Yersinia pestis

treatment

Antibiotics (streptomycin, gentamycin) broad spectrum protein synthesis inhibitors are available and patients are given IV twice daily for 10 days High mortality rate if left untreated No vaccine available

pathogenesis

Bacteria enters host via flea bite, it spreads rapidly through the lymphatic system with bacteria congregating towards the lymph nodes. Y. pestis avoids immune response and multiply causing the lymph nodes to swell, become tender, and bleed excessively (buboes form) As the infection spreads a patient that does not get treated develops a severe case of bacterial pneumonia and death is usually the result of endotoxic shock.

signs/symptoms

Bubonic Plague Fever, headache, chills, weakness, buboes-swollen lymph nodes in the groin/axilla area Septicemic Plague Fever, chills, weakness, abdomen pain, shock, bleeding into skin or organs-Necrosis: blackening of the skin Pneumonic Plague Fever, headache, weakness, pneumonia

disease

Bubonic plague (most common): infects lymph nodes Pneumonic: infection of the lungs Septicemic plague: infection of the bloodstream

incubation

Bubonic plague: 2 to 6 days after infected Pneumonic: 1 to 3 days

characteristics

Gram-negative coccobacillus (round/rod shaped) Encapsulated Has bipolar staining resulting in a safety pin shape Non motile Facultative anaerobe

virulence

Low infectious dose (3-10 cells cause infection) Capsule (this is anti-phagocytic) F1 antigens and VW antigens are anti-phagocytic Gram negative bacterium, means it contains endotoxins (LPS) at the outer part of cell wall which stimulates immune response 1 Pla gene: Activation of Plasminogen allows for adhesion and blood clotting The bacteria can resist phagocytosis by injecting proteins called YOPs (Yersinia Outer Proteins) into macrophages and other immune cells - injected proteins (YOPs) form pores in which other YOPs travel to get to the cell cytoplasm and limit phagocytosis

prevention

Proper sanitation - Remove ideal rodent habitats, keep home clean and clutter-free Use insect repellant on skin and clothes when outside for extended periods to prevent infected fleas from coming near Use flea control products on pets - pets that roam freely are more likely to come into contact with infected rodents/fleas and could bring it home Isolation of infected individuals to prevent spread of disease Use protective clothing when handling rodents - Hunters wear gloves

reservoir/host range

Reservoir: various rodents (rats, gerbils etc.), insects (fleas), other animals Most common vector: rat flea Host range: Humans, rats and other rodents (rabbits, squirrels, chipmunks, and prairie dogs).

transmission

Transmitted via animal/insect vectors Injected into animals/humans via flea bite/infected animal/rodent Pneumonic plague: droplets released by infected host are breathed in by new host