Abnormal host A host that is not the usual one. There are two kinds of abnormal hosts: accidental and aberrant.
Abopercular end The opposite end of an operculum in parasite eggs.
Abortion storm Series of abortions.
Abundance The number of parasites in or on a host including uninfected hosts.
Accidental host An animal/human that harbors an organism that is not usually parasitic in that particular organism. Sometimes the accidental host becomes a dead-end host because the parasite develops but fails to find a portal of exit and cannot continue its life cycle.
Acetabulum A muscular organ of attachment usually associated with the scolex of tapeworms; commonly called a sucker.
Acid fast Property of some microorganisms of resisting destaining of carbolfuchsin stain based on cell wall structure; acid fast organism examples include Mycobacterium and Cryptosporidium.
Adaptive immunity Portion of the immune system that is activated by exposure to antigen.
Adult stage The stage of a parasite that is sexually mature and in which reproduction occurs.
Agar Solid food source for microorganisms.
Agglutinate To clump together.
Agglutination reaction Antigen-antibody reaction that produces a visible clumping of particles.
Alternate host The host that alternates with another host in the life cycle of a parasite; another term used for intermediate host.
Amastigote Aflagellated, developmental stage found in some hemoflagellated protozoa.
Amoeba Protozoa that move by pseudopodia.
Amoeboid Cells that resemble amoebae by forming pseudopods.
Amplifying vector Designation given to an arthropod that contributes to the buildup and transmission of a disease-causing agent by transmitting the agent among vertebrate hosts; also called amplifying host.
Antibody A large protein molecule produced in response to an antigen; an antibody interacts with a specific antigen.
Antigen A foreign substance; any cell, particle, or chemical that induces a specific immune response.
Antigenic determinant Small region of the antigen that a lymphocyte recognizes; also called the epitope.
Antiseptic A chemical that inhibits the growth of or kills microorganisms on living tissue.
Antitoxin Antibodies that bind to and inactivate toxins.
APHIS Animal and Plant Health Inspection Service.
Artifically acquired active immunity Protection from disease stimulated by intensional means such as a vaccine.
Artifically acquired passive immunity Protection from disease conferred byintensionally administering antibodies fromed by another another or person.
Asexual reproduction Reproduction without the formation and fusion of gametes, for example binary fission, budding, schizogony, etc.
Attenuated vaccine Vaccine composed of weakened, nonpathogenic, live microorganisms.
Autoinfection Reinfection by a parasite from within the host and is not exposed to the outside environment; also known as hyperinfection.
Axostyle A rod-like structure that gives rigidity to the bodies of some flagellates.
B lymphocytes Lymphocytes that differentiate to produce antibodies.
Bacillus Rod-shaped bacterium when used with lower case b; bacilli is plural.
Bacteria Prokaryotic, single-celled microorganism.
Bacteriophage Viruses that infect bacteria.
Baerman technique Fecal test used to recover and identify parasitic larvae from feces using sedimentation principles.
Barophiles Organisms that grow only or more rapidly at pressures greater than 1 atmosphere.
Basal granule The granule-like body from which each cilium arises in cilates.
Binary fission Reproduction by division of an individual that produces two duplicates of the original; occurs in bacteria and some parasites.
Binomial nomenclature A system of naming organisms in which each organism is identified by a genus designation and a species designation.
Biological vector A vector in whose body the infecting organism develops or multiplies before becoming infective; a living obligate host in which morphologic change and/or replication occurs.
Biovar A bacterial strain differentiated by biochemical or non-serological methods.
Blepharoplast A small granule-like body in the cytoplasm of some parasites.
Bothrium An organ of attachment (sucker) in the form of a grove on the scolex of some tapeworms.
Bradykinin A substance released during inflammation that causes vasodilation and increased blood vessel permeability.
Broad-spectrum antibiotics Antibiotics that are effective against both gram-positive and gram-negative bacteria.
Broth Liquid food source for microorganisms.
Budding A form of asexual reproduction common in yeasts in which a bubble forms on the cell surface, grows, and pinches off, forming a new cell.
Caecum A sac-like extension of the intestine that is open only at one end; seen in organisms with a true intestine.
Capnophile An organism requiring CO2 at a level higher than air for growth.
Carrier Healthy animal or person who are reservoirs of infection.
CD4 cells Lymphocytes that increase immune responsiveness; also known as helper T cells or TH cells.
CD8 cells Cytotoxic lymphocytes that kill infected cells; also known as cytotoxic T cells or TC cells.
CDC Centers for Disease Control and Prevention.
Cell-mediated immunity Immune response carried out by T lymphocytes.
Centers for Disease Control and Prevention The U.S. national agency located in Atlanta, Georgia that does research, collects statistics, and publishes information on infectious disease; also known as the CDC.
Cercaria Free-swimming larva of a trematode that escapes from a sporocyst or redia generation in the intermediate host (mollusk). Cercaria typically have a tail and is the transfer stage to the next host.
Chagoma An erythematous primary lesion of Chagas' disease.
Charcot-Leyden crystals Slender, pointed crystals formed from the breakdown product of eosinophils and are found in stool (typically indicating a parasitic infection); commonly called CL crystals.
Chemotaxis Process by which cells sense certain chemicals and move toward regions that contain optimal concentrations of them.
Chitinous shell The hard shell of nematode eggs that encases the embryo.
Chromatoid body Rod-shaped mass of RNA found in the cysts of amebae.
Cilia Small fibrils that function in movement.
Ciliates A class of protozoa bearing cilia.
Coccus Spherical-shaped bacteria when used with lower case c; cocci is plural.
Coenurus A larval cystic stage of a tapeworm.
Colony A clone of cells all originating from the same parent that is large enough to be visible on solid medium.
Communicable disease Disease that can be transmitted from one host to another.
Communsalism A symbiotic relationship where one organism (commensal) dervies benefit from another (host) without harming or helping the other.
Complement A family of more than 30 different proteins in serum that function together as a nonspecific defense against infection.
Complement fixation assays Tests that detect antigen-antibody reactions by their utilization (fixation) of complement.
Complete metamorphosis Process of growth and development of insects in which an individual insect develops through several larval stages and then a nonfeeding pupal stage before reaching adulthood.
Concentration method A procedure for increasing the strength of or the number of organisms in a medium. Fecal concentration methods are performed on a fecal specimen increasing the number of organisms found per given unit.
Cord factor A mycolic acid found only in virulent strains of Mycobacterium tuberculosis that causes these strains to form parallel rows of cells called cords.
Crustacea An arthropod class that is a group of aquatic animals having hard shells, jointed bodies and appendages, and gills for breathing such as crabs, shrimp, and copepods.
Cuticle The epidermis of vertebrates; the outer covering secreted from the hypodermis or subcuticular layer in helminths.
Cyclophyllidiea Tapeworm order in which the worms have four sucker discs encircling the scolex with or without a rostellum (for example Taenia spp.).
Cyst The protozoan stage in which the organism is encased in a cyst wall producing a more resistant stage that may be transmitted to a new host; an organism together with the enveloping membrane or wall secreted by that organism.
Cyst wall The outermost protective coating of an encysted protozoan.
Cysticercoid Tapeworm larva in which the scolex is invaginated into a cystic cavity.
Cysticercus Tapeworm larva in which the scolex is invaginated into a bladder filled with fluid.
Cytostome In flagellates and ciliates, the cavity that opens by way of the peristome (lips) to allow solid food particles to enter the mouth.
Dead-end host Host in which the parasite reaches an end point and is unable to continue its life cycle; also known as an aberrant host.
Decorticated Loss of characteristic mamillated outer covering of Ascaris lumbricoides egg.
Definitive host Host in which sexual reproduction (fertilization) of a parasite occurs.
Density The number of organisms per quantity of tissue.
Density gradient The varying sequence of densities of materials suspended in a liquid in which the most dense material is found at the bottom and the least dense material is found at the top due to gravity sedimentation.
Diecious Distinctly separate sexes; male reproductive organs are present in one and female organs are present in another.
Direct life cycle Single-host life cycle; does not have intermediate host.
Disc diffusion method Determining the sensitivity of a microorganism to antimicrobial drugs by seeding a plate with the microorganism and placing filter paper discs embedded with known quantities of different antimicrobial agents; also known as the Kirby-Bauer method.
Disease Deviation from normal health or production.
Disinfectant A chemical that inhibits the growth of or kills microorganisms on inanimate objects.
Doubling time The period required for a microbial population to produce two new cells for each one that previously existed; also called generation time.
Ectoparasite Parasite that lives on the host's body surfaces.
Ectoplasm Granule free cytoplasm of ameba lying immediately under the plasma membrane.
Edema Swelling of tissue by accumulation of fluid between cells.
Egg Female reproductive cell after fertilization.
Embryo The developmental stage following cleavage of the egg up to the first larval or first juvenile stage.
Embryonated Containing a developing embryo; used to describe eggs that are infective.
Endemic The ongoing, low-level presence of disease within a group; present in the group at all times.
Endoparasite Parasite that lives within the body or internal organs of its host. Endoplasm Inner, granule-rich cytoplasm of ameba.
Endosome Nucleolus-type organelle found in some protozoa.
Endospores Extremely resistant dormant structures that form within the cells of certain genera of bacteria.
Endotoxin The lipopolysaccharide component of the outer membrane of gram-negative bacteria that is harmful to animals and humans.
Enterotoxins Compounds that are harmful to the epithelial cells lining the intestinal tract.
Enzootic The ongoing, low-level presence of disease within an animal group; present in the animal group at all times.
Enzyme Protein that catalyze specific metabolic reactions.
Enzyme-linked immunosorbent assay Diagnostic immunological test that contains an enzyme linked to an indicator antibody; abbreviated ELISA.
EPA Environmental Protection Agency.
Epidemic Sudden, widespread, and rapidly spreading disease within a group of humans at the same time.
Epidemiology The study of relationships of the factors determining frequency and distribution of disease.
Epitope Small region of the antigen that a lymphocyte recognizes; also called the antigenic determinant.
Epizootic Sudden, widespread, and rapidly spreading disease within a group of animals at the same time.
Epizootiology The study of distribution and abundance of animal diseases.
Erythema Abnormal skin redness.
Erythema migrans A reddish skin rash associated with Lyme disease that is caused by infection and initial spread of Borrelia burgdorferi spirochetes in the vicinity of the bite of an infected tick.
Erythrocytes Red blood cells.
Etiology The study of causative agents of disease.
Eukaryote Organisms composed of a membrane-bound nucleus.
Exotoxin Highly destructive protein produced by some gram-positive and gram-negative bacteria.
Facultative Capable of adapting to different conditions.
Facultative anaerobe Organism that uses oxygen to grow when it is available, but can grow without oxygen.
Facultative parasite A parasite that has free-living stages that do not require hosts.
Fastidious organism Organism that requires numerous complex nutrients to grow.
FDA Food and Drug Administration.
Fecal-oral route A pattern of disease transmission by which pathogens shed in feces enter a new host through the mouth.
Filariasis Disease caused by a group of parasitic filiarial nematodes.
Filariform A juvenile postfeeding stage of a nematode; the infective stage of hookworms, filarial worms, and some other nematodes.
Final host Another term used for definitive host.
Flagellates A class of protozoa that move by means of flagella.
Flagellum A filament that usually projects from the body of an organism; functions as an organelle of locomotion or when in the groove in the cytostome causes movement of fluid; flagella is plural.
Florid plaques Focal amyloid protein deposits surrounded by vacuolized cells.
Flotation methods Fecal test in which feces with worm eggs are suspended in a liquid with a specific gravity greater than that of the eggs making the eggs float to the surface.
Fluke Common name for trematodes.
Fluorescent-labeled antibodies Antibodies chemically bonded to fluorochromes (fluorescent chemicals).
Fomite An object that mechanically transfers disease organisms.
Free-living Living free of a host.
Fungi Group of nonphototrophic eukaryotic organisms that includes yeasts, molds, and mushrooms.
Gas gangrene Infection caused by Clostridium perfringens.
Gel electrophoresis Movement of charged molecules through a gel driven by an electric current resulting in molecules of different size and/or charge becoming separated.
Generation time The period required for a microbial population to produce two new cells for each one that previously existed; also called doubling time.
Ghon complexes Calcified caseous tubercles that indicate a past primary tuberculosis infection.
Gingivitis Inflammation of the gums.
Gram stain A differential staining technique that is based on differences in cell wall structure allowing gram-positive bacteria to stain deep blue and gram-negative bacteria to stain light red.
Gram-negative bacteria Bacteria that have a thin cell wall surrounded by an outer membrane.
Gram-positive bacteria Bacteria that have a thick cell wall and no outer membrane.
Gravid Filled with eggs.
Halophile Organism that grows well in environments with high salt concentrations.
Halteres Reduced hind wings of flies.
Helminth Worm; consists of nematodes, trematodes, cestodes, and acanthocephalans (thorny-headed worms).
Hemagglutination Clumping of red blood cells.
Hemagglutinin Protein that clumps red blood cells.
Hematophage Blood feeing arthropod.
Hemocoele A body cavity in mollusks and arthropods through which hemocoeles fluid (blood) circulates carrying nutrients to the organs.
Hemolysin Protein that destroys red blood cells.
Herd immunity Prevention of disease due to the scarcity of new susceptible hosts.
Hermaphroditic Containing both male and female reproductive organs; also known as monecious.
Hooklet The small hook-like organ of attachment present on the rostellum of the tapeworm scolex.
Horizontal transmission Transfer of an infectious agent from one animal to another.
Host An organism that harbors or nourishes another organism.
Humoral immunity Protection conferred by antibodies.
Hydatid cyst A cystic larval stage of Echinococcus spp.
Hyperinfection Reinfection by a parasite from within the host and is not exposed to the outside environment; also known as autoinfection.
Hyphae Tubelike filaments in mold that make up a mycelium.
Immune system Cells (mainly lymphocytes) and organs that extends throughout the body and functions as a defense against infection.
Immunization Artificially stimulating the body's immune defenses.
Immunocompetence The process by which lymphocytes acquire the capability to function fully in the body's defense.
Immunodiffusion test A type of precipitation reaction in which antigens and antibodies are diluted and mixed by diffusion through a gel.
Immunoelectrophoresis assay A type of precipitation reaction in which antigens and antibodies are diluted and mixed by electrophoresis through a gel.
Immunofluorescence assay Tests in which antigen-antibody reactions are detected by fluorescence because one of the reactants is tagged with a fluorescent dye.
Immunological memory The ability of memory lymphocytes to recognize an antigen if they encounter it again with better speed and amplification.
Inactivated vaccine Vaccine containing killed microorganisms.
Inapparent infection Subclinical infection; infection that does not produce clinical signs.
Incidence An expression of the rate at which a certain event occurs; the percentage of new infections in a given population during a specific time; number of new infections divided by the number examined.
Indirect life cycle Multiple hosts used in the life cycle.
Infection Colonization of the body with pathogenic organisms.
Infection source The medium, object, or living entity containing an infective stage of an organism.
Infectious disease A disease that is caused by a transmissible agent, such as viral, bacterial, fungal, or parasitic organisms.
Infective stage The stage in the parasitic life cycle during which it is capable of producting infection.
Infestation A host/ectoparasite relationship in which the parasite lives on the surface of the host.
Inflammatory mediators Molecular messengers that initiate inflammation.
Inflammatory response The body's nonspecific reaction to injury or infection; signs include redness, pain, swelling, heat, and loss of function.
Innate immunity Protection that does not depend on exposure to antigens to be active.
Instar The growth period between molts.
Interferons Small glycoproteins produced by host cells in response to viral infection.
Interleukin-1 Cytokine produced by white blood cells that functions to induce fever.
Intermediate host Host necessary for development, asexual reproduction, or transmission of a parasite; also called the alternate host.
Isolate Pure culture derived from a heterogeneous population of microbes.
Juvenile stage Any stage in the development of a helminth parasite between the egg and the mature adult stage that appears similar in shape and structure to the adult.
Karyosome A structure within the nuclue of amoebae having a relatively constant size and location in each species.
Kinetoplast Mass of mitochondrial DNA in flagellate protozoa.
Kinetosome Basal body of cilia (found in cilated protozoa).
Knott's test Concentration procedure used to identify microfilariae.
Larva The postembryonic parasite or arthropod stage in which internal organs are developing and are at least partially functioning; any preadult stage in the life cycle of a parasite that is morphologically distinct from the adult stage (not used for immature nematodes, because they are not morphologically distinct from the adults).
Larviparous Organisms such as flies that deposit first-stage larvae instead of laying eggs.
Leukocidin Enzymes that kill leukocytes.
Leukocytes White blood cells.
Lumen The space within a tubular organ.
Lymphokines Messenger proteins produced by lymphocytes.
Lysis Rupture of the cytoplasmic membrane resulting in cell destruction.
Lysogeny State in which an infecting phage exists as a prophage.
Macrogamete Female gamete of Toxoplasma; the larger of two gametes.
Macronucleus The large kidney-shaped nucleus found in some ciliates.
Mechanical vector A vector which transmits an infective organism from one host to another, but is not essential to the parasite life cycle.
Mesophile Organism that grows best at moderate temperatures (around 37[degrees]C).
Metacercaria The encysted stage of a monecious trematode; this stage succeeds the cercaria; metacercariae is plural.
Microgamete Male gamate of Toxoplasma; the smaller of two gamete.
Micronucleus A small nucleus closely associated with the macronucleus in ciliates.
Micropyle In coccidia, a pore in the cyst wall closed by a plug of material which is more easily dissolved that the cyst wall; this is where structures formed in the cyst emerge.
Minus strand Single-stranded RNA comprising a viral genome that must be transcribed by RNA-dependent RNA polymerase to act as mRNA; also called negative sense.
Miracidium The larve that emerges from the egg in trematodes.
Molt The process of shedding the outer body covering.
Monecious Containing both male and female reproductive organs; also known as hermaphroditic.
Morbid Afflicted with disease.
Morbidity The sick rate; the ratio of diseased animals/ humans to well animals/persons in a population.
Moribund Dying; near death.
Mortal Fatal; causing death.
Mortality The death rate; the ratio of diseased animals/ humans to diseased animals/human that die.
Morula The cleaving stage of an egg that forms a solid mass of cells.
Mutualism A symbiotic relationship where both organisms benefit.
Mycelium Mass of hyphae produced by some mold.
Narrow-spectrum antibiotics Antibiotics that are effective against only either gram-positive or gram-negative bacteria.
Natural host The usual host; also known as the typical host and normal host.
Natural killer cells Non-B cells and non-T cells that lyse cells by secreting perforins.
Naturally acquired active immunity Immunological protection that occurs unintentionally following exposure to an organism such as with infectious disease.
Naturally acquired passive immunity Immunological protection that occurs unintentionally following antibodies transferred from mother to fetus across the placenta or to the newborn through colostrum.
Negative sense Single-stranded RNA comprising a viral genome that must be transcribed by RNA-dependent RNA polymerase to act as mRNA; also called minus strand.
Negri bodies Inclusion bodies that develop in the brains of animals or people with rabies.
Neurotoxin Toxic protein that specifically affect nerve function.
Non-infectious disease A disease that is not caused by a transmissible agent, such as nutritional or genetic.
Normal flora Microorganisms that coexist with animals/ humans in a stable, nonpathogenic relationship.
Nucleoli Dense masses of RNA and protein in the eukaryotic nucleus that manufactures ribosomes.
Nucleus Cell organelle that contains DNA and controls growth, cell division, and other activities of the cell.
Nuisance biter A bloodsucking arthropod that causes discomfort when biting, but is not known to be involved in the transmission of a disease-causing agent.
Obligate Must have; also called strict.
Obligate aerobe Organism that grows only in the presence of oxygen.
Obligate anaerobe Organism that grows only in the absence of oxygen.
Obligate barophiles Organisms that grow only at pressures greater than 1 atmosphere.
Obligate intracellular parasites Parasites that can only reproduce inside a host cell.
Obligate parasite A parasite that requires certain hosts to develop and cannot live apart from their host.
Occult blood Blood present in such small quantities that it is not detectable except by chemical means.
Onchospher The stage that emerges from the egg shell and later from the embryophore of tapeworms.
Oocyst Coccidian protozoal stage that is shed with the feces.
Operculum Cap-like structure at one end of some trematode and cestode eggs through which the embryo or larva emerges.
Opportunistic An organism that is not typically a parasite or disease-causing organism but may become so under specific conditions.
Opsonin Protein that facilitates phagocytosis.
Opsonization Process by which an opsonin faciliatate phagocytosis.
Ovum An unfertilized egg.
Pandemic Widely epidemic; occurring over a large region, continent, or geographic area.
Parabasal body A heavy fiber present in some flagellates.
Parasite An organism that lives on or within another organism at the expense of that organism.
Parasitism A symbiotic relationship where one organism (parasite) is metabolically and obligately dependent upon the other (host).
Paratenic host An animal acting as a substitute intermediate host of a parasite; no additional development of the parasite occurs in the paratenic host; also known as a transport host.
Parthenogenesis Reproduction without any male element.
Passive immunity Immunity conferred by administering antibodies.
Passive transmission A form of transmission in which the host/parastie contact is accidental.
Patent period Period of time in which the diagnostic stage of a parasite can be demonstrated.
Pathogen A disease-causing organism.
Pathogenesis The manner of disease development.
Pathogenic Disease causing.
Pathology The study of disease.
Periplast The limiting, outer memebrane of protozoa.
Peristome Any parts around the mouth or oral opening of invertebrates (comparable to lips).
Phage Virus that infects bacteria; shortened name for bacteriophage.
Phage typing Identifying bacterial strains by their pattern of susceptibility to phages.
Phagocytosis Engulfment of one cell by another.
Pili Straight, hair-like appendages that extend from the surface of a bacterial cell.
Piroplasm Any organism in the class Piroplasmea, while in a circulating red blood cell; for example, Babesia.
Plaque Circular clear zones on a lawn of cells.
Plaque count Procedure for determining the number of bacteriophages and phage-infected cells in a sample.
Plaque-forming units Virions and virus-infected cells; abbreviated PFUs.
Plerocercoid Tapeworm larva in which the scolex is embedded in an enlarged tail; for example in Diphyllobothrium latum.
Plus strand Single-stranded RNA constituting a viral genome that can act directly as mRNA; also called positive sense.
Polar plugs Mucoid plugs located at both ends of eggs of Trichuris worms.
Portal of entry Anatomic site through which a pathogen enters a host.
Portal of exit Anatomic site through which a pathogen leaves a host.
Positive sense Single-stranded RNA constituting a viral genome that can act directly as mRNA; also called plus strand.
Precipitation reaction An antigen-antibody reaction that forms lattices large enough to precipitate.
Prepatent period Time from infection until the infection is detectable.
Prevalence The total number of disease cases in existence at a certain time in a certain location; percentage of infected animals in a given population at a given time.
Primary host Another term used for definitive host.
Primary immune response Production of antibody that occurs when a person first encounters a particular antigen.
Prion An infections agent composed only of protein.
Procercoid The first larval stage of pseudophyllidian tapeworms which develops from the onchosphere.
Proglottid One complete unit of a tapeworm below the scolex; also known as a tapeworm segment.
Prokaryotes Organisms that do not have a membrane bound nucleus; bacteria.
Promastigote Developmental stage of a protozoan that possesses a prominent flagellum.
Prophage A phage genome integrated into the chromosome of a host cell.
Protozoa Nonphotosynthetic, unicellular eukaryotes; protozoan is singular.
Pseudophyllidian An order of tapeworms in which the scolex has a single terminal bothria (such as in Diphyllobotrium latum).
Pseudopod Tubelike structures that amoeboid cells use for movement.
Pus A mixture of dead leukocytes, microoganisms, and host cells.
Radioimmunoassay A test to detect antigen-antibody reactions in which one of the reactants is tagged radioactively.
Reservoir host An animal/human that is infected by a parasite and serves as a source of infection for others.
Reticuloendothelial system The aggregate of the phagocytic cells (including certain cells of the bone marrow, lymphatic system, liver, and spleen), that function in the immune system's defense against foreign bodies; abbreviated RES.
Reverse zoonosis A disease that can be naturally transmitted from humans and animals.
Rhabditoid juvenille The first feeding stage of a juvenile nematode.
Ringworm Common name for dermatophyte infections.
Rostellum Apical portion of the scoles of some tapeworms.
Schizogony Multiplication in protozoa in which repeated division of the nucleus and daughter nuclei occurs within the cell.
Scolex The attachement end of a tapeworm from which the neck arises and gives rise to proglottids; scolices is plural.
Secondary host Another term used for intermediate host.
Secondary immune response Immune response initiated by memory cells.
Selective media Media that favor that growth of certain microorganisms over others.
Sensilium On the flea abdomen a structure that detects vibrations and temperature changes for host detection.
Septa Cross walls in fungi.
Septicemia Persistent infection of bacteria and their toxins in blood.
Serology Diagnostic tests using blood serum.
Serotype Taxonomic classification identified by serology; also called a serovar.
Serovar A bacterial strain differentiated by serological methods; also called a serotype.
Serum Liquid portion of blood minus the clotting factors/ proteins.
Sign A characteristic of disease that can be observed by others.
Smear A thin film spread on a microscope slide.
Sparganum The second larval stage of pseudophyllidian tapeworms.
Species barrier Factors that restrict pathogens to certain host species.
Sporadic Occuring occasionally in a population.
Sporocyst A cyst that develops within an oocyst of a coccidain protozoa in which sporozoites develop.
Sporogenesis Development of a spore.
Sporozoa Nonmotile protozoa.
Sporozoite The infective unit that develops within an oocyst that penetrates the intestinal wall initiating infection.
Stage Any particular form in the parasitic life cycle which can be distinguished from its other forms.
Stains Dyes used to increase contrast.
Strain A subset of a bacterial species that is different from other bacteria of the same species by a minor, identifiable difference.
Strict Must have; also called obligate.
Strobila A complete tapeworm consisting of scolex, neck, and all proglottid stages.
Symbiosis The close association of two dissimilar organisms.
Syngamy Multiplication by a sexual process.
Tachyzoite Actively proliferating trophozoites.
Taxonomy Science of classifying organisms.
Thermophil Organism that grows at high temperatures.
Tinea Common name for dermatophyte infections in humans.
Tissue culture Cultivation of eukaryotic cells or tissues in vitro.
Titer Highest dilution of a test solution that is active.
Toxoid Treated toxins that have lost their pathogenicity but still stimulate the immune system to produce antitoxin.
Transfer host An animal/human that serves as a host until the appropriate definitive host is reached (not necessary for the life cycle of the parasite).
Transmission Transfer from one animal to another.
Transovarial transmission Passage of infectious microorganisms from one generation of host to the next through their eggs.
Transport host An animal acting as a substitute intermediate host of a parasite; no additional development of the parasite occurs in the paratenic host; also known as a paratenic host.
Transstadial transmission Passage of a disease-causing agent from an infected immature stage to the next stage of an arthropod vector.
Trophozoite The active, vegetative stage of a protozoan.
Tubercles Granulomas produced by tuberculosis infection; dense nodules containing activated macrophages and monocytes.
Turbidity Cloudiness of a liquid caused by suspended particles.
Typical host Host in which the parasite is usually found and in which it can continue development.
Ubiquitous Existing or being everywhere.
Uncoating The process by which the capsid and envelope of a virion are removed.
Undulating membrane Wavy membranous structure attached to the other portion of some flagellate protozoa.
Unembryonated Not containing a developing embryo; used to describe eggs that do not contain developing embryoes and are not infective.
Unilocular An intermediate larval stage (cyst) of tapeworms having only a single cavity.
Vaccination The use of vaccines to produce artificial active immunity.
Vaccine Agents that confer immunity without causing disease.
Variant Something that differs in its characteristic from the classification to which it belongs.
Vector An animal (usually an arthropod) that transmits disease organisms.
Vegetative cell Cell that grows and reproduces asexually.
Vertical transmission Transfer from one generation to another.
Vesicle Tiny, fluid-filled skin lesion.
Virion Intact, nonreplicating virus particle.
Virulence The degree of pathogenicity; the ability to cause overt disease.
Virus Microscopic packet of nucleic acid typically wrapped in a protein coat.
Vitelline gland The glands in Platyhelminthes that produce yoke material and the egg shell.
Wet mount A drop of liquid containing microorganisms on a microscope slide covered by a cover slip.
Xenodiagnosis A diagnostic technique in which uninfected arthropods are allowed to feed on a suspect individual and then examined in an attempt to recover the parasite.
Yeast A single-celled fungus.
Ziehl-Neelsen stain Special staining techniqe used to indentify Mycobacterium tuberculosis and closely related bacteria.
Zoonosis A disease that can be naturally transmitted from animals and humans; plural is zoonoses.
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|Author:||Romich, Janet Amundson|
|Publication:||Understanding Zoonotic Diseases|
|Date:||Jan 1, 2008|
|Previous Article:||Appendix D: nationally notifiable zoonotic infectious diseases of the United States--2007.|