Andre Norton 
Voodoo Planet 

Voodoo Planet is the sequel to Plague Ship, featuring the Free Trader ship, the “Solar Queen.” Plying their trade among the stars, Free Traders visit planets–known and unknown–in search of profit. Captain Gaelic and the ship’s crew are invited to help unravel the secret of a witch doctor’s growing power. With mysterious, possibly supernatural deaths at the hands of otherworldly creatures, disappearing equipment, and a witch doctor’s “magic”, it may be more than the crew of the Solar Queen can handle!