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. In 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.

14. 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.

15.  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.

16. 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 :
(a) TOTAL FLEA INDEX : the average number of fleas of all species per rat.
(b) CHEOPIS INDEX: it is the average number of X-cheopis per rat.
(c) SPECIFIC PERCENTAGE OF FLEAS : It is the percentage of different species of fleas that
are found on rats.
(d) BURROW INDEX : It is the average number of free-living fleas per species per rodent
burrow

17. 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.

18. 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

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

20. 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.

21. (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

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

23. 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.

24. 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.

25.  (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.

26. (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.

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

28. 2. Control of fleas
 The most effective method to break the chain of transmission (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 .

29. 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.

30. 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

31. 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.

32. 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 .

33. 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.