Plague

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Plague is a deadly infectious disease caused by the enterobacteria Yersinia pestis (Pasteurella pestis). Plague is a zoonotic, primarily carried by rodents (most notably rats) and spread to humans via fleas. Plague is notorious throughout history, due to the unprecedented scale of death and devastation it brought. Plague is still endemic in some parts of the world.

Contents 1 Name 2 Infection and transmission 3 Pathology 3.1 Bubonic plague 3.2 Septicemic plague 3.3 Pneumonic plague 3.4 Other forms 4 Treatments 5 1994 Epidemic in Surat, India 6 Other Contemporary cases 7 See also 8 External links 9 Original Source

[edit] Name

The epidemiological use of the term plague is currently applied to bacterial infections that cause buboes, although historically the medical use of the term plague has been applied to pandemic infections in general. Plague is often synonymous with "bubonic plague" but this only describes one of its manifestations. Other names have been used to describe this disease, such as "The Black Plague" and "The Black Death", the latter is now used primarily to describe the second, and most devastating pandemic of the disease.

[edit] Infection and transmission

Bubonic plague is mainly a disease in rodents and fleas (Xenopsylla cheopis). Infection in a human occurs when a person is bitten by a flea that has been infected by biting a rodent that itself has been infected by the bite of a flea carrying the disease. The bacteria multiply inside the flea, sticking together to form a plug that blocks its stomach and causes it to begin to starve. The flea then voraciously bites a host and continues to feed, even though it cannot quell its hunger, and consequently the flea vomits blood tainted with the bacteria back into the bite wound. The bubonic plague bacterium then infects a new victim, and the flea eventually dies from starvation. Serious outbreaks of plague are usually started by other disease outbreaks in rodents, or a rise in the rodent population.

In 1894, two bacteriologists, Alexandre Yersin of France and Shibasaburo Kitasato of Japan, independently isolated the bacterium in Hong Kong responsible for the Third Pandemic. Though both investigators reported their findings, a series of confusing and contradictory statements by Kitasato eventually led to the acceptance of Yersin as the primary discoverer of the organism. Yersin named it Pasteurella pestis in honor of the Pasteur Institute, where he worked, but in 1967 it was moved to a new genus, renamed Yersinia pestis in honor of Yersin. Yersin also noted that rats were affected by plague not only during plague epidemics but also often preceding such epidemics in humans, and that plague was regarded by many locals as a disease of rats: villagers in China and India asserted that, when large numbers of rats were found dead, plague outbreaks in people soon followed.

In 1898, the French scientist Paul-Louis Simond (who had also come to China to battle the Third Pandemic) established the rat-flea vector that drives the disease. He had noted that persons who became ill did not have to be in close contact with each other to acquire the disease. In Yunnan, China, inhabitants would flee from their homes as soon as they saw dead rats, and on the island of Formosa (Taiwan), residents considered handling dead rats a risk for developing plague. These observations led him to suspect that the flea might be an intermediary factor in the transmission of plague, since people acquired plague only if they were in contact with recently dead rats, but not affected if they touched rats that had been dead for more than 24 hours. In a now classic experiment, Simond demonstrated how a healthy rat died of plague after infected fleas had jumped to it from a plague-dead rat.

[edit] Pathology

[edit] Bubonic plague

When a flea bites a human and contaminates the wound with regurgitated blood, the plague carrying bacteria are passed into the tissue. Y. pestis can reproduce inside cells, so even if phagocytosed, they can still survive. Once in the body, the bacteria can enter the lymphatic system, which drains interstitial fluid. Plague bacteria secrete several toxins, one of which is known to cause dangerous beta-adrenergic blockade.

Y. pestis spreads through the lymphatics of the infected human until it reaches a lymph node, where it stimulates severe haemorrhagic inflammation (the root "haem" means "blood" and "haemorrhage" means to bleed) that causes the lymph nodes to expand. The expansion of lymph nodes is the cause of the characteristic "bubo" associated with the disease.

[edit] Septicemic plague

Lymphatics ultimately drain into the bloodstream, so the plague bacteria may enter the blood and travel to almost any part of the body. In septicemic plague, bacterial endotoxins cause disseminated intravascular coagulation (DIC), causing tiny clots throughout the body and possibly ischaemic necrosis (tissue death due to lack of circulation/perfusion to that tissue) from the clots. 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, which can cause red and/or black patchy rash and hemoptysis/haemoptysis (coughing up or vomiting of blood). There are bumps on the skin that look somewhat like insect bites; these are usually red, and sometimes white in the center. Untreated, septicemic plague is usually fatal. However, during the plague epidemics many people must have come in contact with the bacteria but survived; otherwise nearly everyone in Europe would have died. Early treatment with antibiotics reduces the mortality rate to between 4 and 15 percent. People who die from this form of plague often die on the same day symptoms first appear.

[edit] Pneumonic plague

The pneumonic plague infects the lungs, and with that infection comes the possibility of person-to-person transmission through respiratory droplets. The incubation period for pneumonic plague is usually between two and four days, but can be as little as a few hours. The initial symptoms, of headache, weakness, and coughing with hemoptysis, vomiting blood, are indistinguishable from other respiratory illnesses. Without diagnosis and treatment, the infection can be fatal in one to six days; mortality in untreated cases is 50–90%.

[edit] Other forms

There are a few other rare manifestations of plague, including asymptomatic plague and abortive plague. Cellulocutaneous plague sometimes results in infection of the skin and soft tissue, often around the bite site of a flea. Plague meningitis can occur in very rare cases of septicemic plague.

[edit] Treatments

Vladimir Havkin, a doctor of Russian-Jewish origin who worked in India, was the first to invent and test a bubonic plague vaccine, on January 10, 1897

• The traditional treatments are:
  • Streptomycin 30 mg/kg IM twice daily for 7 days
  • Chloramphenicol 25–30 mg/kg single dose, followed by 12.5–15 mg/kg four times daily
  • Tetracycline 2 g single dose, followed by 500 mg four times daily for 7–10 days (not suitable for children)

• More recently,
  • Gentamicin 2.5 mg/kg IV or IM twice daily for 7 days
  • Doxycycline 100 mg (adults) or 2.2 mg/kg (children) orally twice daily have also been shown to be effective.

[edit] 1994 Epidemic in Surat, India

In 1994, there was a pneumonic plague epidemic in Surat, India that resulted in 52 deaths and in a large internal migration of about 300,000 residents, who fled fearing quarantine.

A combination of heavy monsoon rain and clogged sewers led to massive flooding which resulted in unhygienic conditions and a number of uncleared animal carcasses. It is believed that this situation precipitated the epidemic. There was widespread fear that the flood of refugees might spread the epidemic to other parts of India and the world, but that scenario was averted, probably as a result of effective public health response mounted by the Indian health authorities .

Much like the Black Death that spread through medieval Europe, some questions still remain unanswered about the 1994 epidemic in Surat.

Initial questions about whether it was an epidemic of plague arose because the Indian health authorities were unable to culture Yersinia pestis, but this could have been due to poor laboratory procedures. Yet, there are several lines of evidence strongly suggesting that it was a plague epidemic: blood tests for Yersinia were positive, a number of individuals showed antibodies against Yersinia and the clinical symptoms displayed by the affected were all consistent with the disease being plague.

[edit] Other Contemporary cases

Two non-plague Yersinia - Yersinia pseudotuberculosis and Yersinia enterocolitica - still exist in fruit and vegetables from the Caucasus Mountains east across southern Russia and Siberia, to Kazakhstan, Mongolia, and parts of China; in Southwest and Southeast Asia, Southern and East Africa (including the island of Madagascar); in North America, from the Pacific Coast eastward to the western Great Plains, and from British Columbia south to Mexico; and in South America in two areas: the Andes mountains and Brazil. There is no plague-infected animal population in Europe or Australia.

• On 31 August 1984, the Centers for Disease Control and Prevention reported a case of pneumonic plague in Claremont, California. The CDC believes that the patient, a veterinarian, contracted plague from a stray cat. This could not be confirmed since the cat was destroyed prior to the onset of symptoms.
• From 1995 to 1998, annual outbreaks of plague were witnessed in Mahajanga, Madagascar as per a study done by Pascal Boisier and other scientists and publish in Emerging Infectious Diseases journal in March 2002.
• In the U.S., about half of all food cases of plague since 1970 have occurred in New Mexico. There were 2 plague deaths in the state in 2006, the first fatalities in 12 years.
• In Fall of 2002, a New Mexico couple contracted the disease, just prior to a visit to New York City. They both were treated by antibiotics, but the male required amputation of both feet to fully recover, due to the lack of blood flow to his feet, cut off by the bacteria.
• On 19 April 2006, CNN News and others reported a case of plague in Los Angeles, California, lab technician Nirvana Kowlessar, the first reported case in that city since 1984.
• In May 2006, KSL Newsradio reported a case of plague found in dead field mice and chipmunks at Natural Bridges about 40 miles (64 km) west of Blanding in San Juan County, Utah.
• In May 2006, AZ Central reported a case of plague found in a cat.
• One hundred deaths resulting from pneumonic plague were reported in Ituri district of the eastern Democratic Republic of the Congo in June 2006. Control of the plague was proving difficult due to the ongoing conflict.
• It was reported in September 2006 that three mice infected with Yersinia pestis apparently disappeared from a laboratory belonging to the Public Health Research Institute, located on the campus of the University of Medicine and Dentistry of New Jersey, which conducts anti-bioterrorism research for the United States government.
• On 16 May 2007, an 8-year-old hooded capuchin monkey in the Denver Zoo died of the bubonic plague. Five squirrels and a rabbit were also found dead on zoo grounds and tested positive for the disease.
• On 5 June 2007 in Scotland, UK a 68 year old woman developed bubonic plague, which progressed to pneumonic plague.
• On 2 November 2007, Eric York, a 37 year old wildlife biologist for the National Park Service's Mountain Lion Conservation program and The Felidae Conservation Fund, was found dead in his home at Grand Canyon National Park. On 27 October, York performed a necropsy on a mountain lion that had likely perished from the disease and three days afterward York complained of flu-like symptoms and called in sick from work. He was treated at a local clinic but was not diagnosed with any serious ailment. The discovery of his death sparked a minor health scare, with officials stating he likely died of either plague or hantavirus, and 49 people who had come in to contact with York were given aggressive antibiotic treatments. None of them fell ill. Autopsy results released on November 9th, confirmed the presence of Y. pestis in his body, confirming plague as a likely cause of death.

[edit] See also

• Bacterial diseases in India
• Anthrax
• Bacterial meningitis
• Cholera
• Diphtheria
• Leprosy
• Rickettsial diseases
• Tuberculosis
• Yaws

[edit] External links

• World Health Organization
  • Health topic
  • Communicable Disease Surveillance & Response - Impact of plague & Information resources
• Centers for Disease Control and Prevention
  • CDC Plague map world distribution, publications, information on bioterrorism preparedness and response regarding plague
  • Infectious Disease Information more links including travelers' health
• Symptoms, causes, pictures of bubonic plague
• Secrets of the Dead . Mystery of the Black Death PBS

• Researchers sound the alarm: the multidrug resistance of the plague bacillus could spread
• Plague - LoveToKnow 1911
• Genome information is available from the NIAID Enteropathogen Resource Integration Center (ERIC)

[edit] Original Source

This article was originally posted in Wikipedia.