The world is, to say the least, filled with bacteria. They are everywhere, both inside and outside of all living and non-living surfaces on our planet. Most are at best harmless and many provide important functions such as helping with digestion, improving soil quality, and some, with manipulation by man, produce life-giving medicines. Given whatever food sources a particular bacterium needs to survive they can reproduce in astronomical numbers.

Certain bacteria, however, are not the friends of man or dog. Others may live in or on the pet, causing no harm until some other circumstance opens the way for invasion. These are called opportunistic organisms. There are literally thousands of bacterial species in our world. The ones that cause specific illness or the most common opportunists are listed below.

Staph bacteria, located on most skin and hair surfaces, are extremely common. Normal levels of these bacteria help maintain the health of the skin and coat. This bacterium is very opportunistic and can become involved in many types of skin infections including pyoderma or folliculitis among others. Many different strains of staph exist and many of these can be quite resistant to antibiotics. ((Staph Infection))

The bacteria Bordatella bronchiseptica has been noted to be present in many cases of infectious tracheobronchitis or kennel cough. While these bacteria can cause disease on its own, most cases are probably secondary to the invasion of the respiratory tract by viral organisms, with bordatella becoming part of a mixed infection. A vaccine, which is administered through the nose, is commonly given to dogs going into boarding kennels to help prevent the infection. For clinical signs please refer to the above noted disease associated with this bacteria.

Lyme disease has been a growing problem for dogs and man in the last decade. The bacteria Borrelia burgdorferi has been isolated in several different species of ticks, but is hard to find in dogs that actually have Lyme disease. Dogs are considered an incidental host, meaning that they are not the preferred species for the bacteria to live in. Once an infected tick bites a dog, the most common symptom is that of polyarthritis, meaning inflammation and pain of more than one joint.

Most dogs show clinical signs of lameness, which may get worse with time, and some will have loss of appetite, weight loss, enlargement of lymph nodes and fever. Diagnosis is based on the possible history of exposure to a tick, the clinical signs, X-rays, joint fluid analysis and a special IFA test for the presence of the bacteria. Some dogs may test positive without having symptoms, this being typical of many dogs exposed to the bacteria. A vaccine for prevention of the problem in high-risk areas or in high-risk dogs, such as hunting dogs, is available.

Most dogs showing clinical signs of infection and blood tests suggestive of the disease will respond very well to tetracycline type antibiotics. If they respond well, one or two follow-up tests are used to confirm the infection and monitor the course of therapy. If a dog does not respond rapidly another diagnosis should be sought.

Leptospirosis is a bacterial infection of dogs that can also be transmitted to man. The bacteria Leptospira interrogans, of which there are over 100 subtypes, commonly attacks the kidneys and liver of the dog. The bacteria is passed from infected animals in their urine and can reside in pools (large and small) of water. The bacteria will enter the dog through abrasions in the skin or directly through mucus membranes (gums, lips, genital areas and around the eyes) and will generally attack the organs in 4-10 days. It is felt that toxins released by the bacteria are what actually damage liver and kidney tissues.

Clinical signs will vary with the resistance of the patient and the "strength" of the bacterial subtype causing the infection. Some infections can progress so rapidly as to cause fever, dehydration, shock and death in only a day or two. Less serious infections will show clinical signs of fever, poor appetite, vomiting, dehydration, hemorrhages on the skin or mucus membranes, decreased urinary output, jaundice, pain and a decreased desire to move. Uveitis may also occur in some cases. If severe liver and/or kidney damage occurs these organs may completely fail.

Diagnosis is based on history, clinical signs, blood counts, serum chemistries, urinalysis and culture of the urine for the organism. Sometimes, the bacteria can be seen under the microscope in the urine. Serologic tests also exist to aid detection of the disease.

Penicillin and related drugs are effective in controlling the disease most of the time. Because of the organ damage/dysfunction, however, most dogs will need several days of hospitalization, IV fluid treatment and general supportive care. Most dogs do well with good nursing care and can recover. A vaccine is available and commonly used although some dogs may have allergic reactions to the injection.

Caused by the organism Brucella canis, canine brucellosis is a common disease that most often causes reproductive disease in the dog. The organism can reside in the genital tract of both male and female dogs. It is transmitted during mating although exposure to infected aborted fetal tissue; vaginal discharges and milk can also lead to an infection. Besides the more common reproductive problems described below, the bacteria can also cause meningitis, diskospondylitis and immune-complex disease.

Unless the dog has some of the above illnesses, they are rarely seriously ill when infected with this organism. On occasion dogs may have a mild fever, enlarged nodes, be off their food and loosing weight, but these symptoms are, to say the least, not specific for brucellosis. Female dogs may abort fetuses in the last trimester of pregnancy, fail to conceive, have reduced litter size or have puppies that die after birth.

Male dogs may have pain and swelling of the testes or scrotum or in longer standing cases, have small and shriveled testicles. It is important to reiterate that dogs can carry the infection for some time before it is diagnosed. Unless one painstakingly works to culture the bacterium from infected dogs, the only reliable methods of detection are special serologic tests commonly available. Serious breeders routinely test their males and females before they are bred.

Brucellosis is very difficult to totally eradicate from infected animals. Any dog with confirmed harboring of the bacteria should not be bred and should be spayed or neutered. Treatment of any form of the illness should be undertaken with long term use of certain antibiotic combinations as prescribed by one's veterinarian. Even with such, it would most always be impossible to totally cure an infected dog.

Most people should, in today's world, be aware of the potential dangers of salmonellosis, a prominent type of food poisoning. There are many different subspecies of Salmonella bacteria and many can easily cause infection. Most often they are contacted through direct or indirect contact with unprocessed or poorly cooked food items, especially dead birds or chicken and turkey meats.

Once an exposed dog swallows the bacteria, the organism invades and reproduces in the small intestine and can travel to lymph nodes, the spleen or the liver. The bacteria are also passed out of an infected dog in large quantities in the feces. Clinical signs include fever, lethargy, poor appetite, vomiting, diarrhea and abdominal pain. Mucus and blood is often noted in the feces. Some dogs may develop trouble breathing or signs of shock. Diagnosis is based on history of possible exposure, clinical signs, fecal analysis including fecal culture and possibly an intestinal biopsy.

Although most veterinarians would use antibiotics to treat salmonella, they may not be the best choice in many of the cases. Good supportive care including IV fluids, anti-vomiting drugs, and intestinal protectants are all commonly employed. Some dogs can become carriers of the bacteria, but this is not a major human health concern.

Caused by the organism Camphylobacter jejuni, this gastrointestinal disease is uncommon in the dog but can, on occasion, affect man. It is not certain that this organism, however, is a primary or secondary pathogen. Parvo, coronavirus, giardia infections and stress can all allow camphylobacter to cause disease. It is felt that infected dogs can pass the bacteria in their feces for months. Disease occurs after oral exposure to contaminated food materials.

Clinical signs include vomiting, fever, and a very watery, possibly bloody diarrhea that can last for a couple of weeks, especially in young pups. Some dogs have been known to have a chronic, continual diarrhea that never seems to end. Most dogs, however, do not progress to this extreme. Diagnosis is based on the clinical symptoms and culturing the organism from the fecal material.

In general, dogs with fever and bloody stools should receive antibiotic therapy with some type of fluid and electrolyte therapy being instituted to combat dehydration and emaciation caused by long-term diarrhea. Disinfection of areas the dog lives in is also quite important.

Tetanus is a bacterial infection that leads to some degree of muscle spasms in the dog. It occurs when the bacteria Clostridium tetani enters a wound, causes an infection and then releases a toxin that attacks the nervous system. This is a relatively rare condition today. It will be more likely in dogs kept near or around horses, which shed the bacteria in their (normal) feces.

As this infection, like many others, starts simply and innocently with a wound that becomes infected, it is important to be reminded that all wounds should be properly tended to early and not just allowed to heal or "see what happens". In less serious cases, symptoms include the dog holding their ears and tails up, walking stiffly and pulling the lips back. In more advanced cases, dogs cannot stand, will have all legs out and very rigid, be unable to open their mouths (hence the old term "lockjaw"), have a type of seizure activity and die due to respiratory failure. All these symptoms will generally appear 5-10 days after the wound occurred. Diagnosis is based on the clinical signs and history of having a wound recently.

Once tetanus is suspected, rapid treatment is essential. Any infected wound should be cleaned. Dead, infected tissue should be cut away under sedation. Flushing the wound free of any pus and administration of antibiotics is basic. Administration of a tetanus antitoxin should also be given if available.

Dogs that have developed the more severe clinical signs of toxemia can be saved. They should be cared for as above, plus hospitalized on IV fluids with strong muscle relaxants and anti-spasmotics or anti-seizure medication. Keeping the dog in a dark and very quiet environment is also important. Feeding through the IV or with a feeding tube can be used to maintain the patient. As long as the dog does not stop breathing and can be sustained for 7-10 days, they can recover completely in about a month.

Although rare nowadays, the bacteria Clostridium botulinum, which is most commonly found in raw or rotten meat products, can produce a rapidly progressive and sometimes fatal paralysis in the dog. The onset of clinical signs can occur hours or days after eating the contaminated food. Weakness followed by paralysis first in the hind legs then in all four legs is the common presentation although dogs can often still wag their tails. Death from respiratory paralysis can occur quickly.

Clinical signs may be suggestive but specific tests of blood, vomit, or feces would be needed to confirm the diagnosis. Culture may or may not be useful, as some normal dogs will harbor the bacteria on occasion.

If the amount of toxin is not too large, if respiratory or urinary infections are avoided, and with excellent supportive care, most dogs can be saved with 2-3 weeks of treatment. There is an antitoxin, but it must be given early in the disease process to be effective. Supportive care consisting of heavy, soft bedding, physical therapy, fluids, proper nutrition and antibiotics are all part of the process. Most animals that survive and after a few days will fully recover.

Although this bacterium is not a primary pathogen, it is a common organism found in chronic and recurrent infections, often of the ear canal. This organism has the nasty tendency to be very resistant to treatment, to have few antibiotics that will work to kill the infection and even when it has seemingly been eradicated, somehow makes a return appearance. Many dogs with chronic pseudomonas infections of the ear require constant treatment with antibiotic mixtures simply to keep the infection in check. All recurrent or chronic infections should have culture and sensitivity analysis done so that the most direct and practical treatment can be quickly begun. ((Pseudomonas Ear Infection)) 

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©2007 James W. Day D.V.M., P.C.