Meningitis

 Meningitis caused by differnt M.O (bacteria,viruses, fungi.....etc) but the commonest type of meningitis is bacterial meningitis which caused primarily by 3 M.O: 1. Neisseria meningitidis. meningo-coccal meningitis. 2. Streptococcus pneumoniae 3. Haemophilus infuenzae type b (Hib).  Those m.o constitutes 80-90% of all types of meningitis,

MENINGOCOCCAL MENINGITIS

It is an acute bacterial disease characterized by sudden onset of fever, intense headache, nausea, vomiting, neck stiffness ± pink petechial rash (in 50%).The condition may progress to coma (vary from cloudy consciousness to deep coma). CFR: Before Rx > 50 %.,After Rx → 8 – 15 %. In addition % of survivors will suffer from long-term squeal as epilepsy, hearing loss (once cranial nerves damage occur, it never return to normal). So the earlier the diagnosis, the least the complications and the better the prognosis.

Diagnosis 1.Clinical picture. 2.CSF examination and culture (lumber puncture). 3.Blood culture. Infectious agent: Infectious agent: Neisseria meningitidis, 12 sero-groups, only 5 of which (A, B, C, and recently W-135 and X) can cause epidemics. These are important in prevention, control and vaccine preparation

Occurence Distribution world-wide. Disease occurring sporadically, some time endemic, and in small outbreaks in most part of the world. In Europe and North America the incidence of meningococcal disease is higher during winter and spring; in Sub-Saharan Africa the disease classically peaks during the dry season.

Occurence Risk factors for meningococcal meneigitis includes 1) Age: Infants have the highest risk of meningococcal disease & decrease after infancy and then increase in adolescence and young adulthood. 2) Underlying immune deficiencies. 3) Crowding. 4) Low socioeconomic status. 5) Active or passive exposure to tobacco smoke. 6) Concurrent upper respiratory track tract infections increase the risk of meningococcal disease.

Reservoir Reservoir : Humans. Mode of transmission: Mode of transmission: Direct contacts including respiratory droplets from nose and throat of infected people. Up to 10-20% of people may be asymptomatic carrier with nasopharyngeal colonization. Less than 1% of them progress to invasive disease. Polluted fomites transmission is insignificant i.e. indirect transmission is not an important route (since the M.O is delicate one and easily destroyed by U.V light and heat).

Incubation period Incubation period: 2 – 10 days, commonly 3 – 4 days. Period of communicability Without treatment until the M.O is no longer present in nose and mouth discharges. But usually disappear from nasopharynx within 24 hours after start antibiotic treatment.Susceptibility: Susceptibility to clinical disease is low and decrease with age; this induces a higher ratio of carriers to cases. Risk factors for meningococcal disease:age, crowding, low socioeconomic status etc.

Control and prevention A. Preventive measures: 1. Public health education about the need to reduce droplet infection. 2. Avoid overcrowding. 3. Vaccines: Vaccines containing groups A, C, Y and W-135 meningococcal polysaccharides are been available. Quadrivalent ACYW-135 vaccine is safe, effective in adults & children above 2 years, but do not elicit long term protection, particularly in children under 5 years of age.(so not used in routine childhood immunization program).

Quadrivalent A,C,Y,W-135 indicated in: Outbreak control. High risk groups:- 1.Hajj pilgrims, military groups. 2.Travelers to countries where disease is epidemic. Reimmunization may be considered within 3–5 years if indications still exist. No vaccine effective against group B meningococci

B) Control of patient, contacts and environment: 1. Reporting. 2. Isolation: respiratory isolation, usually at hospital for 24 hours after start R X. 3. Concurrent disinfection & terminal disinfections. 4. Quarantine: not applicable. 5. Protection of contacts: Daily surveillance of house-hold contacts for early signs and symptoms of illness. Prophylactic chemotherapy for house contacts, close friends in schools, military personnel, young children in day-care.

Antibiotic prophylaxis : Rifampicin (600 mg twice daily for 2 days in adults, children over 1month old, 10 mg/kg; under 1 month, 5 mg/kg), or ciprofloxacin (500 mg, single dose). Generally immunization not recommended 6. Specific Rx: Penicillin in high doses given parenteral is the drug of choice; ampicillin and chloramphenicol are also effective. Treatment should be start as early as possible, even before identification of M.O. The patient should be given rifampicin prior to discharge from hospital to ensure elimination of the M.O.

C- Epidemic measures: 1) Careful surveillance, early diagnosis, and immediate treatment of suspected cases. 2) Immunization campaign must be implemented for children 2- 5 years of age if an outbreak occur in a large institution when group A,C,Y,W-135 are responsible. 3) Reduce overcrowding & ventilating living quarters. 4) Mass chemoprophylaxis is usually not effective in controlling outbreaks, except for small population.

Haemophilus Meningitis It was the most common bacterial M. in child aged 2 months – 5 years before Hib vaccine wide spread. Infectious agent: Haemophilus infuenzae type b (Hib). Occurrence Occurrence: worldwide, 2 months – 3 years, unusual > 5 years. Reservoir Reservoir: Humans I.P, period of communicability and susciptibility I.P, period of communicability and susciptibility : same.

Method of control A) preventive measures: Vaccines: routine childhood immunization (introduce in Iraq since end of 2011): 1 st dose → age 2 months (Hib+DPT+HB) 2 nd dose → age 4 months (Hib+DPT) 3 rd dose → age 6 months (Hib+DPT+HB) Booster → age 18 months (Hib+DPT) B) Control of patient, contacts and environment: Protection of house contacts: By using rifampicin. Specific Rx: Ampicillin parenteral is drug of choice, chloramphenicol, ceftriaxone are also effective. The patient should be given rifampicin prior to discharge from hospital.

Influenza

Acute viral respiratory infection, characterized by systemic manifestations fever, rigors, headache, malaise & muscle pains with local manifestations- of coryza, sore throat and severe protracted cough. The important complication is secondary bacterial pneumonia. Severe illness and death during annual influenza epidemics (seasonal influenza) occur primarily among elderly (80-90% of deaths occur in persons over 65 yrs) and those debilitated by chronic illnesses. The excess mortality varies and depends on the prevalent virus type.

Infectiuos agents Influenza Virus Types A, B & C according to antigenic properties. Type A 1. Type A usually associated with widespread epidemics (seasonal flu) & pandemics (pandemic flu). Influenza A subtypes are classified depend on surface Ag which are; Haemagglutinin H (H1, H2, H3) &Neuraminidase N (N1, N2) Ag. Influenza A include 3 subtypes {H1N1, H2N2, H3N2}. Type B 2. Type B is infrequently associated with regional or widespread epidemics (seasonal flu). Type C 3. Type C is associated with sporadic and minor localized outbreaks.

Antigenic variation o Antigenic shift: Emergence of completely new virus subtypes- at irregular intervals and only for type A viruses- result from antigenic shift in HA gene or unpredictable recombination of human and mammalian or avian antigens and lead to pandemics. Type B has no animal reservoir → no antigenic shift. o Antigenic drift: The relatively minor antigenic changes or spontaneous mutation (antigenic drift) of A & B viruses responsible for frequent epidemics and regional outbreaks which occur constantly (annually) and require annual reformulation of influenza vaccine.

Occurence Pandemics (rare) -type A. Epidemics ( almost annual)-type A, B or both. Localized out breaks and sporadic cases (every year) –type C. Pandemics of Influenza: Is the emergence of the disease among humans by new subtype of influenza viruses with new surface proteins, and ranking as global health emergencies, here children and adults are equally susceptible. e.g. 1889, 1918, 1957, 1968, 2009.

Occurrence Influenza epidemic (seasonal flu): Attack rate during epidemics 10-20% in the general community to more than 50 % in closed community (schools). Epidemics generally last 3-6 weeks, usually in winter, while outbreaks or sporadic cases may occur in any month.

Reservoir: -Human Modes of transmission: Airborne spread among crowded populations in enclosed spaces. - Direct contacts. - Handling of contaminated articles. I.P: 1-3 days. Period of communicability: 3-5 days from clinical onset (adult). Up to 7 days in young children.

Susceptibility & resistance Infection produces immunity to the specific antigenic variant of the infecting virus, and the duration of immunity depend on the degree of antigenic similarity between viruses causing immunity. Pandemics (emergence of new subtype) → all susceptible.

Methods of control A. Preventive measures: Health education to the public about personal hygiene to avoid unprotected cough and sneezes, overcrowding etc. Inactivated influenza vaccines (killed) derived from A and B viruses that circulated during previous season, 70-90% protection.Given at autumn & repeated annually (routinely given for those risky groups).It may cause low grade fever and redness.2 doses one month apart, repeated annually Recently: live attenuated trivalent vaccine A Given intranasal, promising results Chemoprophylaxis (Anti-viral drugs)

Indication of vaccine 1. Healthy individuals >65 years (the vaccine less effective in preventing infection but: ↓ severity, ↓ complications, ↓ death by 80%) 2. Individual with chronic diseasese.g. DM, renal failure,haemoglobinopathies and immunosuppresed. 3. Individual provides care to those at high risk including close contacts and health staff.

3. Chemoprophylaxis of type A Amantadine or rimantadine. Its effective chemoprophylaxis of influenza A but not B (about %). Same indications as vaccine. Chemoprophylaxis used when vaccine not available or as a supplement to vaccine when immediate maximal protection is desired against type A.

B) Control of pts, contacts and environment: 1. Reporting: Only for outbreaks. 2. Isolation: Impractical because of delay Dx. 3. Concurrent disinfection: Not Applicable. 4. Quarantine: Not Applicable. 5. Protection of contacts: by chemoprophylaxis. 6. Investigation of contacts and source of infection: None.

7. Specific Rx: Amantadine or rimantadine 100 mg twice daily, within 48 hrs of onset of illness and for 3-5 days can reduce symptoms and virus titer in respiratory secretion. - Rx of secondary bacterial infections. - Avoid salicylates in children.

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