Plague is an infection caused by the bacterium Yersinia pestis. This organism is carried by rats and other rodents and spread by the bite of a flea (Xenopsylla cheopsis) or ingestion of the faeces of fleas through contaminated food.
How does it spread?
Plague usually begins with the rat carrying the bacteria. When a flea feeds on the infected rat’s blood, this organism begins to multiply inside the body of the flea. The flea may also bite other organisms such as dogs and man. When it bites it regurgitates its contaminated blood onto its prey, where the plague-causing organism enters the new host’s body through the mouth or an exposed wound.
Plague may also spread from one infected person to another, through droplets while coughing. An epidemic may start this way.
What are the symptoms?
The symptoms vary with the type of the infection. There are three types of
plague infection: Bubonic, Pneumonic and Septicaemic.
Bubonic plague: In
this case, the bacteria invade lymph nodes, which swell and are called ‘Buboes’.
Blood vessels break, causing internal bleeding. This blood dries and the skin
above it turns black hence it is called “Black Death”. Spread is slow from
person to person, but the mortality rate is very high (upto 75%) in untreated
cases. The signs of bubonic plague occur within 1-7 days of infection and
Sudden onset of high fever
General discomfort, uneasiness, or malaise
Smooth, oval, reddened, painful swellings called buboes in the groin,
armpits, neck, or elsewhere in the body
Swollen lymph glands
Pneumonic plague: The bacteria invade the
lungs of the victim causing pneumonia. The lungs are filled with frothy bloody
liquid. Other signs include:
Frothy, bloody sputum
Septicaemic plague results in sudden and intense
shock without signs of infections.
How is it diagnosed?
The doctor may suggest the following tests to diagnose plague:
Culture from the buboes
Lymph node culture
What is the treatment?
Plague can be effectively treated by giving antibiotics such as streptomycin, chloramphenicol, or tetracycline. Oxygen, intravenous fluids and respiratory support are additional treatments. Patients with pneumonic plague need to be isolated from other patients. People in contact with the patients of pneumonic plague are observed closely and may be given antibiotics as a preventive measure. Oral tetracycline is usually not prescribed for children whose permanent teeth have not erupted as it can permanently discolour teeth that are still forming.
How can it be prevented?
Rat control and monitoring of the disease are the main measures used to control
the risk of epidemics. A vaccination is available, but its effectiveness is not
clearly established. Other preventive measures that should be adopted are:
Keep food in closed containers
Burn or bury garbage
Use insect repellents on the skin
Use Permethrin insecticide on clothing and bedding
Spray or dust insecticides on floors inside and outside home