Although the idea may sound ridiculous if you have never experienced it with your pet, dogs might have green stool. This can be a sign of a serious ailment, and if you notice an unusual green colour, or an unusually foul odour from your dog's stool, you should watch for other symptoms that signal a threat to the dog's health. Fever, vomiting, coughing and general malaise are some additional symptoms to watch for. Noting them can help your veterinarian make a diagnosis.
One common cause of green diarrhoea is a protozoan parasite called giardia. It lives in open groundwater, such as creeks, ponds and puddles. Giardia forms a hard shell-like cyst around itself and it lives in a dog's intestines for a long time. Once a dog has giardia, it is a carrier for life. Whether the animal exhibits symptoms (known as a flare-up) or not, it still has the parasites in its body.
If your dog's stool is bright green or neon green, the dog may have eaten rodent poison, or a rodent that had eaten the poison. Consult your veterinarian immediately.
Giardia is common in rural areas where there are many mammals sharing space. White tail deer are carriers, as are coyotes, wolves, rabbits, raccoons and any mammals that share a groundwater source. Dogs that play in infected water or drink it are likely to become infected. The dog can pick up the parasite by simply walking across an area where the parasite has been transferred. Then when the dog licks its feet, it will become infected. A healthy dog with a good immune system may keep symptoms in check for a long time. The diarrhoea may develop quickly if the dog's health is compromised by another illness or it may flare-up on its own.
The consistency of diarrhoea from giardia is often like pea soup. A flare-up is usually accompanied by abdominal pain, tenderness and gas, and will often progress to blood and mucous in the stool. A single fecal sample may not show any cysts, and samples need to be taken for two to three days to get an accurate check.
The medication given for giardia is metronidazole. It kills down the population during a flare-up, and it seems to boost the dog's immune system. Nothing gets rid of the parasite completely.
Transfer to Humans
Giardia can infect humans, with the risk being higher in developing countries. People get it from touching surfaces that have been in contact with faeces of an infected animal, from ingesting groundwater that has been contaminated, or by eating uncooked food that has touched infected surfaces.
Recreational water is a common cause in the United States. Humans are also treated with metronidazole.
Cleanliness is the key to preventing giardia infection. Keep your dog away from areas that are prone to be infected and from dogs that are known carriers. Wash your hands often with warm soap and water to prevent ingesting the parasite yourself and from spreading it to other people or pets.
Pick up after your dog, wherever it goes. Designate one area of your yard for doggy potty. Bathe your dog's hindquarters, especially after every episode of diarrhoea.