1. (insert screaming now)
The Plague
(insert screaming now)
Vaughn and Tess February 4, 2008

2. 4 Flavours of The Plague
Bubonic – Fever, buboes (very swollen, painful lymph nodes that can form abscesses), % mortality
*Pneumonic – coughing, sputum, crackling, dyspnea; near 100% mortality within 2-4 days
*Septicaemic – Fever, GI symptoms (vomitting, diarrhea, pain), purpura, petechiae in late stages; 75% mortality within a few days, quite rare
Meningeal – Fever, same as meningitis; Very rare
*Can be primary or secondary plague infection

3. Clinical Signs of Bubonic Plague
Buboes – Painful, swollen lymph nodes (axillary, inguinal, femoral or cervical)
- Can supparate.
Bacteria migrate to lymph nodes, resist destruction by phagocytes and multiply rapidly leading to necrosis and hemorrhage

4. Disease course Incubation of 1-7 days
Usually starts as bubonic plague, then bacteria spread via lymph nodes through blood (sepsis)
Patients die of pneumonic plague, or septicaemic plague (multi-organ failure)
Necrosis and petechiae characteristic of late stage disease.

5. Disease Source Yersinia pestis – rod shaped, gram neg. bacteria
Most are killed by neutrophils, but a few are taken up by histiocytes which can not kill them. Re-synthesize their capsule resist phagocytosismultiply rapidly

6. Vectors Main vector – Oriental Rat Flea (Xenopsylla cheopsis)
Stomach becomes blocked from abundance of bacteria. When the flea bites it’s next victim, the bacteria are regurgitated into the blood.

7. Reservoirs Many wild rodents
Black rat (Rattus rattus) is the main culprit
Lives in close proximity to humans (homes)
“Rat-fall” is common omen of an epidemic
Domesticated rodents and pets

8. Transmission Fleas live in nests of wild rodents
Disturbance (war, flood etc) cause wild rodents to migrate to urban areas.
Infected fleas jump from wild rodents to domesticated rodents, pets Humans
Direct infection from animals possible
Human-to-human transmission via respiratory droplet (pneumonic plague)

9. Diagnosis
Y. pestis is easily recovered from: blood (septicaemic plague), aspirates of bulboes (bubonic plague), sputum (pneumatic plague) and differentiated in the lab
Capsular fraction 1 antigen basis of serological tests
Note: Can be confused with Y. psuedotuberculosis in labs with little or no experience in dealing with it.

10. Management Requires prompt antibiotic treatment.
With pneumonic or septicemic plague, must be administered within 1 day of symptoms.
Treatment: Use 1 antibiotic; Streptomycin preferred; gentamicin and tetracycline group also effective
Course of treatment: at least 7-10 days
Resistance: Only 1 case of multi-drug resistance found in Madagascar.
When given early, reduces mortality to 5-14%

11. Prevention
Formol-killed vaccine once available for health care workers that conferred some immunity against bubonic plague, but not pneumonic plague
Mass immunization not in place
Not practical as immunity too slow to develop in the case of an outbreak
Promise in new vaccines that are under development

12. Y. pestis Epidemics
Recorded since biblical times, many epidemics throughout history
Examples:
1st epidemic (Antiqua) – 541 AD; Mediterranean region, 50-60% of pop.
2nd epidemic (Medievalis) – ; 1/3 of the pop. of Europe died (20-30 million)
3rd epidemic (Orientalis) – ; started in China, spread through Asia; 10 million died in India alone

13. The Black Death Epidemic

14. The Modern Day Situation
Roughly 2000 cases and 200 deaths per year (WHO)
Vast majority in Africa
About 13 cases a year in the US

15. Anatomy of the Plague

16. Plague Control Isolation of patients with pneumonic plague
Flea and rodent control
Start therapy if plague is suspected – can take too long to confirm.

17. Plague as a Weapon Aerosolized bacteria  Pneumonic plague
Takes hours to confirm diagnosis
50kg of Y. pestis could infect 150,000 and kill 36,000 in a city of 5 million in a worst-case scenario.
Bacteria would remain viable in an aerosol for 1 hour for a distance of 10 km.

18. Discussion
Would we be better off putting money toward vaccines or emergency response with regards to a bio-terrorist attack? Why?