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Communicable Illnesses in Dogs


Tammy Callen

Canine Distemper

Canine Distemper is a viral illness that attacks the respiratory, gastrointestinal, and nervous system of canines. It is a very contagious and potentially fatal viral illness, spread by airborne exposure in respiratory droplets from an infected dog or wild animal. Therefore, prevention is based on insuring your dog is vaccinated properly, avoiding large groups of dogs with your dog prior to vaccination (i.e. puppies), and preventing exposure to wild canines. All dogs are susceptible to canine distemper; however, as is the case for most illnesses, the very young and elderly dogs, and non-vaccinated dogs, are at the highest risk.

Signs and Symptoms

Typically, the first sign of distemper is eye discharge, progressing to fever, nasal discharge, coughing, decreased energy, decreased appetite, vomiting and diarrhea. Although it is not uncommon with Kerry’s to have eye discharge, if it changes or is in any way different than the usual, or is combined with other symptoms, it is worth getting checked. If left untreated, distemper can cause seizures, twitching and paralysis secondary to the involvement of the nervous system. Due to the varied nature of these symptoms, any suspicion that your dog may have acquired the distemper virus should be treated seriously, and a veterinary visit is warranted.


Your veterinarian will diagnose distemper on clinical appearance and history. In addition to this, because distemper is a viral illness, treatment is based on supportive care and preventing secondary infections due to weakened immunity.


Rabies is a fatal virus secreted in the saliva that attacks the nervous system. It is transmitted to both humans and animals through a bite from an infected source. Only mammals can contract rabies, mainly skunks, raccoons, bats, coyotes, and foxes, but also cats, dogs and cattle. Dogs are a significant source of rabies in other countries, and travelers outside of North America should be aware of this. Vaccination for both humans and dogs is the best way to prevent rabies.

Signs and Symptoms

Once the signs of rabies are exhibited, it is almost always fatal. It enters the body and travels through the nerves to the brain, causing fearfulness, aggression, excessive drooling, difficulty swallowing, staggering, tremors, seizures, photophobia, and generalized bizarre or uncharacteristic behaviour.


Again, treatment is usually supportive, but as previously stated, if your dog becomes symptomatic, rabies is almost always fatal.

Heartworm Disease

Heartworm disease is a parasitic illness that affects dogs, cats, and ferrets. It is spread from animal to animal by mosquitoes. Once infected, the larvae mature into adults over approximately six months. During the first three months they migrate through the host body to eventually reach the blood vessels of the lungs. In the next three months the adult heartworms will enter the heart and will grow up to about 14 inches in length. Over time the heartworms will cause significant damage to the heart and lungs, and may survive for five to seven years in canines.

Signs and Symptoms

The disease may not show any initial signs or symptoms. However, as heartworm progresses your dog may exhibit coughing, lethargy, loss of appetite, difficulty breathing, and shortness of breath or may easily tire with any activity.


Heartworm is diagnosed through a blood test. Sometimes it is necessary to also perform a chest x-ray and echocardiogram. Prevention is the key with heartworm, and is almost 100% preventable with the use of a variety of formulations. (Ask your vet what they recommend, especially if travelling to an area with Heartworm presence). Heartworm is treatable, especially if caught early and your dog is in otherwise good health. The goal of treatment is to kill the adult worms and any larvae present in the dogs system. Your dog will need a period of hospitalization and complete rest to reduce any inflammatory response as the worms die and are absorbed by the body.

Internal Parasites

Most of the internal parasites found in dogs are worms and single celled organisms that live in the intestines. The most common are roundworms, hookworms, tapeworms, coccidian, and giardia.


Roundworms are the most common internal parasite found in dogs. It is passed from animal to animal through feces. Dogs can then ingest the parasite through eating infected soil, licking contaminated fur or paws, or by drinking contaminated water. Female dogs can also pass roundworms onto their puppies before or after birth.

The main health issue with a roundworm infection is malnutrition, as the roundworms live in the small intestine and steal nutrients. This infection is also zoonotic, meaning it can be passed to humans.


These are the second most common intestinal parasite found in canines. Your dog can become infected when the larvae enter the lining of the mouth or penetrate the skin. These parasites are particularly dangerous as they hook into the intestine of the canine and suck blood, leading to life-threatening blood loss, anemia and malnutrition. Hookworms are also zoonotic.


Whipworms are passed in the same way as roundworms and hookworms. Your dog may become infected through ingestion of fecal matter (i.e. infected soil, licking paws). Whipworms also bury their heads into the intestine of the dog and suck blood, however they are generally less harmful and usually do not cause health issues unless your dog has a previous health issue making them more susceptible.


Dogs become infected with tapeworms when they eat infected fleas or lice. They live in the small intestine and steal nutrients from the food the dog eats. It is usually diagnosed when the egg sacs are noticed in the stool or under the dogs tail (they look like small grains of rice).


This single-celled parasite is also contracted by eating contaminated soil or licking paws. Coccidia damages the lining of the intestine, preventing your dog from absorbing nutrients from food. The usual signs and symptoms are bloody, watery diarrhea, causing dehydration and malnutrition. Coccidia is highly contagious, good hygiene is essential in prevention of this parasite.


This is a parasite that I know all to well! Both Mac and I contracted it, on separate occasions, through water contamination while camping. It is a single celled parasite that damages the lining of the intestine, leading to malnutrition. Diarrhea, vomiting and abdominal pain are the main signs and symptoms of this parasite. Giardia is very difficult to diagnose because it may take testing several stool samples before it can be found. The damage caused to Mac’s intestines caused a secondary illness of pancreatitis, and he now has ongoing ulcerative colitis. Below is a picture of Mac on intravenous fluids at home, to treat dehydration.

General Signs and Symptoms

As a rule, healthy dogs may not show signs of a worm infection, however, if there is a change in appetite, change in skin/coat, diarrhea, or excessive coughing it is worth a visit to the vet. Cross contamination can easily be prevented through good hand washing, ensuring droppings are picked up, and if you have a pregnant dog or new puppies, a deworming program may be suggested.

External Parasites

Demodectic Mange Mites

These are microscopic and not highly contagious, with the exception of a mother dog to puppies. It appears are patches of scaly skin and redness around the eyes, mouth, legs, and trunk and may indicate an underlying medical condition.

Sarcoptic Mange Mites

These mites are also know as scabies, and can affect all dogs at any time of year. Sarcoptic Mange is also highly contagious. They burrow into the skin and cause extreme itching. Medication is required to kill these mites and sanitizing the dogs’ environment is necessary to prevent a subsequent infestation.

Ear Mites

These mites confine themselves to the ears and immediate surrounding area. They cause intense itching and irritation of the ear canal. Your dog may exhibit excessive head shaking and scratching at the ears, causing bleeding and sores. Through ear cleaning and medication is necessary to treat ear mites.


Ticks are most often found around the neck, ears, and underarms or groin areas. They bite and burrow their heads into the host, sucking blood. Tick bites can cause skin irritation, anemia, and also infectious diseases like Lyme Disease and Rocky Mountain Spotted Fever, depending on geographic area and type of tick. The most worrisome tick if the blacklegged or deer tick. Prompt removal of ticks is the best treatment. To remove a tick, grab it with a pair of tweezers as close to the skin of your dog as possible, and pull gently without twisting. Following removal, crush it without touching the fluids that may carry disease. Don’t try to smother it with Vaseline or alcohol, or try to burn it; these tactics may cause the tick to regurgitate its saliva into the dog, increasing the risk of disease. Your dog can be treated with a tick preventative treatment during tick season.

Table indicating areas of most serious communicable illnesses




Deer Ticks

USA All United States with the exception of Alaska All USA with prevalence in South-Eastern USA Potential everywhere North Eastern, Mid-Atlantic, and North-Central USA
Endemic in:
New Jersey
New York
Rhode Island
Canada Southern Ontario
Southern Quebec
Southern Manitoba
Potential for all of Canada with prevalence in Southern sections Potential everywhere Southern Nova Scotia
Southern Ontario
Southern Manitoba
Southern B.C.
Southern Alberta

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Today is July 21, 2019

In this month in 1974:

At the World Series Dog Show in Detroit MI, KBT Little Princess O'Malley, U.D., received eighth place in world-class obedience competition. Owned and trained by Orville Mittchell.

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