OK, come on you know it's happened before. If you own both a dog and a cat you know you've probably on more than one occasion noticed your little dachshund going over to the litter box and checking it out like it's a box of chocolates and picking out the right piece to eat. And to make matters worse then he wants to come over and give you a kiss. Yuck! This is probably extremely common in puppies but older dogs have been known to do this gross thing as well. You can however; stop this disgusting behavior before it gets out of control.
You might want to consider changing your dogs eating habits by switching from feeding him once a day to feeding him twice a day instead and then also make sure that he gets plenty of exercise so take him out for a walk on a daily basis. A lot of professionals think one of the reasons a dog will eat the cats poop is because they are bored. Honestly though, you'd think they'd find better things to do than eat poop if they're bored!
You should also make sure that you either keep the cat litter box extremely clean at all times, or go over and spray the poop with some sort of bitter spray like cayenne pepper spray or bitter apple spray to discourage him from using the litter box like his own personal box of chocolates. You could also try putting the box in a place that is hard for him to get at.
You can also go out and a solution that you can ask for at your pet store that you put in with your cat's food that they will ingest and it will make the poop less appealing for the dog when he goes to eat it. It's suppose to give off a really bitter taste and dogs hate anything that is bitter tasting.
You should also keep a close eye on him and whenever he gets near the cat box you should use the command “Leave it alone!” and then give him something else like a toy to distract him from thinking about it. Make sure that you praise him of course when he obeys your command. And even as gross as it is, never show him how much it upsets you and don't get angry or excited about it. This only reinforces the behavior because your dog takes the excitement as being something good.
Remember, not only is this a gross behavior but think about it, with all of the toxins that can be found in poop, there is no way that this is a healthy behavior that your dog should be involved with. So if nothing seems to work, it's important that you find something that does and that may mean that you will have to take him to an obedience class or get a dog trainer to come out and help you fix this situation.