At a glance

Parasitic glossary

disease listing



Anemia: A reduction in the number of circulating red blood cells or in the quantity of hemoglobin.

Antibodies: (Also known as immunoglobulins.) Proteins that are found in blood or other bodily fluids of vertebrates. Antibodies are produced by the immune system in response to invasion by foreign substances, such as parasites and other microorganisms. Antibodies are produced by a kind of white blood cell called a B cell.

Antigens: Substances that can stimulate an immune response. Antigens are usually proteins or polysaccharides and include the coats, capsules, cell walls, flagella, fimbrae, and toxins of parasites, bacteria, viruses, and other microorganisms.

Avidity: A term used to describe the combined strength of multiple bond interactions [as opposed to affinity, which is a term used to describe the strength of a single bond]. Avidity is a term that can be used to describe antibody-antigen interactions, where multiple, weak bonds form between antigen and antibody. Individually, each bond may be weak; however when multiple individual bonds are present at the same time, the overall effect is strong binding of antigen to antibody.


Cholecystitis: Inflammation of the gall bladder.

Coccidian: Pertaining to or a member of a group of one-celled (protozoan) parasites. Cyclospora and Cryptosporidium are examples of coccidian parasites that infect the epithelial (lining) cells of the intestinal tract.


Disseminated infection: An infection where the germ enters the body through a single entry point and then disperses throughout the body.

Distilling: A technique in which water is boiled until it vaporizes and is then condensed back into water. Dissolved metals and minerals (e.g., arsenic, lead, etc.) are left behind in the distilling process. Distillation systems can have a significant energy cost associated with their use.


Ectoparasite: A classification of animals that includes those with hard, segmented bodies and jointed appendages, such as insects. Ectoparasites are usually arthropods which parasitize the skin.

Elephantiasis: A syndrome brought on from long-term obstruction of lymphatic vessels that leads to engorgement and thickened skin. It causes disfigurement, often of the leg.

Endemic: A disease that is native to a particular geographic region.

Epidemiology: The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.


Granulomatous Amebic Encephalitis (GAE): A serious infection of the brain and spinal cord that typically occurs in persons with a compromised immune system.


Helminth: A large, multicellular organism that is generally visible to the naked eye in its adult stages. Helminths can be free-living or parasitic. They include roundworms, tapeworms, and flukes.


Immunoglobulin A (IgA): A class of immunoglobulin that is the second most common immunoglobulin in blood. It is the main immunoglobulin found in secretions, such as tears, saliva, colostrum, mucous membranes of the intestine, respiratory and reproductive tracts. IgA provides local defense against microorganisms as they try to infect mucous membranes.

Immunoglobulin G (IgG): A class of immunoglobulin. This is the most abundant immunoglobulin and is approximately equally distributed in blood and in tissue liquids. Approximately 75% of serum immunoglobulins in humans is IgG.

Immunoglobulin M (IgM): A class of immunoglobulin and is the third most common immunoglobulin in serum. IgM is the first class of immunoglobulin that is made by immune cells when stimulated by antigen.


Lymphedema: Swelling from fluid build-up caused by improper functioning of the lymph system.


Malabsorption: Poor absorption of nutrients by the intestinal tract.

Morphology: The study of the form, structure, and configuration of an organism, including parasites. This includes shape, struture, color, and pattern as well as the form and structure of internal and external parts.


Oocyst: A hardy, thick-walled stage of the life cycle of coccidian parasites. This is the stage that is shed in the feces of people infected with parasites such as Cyclospora and Cryptosporidium.


Parasite: Any organism that lives in or on another organism without benefiting the host organism; commonly refers to pathogens, most commonly in reference to protozoans and helminths.

Pneumonitis: Inflammation of the lungs.

Polymerase Chain Reaction (PCR): A technique in molecular biology, in which a single or few copies of a piece of DNA are amplified (multiplied) to yield many more copies of the part (DNA sequence) of interest. This technique can make it easier to diagnose certain infections/diseases.

Protozoa: Single-celled, microscopic organisms that can perform all necessary functions of metabolism and reproduction. Some protozoa are free-living, while others parasitize other organisms for their nutrients and life cycle.


Recreational Water: water from swimming pools, hot tubs, Jacuzzis, spas, fountains, lakes, rivers, springs, ponds, streams, or the ocean.

Recreational Water Illnesses (RWIs): illnesses that are spread by swallowing, breathing, or having contact with contaminated water from swimming pools, spas, lakes, rivers, or the ocean.


Serology: The scientific study of blood serum. Antibodies may be formed in response to an infection with a microorganism and detection of these antibodies can help make a disease diagnosis when an infection is suspected. Some serological tests are not limited to blood serum, but can also be performed using other bodily fluids such as cerebrospinal fluid, saliva, and semen, which may also contain antibodies after an infection.

Sinusitis: Inflammation of the sinuses.

Sporulation: The process by which immature (noninfective) coccidian oocysts develop into the mature, infective form. The conditions and setting in which sporulation occurs varies among coccidian parasites. For example, Cryptosporidium oocysts have already sporulated by the time they are shed in feces. In contrast, Cyclospora oocysts must mature in the environment (outside the host), under favorable conditions, to become infective to someone else.


Telediagnosis: The transmission of digital images captured from a clinical specimen and sent via electronic mail to CDC for assistance in identifying suspected parasitic agents.


Zoonotic Diseases: Diseases spread beween animals and people.