Is foul smelling breath symptom of psittacosis?

Breath. Halitosis. Many things can cause it, from teeth, gums, stomach, etc.
Not necesarily. If you already have a good oral hygiene routine, it could be dehydration make sure to drink plenty of water. Eating desserts at night before bed and not brushing your teeth can show up as bad breath in the morning. A whole list of medical conditions also cause bad breath, diabetes is the most common.