Meninges are the protective sheath or covering over the neurons of the body. The brain and spinal cord have the highest number of neurons, which form our central nervous system. This central nervous system in turn controls our body’s metabolism and response. The primary function of meninges is to act as a protective barrier for neurons. Meningitis is a disease that causes inflammation in the meningeal sheath. Inflammation is a localized physical condition that occurs as the body’s natural immune response, it has five main symptoms which are, redness, swelling, pain, heat, and loss of function. There are various causative agents of the disease which include, bacteria, viruses, and protozoans. Among all these meningitis caused by bacteria the most common has the highest death rates.
Bacterial meningitis is the most common type of meningeal disease. It is caused by bacteria named Neisseria meningitidis, it is commonly known as meningococcus. Thus the more common name of bacterial meningitis is meningococcal meningitis. It affects all age groups but is primarily found in children below the age of ten. Before the development of antibiotics for its treatment, it has a death rate of nearly 40-50% and certain parts of Africa are still widely affected by this pandemic, and is known as the meningitis belt. There are various types of serogroups responsible for causing meningococcal meningitis, serogroup A is widely responsible for the meningitis epidemic in Africa. Other serotypes are, B, C, Y, and W-135.
There are also some other bacteria that cause meningitis these include strains of staphylococci, pneumococci, streptococci, and viruses like H. influenzae. H influenzae causes meningitis mostly in infants and has symptoms common to meningococcal meningitis. Sometimes nasal infection or infection in the mid-ear can carry the pathogen to the meninges, where they multiply and cause disease. Blood can also carry various pathogens to the meninges.
Route of Pathogen Entry
Meningitis bacteria usually enter the body through the nasal cavity, it is transmitted via nasal droplets. Sometimes infected blood transfusion also causes this. Blood carries pathogens to the associated organs where they reach the meninges, and pathogens multiply there increasing their population. This leads to inflammation of the region and pus formation. Pus formation usually results in the thickening of the cerebrospinal fluid which can result in a seizure.
Meningococcal meningitis includes symptoms are as follows
Stiffness in the neck
Some less common symptoms include-
Stages of Meningitis
There are three mainstages of meningitis, in the first stage, pathogens multiply in the throat and nasal cavity, in the second stage pathogens enter the bloodstream and they then reach into the cerebrospinal nerves meninges. During the first stage of infection vomiting and severe pain develops, in the second stage fever and hemorrhagic patches appear in severe cases. During the last stage of disease, inflammation in nerve and pus formation in cerebrospinal fluid, which leads to paralysis and seizure.
Meningitis vaccines against specific serogroups of N. meningitidis are available, they are carbohydrate vaccines, developed by purifying complex carbohydrates associated with the bacterial cell membrane. Carbohydrate vaccines are not very impactful among children and infants.
Another class of vaccine known as the conjugate vaccine is used for meningitis, these are polysaccharides conjugated with proteins to provide an effective immune response. The conjugate vaccine has been successfully developed for the serogroup C and tetravalent serogroup specific vaccine (A, C, W-135, and Y)
Vaccine development for serotype B is primarily difficult due to its complex nature of genetic makeup.
Other treatments include the administration of antibiotics such as penicillin in case of meningococcal meningitis. Ampicillin and chloramphenicol are the antibiotics that are administered in case of meningitis caused by H. influenzae. Rifampin is also an antibiotic derivative that is being used to control the spread of meningitis.
Viral meningitis is caused by viruses such as H. influenza, these are the pathogens mainly responsible for causing meningitis in infants. Some other pathogens include the west nile virus, mumps, measles, herpes simplex types I and II, varicella, and lymphocytic choriomeningitis (LCM) virus. The most common family to cause viral meningitis is an enterovirus. Viral meningitis is commonly called aseptic meningitis. They have symptoms common with meningococcal meningitis, which includes fever, headache, and vomiting. It is not a fatal form, it generally occurs to an immunocompromised patient, they are generally treated with the body’s immune system.
Viral meningitis follows three main stages during the infection cycle, they enter generally through the nasal cavity via inhalation of contaminated nasal droplets, pathogens then replicate and move to the bloodstream, which then carries to the brain.
Rifampin is administered to control viral meningitis. Treatment for viral meningitis is supportive, that is rest, hydration, and anti-inflammatory drugs are only administered. Paitents generally recover within 7-10 days.
Difference Between Viral Meningitis and Bacterial Meningitis