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Parasit
Exam 1
72
Veterinary Medicine
Graduate
08/25/2011

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Term
Phoresis
Definition
organism mechanically carried by the host. No physiologic interaction or dependency is involved
Term
Commensalism
Definition
symbiont feeds off substances captured/ingested by host. No physiologic dependence is involved
Term
Mutualism
Definition
host and mutualist are physiologically dependent on one another.
Term
Parasitism
Definition
parasite is physiologically dependent on the host and typically causes harm
Term
Microparasites
Definition
acellular, multiply in host, short generation time, and usually produce acute infections
Term
Macroparasites
Definition
multicellular, rarely multiply in host, have a long generation time and usually cause chronic infections
Term
Faculative parasites
Definition
parasitism is optional
Term
Endoparasite
Definition
lives in the internal organs of host and causes an infection
Term
Ectoparasite
Definition
lives on the exterior of the host and causes an infestation
Term
Individual parasites
Definition
spend entire life on the host
Term
Lair parsites
Definition
live part of their life in the lair of host
Term
Range parasites
Definition
distributed thru large area occupied by host
Term
Accidental parasite
Definition
infects/infests organism not its usually host
Term
Aberrant parasite
Definition
found in a host other than its natural host but is not transmitted to other host, it is in the wrong location, for instance may be located in an eye
Term
Spurius parasite
Definition
False, i.e. predator that ingested prey with parasites
Term
Host specificity
Definition
range of different host species that a parasite can infect
Term
Definitive (primary) host
Definition
host which parasite reaches sexual maturity. Usually occurs in vertebrates
Term
Intermediate (secondary) host
Definition
obligate host that harbors the larval or non-sexual stages. Usually an invertebrate
Term
Resevoir Host
Definition
host for which the parasite cycles naturally and serves as infective organism for humans
Term
Paratenic Host
Definition
not necessary for completion of life cycles, a host that is just a transport host
Term
Direct cycle
Definition
Does not require an intermendiate host vs indirect
Term
Incubation period
Definition
Interval between exposure and clinical signs
Term
Prepatent period
Definition
interval between exposure and detection of parasite
Term
Patent period
Definition
infection is apparent by detection
Term
What are parasite factors?
Definition
Virulence of parasite, Infecting dose, Route of infection, Rate of parasite acquisition, Ability of parasite to multiply within host, Location in host, and Mechanisms controlling infection (i.e. self-limiting, immune response, death, etc)
Term
What are host factors?
Definition
inflammation, immunologic resistance, premunition (type of acquired immunity wherein resistance to reinfection requires retention of parasite by the host
Term
Ways parasites cause damage to host:
Definition
Acquisition of nutrition, secretions and excretions, and mechanical damage, serve as vectors for other pathogens, dead parasites can release somatic antigens, annoyance, and clinical and subclinical disease
Term
Host rxn to parasite
Definition
Inflammation, hyperplasia, hypertrophy, metaplasia, neoplasia, induction of immunity, altered behavior, altered nutrition, or mutual tolerance and species resistance
Term
Class nematophora, hairworms, horse-hair worms, gordian worms: Morphology
Definition
Dark brown, cylindrical, non-segmented with a translucent anterior
Lack a proboscis
1 to 1.5 meters long; 1 mm wide
Separate sexes
Possess a coelom with a digestive tract that is degenerate
Term
Class Nematophora: life cycle
Definition
Free living in fresh water. Mate and lay eggs in water or on moist soil.
Eggs ingested by insect or they actively penetrate insects body where they mature to adult
Insect hosts include crickets, grasshoppers and beetles
When insect host comes into contact with water, the subadult emerges by boring thru insects exoskeleton and the host is killed in the process
Term
Class Nematoda- type of worm, shape, size, sex differences, cuticle, muscle type.
Definition
roundworm.
Shape - Elongated and cylindrical with a non-segmented body
Size - Varying from 2mm x 35 μm to 1m x 1.2cm.
Sex differences - Females are usually larger than males. In some species males have a curled copulatory bursa that grasps females during copulation
Cuticle – Covers the entire surface of the nematode, extending into body openings. Might be cuticular modifications including alae, papillae, ridges and copulatory bursa. Secreted by the hypodermis
Muscle – Orientated longitudinally and divided into 4 quadrants. Bends the body dorsal/ventral
Term
Definitive (primary) host
Definition
is the host in which the parasite reaches sexual maturity or passes through its sexual stage. In most instances the sexual stages occur in the vertebrate host, but not always.
Term
Intermediate (secondary) host
Definition
is an obligate host that alternates with the definitive host in the life cycle and harbors the larval or non-sexual stage(s) of the parasite. In many instances the secondary host is an invertebrate.
Term
Reservoir hosts
Definition
are animal hosts in which the parasite cycles in nature and that serve as sources of infective organisms for humans. Reservoir hosts can be either domestic or sylvatic (wild).
Term
Paratenic (transport) hosts
Definition
is a host that is not necessary for completion of the parasite life cycle and in which the parasite remains viable but does not multiply or undergo further development.
Term
Prepatent period
Definition
the time interval between entry of an infectious agent into a host and the first time we can detect the agent in the host. The prepatent period is typically longer in duration than the incubation period i.e. clinical signs often occur before the parasite can be detected.
Term
Patent Period
Definition
The time period when infection is apparent as indicated by detection or demonstration of the infectious agent.
Term
Factors influencing damage done to host by parasite
Definition
Virulence of parasite
Strain of parasite
Infecting dose: number of parasites entering/infecting host
Route of infection
Rate of parasite acquisition
Ability of parasite to multiply within the host
Location in host
Mechanisms controlling infection: self-limiting, immune response, death etc.
Term
Host resistance
Definition
Inflammation
Immunologic resistance
Immunity
-Natural vs. acquired
Cellular and humoral
Term
Premunition
Definition
a form of acquired immunity wherein resistance to reinfection depends upon retention of the parasite by the host.
Term
Premunition
Definition
a form of acquired immunity wherein resistance to reinfection depends upon retention of the parasite by the host.
Term
How parasites cause damage to a host
Definition
Acquisition of nutrition: for example, competition for ingesta, sucking of blood and lymph, feeding on parenchyma

Secretions and excretions-substances produced by the host may be inflammatory, immunogenic or toxic to host

Mechanical damage: for example, larval migration causing physical disruption of tissue
Physical obstruction of blood vessels or ducts by parasite itself or tissue reaction to presence of the parasite

Serve as vectors for other pathogens or create conditions for proliferation of pathogens

Host reaction to dead parasites - release of somatic antigens to which the host is not exposed while parasite is alive
Annoyance
Disease, clincal vs subclinical
Term
Host reactions to a parasite- tissue reactions
Definition
inflammation, hyperplasia, hypetertrophy, metaplasia, neoplasia, induction of immunity
Term
Host reactions
Definition
tissue reactions, altered behavior, altered nutrition, mutual tolerance and species reactions
Term
Parasite adaptations to parasitic lifestyle
Definition
mode of feeding and host finding, mechanisms for finding a host, attaching, etc. Stages in life cycle, such as resistant stages for survival during host trans. Loss of organs
Term
Phylum for roundworms
Definition
Nemathelminthes
Term
Phylum for flatworms
Definition
Platyhelminthes
Term
Phylum for thorny headed worms
Definition
Acanthocephala
Term
Class for roundworms
Definition
nematoda
Term
Class for flukes
Definition
Trematoda, phylum platyhelminthes
Term
Class for flukes
Definition
Trematoda, phylum platyhelminthes
Term
Class for tapeworms
Definition
Cestoda, phylum platyhelminthes
Term
How can you differentiate males from females in the class nematoda
Definition
Females are generally larger then males,
Males of some species have a curled tail or bursa copulatrix, or copulatory bursa. Appendage at the posterior end used to grab the female.
Term
Cuticle
Definition
A tough, thick external protective covering of callagen and keratin produced by hypodermal cells. Covers entire surface of nematode and extends into all body openings (mouth, rectum, cloaca, rectum)
Term
Cuticular modifications
Definition
alae, papillae, ridges and copulatory bursa occur at anterior or posterior ends. Useful for identification
Term
Hypodermis
Definition
thin layer beneath cuticle that secretes the cuticle.
Term
Describe the body cavity in nematoda
Definition
Internal organs are suspended in body cavity, pseudocoelom, that has no cellular lining. Contains fluid that is commonly allergenic or toxic to host. Fluid pressure provides turgor that keeps body of worm straight.
Term
Describe male nematodes:
Definition
dioecious: sexes are separate and sexual dimophism is common. Coiled testes, an enlarged seminal vesicle and vas deferens that ends as a muscular ejaculatory duct opening into the cloaca. Spicules, gubernaculum, copulatory bursa
Term
Spicules
Definition
rigid cuticular structures used to dilate the vulva of the female during mating to facilitate sperm transfer
Term
gubernaculum
Definition
cuticular structure used to guide the spicules through the cloaca
Term
Spicule pouch
Definition
present in some species along with the copulatory bursa
Term
Female nematodes
Definition
females have 1-2 sets of repro glands, ovary, oviduct and uterus leading to one vagina that opens at the vulva. Vulva may be posterior or anterior. Some species have a distal unterus elarged to form seminal receptical for storage of sperm. Large numbers of eggs, 1,000 a day
Term
Digestive cavity nematode
Definition
simple tube, anterior mouth may have modifications. Esophagus of adults usually have prominent muscular part. Intestine is a straight tube lined with microvillus absorbtive surface.
Term
Metabolism and nutrition of nematodes
Definition
Faculatative anaerobes that store glycogen and depend on the host as a source of CHO. The host supplies all food whether its blood, lymph, tissue lysate, pre-digested ingesta
Term
Basic nematode life cycle
Definition
5 larval stages, L1 to L5. egg, 5 larval stages and adults.
Term
oviparous
Definition
species produce eggs with a single-cell or morula stage so eggs in fresh feces contain very early stages of development. Further development of larval stages occurs in the environment inside and/or outside of the egg again depending upon the species.
Term
ovoviviparous
Definition
species produce eggs that contain an L1inside. The L1 hatches from the egg either in the host GI tract or in the environment depending upon the species.
Term
laviparous
Definition
species produce first stage larvae in the uterus so fresh feces contain the L1. Further larval development occurs outside the female.
Term
What stage of nematodes is infective to a new host and begins the parasitic phase?
Definition
L3
Term
What happens to the host during larval migration?
Definition
larval migration causes clinical signs in a host. Signs occur before the infection becomes patent, a definate diagnosis can be difficult to make. The incubation period is usually shorter then the prepatent period.
Term
In some species of nematodes, molting from L2 to L3 results in keeping the old cuticle. What are advantages/disadvantages?
Definition
Advantage: prevents it from drying out
Disadvantage: prevents feeding.
Term
Hemonchus contortus
Definition
L3 to L4 It occurs in the rumen after a suitable host has ingested the L3. The process is stimulated by specific conditions in the rumen that activate larval neurosecretory cells near the esophagus. These cells release hormones that stimulate water uptake that activates enzymes. The enzymes are released locally into the space between the new and old cuticle weakening the attachment between them. The old cuticle breaks off and the anterior end is shed as a cap after which the L3 wriggles out of the remainder of the old sheath.
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