Download PRRS Glossary – PRRSglossary

2003 PRRS Compendium Producer Edition
START SCREEN
TABLE OF CONTENTS
SEARCH THIS BOOK
NEXT SEARCH HIGHLIGHT
Glossary of Terms
Acute – A term used to describe the sudden onset of clinical disease.
Antibody – A specific type of protein made by certain cells of the immune system in response to infection.
The purpose of antibodies is to react with disease agents invading the body in an effort to control the
infection. Antibodies are often present in the blood stream (serum) following infection. Piglets do not
have serum antibodies at birth, but antibodies in colostrum are absorbed across the GI tract and may be
detected in the blood stream. Also see "serology."
Antigen – A term describing any kind of particle that is capable of inducing an immune response when
introduced into an animal. Viruses, bacteria, certain proteins, and allergens are examples of antigens.
Assay – A general term that includes many types of laboratory tests.
Carrier - A pig subclinically infected with a specific disease agent for an extended period of time. Carrier
animals serve as a potential source of infection for other pigs. Also see "subclinical infection."
Chronic – A disease or condition that persists for an extended, but generally unspecified, period of time.
Diagnostic sensitivity – The proportion of individuals that are infected and are also test-positive (some
infected individuals will be test-negative.) Also see "diagnostic specificity."
Diagnostic specificity – The proportion of individuals that are not infected and are also test-negative (some
uninfected individuals will be test-positive.) Also see "diagnostic specificity."
ELISA – An acronym for "enzyme-linked immunosorbent assay" in which either an antigen or antibody is
linked to an enzyme to find its corresponding match. ELISA is a rapid laboratory assay most
commonly used to detect and/or measure the amount of antibody present in serum.
Endemic – The constant presence of a disease or infectious agent in a population at a relatively steady rate
(also see "epidemic").
Epidemic – The rapid increase of disease in a population beyond its expected rate (also see "epidemic").
Epidemic, when used as a noun, means the same as "outbreak."
Genome – The sequence of nucleic acids that make up an organism’s DNA or RNA. See also “nucleic
acid.”
Genotype – The genetic makeup of an animal or organism.
Heterologous – A term meaning “different.” For example, two viruses of the same species are considered
heterologous if they are genetically very different.
Homologous – A term meaning “the same.” For example, two viruses of the same species are considered
homologous if they are genetically very similar.
In utero – Literally meaning "in the uterus." A scientific term to describe an event or condition happening
to a fetus during the time it is within the uterus or prior to birth.
In vitro – Literally meaning "in glass." Refers to something occurring in an artificial environment, like a
test tube or culture media. Also see "in vivo."
In vivo – Literally meaning "in life." Refers to something occurring in a living body or organism. Also see
"in vitro."
Lesion – Physical damage to cells or an organ as a result of a disease process. Lesions may be visible
microscopically or grossly.
Macrophage - An important cell of the immune system present throughout the body. Macrophages have
the ability to engulf and destroy many kinds of disease pathogens.
Maternal antibody (also maternal immunity, colostral immunity, or lactogenic immunity) – Passively
acquired immunity, including several types of antibody, found in neonatal pigs. Dams with high
concentrations of antibody against a disease will pass some of these antibodies to their offspring
through colostrum and milk. Antibody tests run on the serum of neonates cannot distinguish between
141
PREVIOUS PAGE
NEXT PAGE
2003 PRRS Compendium Producer Edition
START SCREEN
TABLE OF CONTENTS
SEARCH THIS BOOK
NEXT SEARCH HIGHLIGHT
maternal antibodies and antibodies that the animal has formed as a result of exposure to an infectious
agent.
Nucleic Acid – One of four specific proteins (adenosine, guanine, cytosine, and thymine) that make up
DNA and RNA.
PCR – An acronym for "polymerase chain reaction." PCR is a laboratory technique for amplifying a
specific region of DNA or RNA. In the diagnostic lab, the presence of a pathogen in a clinical sample
can be confirmed by amplifying and detecting a portion of the genome unique to the pathogen.
Persistent infection – In persistent infections, the infectious agent remains in the host for an extended, but
generally undefined, period of time. There are two types of persistent infections: 1) latent persistent
infections - the infectious agent is present in a quiescent state and does not continuously replicate.
Pseudorabies virus is an example of a latent persistent infection. 2) chronic persistent infections - the
agent continually replicates in the pig. PRRS virus is an example of a chronic persistent infection.
Also see "carrier."
Phenotype – The characteristics of an animal or organism that can be seen with the naked eye. Phenotype
is the result of the interaction between animal's genetic potential (genotype) and its environment.
PRRS – Porcine reproductive and respiratory syndrome. "PRRS" typically refers to the clinical disease
caused by infection. "PRRSV" or "PRRS virus" refers to the virus that causes the disease.
Serology – Serology is the testing of serum for the presence of antibodies against infectious agents to
determine if a pig has been infected at some time in its life. The presence of serum antibodies against
an infection only indicates that the pig has been exposed at some time in the past; it does not indicate
whether the animal is currently infected In young pigs, serum antibodies received from the mother's
colostrum may give a positive response in an uninfected animal.
Seronegative – An animal's "negative" status established on the basis of a negative serologic result. Also
see "serology."
Seropositive – An animal's "positive" status established on the basis of a positive serologic result. Also see
"serology."
Serum – The straw-colored, liquid component of whole blood that remains after a blood clot has been
allowed to form.
Subclinical infection – Infection, but without signs of disease. Also see "carrier."
Viral replication – The reproduction of a virus. Unlike bacteria, viruses can only replicate within living
cells.
Viremia – Circulation of virus particles in the blood stream.
Virulence - the relative "disease-producing power" of an infectious agent. A more virulent organism
produces more severe disease than a less virulent organism.
142
PREVIOUS PAGE
NEXT PAGE