Experienced and professional animal trainer provide their insights in answering this question :
A. It could just be a behavioural play thing. But I would ensure that flea and worm treatments are up to date as they can cause itching around the tail end.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

Dogs chase their tails for many reasons. This includes: boredom, excitement, dealing with fleas, expelling some energy (especially in puppies), or something serious like an injury. If you think the latter is the case, make sure to contact your vet.
Tail chasing is an invitation for you to take notice and play with him. Unfortunately, dogs that crave attention respond to both positive and negative attention. Your attention-seeking dog may be satisfied even if you reprimand him.
Just like people, dogs can develop compulsive habits that are hard for them to control. A dog experiencing anxiety may chase and bite their tail in the same way as a person bites their nails. Over time the habit may get worse and happen more often.
In dogs, compulsive behaviors include acral lick dermatitis, flank sucking, pacing, circling, incessant or rhythmic barking, fly snapping or chasing unseen objects, light or shadow chasing, freezing and staring, polydipsia (excessive drinking), sucking, licking surfaces, chewing on objects (or owners), tonguing or …
Many dogs will simply grow out of this behavior, but others will need training to teach them how to stop chasing their tails. Not only can it be bad for your pup, but with all that spinning around, something is sure to get broken. Add to this that obsessive tail chasing can lead to other types of OCD behavior.
Coughing, diarrhea, vomiting and lethargy are the general signs the dog has worms. Other symptoms depend on the type of worm.
Examples of listed compulsive disorders in dogs include shadow chasing, light chasing, spinning, spinning/tail chasing, acral lick dermatitis (ALD), self-mutilation, fly biting, pica, fence running, flank sucking, checking hind end, and excessive licking of objects (12,13).
Common signs of anxiety in dogs include:

Barking or howling when owner isn`t home. Panting and pacing (even when it`s not hot) Shivering. Running away and/or cowering in the corner of a house.

Treatments. Treatment for tail chasing is usually a combination of drug and behavioural therapy that is suited to the cause of tail chasing for the specific animal. Fluoxetine, an SSRI used to treat compulsive disorders, is a common drug used to treat CD and tail chasing.
Happy tail syndrome is more often seen in large, short-haired dogs with muscular tails like Labrador Retrievers, Pit Bulls, Great Danes, Greyhounds, Dobermans, and similar breeds.
The symptoms of depression will vary depending on the individual dog and the severity of the problem. There are some key things to look out for, however, including changes in body language during their interactions with people and other pets, decreased appetite, and lethargic behavior.
Conditions such as prostate trouble, anal gland inflammation and osteoarthritis may cause your pet to hold his tail down to counteract pain and discomfort. Any dog can be affected by a limp tail, although dogs with longer tails tend to be affected more often.
This can be a serious injury as it can affect not only the nerves that control tail movement, but also those that control elimination, which can lead to incontinence. It should go without saying, but never pull a dog`s tail, or allow a child or other person to pull their tail.
Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As heartworm disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen.
Collect a Sample of Your Dog`s Stool

Your veterinarian may ask you to bring a fresh sample of your dog`s stool from home, especially if you are seeing worms in their feces or notice dried, rice-like segments in their fur. You only need a small amount of feces; usually about a teaspoon-size sample will do.

Symptoms of autism in dogs

Avoiding new people or things and minimal interaction with other canines are other signs of canine autism. Some puppies have a blank stare when they look at different things. This could also suggest canine autism. Obsessive Compulsive Disorder (OCD) is a characteristic of autism.

Inappropriate Reactions to Stimuli

As with autistic children, dogs with autism feel everything differently too, and can be hyper-sensitive to any kind of stimuli, such as a gentle pet on the head, which can cause your dog to respond with a reaction of pain, aggression or fear.

Canine cognitive dysfunction (CCD) is a behavioral syndrome that affects old dogs. Dogs with CCD show behavioral alterations such as disorientation, altered interactions with owners, other pets and the environment, sleep-wake cycle disturbance, house-soiling and changes in activity [14].
Physical Contact. There is probably nothing more soothing to an anxious dog than its owner`s touch. Try to identify the signs of anxiety in your dog and nip them in the bud as early as possible by picking them up, cuddling on the couch, or giving them a good long petting session.
Dogs have several reasons for staring at their owners, like to communicate with and understand us. Some dogs stare to manipulate owners, as in with begging for food or asking to be let outside. Training and dog sports are good ways to turn focused staring behavior into a positive experience.
to be busy doing a lot of things but achieving very little. Thesaurus: synonyms, antonyms, and examples.
It`s not uncommon to see dogs chasing their tails. You may even see a dog doing it over and over again in a circle. Sometimes when dogs are chasing their tails, they`re simply having fun. They`re learning about their bodies and seeing what they can do.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. How should I interpret my cat’s tail movements?
ANSWER : A. Our feline friends express themselves in many different ways, including through the use of their tails. Most pet owners pay close attention to a happy or excited dog, but they are sometimes less attentive to the posture and movement of their cat. Here are some of the most common cat tail behaviors, and the underlying emotion behind each action:

A flicking tail: Many anxious, nervous or stressed cats will hold their tail in a low position and flick it quickly back and forth. This is often referred to as angry tail, and a pet owner or veterinarian should be on guard for any possible aggressive or defensive activity. If a cat is moving their tail slowly, and not exhibiting the flicking motion, then this cat is at a much calmer state.

Vertical position: Most of the time when a cat is holding their tail in a straight, vertical position this is indicating curiosity and a playful mood. A cat chasing after a laser pointer or playing toys will often have their tails in a vertical position showing their enjoyment. This position also helps with balanced movements. In contrast, if the tail is in the vertical position and the cat’s back is arched with pinned back ears then this could demonstrate a feeling of being threatened and thus result in defensive or aggressive behaviors.

The Tucked Tail: Similar to a dog, a tucked tail often indicates submission or fear. Your cat is conveying upset feelings and should most likely be left alone. This tucked tail appearance can also make a cat look smaller and less threatening to an aggressive cat.

The Tail Twine: Cats will often hook their tail around another cat’s tail, owner’s legs or other objects to show a friendly and affectionate nature. They are also trying to indicate whether they want to receive affection from their owners, be fed or have playtime.

The next time you are home with your feline companion take note on how they express themselves through their tail movements, their ears, body posture and vocalization. You can start to better understand their needs and wants, in addition to what makes them uncomfortable or happy. Cats will surprise you with their array of emotions and varied expressions they can express.

Q. I have a 13 1/2 year old Shih Tzu. How old is he in dog years?
ANSWER : A. It’s used to be that dog years were 7 years to every 1. Now it normally around 5 years to every year as long as your dog is healthy and kept up with vaccines. So he’s about 68ish in dog years.

Read Full Q/A … : Shih Tzu Age

Q. Why is my one year old chiwawah constantly trying to catch his tail?
ANSWER : A. It could just be a behavioural play thing. But I would ensure that flea and worm treatments are up to date as they can cause itching around the tail end.

Q. Does an indoor cat need to be vaccinated every year?
ANSWER : A. In practice, I recommend a feline combo vaccine every year, but will generally start administering every 3 years once they have had their kitten vaccines and 2 additional yearly vaccines. Rabies, is required yearly by law, and if kept up to date can be good for up to three years also. Based on the age of your cat I would give a yearly feline combo and rabies, and then boost the combo again next year.

Q. My dog won’t stop eating cat litter, old diapers and she even tried eating glass
ANSWER : A. Don’t let your dog have access to cat liter and old diapers. Have a trash with a lid for the diapers and put a hood on the cat box or put it in a room the dog can’t get to. If your dog is trying to eat other things maybe he’s looking for more nutrients in his diet that his food isn’t giving him. Look for a higher quality high protien food at the pet store. Have someone help you at the pet store pick out a food or ask your regular vet their food recommendation. One with the first ingredent as a meat like deboned chicken. If your dogs foods main ingredient (first one listed) is a corn or chicken by product that is bad. You will need to slowly transition the dogs food over by mixing the foods and slowly adding more new and less old to the food for at least a week.

Q. I rescued my Lily at 7months and she was eating Purina puppy chow. I transitioned her to Blue Wilderness and since then she has had GI issues?
ANSWER : A. Stomach upset is a very common problem in our pets and occurs for may different reasons. As a general rule when you switch from one dog food to another it is always a good idea to make a slow transition from one food to the next. Most people would agree that you should mix a small amount of the new food in with the old food and gradually decrease the old food amount and slowly increase the new food amount until you are feeding mostly new food. You may also want to try going back to your old Purina diet until the GI issues quiet down and then try a slower transition to the new diet.

Q. We have a 3 yr old Weiner dog, she is having pus in her eyes, I took her to the vet he gave me derma vet ointment, used it as the doctor prescribed
ANSWER : A. If the pus really isn’t all that bad, and it’s just some discharge, your pup may benefit from a diet change. It could be that the food you’re feeding just isn’t right for your dog, and that’s okay! Dogs grow and change over time, and now that your dog is fully matured, a diet change may be in order. Try something like Taste of the Wild, maybe a grain free dog food, Orijen, or Ziwipeak. These are all really great food options.

If the pus is really bad, and continues to get worse, see your vet again and let them know what’s going on. Maybe you could try a diet change, and then see if there are any improvements.

Remember, you should always gradually change a dogs diet. By gradually, I mean you put a tiny bit of new kibble in with a bowl of the old kibble. Reduce the old kibble by just a few bits of kibble. Throughout the course of at least two weeks (or as long as you want depending on whether or not you want to finish off the old food) you slowly add more of the new kibble while removing some of the old kibble. This makes the process gradual, and won’t cause any tummy-upset in your dog.

Q. My cat is one year old. He has diarrhea, not eating last for one day. This problem is too with my other 2 cats and one is died.
ANSWER : A. His not eating is the most concerning for me. They cannot go more than a few days without eating or they risk liver damage. Your cat needs to be seen by your vet for an exam and bloodwork to determine the cause for your cat’s loss of appetite. Based on the findings, your vet will be able to give you a clearer picture of what is going on with your cat and be able to offer you treatment options.

Try enticing your pet to eat with beef or chicken baby food that does not contain onion or garlic powder. Onion and garlic causes anemia. Warm it in the microwave for a few seconds. Stir it with your finger first to make sure there are no hot spots and that it isn’t too hot. This makes it more aromatic and appealing to your pet. Wetting dry food or mixing wet food with low sodium chicken broth, also warmed, might entice your pet to eat. Some cats like to be petted while they eat, some want to be left alone. You’ll know your cat’s habits and be able to act accordingly.