Every couple of months I'll get a call from a person who
heard that a friend or a coworker has meningitis and wants to know what to do
about it. Meningitis can be deadly. Some of the bacteria that can cause
meningitis are transmitted from person-to-person. People who have had contact
with a person with certain types of meningitis should be treated with
antibiotics to prevent illness.
Nevertheless, my immediate response is usually a variation
of the cover of The Hitchhiker's Guide to the Galaxy:
Don't panic. My first clue that it's
not something that the caller should worry about is the fact that I'm hearing
it from a friend or coworker first and not from a doctor or a microbiology
laboratory. The pathogens require a public health response are notifiable conditions, which means that health care providers and laboratories are
required to notify the local health department of the county in which the
patient lives.
Meningitis means inflammation of the meninges. The meninges
are the membranes that cover the brain and spinal cord. There are three layers,
the pia mater ("gentle mother"), arachnoid mater ("spider mother,"
because of its cobweb-like appearance), and the dura mater ("tough
mother"). Meningitis is characterized by fever, headache, altered mental
status, and stiff neck. Seizures and photophobia
(discomfort in response to light. Imagine walking out of a dark room into bright sunlight) may also occur.
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There are a lot of things that can cause meningitis:
bacteria, viruses, funguses, parasites, drugs, chemicals, tumors, or anything
that can cause meningeal inflammation. The central nervous system (CSN) is a sterile site, so most microorganisms that
pass though the blood-brain barrier can cause meningitis (more about that later). Relatively few of the
infectious causes of meningitis are transmissible from person-to-person. Many
of the bacteria that can cause meningitis are normal flora; that is,
they are normally present on or in our bodies. The viruses that most commonly
cause meningitis usually do not cause severe illness in most people. Fungal and
parasitic meningitis are rare.
There are three vaccine-preventable causes of bacterial
meningitis: Haemophilus influenzae type B (Hib),
Neisseria meningitidis (meningococcus), and Streptococcus pneumoniae (pneumococcus). I plan to go into more
detail about each one of those in future entries. There are several risk
factors for the different types of bacterial meningitis. Streptococcus agalactiae (Group B
streptococcus) is the most common cause of bacterial meningitis in newborn
babies. Listeria monocytogenes also affects
newborn babies as well as adults over 60 years of age and people who are immunosuppressed.
Neurosurgery and head trauma can increase the risk of meningitis from bacteria
normally found on the skin. Gram negative bacteria, including bacteria that are normally found in the gut, can also
cause bacterial meningitis. In the March 2015 issue of the American Journal of
Tropical Medicine and Hygiene there is a case series of people
who developed bacterial meningitis as the result of strongyloidiasis,
an infection with a parasitic worm that can migrate throughout the body.
Bacterial meningitis can be fatal or cause serious long-term
problems. It is treated with antibiotics, however, because many antibiotics do
not easily cross the blood-brain barrier, treatment can require high doses of
antibiotics, treatment with several antibiotics, toxic antibiotics, prolonged
treatment, or antibiotics that easily cross the blood-brain barrier but are not
as effective as those than do not. In some severe cases of bacterial
meningitis, antibiotics have been injected directly into CSF. Also, some of the bacteria that cause
meningitis are resistant to antibiotics, making treatment much more difficult.
Lumbar puncture ("spinal tap") is one of the most
important diagnostic tests for meningitis. A needle is inserted into the spine
below the spinal cord to collect cerebrospinal fluid (CSF). CSF is normally clear and colorless. Cloudy CSF is caused by a high number of white blood cells
present in the fluid and is indicative of bacterial meningitis. In addition to microscopic analysis of CSF, the amounts of glucose and protein are usually measured and the fluid can be cultured
to identify bacteria present in the fluid. Aseptic meningitis is the term used
when bacteria do not grow from a CSF culture. It has become synonymous with viral
meningitis, but tuberculous meningitis and syphilitic meningitis can also be aseptic.
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Enteroviruses
are the most common cause of viral meningitis. Enterovirus is a large family of
viruses that include polioviruses,
viruses that cause hand, foot, and mouth disease, and some of the viruses that cause the common cold. Recently, outbreaks of enterovirus D68 have cause severe respiratory disease and possibly caused polio-like symptoms in children in the U.S. Other viruses that can cause meningitis
include mumps virus, herpes
viruses (including the viruses that cause cold sores, genital herpes, and chickenpox),
and arboviruses (West Nile virus, St. Louis encephalitis virus, La Crosse virus, ), and lymphocytic choriomeningitis virus.
Viral meningitis is usually self-limiting,
treatment is supportive,
and most people with viral meningitis have no long-term effects.
Cryptococcus neoformans is a fungus
that causes meningitis in immunocompromised people. Cryptococcus gattii can cause
meningitis in healthy people. In 2012 there were hundreds of cases of fungal meningitis in the U.S. caused by injections with a steroid
contaminated with funguses that are commonly found in the environment. Other funguses that can cause meningitis
include Aspergillus, Blastomyces dermatitidis, Coccidioides (Valley fever), and Histoplasma. There are a number of
antifungal drugs that can be used to treat fungal meningitis.
Parasites that can cause meningitis include amebas and
worms. Naegleria fowleri is a free-living
ameba that causes primary amebic meningoencephalitis (PAM). The infection,
which is almost always fatal, is acquired by swimming in warm water or through sinus rinsing.
Naegleria has been found in public water systems in Louisiana and there have been two deaths from PAM that
were associated with sinus rinsing.
Rat lungworm (Angiostrongylus cantonensis) causes eosinophilic meningitis in
humans. As the name suggests, rats are the definitive host of A. cantonensis. Snails
and slugs are intermediate hosts. Humans (accidental or dead-end hosts)
are infected by eating snails or eating vegetables contaminated with snail or
slug slime. A. cantonensis is not
native to the continental U.S., but it has been found in Louisiana and
was recently found in Florida.
Although the worms migrate through the brain, the disease is self-limiting, requires no specific treatment, and
usually does not cause long-term complications. Baylisascaris procyonis (raccoon
roundworm), Gnathostoma species, Taenia solium (pork tapeworm), and Toxocara species (cat
and dog roundworms) can also cause eosinophilic meningitis. These worms cannot
reproduce in the central nervous system and eventually die. Treating these
infections with anthelmintic
drugs can sometimes cause more inflammation than allowing the worms to die on
their own, so the goal of treatment is to reduce inflammation and treat any
complications of the infection.
As I mentioned above, I plan to write more about Hib,
meningococcus, and pneumococcus, but there are some other topics I would like
to address first, including some that were raised by people who responded to my HB 2009 entry.
Daddy's red beans
& rice
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| What's this stuff? |
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| I don't think I like it |
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| Okay, I'll try it |
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| I like it! |
References
Adams, D. (1979). Hitchhiker's
Guide to the Galaxy.
Centers for Disease Control and Prevention. (2015).
Enterovirus D68. http://www.cdc.gov/non-polio-enterovirus/about/EV-D68.html.
Centers for Disease Control and Prevention. (2013). Multistate
outbreak of fungal meningitis and other infections. http://www.cdc.gov/hai/outbreaks/meningitis.html.
Center for Infectious Disease Research and Policy. (2015).
Report on polio-like illness in kids supports link to EV-D68. http://www.cidrap.umn.edu/news-perspective/2015/01/report-polio-illness-kids-supports-link-ev-d68.
Hochberg, N. S., Blackburn, B. G., Park, S. Y,. Sejvar, J.
S., Effler, P. V., & Herwaldt, B. L. (2011). Eosinophilic meningitis
attributable to Angiostrongylus
cantonensis infection in Hawaii: clinical characteristics and potential
exposures. American Journal of Tropical
Medicine and Hygiene, 85(4). doi: 10.4269/ajtmh.2011.11-0322.
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Carter, J., White-Mclean, J., et al. (2013). The occurrence of rat lungworm, Angiostrongylus cantonensis, in
nonindigenous snails in the Gulf of Mexico region of the United States. Hawai'i Journal of Medicine & Public
Health, 72(6 Supple. 2), 11-14. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3689474.
Remeš, F., Tomáš, R., Jindrák, V., Vaniš, V,. & Setlík,
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Romero, J. R. (2012). Enteroviruses. In L. Goldman & A.
L. Schafer (Eds.) Goldman's Cecil
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Shimasaki, T., Chung, H., & Shiiki, S. (2015). Five
cases of recurrent meningitis associated with chronic strongyloidiasis. American Journal of Tropical Medicine and
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Tunkel, A. R., van de Beek, D., Scheld, W. M. (2015). Acute
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University of Florida. (2015). Rare parasite colonizing snails
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Verma, A. (2008). Infections of the nervous system:
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