Bacteria are single-cell organisms that, unlike viruses, do not need other living cells in order to multiply. Most bacteria belong to what is called "normal flora" and are beneficial, helping to maintain the environment in which they live. Certain types of bacteria will cause disease. These pathogens are the ones that concern people and dogs.
Leptospirosis is caused by spirochete bacteria, including Leptospira canicola. Many infected dogs may not have clinical signs; they become carriers, spreading the disease to others. When illness does develop, it may cause kidney inflammation or a more generalized disease involving blood in the urine. Clicnical signs of the disease, which appear between 4 and 12 days after infection, include lethargy, fever, vomiting, and redness of the mucous membranes and the conjunctiva of the eyes. In severe cases, there may be jaundice and yellowing of the mucous membranes. Blood tests may reveal increased number of white blood cells, reduced platelet count, and kidney involvement. Serum samples show an increased level of antibodies. Support therapy including intravenous fluids is given.
Treatment with antibiotics will usually continue for at least 3 weeks, or often for longer periods.
Leptospira canicola are spread in the urine of carrier animals such as rodents and skunks, and can contaminate water and soil in places where these animals congregate. In areas where leptospirosis is a potential problem, dogs should be routinely vaccinated. Leptospirosis vaccine does not guarantee protection, however; rather, it protects some dogs and reduces the seriousness of the infection in others. Present vaccine provides immunity lasting for up to 18 months. Routine booster inoculations may be necessary for some dogs. Leptospirosis is a zoonotic disease transmissible to humans. If your dog develops this infections, ensure strict hygiene during the treatment phase.
Brucellosis is a worldwide infection caused by Brucella canis. Geographically, there is considerable variation in its incidence. In some parts of North America up to 5% of stray dogs are infected, while in Great Britain and Australia the incidence is less than 1%. Brucellosis is usually most common among dogs that are kept in kennels. In acute cases, individuals show enlarged lymph nodes in the groin area, sometimes beneath the jaw. Many infected dogs, however, show no clinical signs of illness. The bacteria may remain in an infected animal for as long as 2 years, during which time the dogs develops immunity.
The optimum time for the spread of Brucella bacteria is during breeding. The bacteria are transmitted through infected urine, or through the semen of male dogs and the vaginal discharges of females. Infected male dogs may become infertile, or they may have and inflammatory condition affecting the testicles (orchitis) or the prostate gland (prostatitis). Pregnant females who are infected often abort their fetuses at 6 to 8 weeks of gestation. If the pups are born live, they usually fade and die within a few days. A positive blood culture, in which bacteria are found, is the most definitive method of diagnosis. A test for antibodies is more practical when larger number of dogs need to be screened. A negative test is a true negative, but false positives are not uncommon. If a dog tests positive, more specific tests are available. In breeding kennels, a test-and-remove policy is the most practical option because affected dogs can remain Brucella carriers for years. Antibiotics clear bacteria as long as they are used, but are not always effective in eliminating the disease. All dogs for breeding should be blood-tested. A negative test essentially confirms that a dog is free from the disease. Brucella canis can cause a zoonotic disease in humans, although cases of human infection are very rare. The risks of catching it can be reduced by wearing rubber gloves and taking sensible precautions handling aborted puppies, tissue, or fluids from infected animals.
Nocardiosis is caused by Nocardia bacteria that live mainly in the soil. These threadlike bacteria usually gain entry through skin wounds, and cause visible abscesses. Both actinomycosis and nocardiosis are uncommon diseases, in which the lymph nodes become swollen in the region around the wound site. When infection moves deeper, for example, if it is carried deeper into body tissues on a foreign body such as a migrating grass seed, the infection may break into the chest or the abdomen, causing pus to accumulate there. Clinical signs will be confirmed by a laboratory bacterial cell culture, which will identify the organisms responsible. Simple abscesses are lanced and then flushed with antiseptic. Deeper infection requires more aggressive treatment, which includes daily flushing and cleansing of the area with disinfectant, accompanied by antibiotics for at least a month.