The katha is as follows:
First chant: Ji Jay Ru Ni, Gan Ha Nae Ha
Then recite Namo Tassa Pakawatoh Arahatoh Sammasamputtasa – 3 times.
Then recite: Samasat Phutto – 9 times.
Finally meditate and ask for the purging of the disease, poison, or malaise from your body. You may also wish for other things.