No, or they can be bloated. Wasting or bloating are the main symptoms (obviously as well as the white/translucent strings.)
To get rid of the parasites, do 100% daily water changes with around 3 tsps of aq salt. After 10 days, stop with the salt and keep going with the water changes. Crush up some garlic, soak her pellets in them, put them in the microwave for 30 seconds and feed them to her as you normally would... And get some Prazi-Pro- it really does help with getting rid of the parasites. Keep up the treatment until she starts looking better and there are no white/translucent strings.
Edit- And there are anti-parasitic foods as Malvolti mentioned... but I've tried all there are to be had, and my bettas do not like them at all. Garlic-soaked pellets would be the best option, IME/O.
Last edited by Betta Slave; 02-20-2011 at 08:01 PM.