Sunday, March 8, 2015


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.

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.

Viral meningitis

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

What's this stuff?
I don't think I like it

Okay, I'll try it

I like it!


Adams, D. (1979). Hitchhiker's Guide to the Galaxy.

Centers for Disease Control and Prevention. (2015). Enterovirus D68.

Centers for Disease Control and Prevention. (2013). Multistate outbreak of fungal meningitis and other infections.

Center for Infectious Disease Research and Policy. (2015). Report on polio-like illness in kids supports link to 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.

Michalopoulos, A. S. & Karatza, D. C. (2010) Multidrug-resistant Gram-negative infections: the use of colistin. Expert Review of Anti-infective Therapy, 8(9). doi:10.1586/eri.10.88.

Teem, J. L., Qvarnstrom, Y., Bishop, H. S., da Silva, A. J., 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.

Remeš, F., Tomáš, R., Jindrák, V., Vaniš, V,. & Setlík, M. (2013). Intraventricular and lumbar intrathecal administration of antibiotics in postneurosurgical patients with meningitis and/or ventriculitis in a serious clinical state. Journal of Neurosurgery, 119(6). doi:10.3171/2013.6.JNS122126.

Romero, J. R. (2012). Enteroviruses. In L. Goldman & A. L. Schafer (Eds.) Goldman's Cecil medicine, 24th Ed. [Electronic version]. Elsevier.

Shimasaki, T., Chung, H., & Shiiki, S. (2015). Five cases of recurrent meningitis associated with chronic strongyloidiasis. American Journal of Tropical Medicine and Hygiene, 92(3). doi: 10.4269/ajtmh.14-0564.

Tunkel, A. R., van de Beek, D., Scheld, W. M. (2015). Acute meningitis. In J. E. Bennett, R. Dolin, & M. J. Blaser (Eds.), Mandell, Douglas, and Bennett's principles and practice of infectious diseases, 8th Ed. [Electronic version]. Elsevier.

University of Florida. (2015). Rare parasite colonizing snails in South Florida.

Verma, A. (2008). Infections of the nervous system: bacterial infections. In W. G. Bradley, R. B. Daroff, G. Fenichel, & J. Jankovic (Eds.) Neurology in clinical practice, 5th Ed. [Electronic version]. Elsevier.