Septicemic (or septicaemic) plague is a deadly blood infection, one of the three main forms of plague. It is caused by Yersinia pestis, a gram-negative bacterium. Septicemic plague is a serious bacterial infection that is spread from flea bites.
Like some other forms of gram-negative sepsis, septicemic plague can cause disseminated intravascular coagulation, and is almost always fatal without treatment (the mortality rate in medieval times was 99-100 percent). Fewer than 5000 people a year are infected with the disease. Septicemic plague is the rarest of the three plague varieties; the other forms are bubonic and pneumonic plague.
Septicemic plague in animals
Septicemic plague is a zoonotic disease, meaning that it can be transmitted between humans and animals, such as rodents and carnivores. Goats, sheep and camels also have a possibility of carrying the disease. Cats rarely develop clinical signs but have increased susceptibility of contracting the bacteria. 50% of infected individuals will fully develop the plague. Common areas with infected animals occur in areas west of the Great Plains of North America.
Possible rodents that can be affected by the plague are rock squirrels, wood rats, ground squirrels, prairie dogs, chipmunks, mice, voles, and rabbits. Wild carnivores can also become infected if they eat an infected rodent. Large outbreaks of various strains of the plague, such as the sylvatic plague, have been devastating to black-tailed prairie dog and black-footed ferret populations.
Plague has been active in black-tailed prairie dog populations for the past 40-50 years. Plague outbreaks have only occurred in the western United States and they are extremely devastating to the prairie dog populations. There is a mortality rate near 100% due to no antibodies or immunity to the plague. Any individuals that survive were lucky enough to avoid contact with the plague causing bacteria. Colonies that are recovering from a plague outbreak tend to have a chance of probable reoccurence.
Due to black-footed ferrets preying on black-tailed prairie dogs, wild ferret populations have become infected by the sylvatic plague also. A plague outbreak can kill nearly 100% of ferrets in a population. Surviving ferrets are challenged in a shortage of their main food source, which is the prairie dog. Spray-and-vaccinate campaigns have formed in order to try and prevent the spread of the plague to these wildlife populations.
Transmission and mode of action
The disease is contracted primarily through the bite of an infected rodent or insect, but like bubonic plague can very rarely be contracted through an opening in the skin or by cough from another infected human. After initial infection, the bacteria 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, possibly resulting in ischemic necrosis (tissue death due to lack of circulation/perfusion to that tissue).
DIC results in depletion of the body's clotting resources, so that it can no longer control bleeding. Consequently, there is bleeding into the skin and other organs, leading to red and/or black patchy rash and hemoptysis/hematemesis (respectively coughing up or vomiting up of blood). There are bumps on the skin looking somewhat like insect bites; these are usually red, and sometimes white in the center.
Untreated, septicemic plague is usually fatal. Early treatment with antibiotics reduces the mortality rate to between 4 and 15 percent. People who contract this disease must receive treatment in at most 24 hours, or death is almost inevitable. In some cases, people may even die on the same day they contract it.
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 flea or infected rodent. Most common rodents that can carry the bacteria are:
- Prairie dogs
The bacteria is present in rodents in all continents except Australia. The greatest number of human plague infections have occurred in Africa. The bacteria is most common in rural areas and any area that has poor sanitation, overcrowding, or high rat population (urban areas). Outdoor activities such as hiking, camping, hunting or any other activities outdoors where plague-infected animal can possibly reside can increase chance of contracting septicemic plague. Certain occupations such as veterinarian, veterinary assistants or other animal-related work can also increase chance of contraction.
- Abdominal pain
- Bleeding under skin due to blood clotting problems
- Bleeding from mouth, nose or rectum
- Low blood pressure
- Organ failure
- Death of tissue (gangrene) causing blackening in extremities, mostly fingers, toes and nose
- Difficulty breathing
However, septicemic plague may cause death before any symptoms occur.
Since septicemic plague can be carried by animals, symptoms you should look for are:
- Painfully swollen lymph nodes (with possible abscesses)
- Enlarged tonsils
- Discharge from eyes
- Loss of appetite/Visible weight loss
- Mouth ulcers
- Systemic infection of the blood
- Coma may follow
A doctor or veterinarian will perform a physical exam which includes asking about the medical history and possible sources of exposure. The following possible test could include:
- Blood samples (detect antibodies)
- Culture samples of body fluids(check for the bacteria Yersinia pestis)
- Kidney and liver testing
- Check lymphomic system for signs of infection
- Examine body fluids for abnormal signs
- Check for swelling
- Check for signs of dehydration
- Check for fever
- Check for lung infection
Starting antibiotics early is a first step in treating septicemic plague in humans. One of the following antibiotics may be used:
- Tetracyline or doxycycline
Lymph nodes may require draining and the patient will need close monitoring.
Antibiotics such as tetracyline or doxycycline can be used in animals. Intravenous drip may be used to assist in dehydration scenarios. Flea treatment can also be used. In some cases euthanasia may be the best option for treatment and to prevent further spreading.
Prevention & precaution
- Caregivers of infected patients should wear masks, gloves, goggles and gowns
- Take antibiotics if close contact with infected patient has occurred
- Use insecticides throughout house
- Avoid contact with dead rodents or sick cats
- Set traps if mice or rats are present around the house
- Do not allow family pets to roam in areas where plague is common
- Flea control and treatment for animals (especially rodents)
Septicemic plague in medieval times
Septicemic plague was the least common of the three plague varieties that occurred during the Black Death from 1348 to 1350 (the other two being bubonic plague and pneumonic plague). Like the others, septicemic plague spread from the East through trade routes on the Black Sea and down to the Mediterranean Sea.
Major port cities such as Venice and Florence were hit the hardest. The massive loss of working population in Europe following the Black Death, resulting in increased economic bargaining power of the serf labour force, was a major precipitating factor for the Peasants' Revolt of 1381.
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