Septicemic plague is one of the three forms of plague, and is caused by Yersinia pestis, a gram-negative species of bacterium. Septicemic plague is a systemic disease involving infection of the blood, and is most commonly spread by bites from infected fleas. Septicemic plague can cause disseminated intravascular coagulation, and is almost always fatal when untreated. The other varieties of the plague are bubonic plague and pneumonic plague. Signs and symptoms
The usual symptoms are:
Abdominal pain
Bleeding under skin due to blood clotting problems
Bleeding from mouth, nose or rectum
Gastrointestinal symptoms, including nausea, vomiting, which can be with blood, and diarrhea
Fever
Chills
Low blood pressure
Organ failure
Shock
Death of tissue (gangrene) in extremities, mostly fingers, nose, and toes
Difficulty breathingThese symptoms are common to many human illnesses, and are not considered, in and of themselves, to signify infection with any form of plague.It is important to note that septicemic plague may be asymptomatic, and may cause death absent of any symptoms. Cause
Transmission
Human Yersinia infections most commonly result from the bite of an infected flea or occasionally an infected mammal, but like most bacterial systemic diseases, the disease may be transmitted through an opening in the skin or by inhaling infectious droplets of moisture from sneezes or coughs. In both cases septicemic plague need not be the result, and in particular, not the initial result, but it occasionally happens that bubonic plague for example leads to infection of the blood, and septicemic plague results.
If the bacteria happen to enter the bloodstream rather than the lymph or lungs, they multiply in the blood, causing bacteremia and severe sepsis. In septicemic plague, bacterial endotoxins cause disseminated intravascular coagulation (DIC), where tiny blood clots form throughout the body, commonly resulting in localised ischemic necrosis, tissue death from lack of circulation and perfusion.DIC results in depletion of the bodys clotting resources, so that it can no longer control bleeding. Consequently, the unclotted blood bleeds into the skin and other organs, leading to red or black patchy rash and to hematemesis (vomiting blood) or hemoptysis (coughing up blood). The rash may cause bumps on the skin that look somewhat like insect bites, usually red, sometimes white in the center.Septicemic plague is caused by horizontal and direct transmission. Horizontal transmission is the transmitting of a disease from one individual to another regardless of blood relation. Direct transmission occurs from close physical contact with individuals, through common air usage, from direct bite from a flea or an infected rodent. Most common rodents may carry the bacteria and so may Leporidae such as rabbits:

Significant carriers of the bacteria in the United States include:
- Rats
- Prairie dogs
- Squirrels
- Chipmunks
- Rabbits
- Fleas
The bacteria are cosmopolitan, mainly in rodents in all continents except Australia and Antarctica. The greatest frequency of human plague infections occurs in Africa. The bacteria most commonly appear in rural areas and wherever there is poor sanitation, overcrowding, and high rodent populations in urban areas.