Human parasites consist of tiny
protozoa and amoebae which can only be seen
under a microscope, and parasitic worms and
flukes, which are larger. The small protozoa and
amoebae are spread to people by air, water,
food, insects, animals, and human contact.
Parasitic worms are usually acquired when one
ingests contaminated meat.
It is the small human parasites
that pose the greatest risk to our health. These
tiny protozoa and amoebae can travel from the
intestines to the bloodstream, muscles, and
vital organs where they can impose considerable
damage on their hosts. In their resting stage or
cyst stage, these parasites are very infectious.
They are very small and light, so they can float
in the air and become inhaled. The parasites
have been linked to cancer, rheumatoid disease,
asthma, diabetes, multiple sclerosis, pyorrhea,
and other diseases.
Below, we will take a closer look at some of the
common parasites that can infect humans:
WORMS
Pinworms (enterobius
follicularis) – This is one of the most common
human parasites in the U.S. This worm makes its
home in the host’s colon, but it lays eggs
outside of the host’s body. Transmission can
occur through unclean hands, clothes, and bed
sheets.
Symptoms: irritation and scratching in the anal
area.
Hookworms (necator americanus)
– This is an intestinal human parasite that
begins it’s life outside of the body, in soil or
water, where humans become infected. We can
drink water that contains hookworm larvae, or we
can ingest contaminated fruits and vegetables.
This worm attaches itself to the human
intestines where it drinks blood (this worm
actually has teeth!).
Symptoms: weakness, abdominal pain, nausea,
diarrhea, anemia.
Roundworms(ascaris lumbricoides)
– One of the most common human parasites in the
entire world, these worms are as large as a
writing pencil. People are infected by ingesting
the eggs which can be in the soil, fruits, and
vegetables. The eggs find their way from the
intestines to various organs where the can cause
severe damage.
Symptoms: Weight loss, weakness, infection,
abdominal pain.
Tapeworms (taenia solium,
diphyllobothrium latum, and taenia saginata) –
Common in dogs and cats but rare in humans. To
become infected with this parasite, one must
swallow fleas that are infected with tapeworm
larvae. This worm can take-up residence in the
intestines where it will steal valuable
nutrients and expel dangerous waste. The human
host infected with this worm may not show any
symptoms.
Symptoms: mineral imbalance, bloating and gas,
dizziness, hunger pains, “fuzzy” thinking,
digestive problems, sensitivity to touch, and
allergies.
Liver Fluke (clonorchis
sinensis) - A flat worm that attacks the host’s
liver by causing inflammation and making holes.
It can survive inside a human host for
approximately 30 years. Humans acquire this
parasite through eating undercooked fish,
contaminated vegetables, human feces used as
fertilizer, or by drinking (or swimming) in
contaminated water.
Symptoms: an enlarged liver, pain in the right
side of the body, depression, edema, vertigo,
bile stones, and cancer.
PROTOZOA
Giardia lamblia – After
pinworm, this is the most common parasitic
infection in the U.S. , with several million
cases occuring annually. Giardia resides in the
intestine (or gall bladder) of it’s host and is
spread by fecal contamination and through water.
Poor sanitation and unsafe sexual practices
contribute to the spread of this parasite. Since
it is resistant to chlorination, Giardia can be
found in tap water, but it can be found in
natural streams as well.
Symptoms: abdominal pain, food sensitivity,
vitamin deficiency, diarrhea.
Entamoeba histolytica – This
one-celled organism produces a disease called
amebiasis. It can be found in water and damp
environments, in soil, and it can contaminate
fruits and vegetables. This protozoan spreads
through fecal contamination. Poor sanitation
contributes to infection, unsafe sexual
practices, and it can spread through crops that
are fertilized with human waste. Although most
people with E. histolytica don’t have symptoms,
this parasites is the leading cause of death by
protozoa after malaria.
Symptoms: abdominal pain, weight loss, weakness,
diarrhea.
Cryptosporidium – A single
celled parasite that can infect the digestive
tract, causing serious gastrointestinal
problems. Once again, this parasite is spread
when something has come in contact with feces,
then finds its way to a person’s mouth.
Cryptosporidium can be widely found in the
outdoors. It can contaminate public water
supplies, and lakes and streams. It can also be
spread by food handlers who work in restaurants,
as well as child daycare workers. Unsafe sexual
practice is another way it can be spread.
Symptoms: stomach pain, diarrhea, “fluish”
syptoms.
Toxoplasma gondii - a common,
crescent shaped parasite that invades the
central nervous system. Humans become infected
with this organism by eating undercooked meat or
by handling infected cat litter, which can
contain eggs. Most people have been exposed to
this parasite and show antibodies for it, but
only few individuals show symptoms. Those with a
compromised immune system are more susceptible.
Symptoms: “fluish” symptoms, fever, chills,
fatique, headache.
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