Malaria in Zanzibar

Is malaria a threat in Zanaibar? Is Malarone available in Arusha? Stone City?

Yes, there is serious risk of malaria in Zanzibar.

Malarone is not licensed for sale in Tanzania. I have seen one report of a traveler finding it on the black market.

What Nutrax said.
Doxy and Mefloquine are both available otc, though.

malaria is a threat anywhere in TAnzania, and it is recommended to purchase the antimalarial meds in the USA (assuming that's where you live). I would take a look at the CDC website on TAnzania

http://wwwn.cdc.gov/travel/destinationTanzania.aspx