Plague is caused by Yersinia pestis , parasite of xenopsylla cheopis (Rat flea ) that is accompy by high fever , headache band enlargement of axillary lymph nodes !!!

Plague is caused by:
- Yersinia pestis: Yersinia pestis is the bacterium responsible for causing plague. It is a Gram-negative, rod-shaped bacterium that primarily affects rodents and is transmitted to humans through fleas.


Explanation:
Plague, also known as the Black Death, is a severe infectious disease caused by the bacterium Yersinia pestis. It has been responsible for several major pandemics throughout history, including the Black Death in the 14th century, which decimated the population of Europe.
Here is a detailed explanation of each option and why Yersinia pestis is the correct answer:
- Trichinella pestis: Trichinella is a genus of parasitic roundworms that causes the disease trichinosis. Trichinosis is primarily acquired by consuming raw or undercooked meat infected with Trichinella larvae, not by fleas or rodents. Therefore, Trichinella pestis is not the correct answer for the cause of plague.
- Leishmania donovani: Leishmania donovani is a parasite that causes a tropical disease called visceral leishmaniasis or kala-azar. It is transmitted to humans through the bite of infected sandflies, not through fleas or rodents. Therefore, Leishmania donovani is not the correct answer for the cause of plague.
- Corynebacterium rependonicum: Corynebacterium rependonicum is a species of bacteria that is mainly associated with infections in horses and other animals. It does not cause plague in humans. Therefore, Corynebacterium rependonicum is not the correct answer for the cause of plague.
- Yersinia pestis: Yersinia pestis is the correct answer for the cause of plague. It is a bacterium that primarily affects rodents, especially rats, and is transmitted to humans through fleas that have bitten infected animals. Yersinia pestis can cause three forms of plague in humans: bubonic, septicemic, and pneumonic. Bubonic plague is the most common form and is characterized by swollen lymph nodes (buboes). Septicemic plague occurs when the bacteria spread to the bloodstream, and pneumonic plague affects the lungs and can be transmitted from person to person through respiratory droplets.
In conclusion, the correct answer for the cause of plague is Yersinia pestis, a bacterium transmitted to humans through fleas that have bitten infected rodents.