Coprophagia (the high falutin' term for eating poo) can have several different causes.
As you address this it's first key to determine if there is a medical cause, or if the coprophagia is simply behavioral.
It's generally easier, albeit more expensive, to rule out medical issues first. Possible medical causes are:
Parasites
Diets deficient in nutrients and calories
Malabsorption syndromes
Diabetes,
Cushing’s,
Thyroid disease. There are other conditions that might cause an increase in appetite as well.
Drugs such as steroids. Steroids can cause an increase in appetite, sometimes to the point of polyphagia.
With the exception of the first two, the other conditions listed should have other symptoms. Your vet could rule many potential causes out with a simple chat,. Or a full blood panel might be suggested before concentrating on any other likely suspects.
To look for parasites, you'll likely need a three day stool sample, so you might gather that ahead of an appointment. (Ask when you make the appointment.)
Also, as you discuss coprophagia with your vet, ask if your dog's worming routine is sufficient in light of the poo eating.
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If there is no reason to suspect a medical cause, then the harder work of behavioral training starts. This could be temporary, as a renewed sense of smell as you mention. Or it could be something more deep seated. Coprophagia can be an excitement thing, a response to stress or anxiety, a territorial thing - or just the simply fact that dogs like the taste of poo.
In all behavioral cases, the first thing to do is work (and work and work) on your Leave! command. This is a good exercise anyway, as dogs should not eat off the ground at any time. There have beeen too many poisoning cases, accidental and deliberate, to allow a dog to eat anything on the ground, or indeed that is not given to him by the owner.
If you do 'Giftköder' training, anti-poo eating training is the same thing.
Start by laying a trail of low value contraband, and have a higher value reward to hand. With your dog on lead, follow the trail, interrupting the dog every time he shows even the slightest bit of interest in the contraband. Reward compliance by giving the higher value treat. The dog starts to see contraband as a trigger for a higher reward, rather than a reward in itself.
Don't use poo to start, as that is too high value. Train with low value, such as boring kibble, simply to get your dog used to ignoring whatever is on the ground.
Do this a few thousand times, upping the value of the contraband once your dog is consistently ignoring the lower value. The higher value contraband should, in your case, eventually include poo. (Yes, you will need to collect a supply.)
Then do this a few thousand times more off lead walking to heel.
Then do this a few thousand times more off lead at a distance from you.
The idea is to train the dog to ignore everything on the ground. Food only comes from you, nowhere else.
And of course, always have that high value reward with you on your regular non-training walks. Every time your dog encounters and ignores poo 'in the real world' be sure to reward.
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Anti-contraband training takes time, obviously. So in the meantime, management is the best way forward.
It seems your dog eats both his own poo (and anything else he will find - which from my own experience of coprophagia might indicate behavior rather than medical, but that's for the vet to decide) so the first thing to do is to ensure that he doesn't have a chance to eat his own poo. Which means in your garden or on walks he does not go off lead until he has had a poo and you've picked it up.
I have trained Heffalump - my poo-eater - that he must sit after having a poo. It's always easier to train a dog to do an acceptable behavior than to train out an unacceptable one, so this is mine. After defecating, he was given a Sit! command - a few thousand iterations later this is now his routine. After defecating he automatically sits and waits to be released. The idea is that he is unlikely to turn around and eat his fresh poo because he is sitting, giving me a chance to pick up before he gets to it.
H2 only eats his own poo (it's a malabsorption problem) so I have a relatively controlled situation. If your dog is eating poo from other dogs or species, that's harder to deal with. The only thing you can really do is to keep an eagle eye out, work on that Leave! command, and only let him off lead in places where you have first scouted for poo lying around.
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So while coprophagia is often more disgusting than dangerous, one concern with eating poo is the potential for nasty stuff in it. It's a habit that needs to be trained out.
Parasites can linger in poo, eating it could infect the dog. When H2 had a nasty bout of Giardia I had to be extra vigilant, as he could keep re-infecting himself by eating the larvae in his poo. And certainly I had to be careful that the other dogs did not come near his poo.
Another example: I've had to be very careful around horse poo with my two MDR1 -/- dogs, as horses are regulary treated with Ivermectin. The amount shed in horse poo could have killed my dogs . This is only true if your dog is MDR1 -/-, though - not really a worry for unaffected dogs. A limited example, but because you can't know what's in any other critter's poo your dog needs to be trained to leave it.
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You might have read about adding supplements to your dog's food that would discourage him from poo eating. This, of course, would only be effective if your dog only ate his own poo. But it seems that your dog is eating indiscriminately, so supplements are unlikely to be of any help.
I'd lean towards training, training, training. After, of course, a quick chat with the vet.
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ETA:
Oh, and don't forget a good round of teeth brushing after a coprophagia incident. Why is it that our dogs especially love to kiss us smelling of poo-breath?
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I'm so glad to hear that the op was successful. All the best to you and your pup.
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