General
Information
Diagnosis of
Parasitic Diseases
How are parasitic diseases
diagnosed?
Many kinds of lab tests
are available to diagnose parasitic diseases. The kind of test(s) your
health care provider will order will be based on your signs and symptoms,
any other medical conditions you may have, and your travel history.
Diagnosis may be difficult, so your health care provider may order more
than one kind of test.
What kinds of tests are used to
diagnose parasitic diseases?
See below for a list of
some commonly used tests your health care provider may order.
1. A fecal (stool)
exam, also called an ova and parasite test (O&P)
This test is used to
find parasites that cause diarrhea, loose or watery stools, cramping,
flatulence (gas) and other abdominal illness. CDC recommends that three
or more stool samples, collected on separate days, be examined.
Your health care
provider may request that the lab use special stains to look for
parasites not routinely screened for.
This test is done by
collection of a stool specimen. Your health care provider may ask you to
put your stool specimen into a special container with preservative
fluid. Specimens not collected in a preservative fluid should be
refrigerated, but not frozen, until delivered to the lab or the health
care provider’s office.
This test looks for
ova (eggs) or the parasite.
2. Endoscopy
Endoscopy is used to
find parasites that cause diarrhea, loose or watery stools, cramping,
flatulence (gas) and other abdominal illness.
This test is used
when stool exams do not reveal the cause of your diarrhea.
This test is a
procedure in which a tube is inserted into the mouth or rectum so that
the doctor, usually a gastroenterologist, can examine the intestines.
This test looks for
the parasite.
3. Blood tests
Some, but not all,
parasites can be found by testing your blood. Blood tests look for a
specific parasite infection; there is no blood test that will look for
all parasitic infections. There are two general kinds of blood tests
that your doctor may order:
a. Serology
This test is used
to look for antibodies or for parasite antigens produced when the body
is infected with a parasite and the immune system is trying to fight
off the invader.
This test is done
by your health care provider taking a blood sample and sending it to a
lab.
This test is able
to detect antibodies produced by the body or antigen from the parasite
found in your blood.
b. Blood smear
This test is used
to look for parasites that are found in the blood. By looking at a
blood smear under a microscope, parasitic diseases such as malaria,
filariasis, or babesiosis, can be diagnosed.
This test is done
by placing a drop of blood on a microscope slide. The slide is then
looked at under a microscope.
4. X-ray, Magnetic
Resonance Imaging (MRI) scan, Computerized
Axial Tomography scan (CAT)
These tests are used to
look for some parasitic diseases that may cause swelling of internal
organs or abnormal scarring.
Can my lab work be sent
directly to CDC?
No. CDC is a reference
lab for the 50 states. This means that CDC cannot accept specimens unless
they are sent by your state health lab.
Where should lab specimens be
sent for testing?
It is best to send
stool specimens to a lab with experience, such as the local, county, or
state health lab, a commercial lab, or a hospital lab. Diagnosis of any
stool parasite may be difficult; by submitting several stool specimens,
your chance of being diagnosed correctly is higher than by submitting just
one sample. If you receive a negative lab report, your physician may
choose to send another sample to a different lab for confirmation.
Blood testing is done
by a variety of labs.
Is it true that labs in the
United States cannot diagnose parasites?
No. Labs throughout the
United States are qualified to diagnose parasitic infections.
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