Download Spring 2015-Chapter 23

CARDIOVASCULAR, LYMPHATIC
AND SYSTEMIC DISEASES
CHAPTER 23
Copyright © 2012 John Wiley &
Sons, Inc. All rights reserved.
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Researchers have found that around the world, 160 people die each day from canine
rabies. An estimated 59,000 people are thought to die every year as a result of this
preventable disease“ This ground-breaking study is an essential step towards
improved control and eventual elimination of rabies," reports Prof. Louis Nel,
Executive Director of the Global Alliance for Rabies Control (GARC). "An understanding
of the actual burden helps us determine and advocate for the resources needed to
tackle this fatal disease." . Rabies is a difficult disease to track and underreporting is
believed to be commonplace. As rabies is close to 100% fatal, a large number of rabies
victims never report to health facilities and are never diagnosed. In regions where
malaria is prevalent, misdiagnosis is also frequent. Rabies is a fatal viral disease that is
usually acquired when humans are bitten by infected animals, most typically domestic
dogs. Through the prompt administration of a fast-acting shot to bite victims, the
disease is entirely preventable, yet in populations with limited access to health care,
the disease is prevalent. The researchers found the greatest risk of canine rabies was
in the world's poorest countries. Sub-Saharan Africa is home to the highest death
rates while India reports the highest number of human fatalities - approximately
20,800 deaths per year, over 35% of the global rabies burden. Mass vaccination of
dogs comprised a very small proportion of the economic burden of rabies - less than
1.5%. The researchers report that outside of North America and Europe, a large
investment in dog vaccination has only been sustained in the Americas, leading to a
small rabies burden in this region.
Maple syrup helps antibiotics defeat bacteria Inappropriate and overuse of antibiotics has led
to the emergence of drug-resistant strains and superbugs - a major public health problem that is
in urgent need of solutions. Now, a team of researchers at McGill University in Montreal,
Canada, suggests one solution may lie in the sap of trees that are abundant in North America.
Writing in the journal Applied and Environmental Microbiology, Nathalie Tufenkji, a chemical
engineering professor, and colleagues describe how they found concentrated maple syrup
extract makes disease-causing bacteria more susceptible to antibiotics. Maple syrup contains
phenolic compounds, which are of considerable interest due to their antiseptic and antioxidant
properties. Phenolic compounds play an important role in the growth and development of
plants by helping to defend against pathogens. Phenolic-rich extract made infection-causing
bacteria susceptible to antibiotics They bought the maple syrup at local markets in Montreal
and kept it in the freezer until the start of each experiment where they removed a sample and
put it through a series of steps to produce the phenolic-rich extract.
They then tested the extract on a number of infection-causing bacteria such as Escherichia coli
and Proteus mirabilis - a common cause of urinary tract infection. The maple syrup extract and
antibiotic combination was particularly effective at destroying biofilms - resistant
communities that inhabit surfaces and are particularly hard to shift with antibiotics. Dental
plaque is an example of a biofilm. One effect that the extract has on bacteria is to make their
cell membranes more porous. This makes it easier for the antibiotics to enter the microbial
cells.The maple syrup extract also shuts down the "efflux pumps" that the bacteria use to push
any antibiotic that makes it through the membrane out of the cell.
And a third way that the extract weakens the bacteria is by reducing expression of genes
linked to antibiotic resistance and virulence.
Normal microflora of the cardiovascular systemThe cardiovascular system does not have any normal resident
microflora.
Bacteremia- bacteria in the blood, septicemia-multiplying bacteria
and their products in the blood.
Bacterial septicemias and related diseases-Before
antibiotics, septicemia was often fatal; even with
antibiotics they are still not easily treated.
Septicemia (often referred to as sepsis): the
proliferation of bacteria and the release of bacterial
products in the blood.
Symptoms include:
1. fever
2. hypotension (a decrease in blood
pressure)
3. Shock (which is caused by the decreased
blood pressure)
The bacteria most often associated with septicemia are gram
negative rods, e.g., Escherichia coli, Pseudomonas aeruginosa
and Bacteriodies sp.
It is the endotoxin of these organisms that is released
when the bacterium is lysed that causes the problems. The
endotoxin damages the blood vessels causing vascular leakage
and resulting in low blood pressure and shock.
Rheumatic fever (autoimmune disease). Caused by
Streptococcus pyogenes and leads to a rheumatic condition and often
to destruction of the heart valves. This disease is considered as an
autoimmune disease and most often evolves from a "strept" throat.
Bacterial Endocarditis. Usually caused by alpha-hemolytic
streptococci and is characterized by fever, anemia, general weakness,
and heart murmur.
Infection of the heart often occurs from a primary infection
(e.g., gums) elsewhere in the body. An acute type of bacterial
endocarditis is caused by Staphylococcus aureus or Streptococcus
pneumoniae. In this disease the infection spreads from a primary site
to the heart valves which often leads to their destruction and is
frequently fatal.
Systemic Diseases
Bacterial systemic diseases
Anthrax
Plague
Brucellosis (Undulant Fever).
Lyme Disease
Bacillus anthracis
Yersinia pestis
Brucella abortus, Brucella
suis and Brucella melitensis
Borrelia burgdorferi.
Anthrax. Causes by Bacillus anthracis which is a aerobic
gram positive spore forming rod.
Of human anthrax cases, 90 percent are
cutaneous, 5 percent are respiratory (wool-sorters disease)
and 5 percent are intestinal. Death is caused by
production of a lethal toxin.
A vaccine is available and should be given to workers
with occupational exposure to anthrax. Animal immunization
is an important means of prevention.
Bacterial Systemic – Anthrax
• Bacillus anthracis
• Cutaneous
• Respiratory
• Intestinal
• Virulence factors
© 2012 John Wiley & Sons, Inc. All
rights reserved.
Plague. The disease is caused by a gram-negative rods called
Yersinia pestis.
Normally a disease of rats, plague is transmitted from rat to
rat by the rat flea and when rats are not available to humans.
Mortality rate for untreated plague is 50-75%. If the disease
progresses to the lungs it is called pneumonic plague with a
mortality rate in untreated cases of almost 100%(even with
antibiotics and modern treatment).
The term black death stems from the fact that the infected
tissues hemorrhage and turn the skin black.
Brucellosis (Undulant Fever). Caused
by Brucella abortus, Brucella suis and Brucella
melitensis. Small gram negative rods which often grow
inside macrophages.
The disease is chronic and can last for years. When
death occurs it is usually from endocarditis.
Pasteurization of dairy products and immunization
of animal herds are the best measures to prevent the
disease. Problems with Bison herds- Bison carry Brucella
but are not overtly harmed by it.
Lyme Disease. Borrelia burgdorferi.
Disease that is showing a striking increase and is spreading
throughout the USA; has become an important infectious
bacterial disease because of the potential complications and the
number of cases. In fact it is likely the most common tick-borne
disease in this country; may be spread by ticks attached to
migratory birds.
Symptomology
Rash at bite site. It is a red area that clears in
the center as it expands to a final diameter of about 15 cm. Seen
in about 75% of the cases.
Typical bull’s-eye rash of Lyme disease
Fig. 23.13 Lyme disease
Rickettsial and related systemic diseases- Rickettsias are small gramnegative coccobacilli and are microscopic obligate intracellular parasites.
The organisms invade and damage the cells of blood vessel linings
(endothelial cells) and cause the linings to leak. This leakage causes skin
lesions and especially petechiae, pinpoint-size hemorrhages most common
in skin folds. It also causes necrosis in organs such as brain and heart.
Although each disease produces a particlar kind of skin rash, all rickettsial
diseases cause fever, headache, extreme weakness, and liver and spleen
enlargement.
Infectious mononucleosis- Epstein-Barr (EB) virus.
The disease
which affects primarily the lymph nodes is characterized by enlarged and tender nodes,
enlarged spleen, fever, sore throat, headache, nausea and general weakness.
The virus enters via oral secretions, multiplies in lymphatic tissue, and infects white
blood cells. The virus first infects epithelial cells and eventually B cells. It establishes a persistent
infection in which viruses are shed for months to years.
Infectious mononucleosis causes a proliferation of atypical lymphocytes
which in the early stages is may be confused with leukemia. Diagnosis is usually made
with a serological test for heterophil antibody. These antibodies are not specific for EB
virus but cause the nonspecific agglutination of sheep red blood cells and develop to a very high
titer in response to the disease.
The proliferation of EBV-infected lymphocytes is limited by cytotoxic T cells and
cells that make humoral antibodies and complement. If these defenses fail to limit lymphocyte
proliferation, uncontrolled B cell proliferation can lead to B cell cancer or Burkitt’s Lymphoma.
Most patients have a sore throat during the first week. The spleen is enlarged, and
cells in lymphoid tissues in the oropharynx multiply. The tonsils are coated with a gray
exudate, and the soft palate may be covered with petechiae.