Bacteremia and Septicemia in Cats and Dogs

If a dog or cat who has been doing poorly takes a sudden and dramatic turn for the worse, vets may suspect bacteremia or septicemia as the cause.

By: certified_su
Most cases of septicemia arise due to a source of infection within the body. By: certified_su

Septicemia (septic shock) happens as a result of bacteremia (bacteria spreading in the bloodstream), and the 2 words are often used interchangeably — although this isn’t technically correct because bacteremia comes first and develops into septicemia.

However, the result is largely the same: The condition describes a poor animal taking a sudden turn for the worse and entering a battle for his life.

Septicemia is an overwhelming infection with which the body cannot cope, and as a result, the pet goes into shock. This is very dangerous to the long-term health of organs because when blood pressure drops, the supply to major organs fails, eventually causing kidney and liver failure.


The patient may not necessarily “catch” an infection. The source may be inside the body, such as pyometra (pus in the womb) or pancreatitis. Treatment revolves around aggressive intravenous fluid therapy to support blood pressure and perfuse the organs, antibiotics, pain relief and surgically removing the localized infection (removing the womb in the example of pyometra).


Initially, the dog or cat may seem vaguely unwell, be listless, go off her food and run a fever. If the condition runs out of control, bacteremia and then septicemia may develop.

This means a sudden deterioration akin to collapse. The animal is weak and has rapid, shallow breathing. If you feel for a pulse, you’ll find it speeding because of the pet’s blood pressure dropping into his boots, to which the heart is struggling in response.

Some animals will run a fever, while some are so sick that their temperature is actually below normal (this is a bad sign). The pet requires prompt, aggressive therapy to stand any chance of recovery.

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Septicemia is more likely to happen if the animal either has a suppressed immune system or the infection is overwhelming. Whatever the cause, bacteria or their endotoxins (poisons given off by the bacteria) circulate in the bloodstream.

The endotoxins give off chemical factors (cytokines) that make blood vessels leak, allowing the bacteria to trickle out of circulation and into soft tissues. Another effect is that the toxins cause the blood vessels to dilate, causing a massive drop in blood pressure.


Most cases of septicemia arise due to a source of infection within the body such as pyometra in un-spayed dogs. In this condition, the lining of the womb weakens with age and infection develops. The womb then fills up with pus, and the bacteria leak into the bloodstream and make the dog sick.

Another condition that has the potential to cause septicemia is pancreatitis — an inflammatory condition of the pancreas.

Uncommonly, dogs can pick up infection with clostridial bacteria, and for some reason these bugs often establish themselves in the bloodstream, causing bacteremia and then septicemia.

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Your vet will become suspicious of septicemia if an animal who has been doing poorly takes a sudden and dramatic turn for the worse. The physical symptoms of a racing pulse and rapid, shallow breathing should be enough to prompt immediate supportive care while the seat of infection is investigated.

Tests include a blood panel. Frequently, the white cell count will be sky-high (because the body has mobilized white cells to fight infection) or very low (because the white cells have all been used up in bringing the infection under control).

Imaging, such as taking radiographs or an ultrasound scan, helps identify any underlying disease such as a pyometra. A definitive diagnosis of bacteremia is made on a blood culture, but these results take days to come back — therapy must begin ahead of that.


An animal with septicemia is an animal in crisis. Treatment must be swift and aggressive with intravenous fluids to support blood pressure and protect organ function, plus intravenous antibiotics to stabilize the patient.

If the source of infection is identified, it must be surgically removed if the animal is to pull through. Pain relief is also essential.


Septicemia usually results from the deterioration of a preexisting condition. It is important to seek prompt veterinary attention for any sick animal.


  • “Bacteremia and septicemia in small animal patients.” Nostrandt. Probl Vet Med, 2(2): 348–361.
  • “Septic Shock.” Kirby. Kirk’s Current Veterinary Therapy XII. Publisher: W. B. Saunders.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Dec. 17, 2018.


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