Données sur le cycle d’Onchocerca ochengi chez Simulium damnosum s.l. au Togo

Abstract

O bservations on the life cycle o f O. ochengi in Simulium damnosum s.l. in Togo.In the focus of human onchocerciasis in Togo (Mono River), the authors collected 250 Simulium damnosum s.l. engorged on a cow parasitized by O. dukei, O. ochengi, O. gutturosa and O. armillata. On 39 Simulium damnosum dissected 24 h after the blood meal, 5 had ingested O. gutturosa, 1 O. armillata, 18 O. dukei and 6 O. ochengi; only for O. ochengi, the microfilariae have reached the hemocoel (3 S. damnosum on 6). From 48 h to 5 days, 6 on 132 S. damnosum contained developing larvae (2 Simulium with young first stage larvae at 48th hour ; 1 with young first stage at 3rd day ;1 with first molting at 4th day; 2 with second molting larvae at 5th day). From 6th to 9th days, 2 Simulium on 89 have infective stages. All these larvae cannot be distinguished from those of O. volvulus.A good presumption does exist that O. ochengi can develop in S. damnosum: crossing of the stomach wall only by these microfilariae, presence of larvae of which the development-stage corres ponds to the moment of the blood-meal, observation of the second molting five days later.It is difficult to ascertain that the three infective stages observed from 6th to 9th day pertain to O. ochengi, because the presence of a natural (human or animal) infestation; but it appears quite impossible that larvae which can develop to the second molting cannot be transformed in an infec tive stage.

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

“…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. The animal filariae detected in these vectors are indicators of a high degree of zoophily of the onchocerciasis vectors.…”

Electron microscope observations on Onchocerca ochengi and O. fasciata (Nematoda: Filarioidea)

“…A redescription by Bain et al (1974Bain et al ( , 1976 of the adult worms and the micro®lariae from cattle in Togo and Africa followed, and the synonymous position with O. dermata was established. Several investigators examined the development of O. ochengi in the vector (Denke and Bain 1978;Omar et al 1979;McCall and Trees 1989;Wahl and Ekale 1991). Comparisons between the micro®lariae of O. ochengi and O. volvulus were carried out by Denke (1985) and McCall et al (1992).…”

“…Comparisons between the micro®lariae of O. ochengi and O. volvulus were carried out by Denke (1985) and McCall et al (1992). Several authors (Bwangamoi 1969b;Trees et al 1992;Vuong et al 1994) described the disease caused by O. ochengi, the infective stage of which is transmitted by Simulium damnosum (Denke and Bain 1978;Omar et al 1979;Wahl and Ekale 1991;Wahl and Renz 1991).…”

Is apoptosis involved in mechanisms to eliminate Onchocerca ochengi during Simulium damnosum s.l. immune response?

“…This parasite is naturally transmitted by S. damnosum s.l. (Denke & Bain 1978) and occurs throughout the cattle-breeding areas of Africa. Some of the compounds of the innate immune system such as prophenoloxidase (Hagen et al 1994a;1997a), serine proteases and lectins, are important in controlling the survival and development of parasites (Hagen et al 1997b).…”