Onchocerca ochengi: Mimic, model or modulator of O. volvulus?

Trees, A. J.

doi:10.1016/0169-4758(92)90068-d

Cited by 46 publications

(21 citation statements)

References 21 publications

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“…host-parasite relationship in an outbred population. As such, it can provide an authentic paradigm for O. volvulus (15). In the host population, there is a minority subset of individuals genuinely resistant to infection.…”

Section: Discussionmentioning

confidence: 99%

“…Pregnant Gudali cows were recruited from the area around Ngaoundéré, and their calves were reared in fly-proof accommodations from birth. The calves were assigned to two groups, vaccinated (n ϭ 9) and control (n ϭ 13), which were matched for age at the start of immunization [median (range) ϭ 12 (7)(8)(9)(10)(11)(12)(13)(14) weeks for the vaccinated group and 11 (7)(8)(9)(10)(11)(12)(13)(14)(15)(16) weeks for the controls] and O. ochengi infection status of the dams (67% Mfpositive for the vaccinated group and 77% for the controls).…”

Section: Vaccine Preparation and Protocol (Expsmentioning

confidence: 99%

“…O. ochengi is an excellent analogue of O. volvulus. It is extremely closely related to O. volvulus (14), is transmitted by the same black fly vector as O. volvulus, and because of its intradermal nodular location, is amenable to quantitative estimation of protection in the face of challenge (15). In addition, in areas endemic for O. ochengi, PI cattle occur as a subset within herds of infected animals (16,17); and for experimental purposes, it is possible to generate large numbers of infective parasites [third-stage larvae (L 3 )] in black flies obtained from local breeding sites.…”

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confidence: 99%

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In a bovine model of onchocerciasis, protective immunity exists naturally, is absent in drug-cured hosts, and is induced by vaccination

Tchakouté

Graham

Jensen

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Onchocerciasis (river blindness) is a major parasitic disease of humans in sub-Saharan Africa caused by the microfilarial stage of the nematode Onchocerca volvulus. Using Onchocerca ochengi, a closely related species which infects cattle and is transmitted by the same black fly vector (Simulium damnosum sensu lato) as O. volvulus, we have conducted longitudinal studies after either natural field exposure or experimental infection to determine whether, and under what circumstances, protective immunity exists in onchocerciasis. On the basis of the adult worm burdens (nodules) observed, we determined that cattle reared in endemic areas without detectable parasites (putatively immune) were significantly less susceptible to heavy field challenge than agematched, naïve controls (P ‫؍‬ 0.002), whereas patently infected cattle, cured of infection by adulticide treatment with melarsomine, were fully susceptible. Cattle immunized with irradiated third-stage larvae were significantly protected against experimental challenge (100% reduction in median nodule load, P ‫؍‬ 0.003), and vaccination also conferred resistance to severe and prolonged field challenge (64% reduction in median nodule load, P ‫؍‬ 0.053; and a significant reduction in microfilarial positivity rates and density, P < 0.05). These results constitute evidence of protective immunity in a naturally evolved host-Onchocerca sp. relationship and provide proof-of-principle for immunoprophylaxis under experimental and field conditions. filariasis ͉ irradiation ͉ larvae ͉ ochengi ͉ Onchocerca

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Section: Discussionmentioning

confidence: 99%

Section: Vaccine Preparation and Protocol (Expsmentioning

confidence: 99%

mentioning

confidence: 99%

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In a bovine model of onchocerciasis, protective immunity exists naturally, is absent in drug-cured hosts, and is induced by vaccination

Tchakouté

Graham

Jensen

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…In recent years animal filarial parasites infecting cattle in savanna areas of Africa have attracted research interest [1,16,18,[20][21][22]. This trend has been largely attributed to the demonstration that the bovine Onchocerca species, O. ochengi Bwangamoi, 1969 is so far the best animal model available for studies on drug screens against human onchocerciasis [16].…”

Section: Introductionmentioning

confidence: 99%

“…This trend has been largely attributed to the demonstration that the bovine Onchocerca species, O. ochengi Bwangamoi, 1969 is so far the best animal model available for studies on drug screens against human onchocerciasis [16]. O. ochengi has also been reported to be phylogenetically related to O. volvulus [2] and actually resembles O. volvulus in several aspects [20]. In the African savanna, Simulium damnosum Theobald sensu lato, which transmits O. volvulus is also known to naturally transmit other species of Onchocerca from animals [7,15] including O. ochengi from cattle [6,12,24] and O. ramachandrini [7,25] from the wart hog, Phacochoerus aethiopicus.…”

Section: Introductionmentioning

confidence: 99%

Onchocerca ochengitransmission dynamics and the correlation ofO. ochengimicrofilaria density in cattle with the transmission potential

2000

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-The intensity of natural transmission of Onchocerca ochengi and Onchocerca volvulusby anthropo-boophilic Simulium damnosum s.l. was studied longitudinally in two cattle watering sites of a cattle ranch within a predominantly cattle populated area of the Guinea savanna of Cameroon and related to cattle O. ochengi skin microfilaria abundance. During the 12 months study period, a total of 4 696 flies was individually dissected to examine the monthly transmission potential (MTP) of O. ochengi and O. volvulus. The estimated Simulium damnosum s.l. annual biting rates (ABR) on human baits were 47 529 flies at the bank of the Vina "du sud" river. The ABR at the lake, which was situated at about 2 km upland from the perennial river, was 8 579. The monthly parous rate was highly correlated with monthly biting rate. The annual transmission potentials (ATP) of O. ochengi were calculated to be 7 732 and 1 669 at the riverbank and the lake, respectively. Transmission occurred mainly in the dry season, peaking in the months of January to mid-March when dermal microfilaria density in the animals was also the highest. The O. ochengi microfilaria uptake by the fly vectors was host microfilaria density-dependent. The MTP of O. ochengi was positively correlated with dermal microfilaria density. The mean number of microfilariae per fly taken up during a blood meal was high during the dry season as was the mean number of infective larvae per fly but declined significantly with the onset of the early rains. A similar seasonality of transmission was also observed for O. volvulus that was concurrently transmitted by the same vector flies, but its ATP was comparatively much lower: 1 332 infective larvae per man per year at the riverbank and 107 around the lake. The population dynamics of cattle microfilariae therefore plays an important role in the regulation of O. ochengi transmission.transmission / Onchocerca ochengi / Onchocerca volvulus / microfilariae density / Simulium damnosum s.l. Vet. Res. 31 (2000) 611-621 611

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