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Journal articles on the topic 'Onchocerca ochengi'

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Published: 3 June 2025

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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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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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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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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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Babiaka, Smith B., Conrad V. Simoben, Kennedy O. Abuga, et al. "Alkaloids with Anti-Onchocercal Activity from Voacanga africana Stapf (Apocynaceae): Identification and Molecular Modeling." Molecules 26, no. 1 (2020): 70. http://dx.doi.org/10.3390/molecules26010070.

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A new iboga-vobasine-type isomeric bisindole alkaloid named voacamine A (1), along with eight known compounds—voacangine (2), voacristine (3), coronaridine (4), tabernanthine (5), iboxygaine (6), voacamine (7), voacorine (8) and conoduramine (9)—were isolated from the stem bark of Voacangaafricana. The structures of the compounds were determined by comprehensive spectroscopic analyses. Compounds 1, 2, 3, 4, 6, 7 and 8 were found to inhibit the motility of both the microfilariae (Mf) and adult male worms of Onchocerca ochengi, in a dose-dependent manner, but were only moderately active on the adult female worms upon biochemical assessment at 30 μM drug concentrations. The IC50 values of the isolates are 2.49–5.49 µM for microfilariae and 3.45–17.87 µM for adult males. Homology modeling was used to generate a 3D model of the O. ochengi thioredoxin reductase target and docking simulation, followed by molecular dynamics and binding free energy calculations attempted to offer an explanation of the anti-onchocercal structure–activity relationship (SAR) of the isolated compounds. These alkaloids are new potential leads for the development of antifilarial drugs. The results of this study validate the traditional use of V. africana in the treatment of human onchocerciasis.

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TREES, A. J., S. P. GRAHAM, A. RENZ, A. E. BIANCO, and V. TANYA. "Onchocerca ochengi infections in cattle as a model for human onchocerciasis: recent developments." Parasitology 120, no. 7 (2000): 133–42. http://dx.doi.org/10.1017/s0031182099005788.

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The bovine parasite Onchocerca ochengi is a nodule-dwelling filarial nematode, closely related to O. volvulus, the causal agent of human River Blindness, and, sharing with it, the same vector. This brief review, based on a presentation at the BSP Autumn Symposium 1999, describes recent work supported by the WHO Drug Development Research Macrofil programme and the Edna McConnell Clark Foundation vaccine development programme, to research the chemotherapy and immunology of onchocerciasis utilising this model system, with experimental infections in Liverpool and field infections in northern Cameroon. In a series of chemotherapeutic trials involving 10 compounds in 20 treatment regimes, the comparability of drug efficacy against O. ochengi with that described against O. volvulus has been demonstrated. Repeated, long-term treatment with oxytetracycline has been shown to be macrofilaricidal and the effect is hypothesized to be related to action on Wolbachia endobacteria, abundant in O. ochengi. Avermectins/milbemycins are not macrofilaricidal (even in high and repeated long-term treatments) but induce sustained abrogation of embryogenesis. In prospective, field exposure experiments with naive calves, prophylactic treatments with ivermectin and moxidectin prevented the development of adult worm infection, raising the possibility that drug-attenuated larval challenge infections may induce immunity. Putatively immune adult cattle exist in endemically exposed populations, and these have been shown to be significantly less susceptible to challenge than age-matched naive controls, whereas radically drug-cured, previously patently-infected cattle were not. Experimental infections with O. ochengi have revealed the kinetics of the immune response in relation to parasite development and demonstrate analogous responses to those reported in O. volvulus infection in humans and chimpanzees. In an immunization experiment with irradiated L3 larvae, cattle were significantly protected against experimental challenge – the first such demonstration of the experimental induction of immunity in a natural Onchocerca host–parasite system. Taken collectively, these studies not only demonstrate the similarity between the host–parasite relationships of O. ochengi in cattle and O. volvulus in humans, but promise to advance options for the control of human onchocerciasis.

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Tritten, Lucienne, Maeghan O’Neill, Chuck Nutting, et al. "Loa loa and Onchocerca ochengi miRNAs detected in host circulation." Molecular and Biochemical Parasitology 198, no. 1 (2014): 14–17. http://dx.doi.org/10.1016/j.molbiopara.2014.11.001.

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McCall, P. J., H. Townson, and A. J. Trees. "Morphometric differentiation of Onchocerca volvulus and O. ochengi infective larvae." Transactions of the Royal Society of Tropical Medicine and Hygiene 86, no. 1 (1992): 63–65. http://dx.doi.org/10.1016/0035-9203(92)90443-g.

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Cross, H. F., A. Renz, and A. J. Trees. "In-vitro uptake of ivermectin by adult male Onchocerca ochengi." Annals of Tropical Medicine & Parasitology 92, no. 6 (1998): 711–20. http://dx.doi.org/10.1080/00034983.1998.11813331.

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H. F. CROSS, B. M. BRONSVOORT, G. W, BY. "The entry of ivermectin and suramin into Onchocerca ochengi nodules." Annals of Tropical Medicine And Parasitology 91, no. 4 (1997): 393–402. http://dx.doi.org/10.1080/00034989761012.

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F. CROSS A. RENZ A. J. TREES, H. "In vitro uptake of ivermectin by adult male Onchocerca ochengi." Annals of Tropical Medicine And Parasitology 92, no. 6 (1998): 711–20. http://dx.doi.org/10.1080/00034989859177.

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HAGEN, H. E., and S. L. KLÄGER. "Integrin-like RGD-dependent cell adhesion mechanism is involved in the rapid killing of Onchocerca microfilariae during early infection of Simulium damnosum s.l." Parasitology 122, no. 4 (2001): 433–38. http://dx.doi.org/10.1017/s0031182001007545.

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Injection trials with compatible and non-compatible Onchocerca species into S. damnosum s.l., the vector of human and bovine onchocerciasis, demonstrated that the rapid killing of microfilariae within the blackfly's haemocoel is species specific. In the presence of the peptide RGDS as a blocking agent for integrin-like receptors of haemocytes, the survival of O. ochengi microfilariae in its natural intermediate host was significantly increased. This increased survival 24 h p.i. correlated with a significant decrease of apoptosis levels in the microfilariae following a 2 h exposure to the haemolymph in vivo. These findings suggest that haemocytes are directly involved in the killing of Onchocerca microfilariae in the blackfly.

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Djongra, Mathieu1 Mando Ndou Bertrand1 Djafsia Boursou1 Tchuenguem Fohouo Fernand-Nestor1 Ndjonka Dieudonné1*, Ndou Bertrand Mando, Boursou Djafsia, Fohouo Fernand-Nesto Tchuenguem, and Dieudonné Ndjonka. "In vitro evaluation of the Anthelmintic Activity of PROMAX-C and propolis extract on the Nematode Parasite Onchocerca ochengi Bwangamoi, 1969 (Spirurida: Onchocercidae)." American Journal of PharmTech Research 12, no. 3 (2022): 36–54. https://doi.org/10.5281/zenodo.7103236.

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ABSTRACT The anthelmintic activity of the ethanolic and aqueous extracts of Foumban propolis and PROMAX-C was evaluated in vitro, on the nematode parasite of cattle Onchocerca ochengi. The objective of this study was to find an alternative of synthetic anthelmintic to fight human and animal onchocerciasis. Increasing concentrations of ethanolic and aqueous extracts of propolis and PROMAX-C were prepared in RPMI 1640 culture medium for O. ochengi incubation. Dimethylsulfoxide of 0.5 % concentration was the negative control and the positive control was ivermectin. The anthelmintic activity was assessed every 24 and 48 hours and expressed as mortality rate. Acute oral toxicity was assessed in Mus musculus for 14 days and subacute toxicity was assessed in males and females of Ratus norvegicus for 28 days. Quantification of polyphenols, tannins and flavonoids was performed with a spectrophotometer using gallic acid and rutin as standards. The LC50 value was 52.50 ± 0.04 µg/mL for PROMAX-C, while those of the ethanolic and aqueous extracts were 75.50 ± 0.92 and 261.44 ± 18.98 µg/mL, respectively after 48 hours. The test with ivermectin showed a high efficacy on O. ochengi nematodes with a LC50 value of 100.05 ± 0.35 µg/mL. The ethanolic extract of propolis did not show signs of toxicity on mice. During subacute toxicity, the relative organ weights (kidney, liver, lung, spleen and heart) taken from the rats at the end of treatment did not change significantly. Biochemical showed a decrease in AST and ALT in both sexes at all doses. Thus, the consumption of propolis and PROMAX-C is recommended to fight against onchocerciasis. Keywords: Onchocerca ochengi, anthelmintic, Foumban propolis, PROMAX-C, Ivermectin.

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KLÄGER, S. L., H. E. HAGEN, and J. E. BRADLEY. "Effects of an Onchocerca-derived cysteine protease inhibitor on microfilariae in their simuliid vector." Parasitology 118, no. 3 (1999): 305–10. http://dx.doi.org/10.1017/s0031182098003795.

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A recombinant cysteine protease inhibitor, onchocystatin of the parasitic nematode Onchocerca volvulus, was tested for its role in microfilarial development in the simuliid vector. Onchocystatin was found to be present in female adults and skin microfilariae of the bovine parasite O. ochengi, the closest relative of O. volvulus. In addition the inhibitor could be detected as an excretory–secretory (E–S) product of the microfilariae. Co-injection of onchocystatin and the O. ochengi microfilariae into the surrogate vector Simulium ornatum s.l. significantly enhanced the recovery rates of the parasite within 24 h into the infection (P>0·001). The findings suggest a possible role of onchocystatin in the evasion by the parasite of the immune response of its vector.

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Bah, Germanus S., Sebastian Schneckener, Steffen R. Hahnel, et al. "Emodepside targets SLO-1 channels of Onchocerca ochengi and induces broad anthelmintic effects in a bovine model of onchocerciasis." PLOS Pathogens 17, no. 6 (2021): e1009601. http://dx.doi.org/10.1371/journal.ppat.1009601.

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Onchocerciasis (river blindness), caused by the filarial worm Onchocerca volvulus, is a neglected tropical disease mostly affecting sub-Saharan Africa and is responsible for >1.3 million years lived with disability. Current control relies almost entirely on ivermectin, which suppresses symptoms caused by the first-stage larvae (microfilariae) but does not kill the long-lived adults. Here, we evaluated emodepside, a semi-synthetic cyclooctadepsipeptide registered for deworming applications in companion animals, for activity against adult filariae (i.e., as a macrofilaricide). We demonstrate the equivalence of emodepside activity on SLO-1 potassium channels in Onchocerca volvulus and Onchocerca ochengi, its sister species from cattle. Evaluation of emodepside in cattle as single or 7-day treatments at two doses (0.15 and 0.75 mg/kg) revealed rapid activity against microfilariae, prolonged suppression of female worm fecundity, and macrofilaricidal effects by 18 months post treatment. The drug was well tolerated, causing only transiently increased blood glucose. Female adult worms were mostly paralyzed; however, some retained metabolic activity even in the multiple high-dose group. These data support ongoing clinical development of emodepside to treat river blindness.

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Cho-Ngwa, Fidelis, Monique Akoachere, and Vincent P. K. Titanji. "Sensitive and specific serodiagnosis of river blindness using Onchocerca ochengi antigens." Acta Tropica 89, no. 1 (2003): 25–32. http://dx.doi.org/10.1016/j.actatropica.2003.08.003.

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Determann, A., H. Mehlhorn, and F. A. Ghaffar. "Electron microscope observations on Onchocerca ochengi and O. fasciata (Nematoda: Filarioidea)." Parasitology Research 83, no. 6 (1997): 591–603. http://dx.doi.org/10.1007/s004360050303.

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Vuong, P. N., S. Wanji, J. Prod'Hon, and O. Bain. "Nodules sous-cutanés et lésions cutanées engendrés par diverses onchocerques chez des bovins africains." Revue d’élevage et de médecine vétérinaire des pays tropicaux 47, no. 1 (1994): 47–51. http://dx.doi.org/10.19182/remvt.9131.

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Des nodules sous-cutanés et de la peau ombilicale sont prélevés sur 6 Bos indicus onchocerquiens au Cameroun, pour l'étude anatomopathologiq ue. Les nodules à Onchocerca ochengi et Onchocerca dukei ont la même structure que celle des nodules à Onchocerca volvulus de l'homme; ce sont des pseudo-kystes inflammatoire contenant souvent une fillaire femelle. La composante cellulaire de la paroi du pseudo-kyste permet de classer les nodules en trois types : nodule "jeune", nodule "évolué" et nodule "ancien". Le nodule est circonscrit par des vaisseaux dont la lumière contient parfois des microfilaire et des morulas. La peau parasitée par les microfilaires de ces deux onchocerques et par celles de O. gutturosa et O. armillata, présente diverses lésions de dermite avec sclérose cicatricielle, superposables à celles observées chez les malades onchocerciens. Dans la majorité des cas, les infiltrats inflammatoires circonscrivent les capillaires lymphatiques longeant les vaisseaux sanguins réalisant une lymphangite. Les onchocerques nodulaires bovines constituent un modèle interessant pour l'onchocercose humaine.

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TCHAKOUTÉ, V. L., M. BRONSVOORT, V. TANYA, A. RENZ, and A. J. TREES. "Chemoprophylaxis of Onchocerca infections: in a controlled, prospective study ivermectin prevents calves becoming infected with O. ochengi." Parasitology 118, no. 2 (1999): 195–99. http://dx.doi.org/10.1017/s0031182098003680.

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Onchocerciasis (‘River Blindness’), caused by the filarial nematode Onchocerca volvulus is of major public health importance in West Africa. Ivermectin, a drug originally developed for veterinary use, is now being incorporated in control strategies but whilst it has potent efficacy against L1 larvae (microfilariae), ivermectin is not lethal to adult (L5) O. volvulus, nor to adults of the related cattle parasite O. ochengi. We have exploited this model to determine if ivermectin has prophylactic activity against naturally transmitted, O. ochengi infections in a controlled, prospective study in northern Cameroon. Calves were treated monthly with ivermectin at either 200 μg/kg or 500 μg/kg for 21 months. None of 15 treated calves developed adult worm infection, whereas 5/6 untreated controls became infected (P<0·001) with a total of 54 O. ochengi nodules, and all 5 developed patent microfilaridermia. These results have significant implications for the use of ivermectin in humans, and suggest that strategic chemotherapy at times of maximal transmission will confer prophylactic as well as therapeutic benefits.

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Djetoloum, Martinien Atakewang, Nadlaou Bessimbaye, and Mbaïnguinam Mbailao. "In Vitro Study of the Antiparasitic Activity of Vitellaria paradoxa Gaertn (Sapotaceae) on the Parasite Onchocerca ochengi." Scholars Academic Journal of Biosciences 12, no. 01 (2024): 5–15. http://dx.doi.org/10.36347/sajb.2024.v12i01.002.

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Onchocerciasis is a parasitic disease that affects millions of animals and people around the world. A recipe based on Vitellaria paradoxa is used in traditional medicine against this disease in Chad. The objective of this study was to evaluate the antiparasitic activities of extracts from the roots, fruits, leaves and bark of Vitellaria paradoxa on the parasitic nematode Onchocerca ochengi, a model similar to Onchocerca volvulus used in the research of control drugs. against onchocerciasis. The identification of parasites and the hydroethanolic extracts of the different planar organs were carried out at the Laboratory of Research, Diagnostics and Scientific Expertise (LaboReDES) of the Faculty of Human Sciences, University of N'Djamena using the methods of Ndjonka et al., 2012. The extracts of this plant were tested at different concentrations (0.1; 0.2; 0.3; 0.4 mg/mL) in the RPMI-1640 culture medium. The antiparasitic activity was noted according to the mortality rate after 72 hours of incubation of Onchocerca ochengi at 37°C. The LC50 values were then graphically determined at the end of this incubation. They were 0.05 mg/mL for the roots; 0.06 mg/mL for fruits; 0.05 mg/mL for the leaves and 0.06 mg/mL for the bark. These results confirm the effectiveness of Vitellaria paradoxa used in traditional medicine to treat parasitosis. This plant also has the same effects as ivermectin. The V. paradoxa root test on microfilariae shows an LC50 value of 0.05 mg/mL in 24 hours of incubation. This study showed that the hydroethanolic extracts of the bark of Vitellaria paradoxa had antiparasitic activities, allowing the development of a new molecule active against these parasitic infections and also the extracts of this plant could be used as alternatives to treat infections in case of parasite resistance to ivermectin.

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Ndjonka, D., C. Agyare, K. Lüersen, et al. "In vitro activity of Cameroonian and Ghanaian medicinal plants on parasitic (Onchocerca ochengi) and free-living (Caenorhabditis elegans) nematodes." Journal of Helminthology 85, no. 3 (2010): 304–12. http://dx.doi.org/10.1017/s0022149x10000635.

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AbstractEthanolic and aqueous extracts of selected medicinal plants from Cameroon and Ghana were assessed for their in vitro anthelmintic activity by using the bovine filarial parasite Onchocerca ochengi and the free living nematode Caenorhabditis elegans, a model organism for research on nematode parasites. Worms were incubated in the presence of different concentrations of extracts and inhibitory effects were monitored at different time points. Among the extracts used in this study, ethanolic extracts of Anogeissus leiocarpus, Khaya senegalensis, Euphorbia hirta and aqueous extracts from Annona senegalensis and Parquetina nigrescens affected the growth and survival of C. elegans and O. ochengi significantly. The mortality was concentration dependent with an LC50 ranging between 0.38 and 4.00 mg/ml for C. elegans (after 72 h) and between 0.08 and 0.55 mg/ml for O. ochengi after a 24 h incubation time. Preliminary phytochemical screenings on these extracts revealed the presence of flavonoids, alkaloids, saponins, carbohydrates and tannins in the extracts. Accordingly, application of A. leiocarpus, K. senegalensis, E. hirta and A. senegalensis extracts could provide alternatives in the control of helminthic infections.

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Hagen, H. E., J. Grunewald, and P. J. Ham. "Induction of the prophenoloxidase-activating system of Simulium (Diptera: Simuliidae) following Onchocerca (Nematoda: Filarioidea) infection." Parasitology 109, no. 5 (1994): 649–55. http://dx.doi.org/10.1017/s0031182000076538.

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Trials were carried out to study the humoral immune response of blackflies to filariae following infection using the intrathoracic injection technique. An induced 66 kDa protein was abundant in the haemolymph of the European species Simulium ornatum following infection with bovine Onchocerca lienalis. This protein was apparently at higher concentrations in the haemolymph of sham-inoculated flies, i.e. flies that received sterile medium without the parasites. A molecule of the same size was also observed in the haemolymph of infected S. damnosum s.l. following infection with human O. volvulus or bovine O. ochengi. However, the level of this protein was lower in blackflies injected with microfilariae of bovine O. dukei. Unlike O. volvulus and O. ochengi this species is not transmitted by S. damnosum s.l. under natural conditions. No such reaction was observed if the African blackflies had received a sham inoculation. Feeding experiments with wild-caught nulliparous S. damnosum sl. on Onchocerca-infected cattle supported the results of the injection trials. The 66 kDa protein could only be found in the haemolymph of specimens infected via a blood meal. This 66 kDa molecule was identified as phenoloxidase. It appeared in the haemolymph due to the activation of the prophenoloxidase system following the filarial infection and we hypothesize that it may be sequestered by the parasites, as part of a non-self recognition system.

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Graham, Simon P., Alexander J. Trees, Robert A. Collins, et al. "Down-Regulated Lymphoproliferation Coincides with Parasite Maturation and with the Collapse of Both Gamma Interferon and Interleukin-4 Responses in a Bovine Model of Onchocerciasis." Infection and Immunity 69, no. 7 (2001): 4313–19. http://dx.doi.org/10.1128/iai.69.7.4313-4319.2001.

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ABSTRACT Onchocerciasis is a debilitating parasitic infection caused by the filarial nematode Onchocerca volvulus. Infections are chronic, and persistence of the parasites for several years argues for highly adapted mechanisms of immune evasion. Due to the restricted host repertoire of O. volvulus, we have used the cattle parasite Onchocerca ochengi to investigate the nature of immunomodulation underpinning these long-term infections. Cattle were infected with a single inoculation of 350 infective-stage larvae under laboratory conditions (n = 6). Intradermal nodules containing immature adult worms were detected from 110 days postinfection, and microfilariae in skin were detected from day 280 postinfection. Parasite-specific responses during early infection were nonpolarized with respect to the major Th cytokines (interleukin-4 [IL-4], IL-2, and gamma interferon [IFN-γ]) produced by antigen-stimulated peripheral blood mononuclear cells (PBMC) or serum antibody isotypes. Antigen-induced proliferation of PBMC peaked shortly after exposure and remained high during the prepatent infection. As the parasites matured and animals developed patent infections, there was a profound down-regulation of lymphoproliferation, accompanied by sharp falls in the expression of both IL-4 and IFN-γ and a gradual decline in IL-2. Levels of immunoglobulin G2 (IgG2) fell, while those of IgG1 remained high. We conclude that neither a classical Th2 response nor a simple Th1-to-Th2 switch is sufficient to explain the immunomodulation associated with patent Onchocerca infections. Instead, there is an initial Th0 response, which matures into a response with some, but not all of the features of a Th2 response. The natural host-parasite relationship of O. ochengi in cattle may be useful as both a descriptive and predictive tool to test more refined models of immunomodulation in onchocerciasis.

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Eberle, Raphael, Norbert W. Brattig, Maria Trusch, et al. "Isolation, identification and functional profile of excretory–secretory peptides from Onchocerca ochengi." Acta Tropica 142 (February 2015): 156–66. http://dx.doi.org/10.1016/j.actatropica.2014.11.015.

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Ignagali, Banserne Brey, Borris Rosnay Galani Tietcheu, Theodore Betrosse, Blaise Kamaya, and Dieudonne Ndjonka. "In Vitro Filaricidal Properties of Aqueous Extracts of Combretum nigricans (Combretaceae) on Onchocerca ochengi (Onchocercidae)." Journal of Parasitology Research 2024 (January 31, 2024): 1–11. http://dx.doi.org/10.1155/2024/2119056.

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Aim. Onchocerciasis is an endemic parasitic disease in sub-Saharan Africa that significantly impacts animal and human health. In Northern Cameroon, medicinal plants from the Combretum genus are used for onchocerciasis traditional treatment although there is no scientific evidence of their antifilarial potential. This study evaluates the in vitro macro- and microfilaricidal properties of water extracts from Combretum nigricans in Onchocerca ochengi. Material and Methods. O. ochengi microfilariae and adult male worms were recovered from cowhide fragments. Oxidative stress indicators and motility tests were used to assess the filaricidal impact. Female albino rats were used to test for acute toxicity. The contents of secondary metabolites were quantified. Results. The bark aqueous extract was more active on macrofilariae at 1 mg/mL for 24 h (100%) than the leaf (63.9%) and root (75%) extracts at the same concentration. Likewise, a stronger microfilaricidal effect was found with this extract at 0.5 mg/mL for 1 h (100%) compared to root and leaf extracts. The dose-response effect with the bark extract gave an inhibitory concentration 50 (IC50) of 351 μg/mL vs. 113 μg/mL for flubendazole after 24 h incubation, while the microfilaricidal efficacy revealed an IC50 of 158.7 μg/mL vs. 54.09 μg/mL for ivermectin after one-hour incubation. Examining stress indicators on parasite homogenates showed that macrofilaricidal activity is associated with a significant increase in nitric oxide, glutathione, and malondialdehyde generation and a decrease in catalase activity. At 2000 mg/kg, rats showed no harm. The phytochemical investigation revealed that the barks contained more phenolic acids, condensed tannins, flavonoids, and saponins than the leaves (p<0.001). Conclusion. These findings support C. nigricans’ antifilarial activity and identify oxidative stress indicators as prospective treatment targets in O. ochengi. It would be interesting to conduct in vivo studies to understand their antifilarial activity better.

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Hildebrandt, Julia C., Albert Eisenbarth, Alfons Renz, and Adrian Streit. "Reproductive biology of Onchocerca ochengi, a nodule forming filarial nematode in zebu cattle." Veterinary Parasitology 205, no. 1-2 (2014): 318–29. http://dx.doi.org/10.1016/j.vetpar.2014.06.006.

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GRAHAM, S. P., Y. WU, K. HENKLE-DUEHRSEN, et al. "Patterns of Onchocerca volvulus recombinant antigen recognition in a bovine model of onchocerciasis." Parasitology 119, no. 6 (1999): 603–12. http://dx.doi.org/10.1017/s0031182099005065.

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The antibody responses of 8 cattle experimentally infected with Onchocerca ochengi to 18 recombinant O. volvulus antigens were measured by ELISA. In addition to establishing antigenic cross-reactivity between the species, the dynamics of antigen-specific responses were examined to assess how the recognition of the antigens compared to the known stage-specificity of expression. Six cattle responded to all of the antigens and 2 animals responded to all but 1. The dynamics of the recognition of 4 antigens (B20, MOv-2, MOv-14 and OvNHR2 02E1) were characterized by rapid seroconversion following infection. Antibody levels to 2 antigens (Ov7 and OvALT-1) increased gradually over the course of infection. Antibody levels to 4 antigens (OvTPX-2, OvL3Chitinase, Ov103 and Ov9m) reached maximum levels coincident with the onset of patency. The levels to 3 antigens (OvProalf C50, OvAldolase, Ov39) varied little over the course of infection. Responses to antigens with functional similarities (OvSOD1, OvSOD2 and OvSOD3 or OvGST1 and OvGST2) showed comparable temporal profiles. This study demonstrates the high degree of immunological cross-reactivity between the antigens of O. volvulus and O. ochengi. The immunogenicity of antigens varied over the course of infection in an antigen-specific manner, which not always reflected developmentally regulated expression of the corresponding gene, possibly owing to cross-reactive epitopes on distinct parasite products.

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Ayiseh, Rene Bilingwe, Glory Enjong Mbah, Elvis Monya, et al. "Development and validation of small animal models for onchocerciasis and loiasis microfilaricide discovery." PLOS Neglected Tropical Diseases 17, no. 2 (2023): e0011135. http://dx.doi.org/10.1371/journal.pntd.0011135.

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Background Onchocerciasis (river blindness) caused by the filarial worm Onchocerca volvulus is a neglected tropical disease that affects the skin and eyes of humans. Mass drug administration with ivermectin (IVM) to control the disease often suffers from severe adverse events in individuals co-injected with high loads of Loa loa microfilariae (mf). Thus loiasis animal models for counter-screening of compounds effective against onchocerciasis are needed, as are the corresponding onchocerciasis screening models. The repertoire of such models is highly limiting. Therefore, this study was aimed at developing and validating mf immunocompetent small animal models to increase tools for onchocerciasis drug discovery. Methodology/Principal findings O. ochengi mf from cattle skin and L. loa mf from human blood were used to infect BALB/c mice and Mongolian gerbils, and IVM was used for model validation. O. ochengi mf were given subcutaneously to both rodents while L. loa mf were administered intravenously to mice and intraperitoneally to gerbils. IVM was given orally. In an 8-day model of O. ochengi mf in BALB/c mice, treatment with IVM depleted all mf in the mice, unlike the controls. Also, in a 2.5-day model of L. loa mf in BALB/c, IVM significantly reduced mf in treated mice compared to the untreated. Furthermore, the gerbils were very susceptible to O. ochengi mf and IVM eradicated all mf in the treated animals. In the peritoneal L. loa mf gerbil model, IVM reduced mf motility in treated animals compared to the controls. In a 30-day gerbil co-injection model, IVM treatment cleared all O. ochengi mf and reduced motility of L. loa mf. Both mf survived for up to 50 days in a gerbil co-injection model. Conclusions/Significance We have developed two immunocompetent small animal models for onchocerciasis and loiasis that can be used for microfilaricide discovery and to counter-screen onchocerciasis macrofilarides

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Akafyi, Danlami Elisha, Iliya Shehu Ndams, Ishaya Haruna Nock, et al. "Emergence and genetic diversity of zoonotic Onchocerca species among human populations in Taraba State, Nigeria." German Journal of Microbiology 3, no. 2 (2023): 12–19. http://dx.doi.org/10.51585/gjm.2023.2.0023.

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In the present study, the genetic diversity of Onchocerca (O.) species was investigated by amplifying a fragment of the 16S rRNA gene from the parasite obtained in some endemic areas in Taraba State, Nigeria. Three local government areas were selected: two onchocerciasis-endemic and one non-onchocerciasis-endemic regions. A total of 211 skin snips using a sterile sclera punch were obtained from consenting participants, males and females residing within the areas for at least ten years or since birth, by convenience sampling methods. The emerged microfilariae were examined microscopically. Nine microfilaria-positive skin snips were identified and preserved in RNALater®. DNA was extracted from recovered microfilariae and residual skin snip specimens and was tested by standard Polymerase Chain Reaction (PCR) using primers targeting the 16S gene. Six PCR-positive samples were sequenced and analyzed. Two sequences varied with those from other regions, suggesting a likely diversity of O. volvulus populations in the study area. A novel finding of O. ochengi, the pathogenic cattle parasite, was identified in some samples, suggesting a potential zoonotic species in humans. Further investigation on the extent of emerging zoonotic onchocerciasis by O. ochengi in the light of cattle, Simulium vectors (blackflies), and environmental and human overlap in the study area is required.

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Justin, Kalmobé, Ndjonka Dieudonné, Vildina Dikti Jacqueline, and Liebau Eva. "Antifilarial Activity of Cucurbita pepo ovifera var ovifera (Cucurbitaceae) on Onchocerca ochengi Adult Worms." British Journal of Pharmaceutical Research 17, no. 2 (2017): 1–8. https://doi.org/10.9734/BJPR/2017/33381.

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One of the strategies for developing novel pharmaceutical drugs is to use natural sources such as plants for therapeutic treatment. Plant extracts are a cocktail of compounds which act synergically and can improve treatment effectiveness, reduce therapeutic duration and resistance. The ethanolic extracts of leaves and seeds of Cucurbita pepo ovifera var ovifera from Sudano-Guinean and Sudano-Sahelian zones of Cameroon were evaluated on the cattle parasite nematode Onchocerca ochengi. Worms were incubated with different concentrations of the plant extracts in RPMI-1640 supplemented with streptomycin and gentamicin. Mortality at 37°C was monitored after 24, 48 and 72 h. Ivermectin was used as positive control and DMSO as negative. Plant extracts from the two ecological zones showed anthelminthic activities on O. ochengi after 72 h with LC50 varying from 20 to 1090 µg /mL. The highest antifilarial activity in Sudano-Guinean zone was obtained with leave extract of C. pepo ovifera (LC50 of 20 µg/mL), while highest antifilarial activity in Sudano-Sahelian zone was obtained with seed extracts of the plant with LC50 value of 17 µg/mL after 72 h. These results show that anthelmintic activity depends on the part of the plant and the ecological zones. Additionally, the plant is not toxic. These results on the ethanolic extracts of leaves and seeds of C. pepo ovifera var ovifera confirmed the use of this plant in traditional medicine in Cameroon to treat disease due to nematodes. The plants could be used as alternative anthelmintic to fight against Human and Bovine onchocerciasis.

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Tiku, Tiku Edward, Moses Samje, Napoleon Mfonku, and Fidelis Cho-Ngwa. "Anti-Onchocercal Properties of Extracts of Scoparia dulcis and Cylicodiscus gabunensis." Journal of Tropical Medicine 2022 (November 16, 2022): 1–8. http://dx.doi.org/10.1155/2022/4279689.

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Introduction. The elimination of onchocerciasis is hampered by the absence of suitable drugs that are effective against adult filariae. This study is aimed at assessing the anti-onchocercal effects of extracts of Scoparia dulcis and Cylicodiscus gabunensis that could serve as drug leads against onchocerciasis. Methods. Different parts of the plants (Scoparia dulcis and Cylicodiscus gabunensis) were extracted with hexane, methylene chloride, and methanol. The extracts were tested in vitro against the bovine model parasite, Onchocerca ochengi. Adult female worm viability was determined biochemically by MTT/formazan colorimetry, while the adult male and microfilariae viability were determined by microscopy based on % inhibition of worm motility score. Cytotoxicity and acute toxicity of active extracts were tested on monkey kidney epithelial cells (LLC-MK2) and Balb/C mice, respectively. Results. The hexane extract of Scoparia dulcis recorded the highest activity, with IC50s of 50.78 μg/ml on both adult male and female worms and 3.91 μg/ml on microfilariae. For Cylicodiscus gabunensis extract, the highest activity was seen with the methylene chloride extract, with IC50s of 50.78 μg/ml, 62.50 μg/ml, and 16.28 μg/ml on, respectively, adult male, female, and microfilariae. The 50% cytotoxic concentration on the LLC-MK2 cells was 31.25 μg/ml for the most active extracts. No acute toxicity was recorded for the extracts. Phytochemical analysis of the extracts revealed the presence of alkaloids, flavonoids, sterols, saponins, phenols, and glycosides. Conclusion. This study validates the traditional use of these plants in treating onchocerciasis and suggests S. dulcis and C. gabunensis as new potential sources for the isolation of anti-onchocerca lead compounds.

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Luu, Lisa, Germanus S. Bah, Ndode Herman Okah-Nnane, et al. "Co-Administration of Adjuvanted Recombinant Ov-103 and Ov-RAL-2 Vaccines Confer Protection against Natural Challenge in A Bovine Onchocerca ochengi Infection Model of Human Onchocerciasis." Vaccines 10, no. 6 (2022): 861. http://dx.doi.org/10.3390/vaccines10060861.

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Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a neglected tropical disease mainly of sub-Saharan Africa. Worldwide, an estimated 20.9 million individuals live with infection and a further 205 million are at risk of disease. Current control methods rely on mass drug administration of ivermectin to kill microfilariae and inhibit female worm fecundity. The identification and development of efficacious vaccines as complementary preventive tools to support ongoing elimination efforts are therefore an important objective of onchocerciasis research. We evaluated the protective effects of co-administering leading O. volvulus-derived recombinant vaccine candidates (Ov-103 and Ov-RAL-2) with subsequent natural exposure to the closely related cattle parasite Onchocerca ochengi. Over a 24-month exposure period, vaccinated calves (n = 11) were shown to acquire infection and microfilaridermia at a significantly lower rate compared to unvaccinated control animals (n = 10). Furthermore, adult female worm burdens were negatively correlated with anti-Ov-103 and Ov-RAL-2 IgG1 and IgG2 responses. Peptide arrays identified several Ov-103 and Ov-RAL-2-specific epitopes homologous to those identified as human B-cell and helper T-cell epitope candidates and by naturally-infected human subjects in previous studies. Overall, this study demonstrates co-administration of Ov-103 and Ov-RAL-2 with Montanide™ ISA 206 VG is highly immunogenic in cattle, conferring partial protection against natural challenge with O. ochengi. The strong, antigen-specific IgG1 and IgG2 responses associated with vaccine-induced protection are highly suggestive of a mixed Th1/Th2 associated antibody responses. Collectively, this evidence suggests vaccine formulations for human onchocerciasis should aim to elicit similarly balanced Th1/Th2 immune responses.

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Rakwa, Enock Enock, Benoît Bargui Koubala, Bertrand Ndou Mando, Mathieu Djongra, Francis Nveikoueing, and Dieudonné Ndjonka. "Antifilarial Activity of the Methanolic Extract of Indigofera tinctoria (Fabaceae) on Bovine Parasites (Onchocerca ochengi)." Journal of Parasitology Research 2022 (October 8, 2022): 1–10. http://dx.doi.org/10.1155/2022/7828551.

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Onchocerciasis is a major public health problem caused by Onchocerca volvulus parasite and transmitted to humans via black flies (simulium) bites. The control of onchocerciasis relies much on the use of the chemical drug ivermectin, which is only effective against microfilariae and has led to drug resistance. This study was carried out to assess the in vitro antifilarial activity of methanolic extract of Indigofera tinctoria and its most active fractions on adult male O. ochengi worm, the closest model to O. volvulus, after 48 h and 72 h of treatment. Worms’ viability was determined biochemically by MTT/formazan colorimetry assay. The promising plant extract’s acute and subacute oral toxicity were evaluated on both mice and rats. The result revealed a highest antifilarial activity of the methanolic extract ( L C 50 = 12.28 μ g / mL ) compared to ivermectin ( L C 50 = 26.50 μ g / mL ) after 72 h of treatment. Out of the eight (08), chromatographic fractions screened, only three (03) fractions (C, F, and G) revealed the highest anti-Onchocerca activity after 72 h of treatment. An oral administration of the plant extract at a single dose of 2000 mg/kg did not produce any toxicity in mice. After repeated daily administration of methanolic extract of I. tinctoria (250 mg/kg, 500 mg/kg, and 1000 mg/kg) for 28 days, no significant changes in body weight, biochemical, and haematological parameters was observed. Histopathological examination of organs did not reveal any sign of alteration. The phytochemical analysis of the methanolic extract of I. tinctoria revealed the presence of various phenolic compounds. Therefore, this study demonstrated the potential antifilarial activity of Indigofera tinctoria and offered an alternative to treating onchocerciasis. Moreover, further studies could be developed in promising new antifilarial sources of the isolated compound and in vivo antifilarial activity of Indigofera tinctoria in the animal model needs to be studied.

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Kalmobé, Justin, Dieudonné Ndjonka, Jacqueline Dikti, and Eva Liebau. "Antifilarial Activity of Cucurbita pepo ovifera var ovifera (Cucurbitaceae) on Onchocerca ochengi Adult Worms." British Journal of Pharmaceutical Research 17, no. 2 (2017): 1–8. http://dx.doi.org/10.9734/bjpr/2017/33381.

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Nfon, Charles K., Benjamin L. Makepeace, Leo M. Njongmeta, Vincent N. Tanya, Odile Bain, and Alexander J. Trees. "Eosinophils contribute to killing of adult Onchocerca ochengi within onchocercomata following elimination of Wolbachia." Microbes and Infection 8, no. 12-13 (2006): 2698–705. http://dx.doi.org/10.1016/j.micinf.2006.07.017.

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Boussinesq, Michel, Peter Enyong, Patrick Chounna-Ndongmo, et al. "Effects of an injectable long-acting formulation of ivermectin on Onchocerca ochengi in zebu cattle." Parasite 27 (2020): 36. http://dx.doi.org/10.1051/parasite/2020036.

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The availability of a safe macrofilaricidal drug would help to accelerate onchocerciasis elimination. A trial was conducted in Cameroon to evaluate the effects of a subcutaneous injectable long-acting formulation of ivermectin (LAFI) on the microfilariae (mf) and adult stages of Onchocerca ochengi. Ten zebu cattle naturally infected with the parasite were injected subcutaneously with either 500 mg (group A, N = 4), or 1000 mg long-acting ivermectin (group B, N = 4) or the vehicle (group C, N = 2). Skin samples were collected from each animal before, and 6, 12, and 24 months after treatment to measure microfilarial densities (MFDs). Nodules excised before, and 6 and 12 months after treatment were examined histologically to assess the adult worms’ viability and reproductive status. Blood samples were collected at pre-determined time-points to obtain pharmacokinetic data. Before treatment, the average O. ochengi MFDs were similar in the three groups. Six months after treatment, all animals in groups A and B were free of skin mf, whereas those in group C still showed high MFDs (mean = 324.5 mf/g). Only one ivermectin-treated animal (belonging to group A) had skin mf 12 months after treatment (0.9 mf/g). At 24 months, another animal in group A showed skin mf (10.0 mf/g). The histologic examination of nodules at 6 and 12 months showed that LAFI was not macrofilaricidal but had a strong effect on embryogenesis. The new LAFI regimen might be an additional tool to accelerate the elimination of human onchocerciasis in specific settings.

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Ndjonka, D., E. D. Abladam, B. Djafsia, I. Ajonina-Ekoti, M. D. Achukwi, and E. Liebau. "Anthelmintic activity of phenolic acids from the axlewood tree Anogeissus leiocarpus on the filarial nematode Onchocerca ochengi and drug-resistant strains of the free-living nematode Caenorhabditis elegans." Journal of Helminthology 88, no. 4 (2013): 481–88. http://dx.doi.org/10.1017/s0022149x1300045x.

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AbstractThe effect of three phenols (ellagic, gentisic and gallic acids) from the axlewood tree Anogeissus leiocarpus on Onchocerca ochengi and drug-resistant strains of Caenorhabditis elegans, a model organism for research on nematode parasites, is investigated. Worms were incubated in different concentrations of phenols and their survival was monitored after 48 h. Among the three acids, ellagic acid strongly affected the survival of O. ochengi microfilariae, O. ochengi adults, a wild-type C. elegans and anthelmintic-resistant strains of C. elegans, namely albendazole (CB3474), levamisole (CB211, ZZ16) and ivermectin (VC722, DA1316), with LC50 values ranging from 0.03 mm to 0.96 mm. These results indicate that the binding of ellagic acid in the worm differs from that of resistant strains of C. elegans. The efficacy of both gallic and gentisic acids was not significantly changed in resistant strains of C. elegans treated with levamisole (ZZ16, LC50= 9.98 mm, with gallic acid), albendazole (CB3474, LC50= 7.81 mm, with gentisic acid) and ivermectin (DA1316, LC50= 10.62 mm, with gentisic acid). The efficacy of these three pure compounds is in accordance with the use of A. leiocarpus from its locality of origin. The in vivo toxicity data reveal that the thresholds are up to 200 times higher than the determined LC50 values. Thus, ellagic acid could be a potential option for the treatment of nematode infections, even in cases of drug resistance towards established anthelmintic drugs.

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Bissan, Y., H. F. Ake, I. Toe, and J.-M. Hougard. "Impact of onchocerciasis control on the transmission of Onchocerca volvulus, onchocerca ochengi and other Oncherca species by Simulium sirbanum in West Africa." Parasitology International 47 (August 1998): 108. http://dx.doi.org/10.1016/s1383-5769(98)80225-0.

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Menga, Honoré, Dieudonné Ndjonka, and Remy Mimpfoundi. "Anthelmintic Activity, Acute Toxicity of Anacardium occidentale L. (Anacardiaceae) on Onchocerca ochengi and Caenorhabditis elegans." Asian Journal of Medicine and Health 5, no. 3 (2017): 1–12. http://dx.doi.org/10.9734/ajmah/2017/34454.

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Hagen, Hans‐E, Sabine L. Kläger, and Gwyn T. Williams. "Is apoptosis involved in mechanisms to eliminate Onchocerca ochengi during Simulium damnosum s.l. immune response?" Tropical Medicine & International Health 3, no. 12 (1998): 945–50. http://dx.doi.org/10.1046/j.1365-3156.1998.00331.x.

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deC Bronsvoort, Barend M., Benjamin L. Makepeace, Alfons Renz, et al. "UMF-078: A modified flubendazole with potent macrofilaricidal activity against Onchocerca ochengi in African cattle." Parasites & Vectors 1, no. 1 (2008): 18. http://dx.doi.org/10.1186/1756-3305-1-18.

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NFON, CHARLES K., VINCENT N. TANYA, ALEXANDER J. TREES, BENJAMIN L. MAKEPEACE, and LEO M. NJONGMETA. "LACK OF RESISTANCE AFTER RE-EXPOSURE OF CATTLE CURED OF ONCHOCERCA OCHENGI INFECTION WITH OXYTETRACYCLINE." American Journal of Tropical Medicine and Hygiene 76, no. 1 (2007): 67–72. http://dx.doi.org/10.4269/ajtmh.2007.76.67.

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Denke, A. M. "A comparison between the lengths of microfilariae of Onchocerca ochengi and O. volvulus in Mali." Transactions of the Royal Society of Tropical Medicine and Hygiene 79, no. 5 (1985): 734–35. http://dx.doi.org/10.1016/0035-9203(85)90209-3.

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Hildebrandt, Julia C., Albert Eisenbarth, Alfons Renz, and Adrian Streit. "Single worm genotyping demonstrates that Onchocerca ochengi females simultaneously produce progeny sired by different males." Parasitology Research 111, no. 5 (2012): 2217–21. http://dx.doi.org/10.1007/s00436-012-2983-x.

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