Most puppies will develop a minor case of diarrhoea at some point, typically from stress or a change in diet. If the puppy's diarrhoea lasts more than a of couple days, the puppy will quickly become dehydrated and a visit to a veterinarian may be in order. The vet will request a stool sample and check for bacteria, a virus or parasites.
If parasites are the cause of the diarrhoea, the puppy will be given a worm treatment. Most vets worm puppies at about four weeks of age, and again every two weeks until they are three months old; subsequent annual treatments are recommended.
Tapeworms and roundworms are the most common parasites found in dogs. Fleas carry tapeworms, so if your puppy has fleas, there is a good chance it has tapeworms too. Puppies get roundworms from their mothers. If roundworms go untreated, your puppy may suffer a ruptured bowel.
After performing tests like a blood-chemical profile, a complete blood count, an electrolyte panel and a urinalysis, the vet may determine that your puppy's diarrhoea is being caused by an intestinal bacterial overgrowth. She may then prescribe antibiotics and advise you to feed your puppy a low-fat, highly digestible diet until the condition has resolved.
Your vet will try to determine the source of the diarrhoea, either the small or the large intestine, with a thorough examination of your puppy and with a series of tests. Treatments include fluid therapy if your pet is dehydrated and surgery if the puppy has an intestinal tumour or blockage. He will also instruct you to handle your puppy with caution, as many of the bacteria and parasites that can cause diarrhoea in dogs can also affect humans.
According to Pet MD, there are four basic reasons for diarrhoea: osmotic imbalances, oversecretion, intestinal exudation or motility disorders. If your puppy is mildly ill, it will be treated on an outpatient basis; if the diarrhoea is severe, your pet may be hospitalised and given fluid or electrolyte therapy. The most common medications that vets prescribe for acute diarrhoea are antisecretory drugs, intestinal protectants and dewormers.