Transcript Spring 2015-Chapter 24

DISEASES OF THE NERVOUS
SYSTEM
CHAPTER 24
Copyright © 2012 John Wiley &
Sons, Inc. All rights reserved.
Bison both spread brucella to domestic cattle and are
themselves sensitive to the organism (results in abortion)
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Leading doctors warn that sepsis deaths will not be curbed without radical rethink of research
strategy Leading doctors warn that medical and public recognition of sepsis - thought to
contribute to between a third and a half of all hospital deaths - must improve if the number of
deaths from this common and potentially life-threatening condition are to fall. Sepsis sometimes misleadingly called "blood poisoning" - is a common condition whereby an infection
triggers an extreme immune response, resulting in widespread inflammation, blood clotting,
and swelling. Among the early (but not universal) symptoms of sepsis are high temperature and
fast breathing; if left untreated, it frequently leads to organ failure and death. Although no
specific cure for the condition exists, it can often be treated effectively with intensive medical
care including antibiotics and intravenous fluid, if identified early enough. "Sepsis is both one of
the best known yet most poorly understood medical disorders, and one of the most challenging
medical conditions in routine clinical practice."* In the UK, sepsis is thought to kill 37000
people every year - more than three times the number killed by breast cancer or prostate
cancer. "The number of people dying from sepsis every year - perhaps as many as six million
worldwide - is shocking, yet research into new treatments for the condition seems to have
stalled,"* says Professor Cohen. "Researchers, clinicians, and policymakers need to radically
rethink the way we are researching and diagnosing this devastating condition."*
Recommendations include prioritising research into biomarkers for sepsis, which would allow
quicker diagnosis; better education of medical staff and improving public awareness to ensure
earlier recognition; rethinking clinical trial design; recognising that sepsis affects different
patients differently and using the power of modern genetics to develop targeted treatments
("personalised medicine"); and, after dozens of failed trials in recent decades, ensuring that
universities and drug companies do not abandon research into new drug treatments.
Gut microbes important for serotonin production Serotonin is probably best known
as a brain chemical that affects emotions and behavior, an imbalance of which is
thought to contribute to depression. Less well-known is that scientists estimate 90% of
serotonin is made in the gut, and imbalances in this peripheral serotonin have been
linked to diseases ranging from irritable bowel syndrome and cardiovascular disease, to
osteoporosis. Now, researchers from the California Institute of Technology (Caltech) in
Pasadena report a study in the journal Cell that shows certain bacteria in the gut play
an important role in the production of peripheral serotonin. "To start, we explored the
idea that normal gut microbes could influence levels of neurotransmitters in their
hosts."In the gut, there are three types of cell we know of that produce serotonin:
immune cells, nerve cells or neurons, and enterochromaffin (EC) cells. The team
found that in the germ-free mice, their EC cells produced around 60% less
serotonin than the mice with normal gut bacteria. And when they restored
bacteria colonies in the gut of the germ-free mice, their EC cells began producing
normal levels of serotonin - showing the effect on the EC cells can be reversed.
Further exploration in cell cultures revealed some of the molecular mechanisms
underpinning the findings. The team found several metabolic byproducts of gut
bacteria are controlled by the mix of spore-forming bacteria and act on EC cells to
alter serotonin production. Other investigations have shown bacteria can make
serotonin on their own. The researchers say their study suggests a lot of the serotonin
in the body relies on the interaction between bacteria and host cells.
Diseases of the Brain and Meninges
Do not need to know the
structure of the nervous
system- the figure is for
your reference
Figure 24.1-The structure of the nervous system
Central nervous system = brain and the spinal cord
Peripheral nervous system = all nerves that branch off
from the brain and spinal cord
The brain and spinal cord are covered and protected by three
continuous membranes called meninges. An infection of the
meninges is called meningitis. An infection of the brain is called
encephalitis.
Bacterial Diseases of the Brain and
Meninges - Meningitis
• Meninges
• Symptoms
• Meningococcal meningitis
• Heamophilus Meningitis
• Streptococcus pneumoniae meningitis
© 2012 John Wiley & Sons, Inc. All
rights reserved.
Bacterial meningitis
Three major types of bacterial meningitis caused by:
1. Neisseria meningitides
2. Streptococcus pneumoniae
3. Hemophilus influenzae
Listeriosis-Another kind of meningitis, listeriosis, is caused by
Listeria monocytogenes, a small Gram positive bacillus that is
widely distributed in nature.
Food borne transmission by improperly processed milk,
cheese, meat, and vegetables is the most common source of
infection. Cantaloup was responsible for about 30 deaths
this year (2011)
In pregnant women the bacillus can cross the placenta, infect
the fetus, and cause abortion, stillbirth or neonatal death.
Listeriosis is responsible for many cases of fetal damage.
Viral disease of the brain and meninges
Viral meningitis-Unlike bacterial meningitis, which is
always fatal if untreated, viral meningitis usually selflimiting and nonfatal.
Enteroviruses account for approximately 40 percent of
viral meningitis cases and mumps virus for 15 percent. The
causative virus in 30 percent of cases remains unidentified.
Rabies. Disease is caused by a small RNA virus, rabies virus, which is typically
transmitted by the bite of an animal whose saliva contains the virus. The virus
belongs to the rhabdovirus family (negative stranded RNA-containing virus).
Initially, the virus multiplies in skeletal muscle and connective tissue and
remains localized for periods ranging from days to months. It is during this localized
period that the rabies vaccine must be given. Following the localized period the virus
travels along the peripheral nerves to the central nervous system, where it produces
encephalitis. Neurological damage is often severe and the disease almost always results
in death.
Diagnosis is generally done using a fluorescent-antibody test (IFAT) made on
smears of cells.
The virus is propagated in human diploid cell culture and then chemically
inactivated to produce the vaccine. Five intramuscular injections of the virus thus
produced are recommended with a sixth dose often taken several months later. The
best means of preventing rabies is to immunize pets, and such immunization is required
in many countries.
Viral Diseases of the Brain and
Meninges - Rabies
• Diagnosis
• Transmission
• Animal susceptibility
• Symptoms
• Prevention
© 2012 John Wiley & Sons, Inc. All
rights reserved.
Encephalitis
• Togavirus
– Eastern Equine Encephalitis (EEE)
– Western Equine Encephalitis (WEE)
– Venezuelan Equine Encephalitis (EEE)
• Flavivirus
– St. Louis Encephalitis (EEE)
• Symptoms and prevention
© 2012 John Wiley & Sons, Inc. All
rights reserved.
West Nile Fever
• U.S. transmission
• Diagnosis
• Preventions
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rights reserved.
Other diseases of the Nervous System
Bacterial Nerve diseases – Hansen’s
Disease
• Mycobacterium leprae
• Incidence and Distribution
– Tuberculoid
– Nodular
• Diagnosis
• Prevention
• Treatment and Elimination
© 2012 John Wiley & Sons, Inc. All
rights reserved.
Other Diseases of the Nervous System
Hansen’s disease ( Leprosy). Caused by Mycobacterium leprae which is closely related to
the tuberculosis organisms (M. tuberculosis) and is an acid fast pleomorphic rod-shaped
organism. The organism is often referred to as Hansen's bacillus to avoid the stigma of using the
term leprosy. The disease is vastly underreported, but an estimated 15 million cases exist
worldwide today mainly in Asia, Africa and South America
Tetanus
• Clostridium tetani
• Disease
• Treatment
• Prevention
© 2012 John Wiley & Sons, Inc. All
rights reserved.
Botulism
• Clostridium botulinum
• Disease
– Infant botulism
– Wound botulism
• Diagnosis
• Treatment
© 2012 John Wiley & Sons, Inc. All
rights reserved.