It looks like one of mine witch come from the Mandara mountains, North-Cameroon, region of the Kirdi.
The handle is made of horn.
In the 2 exemples on my website, the blade is enlarge at his middle part.
http://lulef.free.fr/html/kirdi_2.html
More about Mandara:
http://www.mandaras.info/EthnicGroups.html
Luc
Another exemple with the same blade: