Meningitis

Introduction

Meningitis is an inflammation of the meninges (membranes) and cerebrospinal fluid surrounding the brain and spinal cord. This inflammation can be caused by almost any bacteria, virus or fungus, but particular members of each of these three groups are the most responsible agents of infection. Viral menigitis is the most common and the least severe form of the disease. Bacterial meningitis is next in the number of reported cases and is more serious as it causes more damage. If untreated, bacterial meningitis can cause death. Fungal meningitis is uncommon, usually affecting persons who immune-deficient. For many years, meningitis was broken down into two catagories - cerebral and spinal. Both the brain and spinal cord are "bathed" in the fluid which is now refered to as cerebrospinal fluid. Cerebral meningitis and spinal meningitis are not mutually exclusive - just one disease attacking two parts of the body simultaneously.^[1][2][3]

Meningitis does occur in almost every country around the world. The area between Mali and Ethiopia is known as the Sub-Saharan African "Meningitis Belt" and outbreaks of the disease appear regularly during the dry season (December - June). The region also suffers major epidemics approximately every 8-12 years. Persons traveling to this area should consider receiving pre-exposure vaccinations.^[1]

Prevention

General Information

VIRAL MENINGITIS
This form of the disease is most often caused by the same viruses responsible for the common cold, influenza and viral pneumonia, but any virus can become the culprit.. It is also the most common form of the disease.^[3]

BACTERIAL MENINGITIS
This form of the disease can be caused by any bacteria. The following list contains the bacterial strains most associated with meningitis infection.

Neisseria meningitidis (meningococcus)
The 5 major types (serogroups) of the N. meningitis bacteria associated with the disease are A, B, C, Y and W-135. Serogroup A, and to a lesser extect serogroup C, are responsible for the meningitis cases in Africa and parts of Asia. Serogroups B and C account for the majority of cases reported in the Americas and Europe. Recently, serogroup Y has been the cause of outbreaks in North America. In Saudi Arabia, serogroup A was responsible for the 1987 epidemic and serogroup W-135 for the 2000 epidemic - both associated with the Hajj pilrimage. These outbreaks also prompted Sauid Arabia to require all Hajj and Umrah visitors provide proof of vaccination (with the tetravalent A,C,Y,W-135 vaccine) before entering the country. Serogroup W135 is associated with the Burkina Faso 2002 epidemic and the serogroup has been realized in several African countries but without causing major epidemics.
N. meningitidis is highly contagious and localized epidemics in college dormitories, boarding schools and military bases are not uncommon.^[1][3]

Streptococcus pneumoniae (pneumococcus)
This bacteria is most closely associated with the upper respiratory disease, (bacterial) pneumonia. It can also be a cause for sinus and ear infections. S. pneumoniae is the leading cause of bacterial meningitis among infants and young children in the United States and Europe. When meningitis and an ear infection are both diagnosed, it is not always clear which condition began first as they usually present simultaneaously.^[3]

Haemophilus influenzae (haemophilus)
Prior to the early 1990s, H. influenzae type b (Hib) was the most common cause of bacterial meningitis in people of all ages. With the advent of the Hib vaccine, which has been incorporated into the routine childhood vaccination schedule, the incidence of Hib meningitis has been greatly reduced in the United States and several other developed countries. Hib is associated with upper respiratory infections, ear infections and sinusitis.^[3]

Listeria monocytogenes (listeria)
L. monocytogenes is a common bacteria found in the soil and in contaminated foods, including soft cheeses and processed meat products (ie: hot dogs, etc.). Several wild and domestic animals (especially livestock) are also carriers. Most healthy individuals exposed to listeria never become ill. Pregnant women, newborns and the elderly see the highest rate of infection. The bacteria can cross the placental barrier with infections during late pregnancy causing possible stillbirths.^[3]

FUNGAL MENINGITIS
This form of the disease is quite uncommon. It is associated with Cryptococcus neoformans which is found in soil and in the feces of birds worldwide. Most often, it affects persons with immune deficiencies, such as those with HIV, AIDS, multiple schlerosis and rheumatoid arthritis, amoung others.^[3][4]

CHRONIC MENINGITIS
Any munber of agents can cause chronic meningitis. Unlike the acute forms of the disease, which sees a rapid onset of symptoms, this form will develop slowly over 4 weeks or more. Chronic meningitis is extremely rare.^[3]

NON-INFECTIOUS CAUSES
Meningitis can develop from other causes and is usually associated with drug allergies, certain types of cancers and inflammatory diseases such as lupus. The incidence of non-infectious meningitis is rare.^[3]

Preventive Measures

• Pre-exposure vaccinations*
• Follow good hygiene practices, such as frequent and thorough hand-washing.
• Limit exposure to people with a cold, flu or upper respiratory illness.
• Avoid traveling to areas during "peak" meningitis periods, such as the African Meningitis Belt (see above) during the December to June dry season.
• Antibiotic prophylactic treatment for persons (family/co-workers) with prolonged exposure to someone diagnosed with meningitis.**^[1][2][5]

Pre-Exposure Vaccinations / Antibiotic Prophylaxis

PRE-EXPOSURE VACCINES
Presently, there are two (tetravalent) vaccines, MPV4 and MPSV4, available.

MPV4 Vaccine
The MPV4 vaccine is recommended for use in persons 2-55 years of age and protects against serogroups A,C,Y and W-135. This particular vaccine appears to be very effecacious in children and imparts long-term protection and immunity by reducing nasopharyngeal (nose/throat) transmission. Both the world Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) recommend children between the ages of 11-18 be immunized as early as possible. The MPV4 vaccine is also highly recommended for college freshman to reduce localized epidemics within dormitories. Those traveling to the African "Meningitis Belt" during the dry season should also consider immunization. Use of this vaccine in people over 55 years of age is not recommended.

MPVS4 Vaccine
The MPVS4 vaccine is recommended for persons over 55 years of age. It is also an acceptable alternative for those 2-55 years of age, if MPV4 is not readily available.

Currently, immunization is a one-time injection of either MPV4 or MPVS4 and should be received at least 7-10 days prior to travel to affect sufficient antibody development. Children as young as 3 months of age can receive the MVPS4 vaccine to impart short-term immunity to serogroup A meningitis. Serogroup C vaccines have been used in infants and children in both Europe and Canada. At this time, there is no vaccine effective against serogroup B meningitis.^[1][2][5]

ANTIBIOTIC PROPHYLAXIS
The use of certain antibiotics as a second line of defense is highly recommend for persons with prolonged exposure to meningitis patients, such as family members and co-workers, and for airline passengers who have had direct contact and/or have sat next to someone (for longer than 8 hours) that is then diagnosed with the disease. The preferred antibiotics include rifampin, ciprofloxacin or ceftriaxone. Rifampin should not be administered to women who are pregnant.^[1]

Symptoms and Treatment

Symptoms

The signs and symptoms of meningitis are relatively identical whether the disease is the result of a bacterial, viral or fungal infection. The early signs of the disease are usually confused with influenza but quickly progress with more serious symptoms appearing in a matter of hours. Patients will experience a sudden onset of high fever, severe headache, nausea, vomiting, anorexia, sleepiness, stiff neck, sensitivity to light, confusion, skin rash and possible seizures. The patient may be difficult to arouse from sleep.^[1][2][6]

Diagnosis

Swift and accurate diagnosis is imparative. Persons who display the above symptoms should seek immediate medical attention. A series of diagnostic tests will be performed to identify the agent of infection and insure proper treatment. These tests will include throat culture, MRI and/or CT scan and lumbar puncture (spinal tap). The throat culture is used to identify bacteria that may be causing throat and neck pain. The MRI/CT scan revel any swelling and inflammation of the membranes surrounding the spinal cord and brain. The lumbar pucture is important in the identification of the causative agent - bacteria, virus or fungus.^[7]

Treatment

Viral Meningitis
This form of the disease, though still serious, is the mildest form and usually clears on it's own within 10 days. It rarely causes residual damage to the brain and/or spianl cord. Patients with viral meningitis may require supportive therapy to replace fluids/electrolytes lost due to vomiting. (Without medical attention, viral meningitis can not be accurately diagnosed.)

Bacterial Meningitis
This form of the disease is extrememly serious, requiring antibiotic and supportive treatments. Bacterial meningitis causes death in 5-10% of infected patients receiving treatment, usually within 24-48 hours of symptom onset. Left untreated, the death rate is approximately 100% for all age groups. Long-term effects of the disease include hearing loss, neurologic disabilities and possible limb loss. These effects are seen in 10-20% of the surviving patients. (Without medical attention, bacterial meningitis can not be accurately diagnosed.)

Fungal Meningitis
This form of the disease is uncommon and usually affects persons who are immune-deficient, such as HIV and AIDS patients. It is still a serious infection. Patients will receive IV and oral anti-fungal medications. AIDS patients may be placed on long-term treatment to prevent reocurrances of the disease. (Without medical attention, fungal meningitis can not be accurately diagnosed.)^[1][2][4][8]