**Acknowledgements**

We acknowledge the support received from the National Research Foundation of South Africa and the *Sandisa Imbewu* Programme of Rhodes University. CI Nkanga and AM Bapolisi are grateful to the NGO *Förderverein Uni Kinshasa e. V.-BEBUC/ Else-KroenerFresenius Stiftung* and *Holger-Poehlmann* for the advice.
