Malaria risks on Koh Chang Island?

[Manicek]

Hi all,

I would like to visit Koh Chang island during September 2005. In Lonely Planet guide I found out that Trat province is considered as malaria risk area but other information sources noted that this disease is appearing only on adjacent smaller islands but Koh Chang should be perhaps malaria free place.(Due to official killing of anopheles mosquitos executed by state organizations at decade 1990 -1999). Please let me know which of above mentioned information is correct, whether I must use antimalarical tabs like Lariam or generally whether I must behave more cautiously than for example when I would visit such areas like Phuket.

Thanks for your answers.

PS: Are safe (i.e. without malaria) such islands as Koh Phangan and Koh Samui?