Plague

(Survival manual/6. Medical/b) Disease/Plague)
http://www.mayoclinic.com/health/plague/DS00493

Definition
Plague was known as the Black Death during medieval times, when it killed up to a third of the population of Europe. Currently, plague occurs in fewer than 3,000 people per year worldwide. It can be deadly if not treated promptly with antibiotics.

The organism that causes plague, Yersinia pestis, lives in a variety of small rodents on every continent except Australia. The organism is transmitted to humans when they are bitten by fleas that have previously fed on infected rodents.

The most common form of plague results in swollen and tender lymph nodes — called buboes — in the groin, armpits or neck. The rarest and deadliest form of plague affects the lungs, and it can be spread from person to person.

Symptoms
Plague is divided into three main types — bubonic, septicemic and pneumonic — depending on which part of your body is involved. Signs and symptoms vary depending on the type of plague.

1.  Bubonic plague
Bubonic plague is the most common variety of the disease. It’s named after the buboes — swollen lymph nodes — which typically develop within a week after an infected flea bites you. Buboes may be:
•  Located in the groin, armpit or neck
•  About the size of a chicken egg
•  Tender and warm to the touch

Other signs and symptoms may include:
•  Sudden onset of fever and chills
•  Headache
•  Fatigue or malaise
•  Muscle aches

2.  Septicemic plague
Septicemic plague occurs when plague bacteria multiply in your bloodstream. Signs and symptoms include:
•  Fever and chills
•  Abdominal pain, diarrhea and vomiting
•  Bleeding from your mouth, nose or rectum, or under your skin
•  Shock
•  Blackening and death of tissue (gangrene) in your extremities, most commonly your fingers, toes and nose

3.  Pneumonic plague
Pneumonic plague affects the lungs. It’s the least common variety of plague but the most dangerous, because it can be spread from person to person via cough droplets. Signs and symptoms can begin within a few hours after infection, and may include:
•  Cough, with bloody sputum
•  Difficulty breathing
•  High fever
•  Nausea and vomiting
•  Weakness

Pneumonic plague progresses rapidly and may cause respiratory failure and shock within two days of infection. If antibiotic treatment isn’t initiated within a day after signs and symptoms first appear, the infection is likely to be fatal.

 When to see a doctor
Seek immediate medical attention if you begin to feel ill and have been in an area where plague has been known to occur. Thisincludes parts of several states in the western portion of the United States — primarily New Mexico, Arizona and Colorado.

Causes
The plague bacteria, Yersinia pestis, is transmitted to humans when they are bitten by fleas that have previously fed on infected animals, such as:
•  Rats
•  Squirrels
•  Rabbits
•  Prairie dogs
•  Chipmunks

The bacteria can also enter your body if you have a break in your skin that comes into contact with an infected animal’s blood. Domestic cats can become infected with plague from flea bites or from eating infected rodents.
Pneumonic plague, which affects the lungs, is spread by inhaling infectious droplets coughed into the air by a sick animal or person.

Risk factors
The risk of developing plaque is very low. Worldwide, only a few thousand people develop plague each year. However, your risk of plague can be increased by where you live and travel, your occupation, and even by some of your hobbies.
When traveling in areas where plague is prevalent, use generous amounts of insecticide on your clothes, stay out of areas likely to be infested by rats and have a speedily administer antibiotics in the event of a sudden fever, chills or headache.

 Location
Plague outbreaks are most common in rural areas and in urban areas characterized by overcrowding, poor sanitation and a high rat population.
The greatest number of human plague infections occurs in Africa. But the largest concentration of infected animals is in the United States — particularly in New Mexico, Arizona and Colorado — and in the former Soviet Union.

 Occupation
Veterinarians and their assistants have a higher risk of coming into contact with domestic cats that may have become infected with plague. Also at higher risk are people who work outdoors in areas where plague-infested animals are common.

 Hobbies
Camping, hunting or hiking in areas where plague-infected animals reside can increase your risk of being bitten by an infected flea.

Complications of plague may include:
•  Death. Most people who receive prompt antibiotic treatment survive plague. Untreated plague has a fatality rate over 50 percent.
•  Gangrene. Blood clots in the tiny blood vessels of your fingers and toes can disrupt the flow of blood and cause that tissue to die. The portions of your fingers and toes that have died may need to be amputated.
•  Meningitis. Rarely, plague may cause meningitis, an inflammation of the membranes surrounding your brain and spinal cord.

Tests and diagnosis
If your doctor suspects plague, he or she may look for the Yersinia pestis bacteria in samples taken from your
•  Buboes. If you have the swollen lymph nodes (buboes) characteristic of bubonic plague, a fluid sample can be taken from them with a needle.
•  Blood. Yersinia pestis bacteria generally are present in your bloodstream only if you have septicemic plague.
•  Lungs. To check for pneumonic plague, fluid is extracted from your airways using endoscopy — a thin, flexible tube inserted through your nose or mouth and down your throat.

As soon as a diagnosis of suspected plague is made, the patient should be isolated, and local and state health departments should be notified. Confirmatory laboratory work should be initiated, including blood cultures and examination of lymph node specimens if possible. Drug therapy should begin as soon as possible after the laboratory specimens are taken.

The drugs of choice are streptomycin or gentamycin, but a number of other antibiotics are also effective.

Those individuals closely associated with the patient, particularly in cases with pneumonia, should be traced, identified, and evaluated. Contacts of pneumonic plague patients should be placed under observation or given preventive antibiotic therapy, depending on the degree and timing of contact.

Source : CDC’s home page on Plague

Treatments and drugs
As soon as your doctor suspects that you have plague, you’ll need to be admitted to an isolation room in a hospital. There, you’ll receive powerful antibiotics, such as:
•  Streptomycin
•  Gentamicin
•  Doxycycline (Vibramycin)
•  Ciprofloxacin (Cipro)
•  Chloramphenicol

Streptomycin is the most effective antibiotic against Y. pestis and the drug of choice for treatment of plague, particularly the pneumonic form. Therapeutic effect may be expected with 30 mg/kg/day (up to a total of 2 g/day) in divided doses given intramuscularly, to be continued for a full course of 10 days of therapy or until 3 days after the temperature has returned to normal. Gentamicin has been found to be effective in animal studies, and is used to treat human plague patients.

Chloramphenicol is a suitable alternative to aminoglycosides in the treatment of bubonic or septicaemic plague and is the drug of choice for treatment of patients with Y. pestis invasion of tissue spaces into which other drugs pass poorly or not at all (such as plague meningitis, pleuritis, or endophthalmitis). Dosage should be 50 mg/kg/day administered in divided doses either parenterally or, if tolerated, orally for 10 days. Chloramphenicol may be used adjunctively with aminoglycosides.

Different modalities of treatment are used:
<http://sprojects.mmi.mcgill.ca/tropmed/disease/plague/treatment.htm>
•  Aminoglycosides
•  Chloramphenicol
•  Tetracyclines
•  Sulfonamides
•  Fluoroquinolones
•  Aminoglycosides: streptomycin and gentamicin

Tetracyclines:  This group of antibiotics is bacteriostatic but effective in the primary treatment of patients with uncomplicated plague. An oral loading dose of 15 mg/kg tetracycline (not to exceed 1 g total) should be followed by 25-50 mg/kg/day (up to a total of 2 g/day) for 10 days. Tetracyclines may also be used adjunctively with other antibiotics.

Sulfonamides: Sulfonamides have been used extensively in plague treatment and prevention; however, some studies have shown higher mortality, increased complications, and longer duration of fever as compared with the use of streptomycin, chloramphenicol or tetracycline antibiotics. Sulfadiazine is given as a loading dose of 2-4 g followed by a dose of 1 g every 4-6 hours for a period of 10 days. In children, the oral loading dose is 75 mg/kg, followed by 150 mg/kg/day orally in six divided doses. The combination drug trimethoprim-sulfamethoxazole has been used both in treatment and prevention of plague.

Fluoroquinolones: Fluoroquinolones, such as ciprofloxacin, have been shown to have good effect against Y. pestis in both in vitro and animal studies. Ciprofloxacin is bacteriocidal and has broad spectrum activity against most Gram-negative aerobic bacteria, including Enterobacteriaceae and Pseudomonas aeruginosa, as well as against many Gram-positive bacteria. Although it has been used successfully to treat humans with Francisella tularensis infection, no studies have been published on its use in treating human plague.

Other classes of antibiotics (penicillins, cephalosporins, macrolides):  These classes of antibiotics have been shown to be ineffective or of variable effect in treatment of plague and they should not be used for this purpose.

Supportive therapy
 The clinician must prepare for intense supportive management of plague complications, utilizing the latest developments for dealing with Gram-negative sepsis. Aggressive monitoring and management of possible septic shock, multiple organ failure, adult respiratory distresssyndrome (ARDS) and disseminated intravascular coagulopathy should be instituted.

Treatment of plague during pregnancy and in children
With correct and early therapy, complications of plague in pregnancy can be prevented. The choice of antibiotics during pregnancy is confounded by the potential adverse effects of three of the most effective drugs.
•  Streptomycin may be ototoxic and nephrotoxic to the foetus. Tetracycline has an adverse effect on developing teeth and bones of the foetus.
•  Chloramphenicol carries a low risk of “grey baby” syndrome or bone-marrow suppression.
•  Experience has shown that an aminoglycoside judiciously administered is effective and safe for both mother and foetus, and in children.
•  Because of its safety, intravenous or intramuscular administration, and ability to have blood concentrations monitored, gentamicin is the preferred antibiotic for treating plague in pregnancy.

Prophylactic therapy
Persons in close contact with pneumonic plague patients, or persons likely to have been exposed to Y. pestis-infected fleas, to have had direct contact with body fluids or tissues of a Y. pestis-infected mammal, or exposed during a laboratory accident to known infectious materials should receive antibiotic preventive therapy, if the exposure was in the previous six days.

The preferred antimicrobials for preventive or abortive therapy are the tetracyclines, chloramphenicol, or one of the effective

Prevention
Although no effective vaccine is available, antibiotics can help prevent infection if you’re at risk of or have been exposed to plague. Take the following precautions if you live or spend time in regions where plague outbreaks occur:
•  Rodent-proof your home. Remove potential nesting areas, such as piles of brush, rock, firewood and junk. Don’t leave pet food in areas that rodents can easily access.
•  Keep your pets free of fleas. Ask your veterinarian which flea-control products will work best.
•  Use insect repellent. Closely supervise your children and pets when spending time outside in areas with large rodent populations. Use insect repellent.

Additional sources:
<http://www.cdc.gov/ncidod/dvbid/plague/facts.htm>

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