[Threshold]

You need to be using the 0.3z version of pawno which can be found in http://sa-mp.com/download

If you read this: https://sampwiki.blast.hk/wiki/OnPlayerTakeDamage
you will notice that the 'bodypart' parameter should only be added once you are using the 0.3z server package. This will not work for 0.3x and earlier.