Black Death Or Great Death is acute highly fatal zoonotic bacterial disease mainly affects wild rodents and commensal rats , man and small animals affected incidentally
.Infectious agent : Yersinia Pestis , also called Pasteurella Perstis -
It is gram negative bacillus , easily affected by sun rays after exposure for hours and dehydrated at low temperature
Its virulence related to to ability to produce exotoxin , endotoxin and substance called '' Fraction"1. Bacillus can survive and multiply in the soil of rodents burrows where conditions are favorable
: Reservoir of infection
Wild rodents are natural reservoir of infection and the disease spread by resistent species . The immunity disappear after 2 or 3 generation
: Mode of transmission
Vector transmission in which disease transmitted by bite of infected rat fleas during act of feeding
Mechanical transmission in which the contaminated mouth parts of fleas transmit the disease through human skin or site of bite wound
Droplet infection that considered man to man transmission result from inhalation of air- borne
droplets coming out from patient with pneumonic plague or bubonic plague , also droplets of household pets ,especially cats , with Plague Pharyngitis can transmit the disease in both sides
:Source of infection to man
( Infected rat - fleas (Xenopsylla Cheopis
Tissues of infected rodents
Air - borne droplets
:Host factors
All ages and sexes are susceptible
- People activities and car goes by sea and land increase incidence of infection because rats and fleas transported by this way
Immunity : man gains life long immunity after an infection
Environmental factors
The favorable temperature for spread of infection is 20- 35 C and relative humidity 60% and above . Summer season is favorable than winter
:Clinical picture of Plague in man
There are 3 types or forms of Plague in man after incubation period of 2 - 6 days
Bubonic Plague in which there is painful enlargement of lymphatic glands , usually in groin or axilla . Often suppuration occurs and it is considered favorable sign. The microbe may escape from lymph bode and invade the blood stream and generalized infection occurs . The generalized infection cause death due to heart failure . fefer usually present . This form produced after bite of infected fleas and it conistitutes 75% 0f cases ( the most common form of plague ) and the rest is for others
2 - Pneumonic plague is highly fatal and occurs due to inhalation of air - borne droplets or as complication of bubonic- septicemic plague . This form transmit from man to man. Findings include malaise , headache , nausea , coughs and expectorations. The sputum tinged with blood . The body .
exhibits cyanosis in latter stage and death occurs on the fourth or fifth day or earlier due to suffocation .
3 - Septicemic Plague occurs when the microbe spread haematogenously to virtually every organ. It may produced from the first type . Findings include fever , nose bleedibg , diarrhea . It s course is 18 hours to 3 days .Septicemic Plague is invariably fatal .
