Risk Factors Of Meningitis Biology Essay

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Meningitis is swelling and inflammation of the protective membranes that cover brain and spinal cord. Depending on the duration of symptoms, meningitis may be classified as acute or chronic. Acute meningitis denotes the evolution of symptoms within hours to several days, while chronic meningitis has an onset and duration of weeks to months. Meningitis is mainly caused by infection with viruses, several different types of bacteria, or sometimes by a fungus, and less commonly by certain drugs. Meningitis can be life-threatening because of the inflammation's proximity to the brain and spinal cord. All types of meningitis tend to cause symptoms that include fever, headache and stiff neck. Knowing whether meningitis is caused by a virus or bacterium is important because the severity of illness and the treatment differ depending on the cause. Viral meningitis, the most common form of meningitis, is less severe than bacterial meningitis. Bacterial meningitis is usually more serious than viral meningitis and is sometimes fatal, particularly in infants and the elderly. Bacterial meningitis is a major cause of death and disability world-wide. [1]

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b. The etiology and risk factors

Meningitis is usually caused by infection from viruses or micro-organisms. Most cases are due to infection with viruses, with bacteria, fungi, and parasites being the next most common causes. It may also result from various non-infectious causes.

The etiology of bacterial meningitis varies by age group and region of the world. Worldwide, without epidemics one million cases of bacterial meningitis are estimated to occur and 200,000 of these die annually. [1] Before antibiotics were widely used, 70 percent or more of bacterial meningitis cases were fatal; with antibiotic treatment, the fatality rate has dropped to 15 percent or less. Bacterial meningitis is most common in the winter and spring. Beyond the perinatal period, three organisms, transmitted from person to person through the exchange of respiratory secretions, are responsible for most cases of bacterial meningitis: Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae.

Bacterial meningitis caused by Neisseria meningitidis bacteria (meningococcal disease) can be fatal and should always be viewed as a medical emergency. About 10% of infected people die from the disease. [5] In non-fatal cases, those affected experience long-term disabilities, such as brain damage, loss of limb, or deafness. Preventing the disease through the use of meningococcal vaccine is important. Although anyone can get meningitis, pre-teens and adolescents, college freshmen who live in dormitories and travelers to countries where meningitis is always present are at an increased risk for meningococcal disease. Before the availability of effective vaccines, bacterial meningitis was most commonly diagnosed in young children. Now, as a result of the protection offered by current childhood vaccines, bacterial meningitis is more commonly diagnosed among pre-teens and young adults. As children reach their pre-teen and adolescent years, protection provided by some childhood vaccines can begin to wear off. As a result, pre-teens and adolescents are at a greater risk for catching certain diseases. Introducing vaccinations during the pre-teen years increases the level of protection during adolescence. College freshmen, especially those who live in dormitories, are at a slightly increased risk for bacterial meningitis caused by Neisseria meningitidis bacteria (meningococcal disease) compared with other persons of the same age. vaccination against bacterial meningitis caused by Neisseria meningitidis bacteria (meningococcal disease) is recommended to persons who travel to or reside in countries in which the bacterium Neisseria meningitidis is hyperendemic or epidemic, particularly if contact with the local population will be prolonged.

Meningococcal meningitis, caused by Neisseria meningitidis, is primarily a disease of young children, with the incidence of cases declining in those older than 1 year of age. The disease is most common during winter and spring. In some persons, the bacteria can cause a severe blood infection called meningococcemia. N. meningitidis is classified into serogroups based on the immunological reactivity of the capsular polysaccharide. Although 13 serogroups have been identified, the three serogroups A, B and C account for over 90% of meningococcal disease. [1] Meningococcal disease differs from other leading causes of bacterial meningitis because of its potential to cause large-scale epidemics. A region of sub-Saharan Africa extending from Ethiopia in the East to The Gambia in the West and containing fifteen countries and over 260 million people is known as the “meningitis beltâ€Â because of its high endemic rate of disease with superimposed, periodic, large epidemics caused by serogroup A, and to a lesser extent, serogroup C. [1]

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Haemophilus meningitis is most frequently caused by Haemophilus influenzae type b, also known as Hib. Before effective vaccines became available and widely used, Hib was the most frequent cause of bacterial meningitis in children 5 years of age and younger. While most children are colonized with a species of H. influenzae, only 2-15% harbour Hib. [1] The organism is acquired through the respiratory route. It adheres to the upper respiratory tract epithelial cells and colonizes the nasopharynx. Following acquisition of Hib, illness results when the organism is able to penetrate the respiratory mucosa and enters the blood stream. This is the result of a combination of factors, and subsequently the organism gains access to the cerebrospinal fluid (CSF), where infection is established and inflammation occurs. An essential virulence factor which plays a major role in determining the invasive potential of an organism is the polysaccharide capsule of Hib.

Pneumococcal meningitis, caused by Streptococcus pneumoniae (pneumococci), generally strikes infants, the elderly and individuals with certain chronic medical conditions. Younger adults with anatomic or functional asplenia, haemoglobinopathies, such as sickle cell disease, or who are otherwise immunocompromised, also have an increased susceptibility to S. pneumoniae infection. S. pneumoniae, like Hib, is acquired through the respiratory route. Following the establishment of nasopharyngeal colonization, illness results once bacteria evade the mucosal defences, thus accessing the bloodstream, and eventually reaching the meninges and CSF.

The term aseptic meningitis refers loosely to all cases of meningitis in which no bacterial infection can be demonstrated. This is usually due to viruses, but it may be due to bacterial infection that has already been partially treated, with disappearance of the bacteria from the meninges, or by infection in a space adjacent to the meninges (e.g. sinusitis). Endocarditis (infection of the heart valves with spread of small clusters of bacteria through the bloodstream) may cause aseptic meningitis. Aseptic meningitis may also result from infection with spirochetes, a type of bacteria that includes Treponema pallidum (the cause of syphilis) and Borrelia burgdorferi (known for causing Lyme disease). Meningitis may be encountered in cerebral malaria (malaria infecting the brain). Fungal meningitis, e.g. due to Cryptococcus neoformans, is typically seen in people with immune deficiency such as AIDS. Amoebic meningitis, meningitis due to infection with amoebae such as Naegleria fowleri, is contracted from freshwater sources. [2]

Like bacterial meningitis, viral meningitis can affect anyone but infants younger than 1 month old and people whose immune systems are weak are at higher risk for severe infection. People who are around someone with viral meningitis have a chance of becoming infected with the virus that made that person sick, but they are not likely to develop meningitis as a complication of the illness.

Viral meningitis is common and often goes unreported. It is a central nervous system (CNS) infection characterized by signs and symptoms of meningeal inflammation in the absence of positive bacterial cultures. The incidence varies with season, and the clinical presentation often includes fever, headache, and stiffness of the neck accompanied by symptoms typical of the specific causal virus. Viral meningitis is usually self-limited and resolves without treatment, although case reports suggest that treatment is indicated and beneficial in certain clinical scenarios. Viruses that can cause meningitis include enteroviruses, herpes simplex virus type 2 (and less commonly type 1), varicella zoster virus (known for causing chickenpox and shingles), mumps virus, HIV, and LCMV. [3] In the absence of a lumbar puncture, viral and bacterial meningitis cannot be differentiated with certainty, and all suspected cases should therefore be referred. Lumbar puncture and analysis of cerebrospinal fluid may be done primarily to exclude bacterial meningitis, but identification of the specific viral cause is itself beneficial. Viral diagnosis informs prognosis , enhances care of the patient, reduces the use of antibiotics, decreases length of stay in hospital, and can help to prevent further spread of infection. Over the past 20 years, vaccination policies, the HIV epidemic, altered sexual behavior, and increasing travel have altered the spectrum of causative agents. [4]

A parasitic cause is often assumed when there is a predominance of eosinophils in the CSF. The most common parasites implicated are Angiostrongylus cantonensis and Gnathostoma spinigerum. Tuberculosis, syphilis, cryptococcosis, and coccidiodomycosis are rare causes of eosinophilic meningitis that may need to be considered.

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Meningitis may occur as the result of several non-infectious causes: spread of cancer to the meninges (malignant meningitis) and certain drugs (mainly non-steroidal anti-inflammatory drugs, antibiotics and intravenous immunoglobulins). It may also be caused by several inflammatory conditions such as sarcoidosis (which is then called neurosarcoidosis), connective tissue disorders such as systemic lupus erythematosus, and certain forms of vasculitis. Epidermoid cysts and dermoid cysts may cause meningitis by releasing irritant matter into the subarachnoid space. Mollaret's meningitis is a syndrome of recurring episodes of aseptic meningitis; it is now thought to be caused by herpes simplex virus type 2. Rarely, migraine may cause meningitis, but this diagnosis is usually only made when other causes have been eliminated. [2]

c. Pathophisiology

d. Clinical signs and symptoms

Meningitis infection is characterized by a sudden onset of fever, headache, and stiff neck. It is often accompanied by other symptoms, such as nausea, vomiting, photophobia (sensitivity to light) and altered mental status. The symptoms of bacterial meningitis can appear quickly or over several days. Typically they develop within 3-7 days after exposure. Infants younger than one month old are at a higher risk for severe infection. In newborns and infants, the classic symptoms of fever, headache, and neck stiffness may be absent or difficult to notice. The infant may appear to be slow or inactive, irritable, vomiting or feeding poorly. In young children, doctors may also look at the child’s reflexes, which can also be a sign of meningitis. Although the early symptoms of viral meningitis and bacterial meningitis may be similar, later symptoms of bacterial meningitis can be very severe (e.g., seizures, coma). Viral meningitis is an infection of the meninges (the covering of the brain and spinal cord) that is caused by a virus. Enteroviruses, the most common cause of viral meningitis, appear most often during the summer and fall in temperate climates. Viral meningitis can affect babies, children, and adults. It is usually less severe than bacterial meningitis and normally clears up without specific treatment. The symptoms of viral meningitis are similar to those for bacterial meningitis, which can be fatal. Symptoms of viral meningitis in adults may differ from those in children. Common symptoms in infants include fever, irritability, poor eating and hard to awaken. Common symptoms in adults include high fever, severe headache, stiff neck, sensitivity to bright light, sleepiness or trouble waking up, nausea, vomiting and lack of appetite. The symptoms of viral meningitis usually last from 7 to 10 days, and people with normal immune systems usually recover completely. Symptoms of fungal meningitis are similar to symptoms of other forms of meningitis; however, they often appear more gradually. In addition to typical meningitis symptoms, like headache, fever, nausea, and stiffness of the neck, people with fungal meningitis may also experience dislike of bright lights, changes in mental status, confusion, hallucinations and personality changes. [5]

e. Diagnosis and laboratory findings

If meningitis is suspected, samples of blood or cerebrospinal fluid are collected and sent to the laboratory for testing. It is important to know the specific cause of meningitis because the severity of illness and the treatment will differ depending on the cause. In the case of bacterial meningitis, for example, antibiotics can help prevent severe illness and reduce the spread of infection from person to person. If bacteria are present, they can be grown (cultured). Growing the bacteria in the laboratory is important for confirming the presence of bacteria and for identifying the specific type of bacteria that is causing the infection. For viral meningitis, the specific causes of meningitis may be determined by tests used to identify the virus in samples collected from the patient. To confirm fungal meningitis, specific lab tests is performed, depending on the type of fungus suspected.

e. Therapeutic management of disease, medical treatment, pharmacologic, dietary...

Bacterial meningitis can be treated with a number of effective antibiotics. It is important that treatment be started early in the course of the disease. If bacterial meningitis is suspected, initial treatment with ceftriaxone and vancomycin is recommended. Appropriate antibiotic treatment of the most common types of bacterial meningitis should reduce the risk of dying from meningitis to below 15%, although the risk is higher among the elderly. [5] There is no specific treatment for viral meningitis. Antibiotics do not help viral infections, so they are not useful in the treatment of viral meningitis. Most patients completely recover on their own within 7 to 10 days. A hospital stay may be necessary in more severe cases or for people with weak immune systems. Fungal meningitis is treated with long courses of high dose antifungal medications. This is usually given using an IV line and is done in the hospital. The length of treatment depends on the status of the immune system and the type of fungus that caused the infection. For people with immune systems that do not function well because of other conditions, like AIDS, diabetes, or cancer, there is often a need for longer treatment.

g. Teaching self care...

h. Health promotion strategies to prevent ...

Keeping up to date with recommended immunizations is the best defense. Maintaining healthy habits, like getting plenty of rest and not coming into close contact with people who are sick, can also help. There are two kinds of vaccines against Neisseria meningitidis. Meningococcal polysaccharide vaccine (Menomune) has been approved by the Food and Drug Administration (FDA) and available since 1981. Meningococcal conjugate vaccines, Menactra and Menveo, were licensed in 2005 and 2010, respectively. Each vaccine can prevent 2 of the 3 most commonly occurring strains in the US. Meningococcal vaccines cannot prevent all types of the disease, but they do protect many people who might become sick if they didn't get the vaccine. Meningococcal conjugate vaccine is routinely recommended for all 11 through 18 year olds and for certain high-risk children and adults. There are two types of pneumococcal vaccine currently available: a polysaccharide vaccine and a conjugate vaccine. The pneumococcal conjugate vaccine, PCV7 (Prevnar) was the first pneumococcal vaccine for use in children under the age of 2 years. PCV13 (Prevnar 13), which was licensed in early 2010, replaces PCV7. [5] Pneumococcal vaccines for the prevention of disease among children who are 2 years and older and adults have been in use since 1977. Pneumovax is a 23-valent polysaccharide vaccine (PPSV) that is currently recommended for use in adults who are 65 years of age and older, for persons who are 2 years and older and at high risk for pneumococcal disease (including those with sickle cell disease, HIV infection, or other immunocompromising condition), and for persons 19-64 years of age who smoke or have asthma. The Haemophilus influenzae type b (Hib) vaccine is highly effective against bacterial meningitis caused by a type of bacteria called Haemophilus influenzae type b. The Hib vaccine can prevent pneumonia, epiglottitis, and other serious infections caused by Hib bacteria. It is recommended for all children under 5 years old in the US, and it is usually given to infants starting at age 2 months. Hib vaccine can be combined with other vaccines. People with certain viral infections can sometimes develop meningitis. There are no vaccines for the most common causes of viral meningitis. Thus, the best way to prevent it is to prevent viral infections. However, that can be difficult since sometimes people can be infected with a virus and spread the virus even though they do not appear sick. Following are some steps recommended by CDC [5] to help lower the chances of becoming infected with viruses or of passing one on to someone else:

Washing hands thoroughly and often, especially after changing diapers, using the toilet, or coughing or blowing nose.

Cleaning contaminated surfaces, such as doorknobs or the TV remote control, with soap and water and then disinfecting them with a dilute solution of chlorine-containing bleach.

Avoiding kissing or sharing a drinking glass, eating utensil, lipstick, or other such items with sick people or with others when sick.

Making sure of vaccinations. Vaccinations included in the childhood vaccination schedule can protect children against some diseases that can lead to viral meningitis. These include vaccines against measles and mumps (MMR vaccine) and chickenpox (varicella-zoster vaccine).

Avoiding bites from mosquitoes and other insects that carry diseases that can infect humans.

Controlling mice and rats.

There is little evidence that specific activities can lead to developing fungal meningitis, although avoiding exposure to environments likely to contain fungal elements is prudent. People who are immunosuppressed (for example, those with HIV infection) should try to avoid bird droppings and avoid digging and dusty activities, particularly if they live in a geographic region where fungi like Histoplasma, Coccidioides, or Blastomyces species exist. HIV-infected people cannot completely avoid exposure. Some guidelines recommend that HIV-infected people receive antifungal prophylaxis if they live in a geographic area where the incidence of fungal infections is very high.