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294 GLOSSARY

Human monocytic ehrlichiosis (HME) Three tick- host that is infected, but then is ingested by the accidental host
borne diseases caused by the intracellular bacteria of the genus and therefore infected.
Ehrlichia have been described. Human monocytic ehrlichiosis Incysting To enclose or become enclosed in a cyst.
(HME) was first identified in 1986 and is caused by Ehrlichia Indirect test Testing for the evidence of an organism rather
chaffeensis. than for the organism itself, for example, antibodies toward a
Hyaline shell Clear, translucent covering of a cyst. parasite is an indirect test in which the parasite itself was not
Hydatid larva (cyst) Cyst in the tissues, especially the liver found. Several of these are performed as indirect fluorescent
where development of the larvae of the dog tapeworm has been antibody tests for parasitic diseases such as for toxoplasmosis
encysted; may grow for years to extremely large size. and malarial infections.
Hydatid sand Term for the hydatid cyst caused by Echinococ- Infection Growth of microorganisms inside the body.
cus granulosus, where a floating membrane or cyst may contain Infectious jaundice Jaundice is caused by excessive
possibly up to 400,000 protoscolices per milliliter of fluid. destruction of RBCs. It occurs from infections by bacteria or
Hydatiform Fluid-filled cyst that forms most often when an viruses, and in particular the parasite responsible for malaria.
individual is infected by a tapeworm such as in the disease of Infective stage Certain stages in a parasite’s life cycle are in-
echinococcosis. fective; in some, the larval form is infective, in others the eggs
Hypersensitivity reactions The term refers to an exces- may be infective, and for various others, spores are the infective
sive reaction to an allergen (antigen), which includes parasitic stage. For some organisms, there is only one stage and that is
organisms; severity ranges from a mild reaction to severe sys- the infective stage.
temic reactions leading to anaphylactic shock and shut down Infestation Growth of organisms on the body’s surface.
or damage to systems of the body. Insect repellent Agent that discourages the presence of in-
Hypostome Hardened and sharp harpoon-like structure sects but does not kill them. DEET is the most well-known of
found in the mouth area of some certain parasitic insects that these repellents.
includes ticks and mites. The structure enables the ectopara- Insects Any members of the six-legged class within the arthro-
site to maintain a firm grip while withdrawing blood from its pods that have a hard exoskeleton, three-part body, compound
victim. This mechanism is the reason for the difficulty in re- eyes and two antennae that distinguish them from spiders and
moving ticks, during which the head is often left attached when other arachnids.
the body is removed. Integument Commonly refers to a covering that may include
various layers and their appendages or investment and most
I often refers to the covering of the body as the skin.
Intermediate host An organism in which a part of the life
IgE One of the immunoglobulin classes of antibodies is that of cycle of the parasite is spent while undergoing morphological
IgE (immunoglobulin E). These antibodies are found in high changes, before it infects a definitive host.
concentrations in various tissue spaces and are chiefly involved Intestinal coccidian A common intestinal coccidian infect-
in ridding the body of intestinal parasites as well as reacting to ing humans is that of I.belli. This organism causes a self-
allergic conditions. limiting diarrhea in healthy individuals and a chronic disease
Immunocompetent An immunocompetent individual pos- in those who are immunocompromised due to underlying
sesses the ability for the body to react normally in an immune medical conditions or infectious diseases.
response to allergens. Intestinal fluke These organisms are transmitted by humans
Immunocompromised Refers to the inability to develop a and pigs primarily in Asia. Fasciolopsis buski is the most com-
normal and limited immune response, appropriate for the situ- mon and is called the giant intestinal fluke.
ation, which may be due to conditions of disease, malnutrition, Intestinal lumen A cavity or channel within a tube such as
age, or immunosuppressive medications. the intestines is the lumen. The lumen may become constricted
Immunodeficient Being immunodeficient may relate to cel- in a variety of intestinal conditions.
lular (white blood cell reactions) or humoral (production of Intracellular Refers to a condition within the cellular mem-
antibodies against the offending antigen) that results in an im- brane of the cell.
paired immune response; a number of conditions predispose Intra-erythrocytic Refers to a condition in which organ-
one to infections and certain malignancies. isms or inclusions are contained within the membrane of the
Immunoglobulin Refers to five classes of immune globulins RBC. A common intra-erythrocytic parasite is that of the Plas-
that are gamma globulin proteins found in the blood, body flu- modium genus responsible for malaria.
ids, and tissues of vertebrates as antibodies. The immune system Intraperitoneal Refers to the abdominal cavity and digestive
uses these antibodies to aid in identifications of and neutraliza- organs of vertebrates.
tion of foreign bodies such as parasites, bacteria, and viruses. Intrapleural In humans as well as other vertebrates, the
Immunosuppressive Drugs or other agents may be immuno- pleural cavity refers to the body cavity that surrounds the lungs.
suppressive that inhibit or prevent activity of the immune system. Intrauterine Refers to “within the uterus” or womb.
Steroidal use is a prime example of immunosuppressive drugs. Iron deficiency Refers to a condition where insufficient iron
Incidental host Incidental hosts may also be referred to as in the correct form is available for the body’s needs, particu-
accidental; this means that the food source may be the primary larly for hematopoiesis (manufacture of RBCs).