Systemic Bacterial Infectious Diseases

Chapter 19 Systemic Bacterial Infectious Diseases

A large number of bacteria can infect dogs and cats. This chapter focuses on leptospirosis, brucellosis, and bartonellosis. Chapter 18 is devoted to Lyme borreliosis. Other infectious diseases caused by bacteria are summarized in Table 19-1, and most are described in the respective organ-system chapters. Bordetella bronchiseptica is associated with the canine infectious tracheobronchitis (see Chapter 12).Mycoplasma haemofelis and Mycoplasma haemominutum are hemotropic infections (see Chapter 22). Mycobacterial infections are associated with chronic skin disease (see Chapter 39). Actinomycosis and nocardiosis are causes of pyothorax (see Chapter 164). Tetanus and botulism cause severe neuromuscular dysfunction (see Chapters 128 and 130, respectively). Salmonellosis, campylobacteriosis, yersiniosis, and Clostridium perfringens and Cl. difficile primarily involve the intestinal tract (see Chapter 69).



Leptospira are filamentous, motile, spirochete bacteria that infect many wild and domestic animals and humans. Over 200 leptospiral serovars have been described. A universal feature of pathogenic serovars is the ability to colonize the proximal renal tubules resulting in a prolonged renal carrier state and urine shedding.

In North America, canine leptospirosis is most frequently caused by serovars ofLeptospira interrogans (serovarsL. icterohaemorrhagiae, L. canicola, L. pomona, andL. bratislava) andLeptospira kirschneri (serovarL. grippotyphosa). SerovarL. autumnalis may also be emerging in some regions.



Microscopic Agglutination Titer

The MA test is the standard method for presumptive clinical diagnosis of leptospirosis. MA titers become positive after 1 week, peak at 3 to 4 weeks, and remain positive for several months after either natural infection or vaccination.

Identification of Leptospiral Organisms

Leptospirosis can be confirmed by identification of Leptospira organisms by microscopy and culture. These tests are most useful for confirming positive serologic tests, and only positive results are meaningful. Because of low detection rates, negative results never exclude the possibility of leptospirosis. In addition, antibiotics rapidly eliminate the organisms from blood and urine so they will be undetectable by culture. Polymerase chain reaction (PCR) identification of leptospiral DNA may be a more reliable means of documenting infection.


Effective treatment requires general supportive therapy, treatment of the leptospiremic phase of infection, followed by treatment of the leptospiruric carrier phase of infection. With intensive management, survival rates of 75 to 90% can be expected. Most dogs recover completely, but residual chronic renal failure is a potential outcome.

For supportive care: Administer intensive fluid and electrolyte therapy (see Chapter 5) and, depending on clinical findings, initiate appropriate treatment for acute renal failure (see Chapter 77), acute hepatic failure (see Chapter 71), and DIC (see Chapter 23), as recommended in other chapters in this book. Oliguric renal failure and fulminant DIC are life-threatening complications of leptospirosis that often need the most immediate attention and intensive care.




Because other bacteria elicit antibodies that crossreact with B. canis, false-positive results are common with agglutination tests. Hemolysis (hemoglobin) also causes false-positive results. False-negative titers are rare, but can result from sequestration of infection or recent antibiotics. In recent infections, it can take up to 4 weeks to seroconvert; thus, when screening dogs for entry into a breeding kennel, a negative test result on day 1 and again after 4 weeks is required.

Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Systemic Bacterial Infectious Diseases

Full access? Get Clinical Tree

Get Clinical Tree app for offline access