Distemper in Dogs

Distemper virus inside cells

Distemper is a virus (Morbillivirus) that is related to human measles.  It infects dogs and their relatives as well as some other species, such as ferrets. Cats cannot get canine Distemper and what the public knows as Feline Distemper is an unrelated virus, which is more like Parvo virus than Canine Distemper. Distemper affects more than one place in the body at the same time. It affects the immune system, and suppresses the body’s ability to fight off infections which often leads to the respiratory system getting affected – dogs can develop pneumonia as well as constant pussy discharge from their noses and eyes. Dogs also get diarrhea in the early stages of Distemper, as it affects the gut with immunosuppression. Dogs can get a conjunctivitis (the membranes of the eyes are infected) causing pus to accumulate in the corners of the eyes. Finally, it hits the nerves and the brain, stripping the protective myelin sheath off the outside of the nerves and attacks the white matter in the brain, leading to twitching and spasms, which can progress to full blown seizures and death.

Distemper can cause seizures or fits before death

There is usually 1-2 weeks from time of exposure to development of initial clinical signs (incubation period), but it can be as long a 4-5 weeks or even more. Occasionally neurological signs develop months after exposure in dogs that never showed initial signs of infection.  The fever spikes 3-6 days post-infection, obvious clinical signs are seen between 1-4 weeks after infection (longer incubation more common),  and nervous signs signs may appear up to 3 months later with or without preceding signs. (2) Dogs shed the virus for 5-7 weeks in the urine and feces.  (3)  Distemper is transmitted in any bodily fluids, such as urine, saliva and nasal discharge. Distemper is found all over the world, but is more prevalent in third world countries,  or where people don’t vaccinate their dogs strictly.

I have listed these in the order they usually appear as the illness progresses, but each dog is different. Some dogs show most of the signs and some dogs only one or two. It depends on the dog’s immune system at the time – for example if they have had some vaccines, or if they received some protection from their mother through the milk, they are more immune and fewer signs would be seen than a dog that had never been exposed to Distemper before and had no protection from it’s parent. (Maternal antibodies to disease only last for the first few weeks of a pup’s life and then wear off, which is why puppies are vaccinated three to four times between 6 and 16 weeks of age)

• An unexplained high fever that does not respond to antibiotics and keeps coming back.

An unexplained high fever can be caused by Distemper

• Lymphopaenia (low numbers of white blood cells known as Lymphocytes, which are produced in the glands)
• Diarrhea and vomiting

Distemper can cause a bloody diarrhea and vomiting

• Pneumonia with soft cough
• Dog is thin and in poor condition

Poor condition and appetite seen with Distemper

• Pustules on the skin
• Depression and innapetance
• Pus in the corners of the eyes (Conjunctivitis and Dry eyes)
• Cloudiness of the eyes (Anterior Uveitis)
• Blindness and sensitivity to light (3)

Puppy with Distemper with pussy nasal discharge

• Pussy discharge from the nose

The skin on the nose and pads becomes very thick with Distemper

• Hardpad – the nose and the pads of the feet become thickened (not that common)
• Enamel hypoplasia – dirty brown marks on the teeth where enamel didn’t develop if a pup gets distemper while teeth were developing in the gums.

Distemper infection in pups affects developing teeth and the enamel doesn’t form well

• Twitching of the muscles of the face (chewing gum fits)
• Twitching of the leg muscles
• Seizures
• Aimless wandering
• Death
• Old dog encephalitis

Distemper is tough to diagnose. You have to test at the correct stage of infection to pick up up the virus.  The following tests exist:

• Conjunctival smears – A cytobrush is rubbed over the surface of the eye and inside the eyelids to pick up cells from the membranes of the eye (conjunctiva). These are then rolled onto a glass slide, stained and checked for particles that stain pink inside the cells called “inclusion bodies (Lentz copuscles)” which are directly from the Distemper virus. It is not common to pick these, up but if you do, you can make a provisional diagnosis of Distemper. These inclusion bodies can also be picked up in internal organs if an autopsy is done. Other viral infections, such as Adenovirus and Parainfluenze can also cause inclusion bodies, so if your vets sees these, he/she should send the sample to the laboratory for diagnosis.

• Blood tests for Distemper Antibodies – These are only useful if your dog has never had a vaccination ever before.  Exposure to the virus or a vaccination against Distemper causes a rise in antibodies which can be picked up in the blood serum. It is also possible to split the antibodies into antibodies that have recently been produced (IgM) and those that have been in the body for a few months or longer (IgG), If , for example, your dog had 1 vaccine as a puppy, and none since and is now 3 years of age and suddenly develops signs of Distemper, your vet could test for IgM and IgG. You would expect IgG to be high due to the puppy vaccine, but if IgM is high as well, it can point towards recent exposure to the virus and your vet will be able to make a provisional diagnosis of Distemper.  IgM only lasts a few weeks.

Blood tests check the serum for antibodies against Distemper