Also, what house plants do you have? Is it possible he munched on one or two or them? A ton of plants are toxic to cats and dogs. Some even just a bite or two on the leaves introduces enough toxins into the system to throw it out of whack.
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!