Parasitic Diseases

A parasitic disease is an infectious disease caused or transmitted by a parasite. Many parasites do not cause disease per se. Parasitic diseases can affect practically all living organisms, from plants to man. The study of parasitic diseases is called by parasitology.

Some parasites like Toxoplasma gondii can cause Toxoplasmosis as a parasitic disease directly caused by the protozoan. In contrast, some of the symptoms caused by parasites are due to the toxins produced by the parasites, rather than the parasites themselves.

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?

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.
Example: pork tapeworm (Taenia solium) and beef tapeworm (Taenia saginata)

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.
Example: Physaloptera (a nematode)

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.


source: wikipedia; Center for disease control and prevention (CDC)