Bacterial Zoonoses
A bacterium is a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organised nucleus. The diseases caused by bacteria are known as bacterial diseases.
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Plague
Plague is a disease that occurs in three forms in humans – Pneumonic, Bubonic and Septicaemic. It is also referred to as Black Death. This is primarily a disease spread via rodents however transmission via domestic animals is also possible. It is caused by the bacterium Yersinia pestis. This is a disease that can be extremely fatal if not treated at the right time. In the year 1994, 56 people died in 5 different states in India. Plague epidemics are not unheard of. Bubonic plague is the most common out of the three plagues.
Primarily a disease of rodents, it is spread to other animals by the bite of infected fleas. It can be spread to humans by the bite of infected rodents as well. Dogs usually get a very mild form of this disease by infected fleas and cannot transmit this infection directly to humans however, the fleas from a dog’s body can spread this infection to humans. Dogs develop antibodies after their first exposure.
The case is not similar to cats. Cats are extremely susceptible to plague. They can get it after ingesting infected rodents or flea bites. Infected cats can spread this disease to humans via transdermal or oral routes. Pneumonic plague from cats can also be spread by aerosol transmission. Sometimes, cats get these large abscesses that become purulent after being infected with the plague and the rupture of these abscesses spread numerous bacilli.
Before diving into the signs and symptoms, let us understand what the three different forms of plague stand for.
Bubonic plague results in swollen lymph nodes. Septicaemic plague results when the bacteria traverse through the bloodstream and spread to different vital organs of the body. Pneumonic plague ideally affects the lungs.
In humans-
- Bubonic plague:
- Fever
- Headache
- Chills
- Weakness
- Swollen and tender lymph nodes (called buboes)
- Septicaemic plague
- Fever
- Chills
- Weakness
- Abdominal pain
- Bleeding into the skin and organs
- Skin and tissues may turn black and die
- Pneumonic plague:
-
- Fever
- Headache
- Weakness
- Pneumonia
- Shortness of breath
- Chest pain
- Cough
- This is the only form of plague that can spread from person to person
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In animals-
Dogs are usually resistant to plague and are not affected. In some cases, they may show signs like fever, lethargy and inflammation of lymph nodes. Lesions under the jaw, in mouth or cough, may also be observed.
Cats are most commonly presented with bubonic plague. They develop fever, lethargy, loss of appetite and enlarged lymph nodes. Ulcers in mouth and skin abscesses have been observed. Diarrhoea, vomition and diffused inflammation can be observed.
Immunochromatographic assays, ELISA, RT-PCR, Identification and source tracing in laboratories and serological diagnostic techniques are some methods used for the diagnosis of plague.
Killed Whole Cell Vaccines are available in different formulations throughout the world. Live attenuated vaccines as EV76 have also been used in men. Rodent habitat around houses, workplaces and recreational areas should be removed. Gloves should be worn while handling potentially infected animals. Repellents should be used against fleas while doing outdoor activities. Active de-fleaing of dogs and cats should be done with the recommendation of your vet. Do not allow stray or indoor-outdoor dogs to sleep on your bed.