved.
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PMID:A transepidermal chemotherapy of onchocerciasis. 67 36

Six drugs in common use for the treatment of parasitic infections of man were given to 18 adult patients suffering from onchocerciasis. None of the six (metronidazole, tinidazole, mebendazole, trichlorophone, oxamniquine and pyrantel pamoate) showed any evidence of substantial activity against the microfilariae or adult worms of O. volvulus. The mean reduction in skin microfilarial counts a week after drug treatment (a measure of microfilaricidal action) was highest in patients treated with trichlorophone (47.0%) and mebendazole (40.0%). The rate of build-up of microfilariae over a follow-up period of 24 months after treatment with the drug under test followed by DEC (a measure of macrofilaricidal action) was slowest in the groups treated with metronidazole and trichlorophone (22.9% and 27.0% of the pre-treatment counts respectively). These results fall short of those expected of drugs with potential value in the treatment of onchocerciasis.
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PMID:Small-scale trials of six drugs against Onchocerca volvulus. 67 37

Increasing concentrations of levamisole and of mebendazole were applied to 1 eye in groups of 4 patients with ocular onchocerciasis in northern Cameroon. No effect resulted from up to 3.0% mebendazole suspensions, but 3.0% levamisole solutions rapidly caused entry of microfilariae, straightening out and subsequent opacification of previously curled-up living microfilariae, the rapid formation of typical limbal globular infiltrates, and the subsequent formation of fluffy opacities around the microfilariae. These changes are typical of all other drugs so far studied that have a microfilaricidal action on O. volvulus--diethlycarbamizine citrate (DEC), suramin, and metrifonate. The efficacy of 3.0% levamisole approximated to that of 0.03% DEC. This is in keeping with published observations on the filaricidal activity of these 2 compounds. It is suggested that this system of drug testing should be considered for systematic use in the search for more effective and safer drugs for onchocerciasis.
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PMID:Evaluation of microfilaricidal effects in the cornea from topically applied drugs in ocular onchocerciasis: Trials with levamisole and mebendazole. 67 95


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