Human Parasitology Exam 1

symbiosis

unlike organisms living together

phoresis

one organism is mechanically carried on or in another species; "to carry"

-no dependence on the part of the symbiont (host)

commensalism

one organism feeds on food not consumed by the host; one partner benefits and the other is neither helped or harmed

mutualism

each member of the association benefits the other; one cannot survive without the other

parasitism

one organism benefits (gains nourishment/habitat on or in the host), host is harmed

protozoa

unicellular eukaryotes

metazoa

multicellular eukaryotes

platyhelminthes

flatworms including flukes and tapeworms

nematodes

elongated worms with rigid cuticles

arthropods

insects, ticks, fleas, lice, mites which either are parasitic or transmit parasites as vectors

ectoparasites

live on, but not in their hosts (can still cause severe illness)

-in humans, attach and burrow in the skin

(all parasitic arthropods are ectoparasites)

endoparasite

live within the body and tissues of their hosts

intercellular parasites

(macroparasites)

-inhabit spaces in the host's body (ex: GI tract, muscle)

-longer generation time and tendency for reinfection

-intermediate hosts common

-larger

-not within cells (between muscle cells)

intracellular parasite

(microparasites- very small)

-inhabit within cells inside host's body

-shorter generation time and infection time

-typically rely on vector for transmission

infectious diesase

caused by transmittable parasitic agents including bacteria, viruses, fungi, protozoa and a variety of metazoans

infection

usually implies replication of agent resulting in a growing number of pathogens

(generally caused by endoparasites)

infestation

characterized by a constant number of pathogens

-severity of disease often depends on infection dose

(generally caused by ectoparasites)

obligate parasite

(most common)

-cannot complete life cycle without spending at least part of time in parasitic relationship

-may have a free-living stage outside any host (in capsule or cyst for protection)

*have to spend some portion of life in the host (can't survive without spending part of their life in host)

facultative parasite

not normally parasitic but can become so when accidentally ingested or invaded

-often severe consequences

accidental or incidental parasite

a parasite that enters or attaches to the body of a species of host different from its normal

-may not survive long

-may be extremely pathogenic

permanent parasite

lives entire life within or on their hosts

temporary or intermittent parasite

(micropredator) parasites that only feed on the host and then leave

definitive host

host in which a parasite reaches sexual maturity

-parasite infects a single host

intermediate host

host in which some development of the parasite occurs but in which it does not reach sexual maturity

vector

a living carrier that transports a pathogenic organism from an infected to a non-infected host

paratenic or transport host

host that harbors a parasite in an arrested state of development even though the parasite remains alive and viable, ready to infect a subsequent suitable host

reservoir host

alternate animal host from which the parasite can be transmitted to humans or domestic animals

-makes parasite control very difficult

carrier host

one that has contracted an infectious disease, but who displays no symptoms but can transmit it to others (asymptomatic carrier)

-have had the pathogen potentially without having symptoms and then harbored the organism within their body and can transmit it to others

ex: typhoid fever - typhoid mary mallon

sylvatic

forest dweller

hyperparasite (epiparasite)

an organism that parasitizes another parasite. common in insect-eating insects

ex: a protozoan (the hyperparasite) living in the digestive tract of a flea living on a dog

(the parasite's parasite)

parasitoid

an organism that, during its development, lives in or on the body of a single host individual which it sterilizes, kills, and sometimes consumes.

-common in insects

prepatency

infected but parasite presence can not be detected yet (false negatives)

patency

established infection, parasite stages can be detected

-(malaria parasites in blood smears, worm eggs in feces, etc.)

incubation period

time between infection and the development of symptoms

acute disease

can lead to crisis which can resolve in spontaneous healing, chronic infection, or death

convalescence

period after healing, absence of infections agents, no symptoms, in certain cases immunity to reinfection

density

average number of parasites per host in a sample of hosts; also referred to as abundance

intensity

number of parasites in an infected host

prevalence

fraction or percentage of a single host species infected at a given time

incidence

number of new infections per unit time divided by the number of uninfected hosts at the beginning of the measured time

aggregated population

a situation in which most of the parasites occur in a relative minority of hosts and most host individuals are either uninfected or lightly infected

immunology first line of defense

barriers to entry

-skin: keratin, dryness, defensins, acid mantle

-mucous membranes: lines digestive, respiratory, urinary, reproductive tracts; mucus, lysozyme

immunology second line of defense

innate: several nonspecific defense

mechanisms; effective against a broad range of pathogens

- PRRs

- Leukocytes, Macrophages (phagocystosis), NK cells

- cytokines, complement system, fever, inflammation

immunology 3rd line of defense

adaptive/acquired = the immune system

- systemic, specific and leaves the body with memory

PRRs

Pattern Recognition receptors- TLR's, dendritic cells

-recognize structures unique to microbes and required for their survival

B cells

humoral immunity

-mediated by antibodies that do not directly destroy a pathogen

-indirect: Abs assault the pathogen

-only works against the extracellular stage of infections

*3 stages: recognition, attack, memory

T cells

cellular immunity

-lymphocytes that directly attack and destroy foreign cells or diseased host cells

-means of ridding the body of pathogens that reside inside human cells, where they are inaccessible to antibodies

-kills cells that harbor them

dendritic cells (DCs)

antigen-presenting cells

-process antigen material and present it on the cell surface to cell of Adaptive Immune System

-act as messengers between the innate and the adaptive immune systems

phagocytes

phagocytic cells with a voracious appetite for foreign matter

neutrophils

*most abundant white blood cell

-wander in connective tissue killing bacteria

-phagocytosis and digestion

-produce a cloud of bactericidal chemicals

-create a killing zone

-kill more bacteria with toxic chemicals than phagocytosis

-kill off themselves in the process

eosinophils

make up tiny amount of WBC's

-stand guard against parasites, pathogens, etc.

-particularly active at killing helminthes

-found especially in mucous membrane

-produce superoxide, hydrogen peroxide, and toxic proteins to kill

basophils

smallest amount of WBC's

-produce chemicals called leukotrienes

-at a site of infection the leukotrienes from the basophils will call for backup at site (neutrophils/eosinophils)

-increased blood flow brings more blood cells into the area

lymphocytes

adaptive immunity

25-45% of WBC's

T cells, B cells, NK cells

-immune surveillance and specific immunity

monocytes

3-8% WBC's

-emigrate from the blood into C.T. and transform into macrophages

macrophage system

all the body's avidly phagocytic cells, except leukocytes

-wandering and fixed macrophages

complement system

a group of 30 or more globular proteins that make powerful contributions to both innate and acquired immunity

-synthesized mainly by liver

-circulate in blood in inactive form, activated by pathogen

*pathogen destruction by inflammation, phagocytosis, cytolysis

cytolysis

cell bursts

NK cells

natural killer cells

-continuously patrol body looking for pathogens and diseased host cells

-not phagocytic

-release chemicals called perforins that poke holes in the target cell membrane (which can no longer maintain homeostasis); dies by apoptosis

-macrophages engulf and digest dying cells

pyrexia

fever

-promotes interferon activity

-elevates metabolic rate and accelerates tissue repair

-inhibits reproduction of bacteria and viruses

major processes in inflammation (3)

1. mobilization of body defenses

2. containment and destruction of pathogens

3. tissue cleanup and repair

cytokines

*chemical messengers

chemicals that regulate inflammation and immunity

-secreted mainly by leukocytes

-alter the physiology or behavior of receiving cell

-include interleukins, tumor necrosis factor, chemotactic factors, and more

3 differences between adaptive immune response and innate response

specificity, memory, systemic (involves entire body)

lymphocytes (3)

NK cells

T lymphocytes (T cells)

B lymphocytes (B cells)

immunoglobulins

antibodies

IgA

immunoglobulin A

-monomer in plasma, dimer in mucus, saliva, tears, milk and intestinal secretions

*epithelial protection

IgD

Immunoglobulin

-monomer

-B cell Ag receptor

-functions in B cell activation by antigens

IgG

immunoglobulin

-monomer

-80% circulating antibodies

-crosses placenta to fetus

-secreted in 2nd immune response

-complement fixation

IgE

-monomer

-transmembrane protein on basophils/mast cells

* attracts eosinophils to parasitic infections

-stimulates histamine release (allergy, inflammation)

IgM

-pentamer in plasma & lymph

-secreted in 1st immune response

ADCC

antibody-dependent cellular cytotoxicity

-particularly important against parasites

-eosinophils and neutrophils

-stimulate NK cells

cytotoxic T cells

killer T cells

-take infected cells out of circulation

-poisonous to infected cells

-need help from helper cells

Helper T cells

*very important

-stimulate other T cell populations, B cell populations, and nonspecific defenses

-crucial cells

Regulatory T cells

bring things to an end and mediate immune response

Memory T cells

descend from the cytotoxic T cells

-responsible for memory in cellular immunity

APCs

antigen presenting cells

-show T cells what the foreign antigen looks like by covering themselves in it- specifically for helper T cells

T(c) cells respond only to which proteins

MHC-1

T(h) cells respond only to which proteins

MHC-II (only occur on APCs and display only foreign antigens)

alimentary transmission route

fecal-oral transmission

-ingestion of raw or undercooked food or drinking water containing the infective stage of the parasite

congenital transmission

through the placenta

fomites transmission

a non-living object such as bedding, towels, toys that can carry disease-causing organisms

parenchymatous/albuminous degeneration

tissue damage (cloudy swelling)

-accumulation of watery fluid, granule accumulation, indistinct nuclei, pale cytoplasm

*swollen cells

fatty degeneration

tissue damage

-accumulation of fat in non-fatty cells, yellowish color

-usually related to liver

necrosis

tissue degeneration

-local death of cells or tissue inside living tissue/body

-well-defined, structureless, dark

-usually liver

hypertrophy

tissue changes

-abnormal increase in cell volume/size and organ size usually due to engorgement by intracellular parasites

hyperplasia

tissue changes

-increase in number of cells and organ size

-often involves liver, endocrine glands, glandular epithelium, lymph nodes

-cells divide

metaplasia

tissue changes

-substitution of one cell type for another within an organ without the intervention of stem cells

neoplasia

tissue changes

-abnormal cell growth in a tissue, producing entirely new entity (tumor); may be benign or malignant

euprotista

unicellular eukaryotes

plasmamella

cell membrane

ectoplasm/endoplasm

contractile vacuoles

pump out excess water

-volume and osmotic regulation

-freshwater protozoans

trichocysts and toxicysts

hair-like structures that come shooting out (protection and feeding)

- Cover body of some parasites

-protection, feeding

cilia

tiny beating hair

-Supported by microtubules

-Propel cell through the water

-Sweep material through surface of cell

flagella

-Bend and rapidly straighten to propel or pull cell through fluid

-Largest of protozoans

-Pretty common

pseudopodia

move cell towards food

-branch-like feet

lobopodia

broad with round tips, clear ectoplasmic area

filopodia

lack hyaline cap

-very slender, often branched

reticulopodia

very elaborate, thin branching filaments

luminal amoebiasis

carrier is asymptomatic and producing large quantities of cysts into the environment

invasive amoebiasis

acutely symptomatic but shedding noninfective trophozoites

Giardia cysts

-can survive outside the host (cyst walls = protection)

* infective

-excyst in small intestine --> divide into 8 metacystic trophozoites