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

Observations on the life cycle of O. ochengi in Simulium damnosum s.l. in Togo

Laboratoire de Zoologie (Vers), associé au C.N.R.S., Muséum national d’Histoire naturelle, 43, rue Cuvier, F 75231 Paris Cedex 05, France.

Accepté : 3 Août 1978

Abstract

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 corresponds 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 infective stage.