Strangles (equine distemper) is a contagious upper respiratory tract infection of horses and other equines caused by a gram-positive bacterium, "Streptococcus equi". As a result the lymph nodes swell, compressing the pharynx, larynx and trachea and can cause airway obstruction leading to death, hence the name Strangles. Strangles is enzootic in domesticated horses worldwide. The contagious nature of the infection has at times led to limitations on sporting events.

A horse with strangles will typically develop abscesses in the lymph nodes of the head and neck causing coughing fits and difficulty swallowing. Clinical signs include fever up to 106 °F and yellow coloured nasal discharge from both the nose and eyes.

Abscesses may form in other areas of the body, such as the abdomen, lungs and brain. This is considered a chronic form of strangles called "bastard strangles" and can have serious implications if the abscesses rupture. Horses develop this form of strangles when their immune systems are compromised or if the bacteria rapidly invades the body.

Strangles has a 8.1% mortality rate. Mortality is lower in cases without complications than it is in cases of bastard strangles. The disease is very contagious and morbidity is high. Precautions to limit the spread of the illness are necessary and those affected are normally isolated. An isolation period of 4–6 weeks is usually necessary to ensure that the disease is not still incubating before ending the quarantine.

External abscesses are the most common form of pigeon fever seen in horses. Abscesses develop on the body, usually in the pectoral region and along the ventral midline of the abdomen. However, abscesses can also develop on other areas of the body such as the prepuce, mammary gland, triceps, limbs and head. The fatality rate for this form infection is very low. The abscess is often drained once it has matured.

This is the least common form of pigeon fever seen in horses. It is characterized by severe limb swelling and cellulitis in one or both hind limbs and can lead to lameness, fever, lethargy and loss of appetite. Antimicrobial and anti-inflammatory treatments are required to prevent further complications such as limb edema, prolonged or recurrent infection, lameness, weakness and weight loss.

The prodromal symptoms are fever, headache, and myalgia, which can be severe, lasting as long as 24 hours. After 1–5 days, typically, these are followed by diarrhea (as many as 10 watery, frequently bloody, bowel movements per day) or dysentery, cramps, abdominal pain, and fever as high as 40 °C (104 °F). In most people, the illness lasts for 2–10 days. It is classified as invasive/inflammatory diarrhea, also described as bloody diarrhea or dysentery.

There are other diseases showing similar symptoms. For instance, abdominal pain and tenderness may be very localized, mimicking acute appendicitis. Furthermore, "Helicobacter pylori" is closely related to Campylobacter and causes peptic ulcer disease.

The period between infection and the first symptoms (incubation period) is typically 1–3 months in humans. Incubation periods as short as four days and longer than six years have been documented, depending on the location and severity of the contaminated wound and the amount of virus introduced. Initial signs and symptoms of rabies are often nonspecific such as fever and headache. As rabies progresses and causes inflammation of the brain and/or meninges, signs and symptoms can include slight or partial paralysis, anxiety, insomnia, confusion, agitation, abnormal behavior, paranoia, terror, and hallucinations, progressing to delirium, and coma. The person may also have hydrophobia.

Death usually occurs 2 to 10 days after first symptoms. Survival is rare once symptoms have presented, even with the administration of proper and intensive care. Jeanna Giese, who in 2004 was the first patient treated with the Milwaukee protocol, became the first person ever recorded to have survived rabies without receiving successful post-exposure prophylaxis. An intention-to-treat analysis has since found this protocol has a survival rate of about 8%.

Complications include toxic megacolon, dehydration and sepsis. Such complications generally occur in young children (< 1 year of age) and immunocompromised people. A chronic course of the disease is possible; this disease process is likely to develop without a distinct acute phase. Chronic campylobacteriosis features a long period of sub-febrile temperature and asthenia; eye damage, arthritis, endocarditis may develop if infection is untreated.

Occasional deaths occur in young, previously healthy individuals because of blood volume depletion (due to dehydration), and in persons who are elderly or immunocompromised.

Some individuals (1–2 in 100,000 cases) develop Guillain–Barré syndrome, in which the nerves that join the spinal cord and brain to the rest of the body are damaged, sometimes permanently. This occurs only with infection of "C. jejuni" and "C. upsaliensis".

Hydrophobia ("fear of water") is the historic name for rabies. It refers to a set of symptoms in the later stages of an infection in which the person has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench his or her thirst. Any mammal infected with the virus may demonstrate hydrophobia.

Saliva production is greatly increased, and attempts to drink, or even the intention or suggestion of drinking, may cause excruciatingly painful spasms of the muscles in the throat and larynx. This can be attributed to the fact that the virus multiplies and assimilates in the salivary glands of the infected animal for the purpose of further transmission through biting. The ability to transmit the virus would decrease significantly if the infected individual could swallow saliva and water.

Hydrophobia is commonly associated with furious rabies, which affects 80% of rabies-infected people. The remaining 20% may experience a paralytic form of rabies that is marked by muscle weakness, loss of sensation, and paralysis; this form of rabies does not usually cause fear of water.

Purpura haemorrhagica is a rare complication of equine strangles and is caused by bleeding from capillaries which results in red spots on the skin and mucous membranes together with oedema (swelling) of the limbs and the head. Purpura hemorrhagica is more common in younger animals.

The most common clinical sign is subcutaneous edema of the limbs and hemorrhages on mucous membranes. Other clinical signs include depression, anorexia, fever, elevated heart and respiratory rate, reluctance to move, drainage from lymph nodes, exudation of serum from the skin, colic, epistaxis and weight loss. Rarely, horses may also develop disseminated intravascular coagulation (DIC), leading to infarction of various organs, or chronic myositis and muscle atrophy.

Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.

While coccidia can infect a wide variety of animals, including humans, birds, and livestock, they are usually species-specific. One well-known exception is toxoplasmosis caused by "Toxoplasma gondii".

Humans may first encounter coccidia when they acquire a puppy or kitten that is infected. Other than "T. gondii", the infectious organisms are canine and feline-specific and are not contagious to humans, unlike the zoonotic diseases.

Puppies are frequently infected with coccidia from the feces of their mother, and are more likely to develop coccidiosis due to their undeveloped immune systems. Stress can trigger symptoms in susceptible animals.

Symptoms in young dogs include diarrhea with mucus and blood, poor appetite, vomiting, and dehydration. Untreated the disease can be fatal.

Treatment is routine and effective. Diagnosis is made by low-powered microscopic examination of the feces, which is generally replete with oocysts. Readily available drugs eliminate the protozoa or reduce them enough that the animal's immune system can clear the infection. Permanent damage to the gastrointestinal system is rare, and a dog will usually suffer no long-lasting negative effects.

The first symptom is a sudden onset of swelling of the face, which develops within two days into papules and pustues on the lips, nose, and around the eyes. These pustules release a purulent discharge, causing a crust to form on the skin. There is also lymphadenopathy (swelling of lymph nodes) in the main lymph nodes of the head. The feet, body, prepuce or perianal area may be affected. Pustular otitis externa can occur, with the pinnae (ear flaps) becoming thickened by edema. Affected areas are painful but not itchy. Approximately half of affected puppies have lethargy and depression. Less common symptoms include pyrexia, anorexia, and joint pain, caused by sterile suppurative arthritis.

Juvenile cellulitis, also known as puppy strangles or juvenile pyoderma, is an uncommon disease of dogs. Symptoms include dermatitis, lethargy, depression and lameness. When puppies are first presented with what appears to be staphylococcal pyoderma, juvenile cellulitis, a relatively rare condition, may not be considered.

A number of studies have demonstrated adverse reactions in pets after administering vaccines to both dogs and cats. Concern about adverse effects has led to revised guidelines that alter the recommended frequency and methods/locations for both vaccination of dogs and feline vaccination.

A little known and often misdiagnosed reaction to the rabies vaccine in dogs, this problem may develop near or over the vaccine administration site and around the vaccine material that was injected, or as a more widespread reaction. Symptoms include ulcers, scabs, darkening of the skin, lumps at the vaccine site, and scarring with loss of hair. In addition to the vaccination site, lesions most often develop on the ear flaps (pinnae), on the elbows and hocks, in the center of the footpads and on the face. Scarring may be permanent. Dogs do not usually seem ill, but may develop fever. Symptoms may show up within weeks of vaccination, or may take months to develop noticeably.

Dogs with active lesion development and / or widespread disease may be treated with pentoxyfylline, a drug that is useful in small vessel vasculitis, or tacrolimus, an ointment that will help suppress the inflammation in the affected areas.

Owners and veterinarians of dogs who have developed this type of reaction should review the vaccination protocol critically and try to reduce future vaccinations to the extent medically and legally possible. At the very least, vaccines from the same manufacturer should be avoided. It is also recommended that the location in which future vaccinations are administered should be changed to the rear leg, as far down on the leg as possible and should be given in the muscle rather than under the skin.

Strangling involves one or several mechanisms that interfere with the normal flow of oxygen into the brain:

- Compression of the carotid arteries or jugular veins—causing cerebral ischemia.

- Compression of the laryngopharynx, larynx, or trachea—causing asphyxia.

- Stimulation of the carotid sinus reflex—causing bradycardia, hypotension, or both.

Depending on the particular method of strangulation, one or several of these typically occur in combination; vascular obstruction is usually the main mechanism. Complete obstruction of blood flow to the brain is associated with irreversible neurological damage and death, but during strangulation there is still unimpeded blood flow in the vertebral arteries. Estimates have been made that significant occlusion of the carotid arteries and jugular veins occurs with a pressure of around , while the trachea demands six times more at approximately .

As in all cases of strangulation, the rapidity of death can be affected by the susceptibility to carotid sinus stimulation. Carotid sinus reflex death is sometimes considered a mechanism of death in cases of strangulation, but it remains highly disputed. The reported time from application to unconsciousness varies from 7–14 seconds if effectively applied to one minute in other cases, with death occurring minutes after unconsciousness.

Strangling is compression of the neck that may lead to unconsciousness or death by causing an increasingly hypoxic state in the brain. Fatal strangling typically occurs in cases of violence, accidents, and is one of two main ways that hanging may cause death (alongside breaking the victim's neck).

Strangling does not have to be fatal; limited or interrupted strangling is practised in erotic asphyxia, in the choking game, and is an important technique in many combat sports and self-defence systems.

Strangling can be divided into three general types according to the mechanism used:

- Hanging—Suspension from a cord wound around the neck

- Ligature strangulation—Strangulation without suspension using some form of cord-like object called a garrote

- Manual strangulation—Strangulation using the fingers or other extremity

Canine subvalvular aortic stenosis (SAS) is an abnormal, congenital heart murmur caused by subaortic stenosis (SAS). There is a high incidence of this condition among Rottweiler dogs.

There is very good evidence that it is heritable, passed on from generation to generation genetically. This genetic trait is what is called polygenic, so that the inheritance is complex. An animal might have the genes for SAS, yet have no actual sign of SAS. Also, an animal might have signs of subaortic stenosis, and yet offspring with signs of SAS may not be seen for a couple of generations. Any animal that has subaortic stenosis should not be bred, because they can definitely pass the defect on to future offspring. There is some controversy as to whether the parents of an animal with SAS should be bred again.

Heart murmurs are graded on a scale of 1 to 6, with one being very mild and six being very serious, with some animals dying before they reach this high stage due to a sudden leap in the grade or through long-term slowing down. Murmurs can exist due to a large number of heart problems (infection, trauma, anemia, etc.; some are innocent, with no cardiac pathology. Tests such as chest X-rays, echocardiography, and electrocardiography can be performed to evaluate the severity of the situation

The condition is usually detected during puppy visits to the veterinarian by hearing a heart murmur during physical examination. A heart murmur is the abnormal sound of blood rushing through one of the heart valves. Instead of just the heartbeat, a whistle of blood flow through a narrowed opening is heard. The puppy will most likely appear normal in all other respects. There is a possibility that the murmur may come and go, or it may develop slowly; this can be determined by frequent checks of a puppy's heart during its first few months. The chance for long-term survival of SAS is low.

Puppies and dogs diagnosed with subaortic stenosis can suffer from heart failure and sudden death. If a dog with SAS develops heart failure, medications can be prescribed to alleviate the clinical signs (sudden/strong lethargicism, continuous heavy panting, rise in temperature etc.)

The OFA has established a Congenital Heart Registry whose guidelines were established by veterinary cardiologists. A dog which auscultates normally at 12 months of age is considered to be free of congenital heart disease; upon confirmation of this, the OFA will issue a certificate.

Petplan Australia reported that signs of arthritis in dogs and cats include stiffness, difficulty moving, lethargy, irritability, and cat or dog may lick, chew or bite at sore joints.

Dogs might exhibit signs of stiffness or soreness after rising from rest, reluctance to exercise, bunny-hopping or other abnormal gait (legs move more together when running rather than swinging alternately), lameness, pain, reluctance to stand on rear legs, jump up, or climb stairs, subluxation or dislocation of the hip joint, or wasting away of the muscle mass in the hip area. Radiographs (X-rays) often confirm the presence of hip dysplasia, but radiographic features may not be present until two years of age in some dogs. Moreover, many affected dogs do not show clinical signs, but some dogs manifest the problem before seven months of age, while others do not show it until well into adulthood.

In part this is because the underlying hip problem may be mild or severe, may be worsening or stable, and the body may be more or less able to keep the joint in repair well enough to cope. Also, different animals have different pain tolerances and different weights, and use their bodies differently, so a light dog who only walks, will have a different joint use than a more heavy or very active dog. Some dogs will have a problem early on, others may never have a real problem at all.

A dysplastic animal has probably lived with the condition since it was only a few months old, and has therefore grown up taking the chronic pain for granted and has learned to live with it. Dogs suffering such pain do not usually exhibit acute signs of pain. Sometimes, they will suddenly and abnormally sit down when walking, or refuse to walk or climb objects which they usually would, but this can equally be a symptom of many other things, including a thorn in the paw, or a temporary muscle pain. So pain recognition is less common a means of detection than the visible gait and other abnormalities described above.

Puppy pregnancy syndrome is a psychosomatic illness in humans brought on by mass hysteria.

The syndrome is thought to be localized to villages in several states of India, including West Bengal, Assam, Bihar, Jharkhand, Orissa, and Chhattisgarh, and has been reported by tens of thousands of individuals. It is far more prevalent in areas with little access to education.

People suffering from this condition believe that shortly after being bitten by a dog, puppies are conceived within their abdomen. This is said to be especially likely if the dog is sexually excited at the time of the attack. Victims are said to bark like dogs, and have reported being able to see the puppies inside them when looking at water, or hear them growling in their abdomen. It is believed that the victims will eventually die – especially men, who will give birth to their puppies through the penis.

Witch doctors offer oral cures, which they claim will dissolve the puppies, allowing them to pass through the digestive system and be excreted "without the knowledge of the patient".

Doctors in India have tried to educate the public about the dangers of believing in this condition. Most sufferers are referred to psychiatric services, but in rare instances patients fail to take anti-rabies medication in time, thinking that they have puppy pregnancy syndrome and thus the witch doctor's medicine will cure them. This is further compounded by witch doctors stating that their medicine will fail if sufferers seek conventional treatment.

Some psychiatrists believe that the syndrome meets the criteria for a culture-bound disorder.

The most common sign of CEA is the presence of an area of undeveloped choroid (appearing as a pale spot) lateral to the optic disc. The choroid is a collection of blood vessels supplying the retina. CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, retinal detachment, or intraocular hemorrhage. It can be diagnosed by fundoscopy by the age of six or seven weeks. Severe cases may be blind.

Collie eye anomaly (CEA) is a congenital, inherited, bilateral eye disease of dogs, which affects the retina, choroid, and sclera. It can be a mild disease or cause blindness. CEA is caused by a simple autosomal recessive gene defect. There is no treatment.

Skin disorders are among the most common health problems in dogs, and have many causes. The condition of a dog's skin and coat are also an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. Skin disorders may be primary or secondary (due to scratching, itch) in nature, making diagnosis complicated.