That could work, though we're still tracking bites on the DC. How abot this?
Venom (Ex): A tatalla's bite injects a toxin that causes weakness and illness, and eventually, death. A victim of a tatalla's bite must succeed on a DC X Fortitude save or become sickened for 1d4 minutes. A victim who is already sickened (such as from a previous bite) instead suffers 1d6 points of Strength damage and must succeed on a DC X Fortitude save or become nauseated for 1d4 rounds. After the nausea passes, it must then succeed on another DC X Fortitude save or become sickened for 1d3 days. A victim who is already nauseated (such as from previous bites) suffers 1d6 points of Constitution damage and must succeed on a DC X Fortitude save or become sickend for an additional 1d3 days. The save DCs are Constitution-based. Recall that sickened creatures take a -2 penalty to saving throws; nauseated creatures take a -4 circumstance penalty to saves against tatalla venom. A delay poison or neutralize poison spell removes the effect from the sickened creature. Creatures with immunity to poison are unaffected, and creatures resistant to poison receive their normal bonus on their saving throws.
Some thoughts: not sure if the Con damage is strong enough, and I'd consider swapping the Str damage for Dex like in the original.