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Indian Journal of Medical Sciences
Medknow Publications on behalf of Indian Journal of Medical Sciences Trust
ISSN: 0019-5359 EISSN: 1998-3654
Vol. 57, Num. 8, 2003, pp. 369-372
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Indian Journal of Medical Sciences, Volume 57, Number 8, August 2003, pp.
369-372 Practitioners Section
MENINGOGOCCAL MENINGITIS
WHO, Fact Sheet N0141, Revised May 2003
Code Number: ms03017
Overview
Meningitis is an infection of the meninges, the thin lining that surrounds
the brain and the spinal cord. Several different bacteria can cause meningitis
and Neisseria meningitidis is one of the most important because
of its potential to cause epidemics. Meningococcal disease was first described
in 1805 when an outbreak swept through Geneva, Switzerland. The causative
agent, Neisseria meningitidis (the men-ingococcus), was identified
in 1887.
Twelve subtypes or serogroups of N. meningitidis have been identified
and four (N. meningitidis. A, B, C and W135) are recognized to cause
epidemics. The pathogenicity, immunogenicity, and epidemic capabilities
differ according to the serogroup. Thus the identification of the serogroup
responsible of a sporadic case is crucial for epidemic containment.
How is the disease transmitted
The bacteria are transmitted from person to person through droplets of
respiratory or throat secretions. Close and prolonged contact (e.g. kissing,
sneezing and coughing on someone, living in close quarters or dormitories
(military recruits, students), sharing eating or drinking utensils, etc.)
facilitate the spread of the disease. The average incubation period is
4 days, ranging between 2 and 10 days.
N. meningitidis only infects humans; there is no animal reservoir.
The bacteria can be carried in the pharynix and sometimes, for reason not
fully known, overwhelm the body's defences allowing infection to spread
through the bloodstream and to the brain. It is estimated that between
10% to 25% of the population carry. N.meningitidis at any
given time, but of course the carriage rate may be much higher in epidemic
situations.
Features of the disease
The most common symptoms are stiff neck, high fever, sensitivity to light,
confusion, headaches and vomiting. Even when the disease is diagnosed early
and adequate therapy instituted, 5% to 10% of patients die, typically within
24-48 hours of onset of symptoms. Bacterial meningitis may result in brain
damage, hearing loss, or learning disability in 10 to 20% of survivors.
A less common but more severe (often fatal) form of meningococcal disease
is meningococcal septicemia which is characterized by haemorrhagic rash
and rapid circulatory collapse.
Diagnosis
The diagnosis of meningococcal meningitis is suspected by the clinical
presentation and a lumbar puncture showing a purulent spinal fluid; sometimes
the bacteria can be seen in microscopic examinations of the spinal fluid.
The diagnosis is confirmed by growing the bacteria from specimens of spinal
fluid or blood. More specialised laboratory tests are needed for the identification
of the serogropus as well as for testing susceptibility to antibiotics.
Treatment
Meningococcal disease is potentially fatal and should always be viewed
as a medical emergency. Admission to a hospital or health centre is necessary.
Isolation of the patient is not necessary. Antimicrobial therapy must be
commenced as soon as possible after the lumber puncture has been carried
out (if started before, it may be difficult to grow the bacteria from the
spinal fluid and thus confirm the diagnosis).
A range of antibiotics may be used for treatment including penicillin, ampicillin,
chloramphenicol, and ceftriaxone. Under epidemic conditions in Africa, oily
chloramphenicol is the drug of choice in areas with limited health facilities
because a single dose of this long-acting formulation has been shown to be
effective.
Epidemiology of meningococcal meningitis: who is affected and where
Meningococcal meningitis occurs sporadically in small clusters throughout
the world with seasonal variations and accounts for a variable proportion of
endemic bacterial meningitis. In temperate regions the number of cases increases
in winter and spring. Serogroups B and C together account for a large majority
of cases in Europe and the Americas. Several local outbreaks due to N. meningitidis serogroup
C have been reported in Canada and USA (1992-93) and in Spain (1995-97). For
10 years, the meningococcal meningitis activity has particularly increased
in New Zeland where an average of 500 cases occurs every year. Most of these
cases are now due to serogroup B.
Major African epidemics are associated with N. meningitidis serogroups
A and C and serogroup A is usually the cause of meningococcal disease in Asia.
Outside Africa, only Mongolia reported a large epidemic in recent years (1994-95).
There is increasing evidence of serogroup W135 being associated with outbreaks
of considerable size. In 2000 to 2001 several hundred pilgrims attending the
Hajj in Saudi Arabia were infected with N. meningitidis W135. Then in
2002, W135 emerged in Burkina Faso, striking 13,000 people and killing 1,500.
The African Meningitis Belt
The highest burden of meningococcal disease occurs in sub-Saharan Africa,
which is known as the "Meningitis Belt," an area that stretches from
Senegal in the west to Ethiopia in the east, with an estimated total population
of 300 million people. This hyperendemic area is characterized by particular
climate and social habits. During the dry season, between December and June,
because of dusty winds and upper respiratory tract infections due to cold nights,
the local immunity of the pharynx is diminished increasing the risk of meningitis.
At the same time, the transmission of N. meningitidis is favoured by
overcrowded housing at family level and by large population displacements due
to pilgrimages and traditional markets at regional level. This conjunction
of factors explains the large epidemics which occur during this season in the
meningitis belt area. Due to herd immunity (whereby transmission is blocked
when a critical percentage of the population had been vaccinated, thus extending
protection to the unvaccinated), these epidemics occur in a cyclic mode. N.
meningitidis A, C and W135 are now the main serogroups involved in the
meningococcal meningitis activity in Africa.
In major African epidemics, attack rates range from 100 to 800 per 100 000
population, but individual communities have reported rates as high as 1000
per 100 000. While in endemic disease the highest attack rates are observed
in young children, during epidemics, older children, teenagers and young adults
are also affected.
In 1996, Africa experienced the largest recorded outbreak of epidemic meningitis
in history, with over 250,000 cases and 25 000 deaths registered. Between that
crisis and 2002, 223,000 new cases of meningococcal meningitis were reported
to the World Health Organization. The countries most
affected countries have been Burkina Faso, Chad, Ethiopia and Niger; in 2002,
the outbreaks occurring in Burkina Faso, Ethiopia and Niger accounted for about
65% of the total cases reported in the African continent. Furthermore, the
meningitis belt appears to be extending further south. In 2002, the Great Lakes
region was affected by outbreaks in villages and refugees camps which caused
more than 2,200 cases, including 200 deaths.
Prevention
Several vaccines are available to prevent the disease. Polysaccharide vaccines,
which have been available for over 30 years, exist against serogroups A, C,
Y and W135 in various combinations. A monovalent conjugate vaccine against
serogroup C has recently been licensed in developed countries for use in children
and adolescents. This vaccine is immunogenic, particularly for children under
two years of age whereas polysaccharide vaccines are not. All these vaccines
have been proven to be safe and effective with infrequent and mild side effects.
The vaccines may not provide adequate protection for 10 to 14 days following
injection.
Vaccination is used in the following circumstances:
Routine vaccination
Routine preventive mass vaccination has been attempted and its effect has
been extensively debated. Saudi Arabia, for example, offers routine immunization
of its entire population. Sudan and other countries routinely vaccinate school
children. Preventive vaccination can be used to protect individuals at risk
(e.g. travellers, military, pilgrims).
Protection of close contacts
When a sporadic case occurs, the close contacts need to be protected by a
vaccine and
chemoprophylaxis with antibiotics to cover the delay between vaccination and
protection (see above), Antibiotics used for chemoprophylaxis are rifampicin,
minocycline, spiramycin, ciprofloxacin and ceftriaxone.
Vaccination for epidemic control
In the African Meningitis Belt context, enhanced epidemiological surveillance
and prompt case management with oily chloramphenicol are used to control the
epidemics. Routine immunization is not possible with the current available
vaccines as the polysaccharide vaccines provide protection for only three to
five years and cannot be used in children under two years of age because the
lack the ability to develop antibodies. Furthermore, even large scale coverage
with current vaccines does not provide sufficient "herd immunity." Consequently,
the current WHO recommendation for outbreak control is to mass vaccinate every
district that is in an epidemic phase, as well as those contiguous districts
that are in alert phase. It is estimated that a mass immunization campaign,
promptly implemented, can avoid 70% of cases.
Emergence of W135
Bivalent AC vaccine is commonly used in Africa but the emergence of N.
meningitidis W135 as an epidemic strain involves revising this control
strategy. A tetravalent ACYW135 polysaccharide vaccine exists but its high
price and limited availability restricts its use in the African context.
In 2003, WHO reached an agreement with a manufacturer to produce an affordable
polysaccharide vaccine for Africa which would protect against A, C and W
135 strains.
WHO's Strategy
WHO promotes a two-pronged strategy which involves epidemic preparedness and
epidemic
response. Preparedness focuses on surveillance, from case detection and investigation
and laboratory confirmation. This implies strengthening of surveillance and
laboratory capacity for early detection of epidemics, the establishment of
national and sub-regional stocks of vaccine, and the development of updating
of national plans for epidemic management (including preparedness, contingency
and response). WHO regularly provides technical support in the field in the
countries facing epidemics.
Following large outbreaks in Africa in 1995-96, WHO was instrumental in establishing
the International Coordinating Group (ICG) on Vaccine Provision for Epidemic
Meningitis, Control
to ensure rapid and equal access to vaccines, injection material and oily chloramphenicol,
as well as for their adequate use when the stocks are limited. The ICG is composed
of partners from the UN, including WHO, nongovernmental organizations, technical
partners and the private sector.
WHO is committed to eliminating meningococcal disease as a public health problem
and ensuring control of sporadic cases through routine health services in the
shortest possible time. The only way to reach this goal will be with an improved
vaccine, WHO supports the development of such a vaccine.
Copyright 2003 - Indian Journal of Medical Sciences.
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