PLAGUE.pptx

Plaque community

1. PLAGUE PREPARED BY: NEETHU.A LECTURER STCON, KATTANAM

2. PLAGUE Plague is primarily and basically a zoonoses, caused by Y. pestis, involving rodents and fleas. Plague occurs in many forms - enzootically, epizootically, sporadically and in epidemics of all types including anthroponotic and primary pneumonic forms.

3. Problem statement WORLD Plaque is often seen as a problem of the past or an ancient disease that is unlikely to reappear. But continued outbreaks throughout the world attest to its tenacious presence. Plague continues to be a threat because vast areas exist where wild rodents are infected, particularly in endemic countries in Africa, Asia and the Americas. Although plague is predominantly a rural disease, there have been outbreaks among urban populations also.

4. The data shows that from 2010 to 2015, a total of 3,270 cases of human plaque, including 584 deaths, were reported globally In 2004, India reported a localized outbreak of bubonic plague (8 cases and 3 deaths) in the Dangud village, District of Uttarkashi.

5. Epidemiological determinants Agent factors (a) AGENT : The causative agent, Y. pestis is a gram-negative, non-motile, cocco-bacillus The bacteria occur in great abundance in the buboes, blood, spleen, liver and other viscera of infected persons, and in the sputum of cases of pneumonic plaque. It has been shown that plague bacilli can survive, and indeed multiply in the soil of rodent burrows where micro-climate and other conditions are favorable .

6. (b) RESERVOIR OF INFECTION : Wild rodents (e.g., field mice, gerbils, skunks and other small animals) are the natural reservoirs of plague. These are found in mountains, deserts, cultivated areas and forests in temperate and tropical regions. In India, the wild rodent, not the domestic rat.

7. (c) SOURCE OF INFECTION : Infected rodents and fleas and case of pneumonic plague.

8. Host factors (a) AGE AND SEX : All ages and both sexes are susceptible. (b)HUMAN ACTIVITIES : Man may come into contact with natural foci in the course of hunting, grazing, cultivation, harvesting and construction activities or while engaging in outdoor recreation.

9. (c) MOVEMENT OF PEOPLE : Plague is associated with movement of people and cargo by sea or land. Rats and rat fleas are transported in this way.

10. Environmental factors (a) SEASON : In northern India, the "plague season” starts from September until May. The disease tends to die out with the onset of hot weather. I n south India, there was no definite plague season. The disease was found to be active all the year round. (b) TEMPERATURE AND HUMIDITY: A mean temperature of 20 to 25 deg. C, and a relative humidity of 60 per cent and above are considered favorable for the spread of plague.

11. (c) RAINFALL : Heavy rainfall, especially in the flat fields tend to flood the rat burrows. (d) URBAN AND RURAL AREAS: Plague had failed to gain a foothold in many towns of India perhaps due to untoward ecological conditions and lack of efficient flea vectors (as in Chennai and Assam). (e) HUMAN DWELLINGS: Rats, frequent dwelling houses and where housing conditions are poor, there may be an abundance of rats and rat fleas all the year round, and contact with man occurs readily.

12. Vectors of plague The commonest and the most efficient vector is the rat flea, X. cheopis, But other fleas may also transmit the infection, e.g., X. astia, X. brasiliensis and Pulex irritans (human flea). Both sexes of the flea bite transmit the disease.

13. Blocked flea A flea may ingest upto 0.5 cu.mm of blood which contain as many as 5,000 plague bacilli. The bacilli multiply enormously in the gut of the rat flea and may block proventriculus so that no food can pass through. Such a flea is called a "blocked flea". A blocked flea eventually face starvation and death because it is unable to obtain a blood meal.

14. It makes frantic efforts to bite and suck blood over and over again; and in so doing, it inoculates (regurgitates) plague bacilli into the bite wound each time it bites. A blocked flea, therefore, becomes an efficient transmitter of plague. A partially blocked flea is more dangerous than a completely blocked flea because it can live longer.

15. Flea indices Flea indices are useful measurements of the density of fleas. They are also useful in evaluating the effectiveness of spraying programme. The following flea indices are widely used in rat flea surveys : TOTAL FLEA INDEX : the average number of fleas of all species per rat. CHEOPIS INDEX: it is the average number of X-cheopis per rat. SPECIFIC PERCENTAGE OF FLEAS : It is the percentage of different species of fleas that are found on rats. BURROW INDEX : It is the average number of free-living fleas per species per rodent burrow

16. HUMAN PLAGUE Mode of transmission Human plague is most frequently contracted from: (a) the bite of an infected flea, (b) occasionally by direct contact with the tissues of the infected animal or (c) by droplet infection from cases of pneumonic plague.

17. There are at least 5 basic types of transmission cycles in plague. These cycles are as follows : 1. Commensal rats → rat fleas → man 2. Wild rodents → wild rodent fleas or direct contact → man 3. Wild rodents, peri domestic rodents, commensal rodents → wild rodent fleas, peri domestic rodent fleas, commensal rodent fleas → man 4. Man → human flea (Pulex irritans) man 5. Man → man

18. Incubation period (a) bubonic plague 2 to 7 days (b) septicemic plague 2 to 7 days (c) pneumonic plague 1 to 3 days

19. Disease in man ( a) Bubonia plague : This is the most common type of the disease. The infected rat fleas usually bite on the lower extremities and inoculate the bacilli. The bacilli are intercepted by the regional lymphatic glands where they proliferate. Typically the patient develops sudden fever, chills, headache. prostration and painful lymphadenitis. Usually within a few days greatly enlarged tender lymph nodes (buboes) develop in the groin and less often in the axilla or neck, depending upon the site of the bite by the flea. Bubonic plague cannot spread from person to person as the bacilli are locked up in the buboes and do not find a way or easy exit.

20. (b) Pneumonic plague : It is rare Follows as complication of other 2 types Incidence usually below 1%. Highly infectious and spread from man to man by droplet infection. Plague bacilli present in the sputum

21. (C) Septicaemic plague Rare except for accidental laboratory infections. Bubonic plague may develop into septicaemic blague

22. Laboratory investigations (a) Staining : It is important to prepare smears of the clinical material (e.g., bubo fluid, sputum) to demonstrate bipolar bacilli in the specimen. (b) Culture : Blood for culture should be collected from all patients. (c) Serology : Acute and convalescent specimens of blood sera should be collected for antibody studies. (d) Other methods : These include inoculation of guinea pigs or mice or immunofluorescent microscopic test.

23. PREVENTION AND CONTROL 1. Control of cases (a)EARLY DIAGNOSIS : During epidemic situations, diagnosis of plague can be made readily on clinical ground In other situations, “rat falls" (dead rats) provide a useful warning of a possible outbreak. It is essential that plaque-suspected humans and rodents be examined bacteriologically to confirm the presence of plague.

24. (b) NOTIFICATION : If a human or rodent case is diagnosed, health authorities must be notified promptly. Case notification is required by International Health Regulations (c) ISOLATION : Although most bubonic plague patients are non-infectious, isolation is recommended whenever possible. All patients with pneumonic plague including suspected cases should be isolated.

25. (d) TREATMENT : Treatment must be started without waiting for confirmation of the diagnosis . The drug of choice is streptomycin (30 mg per kg of body weight daily) administered intramuscularly in two divided doses for 7 to 10 days. Tetracycline orally (30–40 mg per kg of body weight daily) is an alternative drug, and is sometimes given in combination with streptomycin. Gentamycin administered as a 2 mg/kg body wt. loading dose, then 1.7 mg/kg body wt. every 8 hours intravenously is effective. Penicillin is rather ineffective. Sulphonamides may be used if other drugs are not available.

26. (e) DISINFECTION Disinfection of sputum, discharges and articles soiled by patient Dead bodies should be handled with aseptic precautions

27. 2. Control of fleas The most effective method to break the chain of tran smission (rodent → flea → man) is the destruction of rat fleas by the proper application of an effective insecticide. Flea Control must precede or coincide anti-rodent measures. In general DDT and BHC should be used as dusts containing 10 per cent and 3 per cent of the active ingredient respectively. In areas where resistance to one or both of these insecticides occurs, dusts of carbaryl (2%) or malathion (5%) should prove effective. About 2 to 3 g of insecticide formulation will be needed for each sq. meter of surface requiring treatment .

28. 3. Control of rodents Continuous mass destruction of rodents is an important plague-preventive measure. The long-term policy for the control of rodents should be based on improvement of general sanitation, improvement of housing and quality of life.

29. 4. Vaccination Immunization with plague vaccine is a valuable preventive measure. The WHO recommends that under all circumstances, vaccination should be only for the prevention, not the control of human plague . To be effective, vaccination should be carried out at least a week before an anticipated outbreak, and the vaccine should be given in 2 doses. The vaccine is given subcutaneously in two doses of 0.5 and 1.0 ml at an interval of 7 to 14 days

30. 5. Chemoprophylaxis Chemoprophylaxis is a valuable preventive measure, highly recommended. It should be offered to all plague contacts, medical, nursing and public health personnel exposed to the risk of infection. The drug of choice is tetracycline. For adults, the dose is 500 mg 6-hourly for 5 days . A cheaper alternative is sulfonamide, 2 to 3 gram daily for 5 to 7 days.

31. 6. Surveillance Surveillance should cover all aspects of rodent and human plague, e.g., microbiology, serology, entomology, mammalogy, epidemiology and ecology. On the basis of information provided by surveillance, effective control measures must be established . Surveillance of plague in its natural foci should, therefore, replace quarantine measures which have been shown to be ineffective .

32. 7. Health education Education should aim at providing the public with the facts about plague and at enlisting their cooperation. Emphasis must be placed on the need for the prompt reporting of dead rats and suspected human cases so that preventive measures can be taken.