Relevant bibliographies by topics / Onchocerca ochengi

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Academic literature on the topic 'Onchocerca ochengi'

Author: Grafiati
Published: 3 June 2025
Last updated: 22 June 2025

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Journal articles on the topic "Onchocerca ochengi"

1

WAHL, G., P. ENYONG, A. NGOSSO, et al. "Onchocerca ochengi: epidemiological evidence of cross-protection against Onchocerca volvulus in man." Parasitology 116, no. 4 (1998): 349–62. http://dx.doi.org/10.1017/s003118209700228x.

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In North Cameroon, the vector of Onchocerca volvulus (causative agent of human onchocerciasis) also transmits 2 filariae of animals: O. ochengi from cattle and O. ramachandrini from wart hogs. In order to assess the qualitative and quantitative roles of these ‘animal filariae’ in the epidemiology of O. volvulus, the transmission of the 3 parasites was measured in 2 villages and related to the endemicity of human onchocerciasis. In Galim, a cattle-farming Guinea savanna village where wild animals are rare, the overwhelming majority of all filarial infections found in the Simulium damnosum s.l. vectors throughout the year were O. ochengi (89%). The remaining infections were mainly O. volvulus (10·5%), and a few O. ramachandrini (0·5%). In Karna, a crop-farming Sudan savanna village where cattle are rare, but wild animals common, flies were also more frequently infected with animal filariae than with the human parasite. In the dry season, when nomadic cattle are present, 54% of all infections were O. ochengi, 36% O. volvulus and 10% O. ramachindrini. In the rainy season, when the cattle move away, flies were mainly infected with O. ramachandrini (52% of all infections) and secondly with O. volvulus (48%). In Karna, the relationship between the Annual Transmission Potential (ATP) of O. volvulus and its prevalence in the human population conformed to other onchocerciasis foci, in that a moderate ATP led to hyperendemic onchocerciasis. In Galim, however, a 7-fold higher O. volvulus-ATP (caused by a very high biting rate of the flies) contrasted with a strikingly low endemicity of onchocerciasis. Since, at the same time, in Galim the transmission of O. ochengi (measured on man) was very high (15000 L3/fly collector/year), we hypothesize that the reduced endemicity of onchocerciasis in Galim is due to ‘natural heterologous vaccination’ by the large annual number of O. ochengi-L3, inoculated into man by anthropo-boophilic S. damnosum s.l. The importance of micro-epidemiology for the understanding of the interlinkage of human and animal onchocerciasis is discussed.
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Makepeace, Benjamin L., and Vincent N. Tanya. "25 Years of the Onchocerca ochengi Model." Trends in Parasitology 32, no. 12 (2016): 966–78. http://dx.doi.org/10.1016/j.pt.2016.08.013.

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WAHL, G., and J. M. SCHIBEL. "Onchocerca ochengi: morphological identification of the L3 in wild Simulium damnosum s.l., verified by DNA probes." Parasitology 116, no. 4 (1998): 337–48. http://dx.doi.org/10.1017/s0031182097002321.

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In order to assess the prevalence of the cattle filaria Onchocerca ochengi in onchocerciasis vectors (Simulium damnosum s.l.) in North Cameroon, we searched for a means to morphologically identify its developing larvae, which closely resemble those of O. volvulus. To this end microfilariae of the 2 Onchocerca species were isolated from slaughter cattle in Ngaoundéré and injected into neonate Simulium species. Whereas the early developmental stages (sausage stage, L2 and pre-infective larva) were indistinguishable, the infective larvae (L3) of O. ochengi were longer (median: 740 μm), more slender (diameter = 19·3 μm = 2·6% of body length) and had a relatively shorter tail (4·9% of body length) than those of O. volvulus (680 μm, 20·5 μm, 3·0% and 5·8% respectively). The tail of O. ochengi L3 was thick and rounded, whereas it was slightly tapering in O. volvulus L3. O. ochengi L3 produced by feeding flies on infected cattle in a different area in North Cameroon (Sora Mboum) showed the same features as intrathoracically produced O. ochengi L3 from Ngaoundéré, but were even longer (785 μm). On the basis of the differences in length, relative diameter, length of the tail and shape of the tail, a simple key for the separation of O. volvulus and O. ochengi L3 was elaborated, and 248 L3 found in wild S. damnosum s.l. were separated into ‘O. ochengi’ (160 L3) and ‘O. volvulus’ (88 L3) following this key. Sequential dot blot hybridization of each of the 248 larvae with a DNA probe which reacts with O. ochengi and O. volvulus but not with other Onchocerca species (pOo5/1) and with an O. volvulus-specific DNA probe (pOv12) revealed that the morphological identification had been correct in 86–91% of the cases. Only a small proportion (6–9%) of the dot blots did not react with either probe. Since this proportion was equal in experiments using experimentally produced L3 and in experiments using wild L3, the non-hybridization was certainly due to a loss of L3 during washing of the filters and not due to the presence of other unknown L3 species resembling O. volvulus and O. ochengi. Our study shows that in Cameroon it is possible to identify O. volvulus and O. ochengi infective larvae during routine fly dissections by morphology alone.
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Morales-Hojas, R., R. A. Cheke, and R. J. Post. "Molecular systematics of five Onchocerca species (Nematoda: Filarioidea) including the human parasite, O. volvulus, suggest sympatric speciation." Journal of Helminthology 80, no. 3 (2006): 281–90. http://dx.doi.org/10.1079/joh2006331.

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AbstractThe genus Onchocerca (Nematoda: Filarioidea) consists of parasites of ungulate mammals with the exception of O. volvulus, which is a human parasite. The relationship between O. volvulus, O. ochengi and O. gibsoni remains unresolved. Based on morphology of the microfilariae and infective larvae, vector transmission and geographical distribution, O. ochengi and O. volvulus have been placed as sister species. Nevertheless, the cuticle morphology and chromosomal data (O. volvulus and O. gibsoni have n=4 while O. ochengi is n=5) suggest that O. gibsoni could be more closely related to O. volvulus than O. ochengi. Sequences from the 12S rRNA, 16S rRNA and ND5 mitochondrial genes have been used to reconstruct the phylogeny of five Onchocerca species including O. volvulus. Analyses with maximum likelihood and maximum parsimony showed that O. ochengi is the sister species of O. volvulus, in accordance with the classification based on morphology and geographical location. The separate specific status of the species O. gutturosa and O. lienalis was supported, although their phylogenetic relationship was not well resolved. The analyses indicated that the basal species was O. gibsoni, a South-East Asian and Australasian species, but this result was not statistically significant. The possible involvement of sympatric speciation in the evolution of this group of parasites is discussed.
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Hansen, Rowena D. E., Alexander J. Trees, Germanus S. Bah, et al. "A worm's best friend: recruitment of neutrophils by Wolbachia confounds eosinophil degranulation against the filarial nematode Onchocerca ochengi." Proceedings of the Royal Society B: Biological Sciences 278, no. 1716 (2010): 2293–302. http://dx.doi.org/10.1098/rspb.2010.2367.

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Onchocerca ochengi , a filarial parasite of cattle, represents the closest relative of the human pathogen, Onchocerca volvulus . Both species harbour Wolbachia endosymbionts and are remarkable in that adult female worms remain viable but sessile for many years while surrounded by host cells and antibodies. The basis of the symbiosis between filariae and Wolbachia is thought to be metabolic, although a role for Wolbachia in immune evasion has received little attention. Neutrophils are attracted to Wolbachia , but following antibiotic chemotherapy they are replaced by eosinophils that degranulate on the worm cuticle. However, it is unclear whether the eosinophils are involved in parasite killing or if they are attracted secondarily to dying worms. In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine. In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability. Eosinophil degranulation increased significantly only in the oxytetracycline group; whereas nodular gene expression of bovine neutrophilic chemokines was lowest in this group. Moreover, intense eosinophil degranulation was initially associated with worm vitality, not degeneration. Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response.
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WAHL, G., D. EKALE, and A. SCHMITZ. "Onchocerca ochengi: assessment of the Simulium vectors in North Cameroon." Parasitology 116, no. 4 (1998): 327–36. http://dx.doi.org/10.1017/s0031182097002333.

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In the savanna areas of tropical Africa, cattle are frequently infected with the filaria Onchocerca ochengi. This parasite is closely related to Onchocerca volvulus, the causative agent of human onchocerciasis (river blindness), and is capable of developing in the same vector, Simulium damnosum s.l. In North Cameroon, where both O. ochengi and O. volvulus are endemic, we carried out a field study (reported in this and 2 following papers) to examine to which extent the transmission of the 2 parasite species overlap and what influence this has on the epidemiology of human onchocerciasis. In this paper we report our experiments to determine which of the S. damnosum species in North Cameroon act as vectors of O. ochengi, how efficiently they do so and whether other Simulium species play a vector role. To this end, infected cattle were exposed near 5 rivers in different geographical areas. Among 14 Simulium species identified as aquatic and/or adult stages at these rivers, only 6 (S. squamosum, S. damnosum s.s., S. sirbanum, S. bovis, S. wellmanni and S. hargreavesi) were found to bite cattle in important numbers in at least 1 of the sites. The 3 species of the S. damnosum complex were all capable of ingesting microfilariae (mf) of O. ochengi and developing a proportion of them to infective larvae (L3). Whereas S. squamosum and S. damnosum s.s., the prevailing vectors in the Guinea and Sudan savanna respectively, showed a high vector competence (17% of ingested mf developed to L3), S. sirbanum, which was much rarer in both areas, appeared to have a much lower susceptibility (2%). Other boophilic Simulium species were only seen in certain sites and seasons, being either incapable of ingesting important numbers of O. ochengi mf from body regions where these mf were abundant (S. bovis, S. hargreavesi); not able to support the development of ingested mf to L3 (S. wellmanni), or bit cattle preferentially in the ears, where O. ochengi mf do not occur (S. hargreavesi). We conclude that in North Cameroon members of the S. damnosum complex are the only important vectors of O. ochengi, with S. squamosum and S. damnosum s.s. being the main vectors.
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Trees, A. J. "Onchocerca ochengi: Mimic, model or modulator of O. volvulus?" Parasitology Today 8, no. 10 (1992): 337–39. http://dx.doi.org/10.1016/0169-4758(92)90068-d.

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8

ACHUKWI, M. D., W. HARNETT, P. ENYONG, and A. RENZ. "Successful vaccination against Onchocerca ochengi infestation in cattle using live Onchocerca volvulus infective larvae." Parasite Immunology 29, no. 3 (2007): 113–16. http://dx.doi.org/10.1111/j.1365-3024.2006.00917.x.

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9

Jaleta, Tegegn G., Christian Rödelsperger, Babette Abanda, et al. "Full mitochondrial and nuclear genome comparison confirms that Onchocerca sp. “Siisa” is Onchocerca ochengi." Parasitology Research 117, no. 4 (2018): 1069–77. http://dx.doi.org/10.1007/s00436-018-5783-0.

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10

Mbobda, Alexis Sylvain Wafo, Alain Wembe Ngouonpe, Gervais Mouthé Happi, et al. "Pachypodostyflavone, a New 3-methoxy Flavone and Other Constituents with Antifilarial Activities from the Stem Bark of Duguetia staudtii." Planta Medica International Open 8, no. 02 (2021): e56-e61. http://dx.doi.org/10.1055/a-1492-3585.

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AbstractA new flavone derivative named pachypodostyflavone (1), along with 8 known compounds (2–9) and a mixture of β-sitosterol and stigmasterol were isolated from the stem bark of Duguetia staudtii (Annonaceae), based on a bioassay-guided fractionation. Their structures were determined using high-resolution mass spectrometry and NMR spectroscopic data, as well as by comparison with the literature values of their analogs. Selected isolated compounds were evaluated for their in vitro antifilaricidal activities on Onchocerca ochengi microfilariae and adult worms. Inhibition of motility was evaluated spectroscopically on microfilaria and adult male worms. Viability was determined on adult female worms by the MTT/ Formazan assay. Auranofin at 10 µM and 2% DMSO were used as positive and negative controls, respectively. Compounds 1 and 7 showed potent anti-onchocerca activities with 100% activity at 250 µg/mL on both O. ochengi adult male and female worms, while compound 5 displayed 100% activity at 30 µg/mL.
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Dissertations / Theses on the topic "Onchocerca ochengi"

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Tchakoute, Virginia Louise. "Onchocerca ochengi : susceptibility and resistance to natural infection in West African cattle." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366271.

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Njongmeta, Leo Moh. "Immunity in onchocerciasis after ivermectin prophylaxis : studies with Onchocerca ochengi in cattle." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250397.

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Hansen, Rowena Dawn Ellen. "The potential role of Walbachia as a defensive mutualist in the Onchocerca ochengi nodule." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569645.

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Onchocerciasis (River Blindness) is a continuing major cause of human blindness, skin disease and socioeconomic impediment in sub-Saharan Africa and Latin America. An estimated 37 million people are infected and a further 89 million are at risk. Human onchocerciasis is caused by the filarial nematode Onchocerca volvulus, and is spread by the blackfly vector Simulium spp, found in riverine areas, encompassing land which is agriculturally valuable. Ivermectin is currently distributed in these areas to control the microfilarial stage of the parasite, but adult worm viability is unaffected. Thus, due to the long lifespan of the worms (>10 years), treatment regimens must be continued for many years. Furthermore, there are signs that ivermectin resistance is emerging. The bovine filarial parasite Onchocerca ochengi represents the closest phylogenetic relative of 0. volvulus. In both species, female worms reside in nodules, and continue to reproduce for many years whilst surrounded by a milieu of host inflammatory cells and antibodies. In addition, both species harbour endosymbiotic bacteria (Wolbachia) which are essential for worm survival. Although a metabolic role for these bacteria has been hypothesised, the symbiotic mechanisms between filariae and Wolbachia are not fully understood. In the filarial nodule, neutrophils are attracted to Wolbachia-rich worms, but if the bacteria are depleted via antibiotic chemotherapy, the neutrophils are replaced by eosinophils that degranulate on the worm cuticle. However, the specific contribution of eosinophils towards filarial death is unresolved. This study sought to define the role of eosinophils in either the active killing or post-killing clearance of Wolbachia-depleted filariae. In an in-vivo longitudinal study of 0. ochengi- infected cattle receiving adulticidal regimens of oxytetracycline or melarsomine, histopathological analysis of nodules revealed a switch from neutrophils to eosinophils in oxytetracycline-treated animals, but not following melarsomine treatment, and quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) demonstrated that viable Wolbachia were depleted only by oxytetracycline chemotherapy. Eosinophil degranulation increased significantly only in the oxytetracycline group; whereas nodular gene expression of bovine neutrophilic chemokines was lowest in this group. Moreover, intense eosinophil degranulation was initially associated with worm vitality, not degeneration, while transmission electron microscopy (TEM) revealed subsequent cuticular damage in Wolbachia-depleted worms. Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on 0. ochengi through a defensive mutualism, in which neutrophils attracted to Wolbachia divert a potentially lethal effector response by eosinophils.
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Hildebrandt, Julia [Verfasser], and Adrian [Akademischer Betreuer] Streit. "Population genetic studies in the parasitic nematode Onchocerca ochengi / Julia Hildebrandt ; Betreuer: Adrian Streit." Tübingen : Universitätsbibliothek Tübingen, 2014. http://d-nb.info/1196802262/34.

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Cross, Helen Fiona. "A molecular and pharmacological investigation of the action of ivermectin against Onchocerca ochengi of cattle." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266171.

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Nfon, Charles Kongnyu. "The interaction between chemotherapy and immune responses in natural Onchocerca ochengi infection, the bovine host and the endosybiotic bacteria, Wolbachia." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406667.

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Eisenbarth, Albert [Verfasser], and Alfons [Akademischer Betreuer] Renz. "The biology of Onchocerca ochengi, a filarial nematode from African cattle, and the implications on the epidemiology of the causative agent of river blindness, Onchocerca volvulus / Albert Eisenbarth ; Betreuer: Alfons Renz." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/1163665045/34.

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