Here is information regarding Malaria in Namibia, but your outfitter should offer advice
https://www.cdc.gov/malaria/travelers/country_table/n.html
Randy is correct re: doxycycline. Be aware that there is a risk of a photo-allergic rash with lots of sun exposure.
https://www.cdc.gov/malaria/travelers/drugs.html
Also ask the outfitter if Yellow Fever vaccination is required

Some more nasties to avoid frown You REALLY don't want Leishmaniasis
https://wwwnc.cdc.gov/travel/destinations/traveler/none/namibia