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Plague Disease Epidemiology and Prevention

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  1. Plague Dr Navya N Assistant Professor Department Of Community Medicine

  2. SPECIFIC LEARNING OBJECTIVES • To understand the epidemiology of plague disease • To understand the clinical features of plague • To understand the prevention and control of plague

  3. INTRODUCTION • Zoonotic disease • Causative organism – Yersinia Pestis • One of the oldest diseases known to man • Exits in natural foci – transmitted- infected flea bites

  4. INTRODUCTION • Many forms - enzootically, epizootically, sporadically and in epidemics • Endemic in many parts of the world • Widely distributed in the tropics and subtropics • In SEAR, natural foci of plague- India, Indonesia, Myanmar and possibly in Nepal

  5. PLAGUE PANDEMICS • Justinian plague: Sixth century-100 million victims • Black Death: 14th century - 50 million deaths. • 3rd pandemic: Hong Kong in 1894 • This pandemic resulted in 13 million deaths in India

  6. PROBLEM STATEMENT • Plague outbreaks continued to occur- decreasing frequency • Globally in 2013 – 783 cases- human plague – 126 deaths • In India – 2004- localized outbreaks – bubonic plague – 8 cases, 3 deaths- Dangud village- Uttarkashi

  7. AGENT FACTORS • Gram - negative , non motile, coccobacillus • Bipolar staining with special stains – Wayson’s stain • Reclassified as Enterobacteriaceae • Non sporulating, non - lactose fermenting

  8. AGENT: YERSINIA PESTIS

  9. RESERVOIR OF INFECTION • Wild rat (Tatera Indica) • Field mice • Gerbils • Disease -Maintained and spread by resistant species of wild rodents (Rodents immune to plague)

  10. SOURCE OF INFECTION • Infected rodents and flea • Case of pneumonic plague

  11. PLAGUE VECTORS • Xenopsyllacheopis(Oriental rat flea; worldwide) • Oropsyllamontanus(United States) • Nosopsyllusfasciatus(Nearly worldwide) • Xenopsyllabrasiliensis(Africa & India) • Xenopsyllaastia(Indonesia and Southeast Asia) • Xenopsyllavexabilis(Pacific Islands)

  12. TRANSMISSION • Flea bite (78%) • Direct animal contact (20%) − Tissues, body fluids, scratches, bites − Enters through break in skin • Aerosol (2%) • Human cases − April-November (93%) − Increased activity of fleas and hosts

  13. LIFE CYCLE

  14. BLOCKED FLEA • Flea- ingest upto 0.5 cu.mm of blood- 5000 plague bacilli. • Plague bacilli multiply enormously- gut of rat flea- may block the proventriculus- no food - blocked flea • Blocked flea- eventually faces starvation and dies as it is unable to obtain blood meal. • A blocked flea is an efficient transmitter of plague • A partially blocked flea is more dangerous then a completely blocked flea because it can live longer

  15. HOST FACTORS • AGE and SEX : all ages and both sexes • HUMAN ACTIVITIES : activities – increases flea-man contact • MOVEMENT OF PEOPLE : cargo, sea or land • IMMUNITY : no natural immunity

  16. ENVIRONMENTAL FACTORS • SEASON : north india – September – may South- no definite plague season • TEMPERATURE AND HUMIDITY : 20-25 deg C humidity – 60% • RAINFALL : heavy rainfall – flood the burrows – protective factor • URBAN and RURAL AREAS • HUMAN DWELLINGS

  17. PLAGUE IN RODENTS • Primarily a disease of rodents • Infection is maintained- natural foci of the disease in wild rodent colonies • Enzootic (maintenance) hosts • Epizootic (amplification) hosts

  18. PLAGUE IN RODENTS • Enzootic hosts: • Relatively mild illness and low mortality rates. • Voles and mice • Epizootic hosts: • High susceptibility and high mortality. • Mice, rats, voles, gerbils, ground squirrels and marmots • Rats have historically been a primary carrier

  19. URBAN PLAGUE • Infected fleas or rodents move to urban area • Commensal (domestic) rodents infected • Rapid die off • Fleas seek new host − Domestic cats or humans • Poverty, filth, homelessness

  20. HUMAN PLAGUE -CLINICAL FEATURES • Bubonic Plague • Septicaemic Plague • Pneumonic Plague

  21. BUBONIC PLAGUE • Mode of entry: Flea bite • IP: 2-6 days • Infection spreads to the regional lymph nodes • Headache, chills, fever, malaise and pain in the affected regional lymph nodes • Buboes: Inflammation and swelling in one or several nodes (Axillary and supraclavicular) • Mortality – untreated – 50-60% and treated - <5%

  22. Bubonic plague

  23. SEPTICAEMIC PLAGUE • Invades and continues to multiply in the bloodstream. • Secondary to bubonic plague or without detectable lymphadenopathy. • DIC, multiple organ failure and ARDS • Complications : Plague pneumonia, plague meningitis and hepatic or splenic abscesses • Mortality – untreated 100%

  24. SEPTICAEMIC PLAGUE

  25. PNEUMONIC PLAGUE • IP: 1-3 days • Least common-most dangerous and fatal form • Primary – Inhalation of infected droplets – Y Pestis • Secondary complication of septicaemic plague • Chills, fever, headache, body pains, weakness and chest discomfort. • Person to person spread possible • Death if specific antibiotic therapy is not begun within 18 - 24 hours of onset

  26. Plague

  27. PREVENTION & CONTROL • Early diagnosis & Treatment • Chemoprophylaxis • Control of fleas • Control of rodents • Vaccination • Surveillance • Health education

  28. DIAGNOSIS • Demonstrate the bacilli • Blood, sputum & aspirates from suspected buboes • Gram, Giemsa, Wright, or Wayson stain • Supportive but not confirmatory

  29. DIAGNOSIS • Cultures: Specific phage lysis • 4 fold in titre to the Yersiniapestis F1 antigen by passive haemagglutination test • Dipstick PHTs • ELISAs for detecting IgM and IgG antibodies

  30. PREVENTION AND CONTROL • Early diagnosis and treatment • Notification: • Antibiotics: Streptomycin drug of choice – IM -2 divided doses – 7-10 days ( 30mg/kg/BW) • Others - Tetracycline, gentamycin • cephalosporins are NOT effective • Isolation • Disinfection

  31. Plague Prophylaxis • Close contacts of cases- pneumonic plague • Persons suspected to have had direct contact with body fluids or tissues of - infected mammal in previous six days • Tetracycline and Chloramphenicol

  32. FLEA INDICES (Multiplication of this index by 100 gives the percentage index)

  33. FLEA INDICES

  34. RODENT AND FLEA CONTROL • Isolate infected animals −Limit number of people in contact, Personal protection- Surgical mask, gloves, eye protection • Flea control−Most effective method to break the chain of transmission (Rodent-flea-man) −Insecticidal spraying (DDT and BHC), malathion −Indoor spraying, Rat burrows- insufflated- insecticidal dusts

  35. VACCINATION • For prevention, not the control of the human plague • Formalin killed vaccine is used. • 1 week prior to anticipated outbreak • 2 doses- SC - interval of 7-14 days • Immunity develops within 7 days • Booster dose to given every 6 months

  36. PREVENTION AND CONTROL • Public health education −Notification of dead rats and suspected plague case • Surveillance • Epidemiological investigation −To determine source of infection −Distribution −Prevalence −Potential spread to human population

  37. SUMMARY ???

  38. Thank you!

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