Transmission of pathogens and prevention of infection

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Transmission of pathogens and prevention of
infection

• By Tracy Wong
• Yuki Kong

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What is pathogen? Microorganisms that cause
disease and are considered a nuisance(??). These
may either be a virus, bacterium or fungus.
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The routes of transmission of pathogens -air
( e.g. common cold, influenza ????? ) - water
or food ( e.g. cholera ?? ) - vector (e.g.
malaria ?? ) - body fluids ( e.g. hepatitis B
B ???, AIDs)
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Air common cold A common cold is an
illness caused by a virus infection located in
the nose
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Transmission of Disease

• Contact
• Direct Requires close association between
  infected and susceptible host
• Indirect Spread by fomites
• Droplet Transmission via airborne droplets

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Transmission of Disease
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Transmission of Disease

• Vehicle Transmission by an inanimate(????,
  reservoir (food, water)
• Vectors Arthropods???? , especially fleas?,
  ticks??? , and mosquitoes
• Mechanical Arthropod carries pathogen on feet
• Biological Pathogen reproduces in vector

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Transmission of Disease
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The appearance of the virions,
Virions are 42nm in diameter and possess an
isometric nucleocapsid or "core" of 27nm in
diameter, surrounded by an outer coat
approximately 4nm thick. The protein of the
virion coat is termed "surface antigen" or HBsAg.
It is sometimes extended as a tubular tail on one
side of the virus particle. The surface antigen
is generally produced in vast excess, and is
found in the blood of infected individuals in the
form of filamentous and spherical particles.
Filamentous particles are identical to the virion
"tails" - they vary in length and have a mean
diameter of about 22nm. They sometimes display
regular, non-helical transverse striations.
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How does a baby get hepatitis B from his or her
mother? They will get the disease only if the
mother has hepatitis B and a tiny bit of their
mothers blood gets inside the baby at
birth. Can the mother breast-feeds her baby if
she has hepatitis B? YES! If the mothers baby
gets a shot called H-BIG and a shot of hepatitis
B vaccine within 12 hours of birth, it is okay
for the mother to start breast-feeding her baby
right away. Be sure to take good care of her
nipple areas to prevent cracking and bleeding.
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Transmission by food and water

• Cryptosporidium

Cryptosporidium (crip-toe-spor-ID-ee-um) is a
protozoan, a single-celled parasite, that lives
in the intestines of animals and people. This
microscopic pathogen causes a disease called
cryptosporidiosis (crip-toe-spor-id-ee-O-sis.The
dormant (inactive) form of Cryptosporidium,
called an oocyst (O-o-sist), is excreted in the
feces (stool) of infected humans and animals. The
tough-walled oocysts survive under a wide range
of environmental conditions.
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The appearance of the pathogen
Cryptosporidium parvum is a small, crude and
potentially deadly pathogen. cryptosporidium
sickened more than 13,000 people in Carrolton,
Ga. Scientists traced the outbreak back to the
municipal water supply surprising, considering
that the water met all state and federal safety
standards. "It can exist outside its host in a
tough egg-type structure called an oocyst, which
can cause infection once its been ingested by
humans and host species," he adds. Equally
disturbing, Hairston says, is the fact that
scientists are not sure how long these oocysts
can survive under a wide range of environmental
conditions.
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How is the pathogen spread? You can get infected
with Cryptosporidium when you put anything in
your mouth that has been in contact with feces
from an infected animal or person. When large
numbers of people get cryptosporidiosis, the
source of infection can sometimes be tracked
down, but it is impossible to determine the
origin of many individual cases of this disease.
Your hands may be contaminated with
Cryptosporidium through person-to-person contact,
perhaps while changing a child's diaper, caring
for someone with diarrhea or engaging in any
activity that involves touching areas of the body
contaminated with feces. Cryptosporidiosis can be
easily spread among people in close social groups
such as families, day care centers, and nursing
homes. People who work with animals, especially
young animals or animals with diarrhea, have
greater chance of exposure to the parasite. You
may pick up oocysts while handling soil, or any
object contaminated with even a small amount of
feces.
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You can also get cryptosporidiosis by drinking
water or eating food that has been contaminated
with oocysts. Drinking untreated surface water
(such as streams, rivers, and lakes) or
swallowing a small amount of water when swimming,
even in a chlorinated pool, can cause
cryptosporidiosis. The parasite may also be
spread in uncooked foods, beverages, or ice
prepared with contaminated water. Unwashed fresh
fruits or vegetables may carry oocysts if manure
was used or animals grazed where the crop was
grown. People who are infected (or whose hands
become contaminated) with Cryptosporidium can
spread the disease to other people or pets if
they are not careful about their hygiene.
Frequent handwashing is the single most important
thing people can do to avoid spreading
cryptosporidiosis and other illnesses. It is
especially important to wash thoroughly before
preparing food, as well as after using the
toilet.
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How can we prevent the disease?
We can protect our water supplies from
Cryptosporidium. Multiple barriers are needed to
protect our water supplies from Cryptosporidium.
Water treatment methods alone cannot solve the
problem watershed protection and monitoring of
water quality are critical.
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The life cycle of cryptosporidi