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

The history and structure of the WHO Onchocerciasis Control Programme in the Volta River Basin are described. An outline of the vector control operations is given, and the techniques and organisation of the entomological evaluation network are described in detail. During the course of the evaluation and related studies undertaken between November 1974 and October 1978 almost 1.2 million S. damnosum females have been taken in over 52,000 man days of catching, and 674,000 flies were dissected. An assessment based on this effort using Annual Biting Rates and Annual Transmission Potentials shows that the transmission of O. volvulus has been reduced to below a defined maximum permissible level over most of the central part of the Programme Area. The difficulties encountered in the remainder, and at certain problem sites are outlined and relevant data given. The benefits to be expected from extending the area further southwards and the possibilities of later reductions in control activity are discussed.
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PMID:Entomological aspects of the first five years of the Onchocerciasis Control Programme in the Volta River Basin. 54 1

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

Onchocerciasis is a remarkably chronic infection and, in West Africa, there are distinct clinical and pathological differences between the disease in the savanna and in the forest. Experiments were carried out to see whether antigenic diversity among Ochocerca volvulus worms might contribute to these features. Extracts of adult worms and or microfilariae were analysed by disc electrophoresis on polyacrylamide gels and showed a remarkable diversity of protein patterns but no consistent savanna/forest or Nigeria/Cameroon differences. Indirect haemagglutination using cross-absorbed sera was used to look for antigenic diversity or identity between different O. volvulus worms. Sera of patients were absorbed with antigens extracted from worms taken from those paitents and then titrated against sheep erythrocytes coated with the same antigens. It was shown that an adult Onchocerca volvulus could be either antigenically identical with, or distinct from, another worm taken from the same patient. In one Nigerian village identity was shown in two instances nad diversity in five. Microfilariae lack some antigens possessed by adult worms. This test has shown consistent savanna/forest differences in worm antigen patterns and antibody responses. In order to explain the pattern of these differences it was necessary to postulate that forest patients possessed antibodies to another worm which had antigens in common with savanna Onchocerca. The relevance of these findings to the pathology and prevention of onchocerciasis is discussed.
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PMID:Antigenic diversity among Onchocerca volvulus in Nigeria, and immunological differences between onchocerciasis in the savanna and forest of Cameroon. 94 72

A PEG-ELISA was used to demonstrate parasite specific immune complexes in a significant proportion (25/26) of Onchocerca volvulus infection sera from Sierra Leone. The parasite antigen was detected using a peroxidase-conjugated rabbit serum raised to the bovine parasite O. gibsoni. Controls including European control serum, endemic control serum and Rh+ sera gave consistently low readings. Characterization of the parasite component in the immune complexes by Western blotting demonstrated a heat stable antigen of M(r) 46,000. This antigen was not present in the circulating immune complexes (CIC) prepared from patients with Wuchereria bancrofti infection, but a cross-reactive molecule of the same size was weakly recognized in the CIC of Loa loa and Mansonella perstans infected patients. No association between the level of parasite specific CIC and clinical disease was observed in the O. volvulus patients.
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PMID:Identification and characterization of a parasite antigen in the circulating immune complexes of Onchocerca volvulus infected patients. 128 95

An investigation of human infection with Onchocerca volvulus and the resulting clinical disease was carried out for the Nigerian National Onchocerciasis Control Programme between July and August 1989 [corrected]. The survey covered 10.6% of the rural population in 41 savanna villages of central Nigeria. Of the 8451 self-selected individuals examined, 900 (10.6%) had skin microfilariae (Mf). There were differences between villages in both endemicity and intensity of infection, but in general the number of both Mf carriers and cases of clinical onchocerciasis increased with age. The disease in the Mf carriers showed as blindness (0.8%), onchocercal nodules (0.6%), leopard skin (1.6%) and pruritus (2.8%). Of 35 persons with lymphatic complications, 19 had hanging groin, 10 had elephantiasis and six had hydrocoele. Onchocerciasis was mesoendemic in the rocky northern escarpments, and became hypoendemic and sporadic in the southern uplands of sedimentary geological origin.
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PMID:Human onchocerciasis in the lower Jos Plateau, central Nigeria: the prevalence, geographical distribution and epidemiology in Akwanga and Lafia local government areas. 130 6

A double-blind clinical trial was conducted in Monagas State, Venezuela to assess the tolerance and efficacy of albendazole in the therapy of Onchocerca volvulus infection. Forty-nine patients (26 treated and 23 controls) received a 10-day course of albendazole (400 mg/day) or a placebo. Consistent with the excellent tolerance observed, albendazole did not kill microfilariae. However, analysis of changes in microfilarial densities (mf/mg of skin) over one year showed that albendazole was active against O. volvulus, presumably by interfering with embryogenesis. The nature, degree, and duration of this effect remain to be determined.
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PMID:Albendazole in the treatment of onchocerciasis: double-blind clinical trial in Venezuela. 144 50

A remarkably high number of patients with epilepsy was observed in Kyarusozi subcounty, Uganda, where infection with Onchocerca volvulus is hyperendemic. A survey was conducted from April 22 to May 4, 1991, in Kyarusozi subcounty when all patients with epilepsy and growth retardation were invited for medical examination. A full history was taken and a physical examination as well as a mental state assessment were carried out for all patients. A total of 231 persons were screened, of whom, 91% were below the age of 19 years. The infection rate with Onchocerca volvulus in patients with epilepsy (61%) and retarded growth (70%) was significantly higher than in the general population of Kyarusozi subcounty. The prevalence of epilepsy in the study area was estimated to be at least 2%. The cardinal clinical features were pigeon chest, increased curvature of the dorsum, hyperextended joints, poor oral hygiene, and dental caries with disproportionately large, and displaced maloccluded teeth. Additional features were malnutrition, including dry atrophic scaly skin, skin sores, and golden hair. The thyroid gland was enlarged in 7.4% of the children with physical growth retardation. Secondary sexual characteristics were absent or poorly developed in a further 1.3%. The data seemed to indicate that social adaptation and psychological functioning are more often disturbed in individuals who suffer from the combined effects of epilepsy, onchocerciasis, and growth retardation than in patients with onchocerciasis, epilepsy, or growth retardation along. This investigation suggests that onchocerciasis is associated with epilepsy, psychological impairment, retarded growth, and retarded sexual development. Should further studies confirm a relationship between Onchocerca volvulus infection, epilepsy, and mental development, the public health importance of onchocerciasis would have the be reconsidered to control Onchocerca volvulus infection more vigorously.
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PMID:Epilepsy and retarded growth in a hyperendemic focus of onchocerciasis in rural western Uganda. 147 7

Onchocerciasis, or river blindness, results from infection with Onchocerca volvulus. The parasite is endemic to West Africa, in both rain forest and savanna bioclimes. Several lines of evidence suggest that different strains of the parasite exist in the rain forest and savanna. Furthermore, epidemiologic evidence indicates that ocular onchocerciasis is most severe in savanna regions. This has led to the hypothesis that there is a strain association with ocular pathology. To test this hypothesis, parasites from villages in which severe and mild onchocerciasis were endemic were classified with two strain-specific DNA probes. A strong correlation (P less than .001) was found between disease severity and probe recognition, supporting the hypothesis that pathogenicity is strain related. The results suggest that pFS-1 and pSS-1BT may be used to predict the pathogenic potential of parasite populations throughout much of West Africa.
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PMID:Onchocerca volvulus DNA probe classification correlates with epidemiologic patterns of blindness. 156 51

Nine of 18 chimpanzees inoculated with 250 infective third-stage larvae (L3) each developed patent (i.e., positive for microfilariae) Onchocerca volvulus infection. Four of 6 infected chimpanzees that received 200 micrograms/kg ivermectin at 28 days postinfection (pi) became patent, whereas, when ivermectin was given concurrently with L3 challenge only 1 of 6 infected animals developed patent infection. The antibody response to O. volvulus adult worm-derived antigens (OvAg) showed clear differences between patent and nonpatent chimpanzees. Three months pi, all sera detected several OvAg in the range of M(r) 35-120 k. Sera collected 6 mo pi from later patent animals recognized increasing numbers of OvAg, especially in the lower MW range of M(r) 13 to 33 k. Beginning 10 months pi Onchocerca-antigens of M(r) 21, 24, 26, and 28 k were detected only by patent chimpanzee's sera. The antibody response in nonpatent chimpanzees consistently recognized fewer OvAg, most of which were limited to the higher M(r) range (35-120 k). The reactivity of sera from infected chimpanzees to a low molecular weight fraction (LMW) of total OvAg doubled within 6 months pi, and increased continuously in patent animals from 13 until 30 months pi. Serological reactivity of nonpatent animals to LMW-OvAg remained low. The titers of circulating IgG directed against total OvAg increased in all infected chimpanzees, and continued to rise with patency. In nonpatent chimpanzees the antibody production gradually returned to preinfection values. Total and OvAg-specific IgE increased in patent and nonpatent chimpanzees. Also, during prepatency the granulocyte and antibody-mediated in vitro killing of microfilariae of O. volvulus increased in subsequently patent chimpanzees. The in vitro immobilization of L3 remained low.
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PMID:Experimental onchocerciasis in chimpanzees. Antibody response and antigen recognition after primary infection with Onchocerca volvulus. 159 90


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