epi of pertussis .pptx

DISEASES- EPIDEMIOLOGY

1. EPIDEMIOLOGY OF PERTUSSIS

2. PERTUSSIS It is also called as WHOOPING COUGH. Is an acute infectious disease, usually of young children caused by Bordetella pertussis.

3. It is clinically characterized by an insidious onset with mild fever and an irritating cough, gradually becoming paroxysmal with characteristic “ whoop ” (loud crowing inspiration) often with cyanosis and vomiting .

4. The spectrum of the disease varies from severe illness to atypical and mild illness without whoop. The Chinese call it a “ Hundred Day Cough ”.

5. EPIDEMIOLOGICAL DETERMINANTS

6. A GENT The causative agent in large proportion is Bordetella pertussis. In less than 5% cases it is B.pa r apert u ssis.

7. Certain viruses such as adenovirus, parainfluenza virus are also implicated in the whooping cough syndrome. Bordetella pertussis occurs in smooth and rough phases, capsulated and non capsulated form.

8. It elaborates an exo and edotoxin . Clinical disease is associated with encapsulated, phase I strains.

9. SOURCE OF INFECTION B. pertussis infects only man . The source of infection is a case of pertussis. A chronic carrier state does not exist .

10. INFECTIVE MATERIAL The bacilli occurs abundantly in the nasopharyngeal and bronchial secretions , which are infective. Objects freshly contaminated by such discharges are also infective.

11. INFECTIVE PERIOD Whooping cough is most infectious during the catarrhal stage.

12. The infective period may be considered to extend from one week after exposure to about 3 weeks after the onset of the paroxysmal stage although communicability diminishes. rapidly after the catarrhal stage.

13. SECONDARY ATTACK Averages 90% in unimmunized household contacts.

14. HOST FACTORS

15. AGE : Whooping cough is primarily a disease of infants and preschool children. The highest incidence is found below the age of 5 years.

16. In adults pertussis is often unrecognized because of it’s atypical course. However the older age groups represent an important source of infection for susceptible infants.

17. GENDER Incidence and fatality are observed to be more among female than male children.

18. IMMUNITY Adequate immunization ensures a good immunity to the disease. Also recovery from pertussis also confers immunity . Maternal antibodies do not protect

19. ENVIRONMENTAL FACTORS Pertussis occurs throughout the year, but the disease shows a seasonal trend with more cases occurring during winter and spring months, due to overcrowding.

20. Socio economic conditions and ways of life also play a role in the epidemiology of the disease. Thus the exposure of risk is greater in the lower social classes living in overcrowded conditions.

21. MODE OF TRANSMISSION Whooping cough is mainly spread by droplet infections and direct contact . Each time the patient coughs, sneezes or talks the bacilli are spread into the air.

22. Most children contract infection from their playmates who are in the early stages of the disease. The role of fomites appears small, unless they are freshly contaminated.

23. INCUBATION PERIOD Usually 7 to 14 days , but not more than 3 weeks.

24. CLINICAL COURSE B pertussis produces a local infection; the organism is not invasive . It multiplies on the surface epithelium of the respiratory tract and causes inflammation and necrosis of the mucosa leading to secondary bacterial infection.

25. Three stages can be seen in the clinical course of the disease. 1.CATARRHAL STAGE. 2. PAROXYSMAL STAGE. 3. CONVALESCENT STAGE.

26. C AT ARRHAL S T A GE Lasts for 10 days. It is characterized by its insidious onset, lacrimation, sneezing and coryza, anorexia, malaise and general hacking night cough that becomes diurnal.

27. PAROXYSMAL STAGE Lasts for 10 weeks. It is characterized by bursts of rapid, consecutive coughs followed by a deep, high pitched inspiration (whoop).

28. It is usually followed by vomiting. In young infants it may cause cyanosis and apnoea.

29. In adults and adolescents, uncharacteristic, persistent cough may be the only manifestation .

30. CONVALESCENT STAGE Lasts for 1-2 weeks.

31. COMPLICATIONS Complications occur in 5-6 percent cases, most frequently in infants aged less than 6 months. The chief complications are; bronchitis, bronchopneumonia and bronchietasis.

32. The violence of the paroxysms may precipitate subconjunctival haemorrhages, epistaxis, haemoptysis and punctate cerebral haemorrhages which may cause convulsions and coma.

33. Bronchopneumonia occurs in about 5.2 % cases. The incidence of pertussis related encephalopathies is 0.9% /100,000 .

34. CONTROL OF PERTUSSIS

35. CAS E S The general principles of control includes early diagnosis , isolation treatment of cases , disinfection of discharges from nose and throat.

36. Early diagnosis is possible only by bacteriological examination of nose and throat secretions (obtained from nasopharyngeal secretions - swabs). Erythromycin is the drug of choice.

37. A dose of 30-50mg/kg of body weight in 4 divided doses for 10 days has been recommended. Possible alternatives are ampicillin, septran or tetracycline.

38. Antibiotics may prevent or moderate clinical pertussis when given during incubation period or in early catarrhal stage.

39. During paroxysmal phase of disease, antimicrobial drugs will not change the clinical course but may eliminate the bacterium from the nasopharynx and thus reduce the transmission of the disease.

40. C ON T A C T S Infants and young children should be kept away from cases. Close contacts may be given prophylactic antibiotics (erythromycin or ampicillin) for 10 days to prevent the infecting bacteria to become established.

41. The best protection is to administer a dose s of DPT/ PENTAVALENT to his siblings.

42. ACTIVE IMMUNIZATION The vaccine is usually administered in the national immunization programme as combined DPT.

43. In India, the National Policy is to immunize against diptheria, pertussis and tetanus simultaneously, by administering 3 doses (each dose about 0.5 ml) of P entavalent vaccine intramuscularly- at 1 month interval, starting at the age of 6 weeks.

44. A booster dose is given at 18-24 months & 5 years. Children whose vaccination series has been interrupted should have their series resumed, without repeating previous doses.

45. UNTOWARD REACTIONS Pertussis vaccines may give rise to local reactions at the site of injection, mild fever, irritability.

46. The rare vaccine reactions are persistent crying (more than 3 hours) include inconsolable screaming , seizures, hypotonic hypo responsive e pisodes, anaphylactic reaction and very rarely encephalopathy.

47. CONTRAINDICATIONS anaphylactic reaction, encephalopathy , a personal or strong family history of epilepsy , convulsions or similar CNS disorders or reaction to one of the previously given triple antigen injection.

48. PASSIVE IMMUNIZATION Hyperimmune globulin is administered. The merit of passive immunization is yet to be established.

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