Common Bacterial Diseases In Dogs : Part 1

Bacterial Diseases 

Bacteria are single-celled microorganisms that are noted for their ability to cause disease.

RUCELLOSIS

 This disease is caused by the bacteria Brucella canis. It is a major cause of sterility and spontaneous abortion in dogs. Puppies infected in utero are typically aborted at 45 to 59 days after conception. Suspect this disease in any bitch who aborts two weeks before she is due to deliver and whenever a bitch delivers stillborn puppies or puppies who sicken and die.

Dogs with acute infection have enlarged lymph nodes in the groin and/or beneath the jaw. Fever is rare. The testicles of the male may swell in the initial stages, and then become smaller and atrophic as the sperm-producing cells are destroyed. Note, however, that this disease can infect a dog or bitch without producing any signs of illness.

In a dog with an acute infection, bacteria are found in the blood, urine, body secretions, and the products of abortion. In a dog with a chronic or inactive infection, bacteria can be transmitted in vaginal secretions during estrus and in semen.

The most common mode of transmission is by contact with infected vaginal discharges following a spontaneous abortion, and by contact with the urine of infected dogs. The disease can spread rapidly throughout a kennel in this manner. Males can acquire the disease through oral and nasal contact with the vaginal secretions of estrus females. Females can acquire the disease through breeding with an infected male. This is of particular concern to breeders, because males can harbor the bacteria for life.

A positive blood culture obtained during an acute infection is the most conclusive diagnostic test. Bacteria can also be cultured from aborted tissue. Blood serum tests will determine if a dog has ever been infected.

Treatment:

Brucellosis is difficult to eradicate. A course of intramuscular and oral antibiotics given for a minimum of three weeks will eliminate the disease in 80 percent of dogs. To be considered cured, a dog must be free of the bacteria for at least three months. Since it is difficult to achieve a cure, it is recommended to spay or neuter all infected animals to prevent the transmission of disease to other dogs.

LEPTOSPIROSIS 

Canine leptospirosis is caused by an order of bacteria called spirochetes— slender, spirally undulating bacteria. There are at least four species of the leptospira bacteria (or serovars) that can infect dogs: canicola, icterohemorrhagiae, grippotyphosa, and pomona. 

Leptospira are found in wild and domestic animals. The bacteria are spread in the urine, often making their way into water sources and remaining infective in the soil for up to six months. Rats, pigs, raccoons, cattle, skunks, and opossums appear to be the primary reservoirs. With housing spreading into the suburbs, more wildlife are coming into contact with pet dogs. This may be the cause of the upswing in leptospirosis cases. Spirochetes enter a dog’s system through a break in the skin or when the dog drinks contaminated water. Dogs who spend a lot of time in the water are at increased risk, as are dogs who drink out of puddles and dogs who spend time in yards that get a lot of runoff or stay wet after it rains.

Most infections are mild and do not show clinical signs. Signs appear 4 to 12 days after exposure. Fever is present in the early stage. Other signs are loss of appetite for several days, vomiting, lethargy, depression, muscle pain, and sometimes diarrhea or blood in the urine. Leptospirosis primarily affects the kidneys and/or the liver.

In severe cases, the whites of the dog’s eyes turn yellow (jaundice). This indicates hepatitis with destruction of liver cells. Coagulation problems can ensue, with spontaneous bleeding from the mouth and blood in the stools. Following recovery, untreated dogs can become carriers and shed bacteria in their urine for up to a year.

The canicola and gripotyphosa serovars tend to cause kidney damage, and the pomona and icterohemorrhagiae serovars most often affect the liver. Young dogs tend to show liver damage with all of the serovars. The diagnosis can be suspected based on the dog’s clinical signs. Tests of kidney and liver function will be abnormal. Spirochetes can be detected in the urine and blood by fluorescent antibody staining. Blood tests are available to confirm the diagnosis.

Treatment:

Severely ill dogs should be hospitalized for public health reasons and to provide more intensive care. Antibiotic combinations of penicillin and streptomycin are effective against the disease, although doxycycline is now routinely used as well. Enrofloxacin and ciprofloxacin are also sometimes used. Supportive measures includecontrolling vomiting and diarrhea, correcting dehydration with intravenous fluids, and maintaining nutrition.

BORDETELLA BRONCHISEPTICA 

Bordetella bronchiseptica bacteria are frequently found in dogs with the kennel cough complex and other respiratory diseases. Signs of upper respiratory illness caused by bordetella include a dry, hacking cough accompanied by a clear nasal or eye discharge. In puppies and immune-compromised adult animals,secondary bacterial invasion of the lower respiratory tract following viral illness may cause life-threatening pneumonia. Dogs who are carrying the organism and may not even be ill themselves, may still cough or exhale the organism into the air. Healthy dogs can then be infected by breathing in that contaminated air. 

The bacteria can be cultured from nasal swabs or transtracheal washings.

Treatment:

Treat all upper respiratory infections by placing the animal in a warm, draft-free environment, humidifying the atmosphere, and avoiding stressful activities that can interfere with a smooth recovery. Antibiotics are indicated if the dog develops fever and a mucopurulent nasal discharge. Antibiotics are also indicated for all cases of upper respiratory infection in which bordetella is isolated. Antibiotics given by nebulizer may be more effective than those given orally or by injection. This is because the bacteria attach to the mucosal surface of the respiratory tract and are difficult to reach with systemic antibiotics.