Oh the people you meet in Louisiana swamps. While some people in Louisiana practice voodou/voodoo - whichever ones the right way to spell it - as mentioned very rarely do actual practitioners of any magic go around cursing people for no good reason. Most curses are the result of self infliction. This person could of said something of no meaning, and then went "I cursed you" for a laugh when she did nothing of the sort. However, the very notion of a Louisiana voodou priestess curse is so scary your brother could of then scared himself so much he conjured a lot of negative energy and cursed himself. Sounds silly what with him displaying symptoms like this, but most curses are psychosomatic.
If the woman did curse him, she must of had a reason, ask him to recall the days events leading up to the supposed curse, did he do anything to offend her? Big one, did he make fun of her beliefs? If he did, try to make amends with this woman if he can. If he can't, there a couple things he could try, but they key is to believe. Even if he claims curses aren't real, he believes in them, otherwise this would not of worked. Tell him to cleanse and protect himself and your home, daily for a week if needed though I doubt it, and believe it worked. You should feel lighter, safer, and/or calmer as a result. He should also visit a doctor as this could be unrelated to an actual curse but need professional and medical attention. Finally, if he received anything from the woman, place it in a box filled with sea salt and bury it off your property if possible. This should cleanse it and stop the curse since its more likely the object.
Just remember not everyone in Louisiana practice voodou and she could of been messing with him, and believe the curse isn't real and/or the cleansing worked and the curse will weaken. Belief is key to spell casting.