Camallanus worms are a real bear to treat in small fish like bettas. I've lost at least 4 fish out of 5 cases. Might even be 5/6, I can't remember now.
In some cases, treating with levamisole kills the worms but if the fish is not eating, then the dead worms stay in the stomach and cause a severe secondary bacterial infection.
To help, add 3 tsps of epsom salt per gallon and do everything you can to encourage your fish to eat. He cannot expell the dead worms if he isn't passing waste.
In regards to the medication affecting eggs . . . I honestly don't know but it won't matter if they can't get rid of the worms. :(
Should you succeed in ridding them of the worms, treat again in three weeks time. The reason for this followup treatment is because levamisole is only effective on adult worms, not on eggs or larva. So any eggs or larva in the tank and fish's system have time to become adults that the levamisole can kill.
Last edited by Sakura8; 04-12-2013 at 12:32 AM.