10.10 MENINGOCOCCAL INFECTIONS
Meningococcal infections usually occur in small outbreaks, presenting as localized meningococcal meningitis or systemic meningococcemia.
Epidemiology: According to antigenic differences in capsular polysaccharide, Neisseria meningitides are divided into 13 serotypes.
Of these, six (A, B, C, W, X and Y) account for virtually all cases of meningococcal disease. Group A infections are more common in India. High-risk factors: Meningococcal disease is more common in young infants (3-24 months). Newborn lt;3 months are protected by transplacental maternal antibodies. Older children are also relatively protected by antibodies acquired during previous colonization, though those with complement-deficiency states, e.g. nephrotic syndrome, hepatic failure and autoimmune disorders, are more susceptible for these infections.Pathogenesis: Meningococcal infection is a highly contagious droplet infection with nasopharyngeal colonization rate as high as ~100% during outbreaks. Post-colonization, infection may remain asymptomatic (colonization) or disseminate hematogenously (invasive disease), to produce meningococcemia and secondary involvement of meninges, skin, adrenals and other organs.
Pathologically, invasive disease is characterized by acute inflammatory reaction (meningitis), vasculitis (rash) and tissue hemorrhages, especially in adrenals (Waterhouse- Friderichsen syndrome), due to a DIC-like state.
Clinical spectrum of disease varies from mild fever and occult bacteremia to a shock-like state and death. Common presentations include:
• Acute meningococcemia, begins as a flu-like illness with fever, sore-throat, headache, myalgia and pathognomonic purpuric skin rash, but may progress rapidly to septic shock, hypotension, DIC, adrenal hemorrhage (Waterhouse-Friderichsen syndrome) and multi-organ failure. Meningitis may or may not be present.
• Acute meningitis is most common manifestation, with/ without skin lesions or signs of meningococcemia.
• Non-CNS focal disease, e.g. pericarditis, pneumonia or arthritis is rare.
• Chronic meningococcemia is rare, with prolonged intermittent fever and rash, arthralgia and headache during fever, lasting for 6-8 weeks.
Complications of meningococcemia include: (a) metastatic infections, e.g. pneumonia or arthritis (b) adrenal hemorrhage, (c) cutaneous vasculitis, leading to skin gangrene and (d) late complications, e.g. immune complex arthritis or cutaneous vasculitis, after 6-9 months.
Diagnosis rests on isolation of organism from blood, CSF or skin lesion. A positive throat culture is not diagnostic and may reflect only the carrier state. Early diagnostic tests, e.g. latex agglutination test, are useful but not as replacement of the culture. Molecular PCR tests are available with high sensitivity and specificity.
Treatment: IV Ceftriaxone 100 mg/kg/day q12-24 hr for 5-7 days is preferred at present over conventional high-dose Penicillin therapy (2-3 Lac U/kg/d q4-6 hr) due to dosage convenience and eradication of nasopharyngeal carrier state. Allergic cases may be treated with ciprofloxacin or meropenem.
Prevention includes:
• Post-exposure chemoprophylaxis: All close-contacts should receive Rifampicin (PO 10 mg/kg BD for 2 days) or a single dose of ciprofloxacin or ceftriaxone. Since penicillin does not eradicate nasopharyngeal carriage, even index case should receive chemoprophylaxis, if treated by penicillin and not ceftriaxone before discharge.
• Pre-exposure immunization with a quadrivalent conjugate vaccine (MCV) is recommended only in high-risk cases or during outbreaks as follows: (a) high-risk cases with two doses at 8 weeks interval, followed by a booster dose every 5 years, (b) during outbreaks, a single dose to close-contacts above 3 months of age, (c) single dose to laboratory or health care workers at risk of exposure with booster every 5 years, if required, (d) for international travels (Ch 9.2.2)
Polysaccharide vaccines (MPSV) are also available but should be used only in high-risk children gt;2 years if MCV is not available, given as a single dose followed by revaccination every 3-5 years. During outbreaks too, a single dose of PPSV may be given in children gt; 2 years or two doses at 3 months interval in younger children 3-24 months of age (Ch 9.2.2).