Lecture 1 - Parasitism (1)
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Transcript of Lecture 1 - Parasitism (1)
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RELATIONSHIPS
BETWEEN ORGANISMS.
PARASITISM
Assoc. prof. Milena Atanasova, PhD
Dept. Biology , MU-Pleven
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I. DEFINITON AND SUBJECTS OF
PARASITOLOGY
Parasitology
a complex biological science
investigates the phenomenon of parasitism.
It studies:
the origin and evolution of the parasites
biological cycle and geographical distribution
host parasite relationships
parasitic diseases
the ways to prevent the humanity from them
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I I. PARASITES, PARASITISM , AND
HOST RELATIONS
Two different ways in which an animal may obtain food at
the expense of other animals.
Predation: Predator attacks another living animalconsuming part or all of its body for nourishment, in the
process frequently but not necessarily killing it. The victim is
the prey.
ScavengingAn animal may derive its nutrition from already
dead animals: such animals are called as Scavengers.
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A. RELATIONSHIPS BETWEEN
ORGANISMS LIVING TOGETHER
Some animals always seek their food by their own effortsor in association with others of their own species. Otheranimals, still in essence predators or scavengers, havebecome so modified, that they are unable to obtain foodexcept in close association, either continuous or at
intervals, with members of another species.
SYMBIOSIS:This association of two species, perhapsprimarily for food getting on the part of one or bothmembers of the group, is known as symbiosis.
Different forms of symbiosis may be distinguished onthe basis of whether or not the associationdetrimental to one of the two partners.
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C. PARASITISM
Parasitism, like other forms of symbiosis, necessarilliy involves anintimate relationship between the two species, and it is this closeand prolonged contact that differentiates parasitism from thepredatory activities of many nonparasites. A predator must belarger and stronger than its prey, whereas a parasite is small andweak.
Parasite is defined as a living organism which lives upon or inanother organism and derives its nourishment from it thusadapting oneself to live in or on itit is called a host.
The life cycle pattern of a parasite may be:
simple, involving only a single host complex involving two or more intermediate hosts
Parasites employ a variety of ways to effect transmission;ingestion, penetration of skin and mucous membrane,inoculation by arthropod vectors etc.
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D.ORIGIN OF THE PARASITISM
On the basis of logical and historicalconsiderations would be assumed thatparasitism had been arisen after appearance ofthe free-living organisms. In reality to before theparasite exists the host, free-living organism.
Because the size of the parasites are much
smaller then these of their hosts, it may besupposed that they become widespread onlythen the arising of a number organisms withvariety of size.
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D.ORIGIN OF THE PARASITISM
It is supposed that zooparasitesare originated by
three ways:
a) from scavengers(animals living on and feed on
decaying organic substances)
b) from predators(free-living leech)
c) by changing of the relationshipsbetween
symbionts and as a result the one of them turn into a
parasite and the other into a host
d) parasites living within the host may be described as
endoparasites.They originate from predatory
insects and ticks
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D.ORIGIN OF THEPARASITISM
e) Parasites that are found on the surface of the body are calledectoparasites.They originate from former ectoparasites; for ex.some infusoria, specific ectoparasites on the fish gills and fins are
pass to urinary bladder (there is functionally similarity, secretion ofuric acid and ammonia)
Intestinal endoparasites - accidentally get into intestine by food(for ex. Prof. Skryabin, had been found eggs, larvae and adults in
the intestine of miners of two species Rhabditis, usually living insoil)
Blood parasites
i. from intestinal own parasites, somehow get into blood
ii. by intestinal parasites of invertebratesfor ex.Trypanosoma
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III. PARASITES AND HOSTSA. Classification
1) According the place of livingandtheir interactions with hosts
Ectoparasites: a parasite whichlives outside or on the surface ofthe body of host
Endoparasites: a parasite whichlives within the body of the host(cells, tissues, organs)
- Intracellular
- Extracellular
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A. Classification
2) According the number of hostsrequiring to complete their lifecycle
1) Monoxenous(louse , Pediculuscapitis) one host to complete thelife cycle
2) Heteroxenous (taenia,Dyphyllobothrium latum) requiringmore than one host
http://upload.wikimedia.org/wikipedia/commons/f/fe/Pediculus_humanus_capitis_CDC9217.png -
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A. Classification
3) According the amount of timespent on the host there are Temporary andStationary parasites
Temporaryvisit host for food (bloodsucking arthropods - mosquito, ticks,flea, louse).
Usually they multiply and develop outside of the hosts body and get in
relationship with the host only to nourish themselves. Preferablyectoparasites.
Stationaryspend a definitive period of development on or in the body ofthe host. According to the amount of time spent with the host stationaryparasites are subclassified as: periodicremain with the host for only a part of their development and then
leave to complete it and continue nonparasitic life. permanentspend their entire existence in hosts except for the times they
occur free while transferring from one host to another (Malarial plasmodia) -they are predominantly endoparasites (all parasitic protozoa, the most of theparasitic nematodes, some of spiderlike and insects), They cannot survivewithout the host.
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A. Classification
4) Facultative and obligate:Parasitism as a way of lifemay be the only possibilityfor a given organism , or itmay be but one alternative.
An organism that cannot survive in any other manner iscalled an obligate parasite. Parasitism for them is aspecies trait (all individuals of the species are parasites)
A facultativeparasite is an organism that may exist in a
free-living stage or as a commensal and that way, ifopportunity presents itself, may become parasitic.Parasitism for them is not obligate, it is not speciesfeature (only some organisms are parasites).
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A. Classification
Commensal: Parasite does not harm the host evenwhen living within or on the host
Occasional or accidentalparasite: Attacks an unusual
hostfor ex. Larvae of domestic ?
Aberrant or wanderingparasite: The parasite arrivesat a place where it cannot survivefor ex. Larva
currents , Visceral larva migrans, produced bynonhuman species, Toxocara canis
Pathogen: A parasite which is able to cause disease
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III. PARASITES AND HOSTSB. Hosts of parasites
a) Definitive Host: A host in which the definitive or thefinal stages of the parasite develop. What this
means????
The host in which the
sexualreproduction of a
parasite takes place.
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B. Hosts of parasites
b) Intermediate Host: A host in which theintermediate stages of the parasite
develop
The host in which
the asexualreproduction of a
parasite takes
place.
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B. Hosts of parasites
c) Reservoir Host:When the parasite
is maintained in
nature and which
acts as a soursefor individual new
cases
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B. Hosts of parasites
d) Paratenic Host:Transport or
carrier host in
which the parasite
remains viable butdoes not undergo
further
development
http://www.dpd.cdc.gov/dpdx/HTML/Toxocariasis.htm -
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IV. Other Terms used in Parasitology
Habitat: The natural abode of a parasite species
Incubation: The time period between the entrance of a parasiteinto a host and the initiation of the disease
Ecology: The relationship between a population of an organismand the environment; when this is a balanced equation, the hostremains healthy, but break or change in the relationship results indisease outbreak.
Zoonosis: Diseases of animals which are transmissible to men
Opportunistic parasites: Parasites which are not normally
pathogens but become so due to impairment of host resistance
Mutualism: A type of symbiotic process in which both partnerssharing the relationship are benefited
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V. ADAPTATION TO PARASITISM
Some preadaptive changesmight be in the nature of increasedresistanceto enzymatic activities of the host.
Further physiological adaptations to parasitism might involve theloss of enzymes or enzyme systems, which are then supplied by
the host. Such losses may be expected to make a parasitic, or etleast a symbiotic relationship, obligatory.
Sertain groups of parasites exibit profound morphologicadaptationsto their way of life. These modifications are more
striking in those groups that are wholly parasitic than in those thatcontain both free-living and parasitic species.
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V. ADAPTATION TO PARASITISM
Organs not necessary to a parasitic existence are frequently lost. Adigestive tract, moderately complex in the turbellarians, is generallyreducedin the trematodes and is absent in the cestodes.
The reproductive system is very highly developedin the two latter groups;this seems a reflection of the difficulties inherent in transfer of these
organisms to a new hosts.
Specialized attachment organs in the form of suckers and hooks havebeen developed by the parasitic flatworms.
Body size may be greatly affected by the parasitic state. Most free-livingnematodes barely attain naked-eye visibility as adults, but Ascaris canreach 35 cm and some tapeworms as much as 10 m.
On a more basic level, the parasitic mode of existence may result inprofound biochemical changes. The parasite, no longer able to synthesizecertain necessary cellular components, obtains them instead from its host.
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V. ADAPTATION TO PARASITISM
Specialized mechanisms for effecting entranceinto the body ortissues are seen in some parasites: ingestion, penetration ofskin and mucous membrane, inoculation by arthropod vectorsetc.
Immune evasion may involve such factors as location of theparasite in relatively protected sites, changes of the parasitesurface antigenic structure brought about in a variety of ways,and active modification of the host immune response byproducts of parasite metabolism.
The life cycle pattern of a parasite may be simple, involving onlya single host or complex involving 2 or more intermediate hosts.
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VI. EFFECTS OF THE PARASITE
ON THE HOST
Its effects is harmful - produces disease or its effects.Pathogenicity depends on: species, structure and functions,environmental factors etc.
1. Mechanical - it is by nature for parasitic helminthes andarthropods; at invasion, attachment, migration, obstruction ofintestine, injury of mucous membrane and organs. For example:Ascaris, Echinococcus granulosus, Filaria etc.
2. Toxic effect - due to metabolic products of the parasite:secretions, excretions, or other products of the parasite.
Malarial parasites invade and multiply in red blood cells, which aredestroyed in the process and releasing the malarial products intothe blood stream, many of which are also pyrogenic.
Ascaris body fluid is toxic and many sensitizing.
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VI. EFFECTS OF THE PARASITE
ON THE HOST
3. Spoliative effect Some parasites exert their effects by depriving
the host of essential substances.
Hookworms suck blood and bring about anemia.
The broad fish tapeworm, Diphyllobothrium latum,selectively removes vitamin B12 from the alimentarytract, producing megaloblastic anemia in somepersons.
Another parasites feed on blood, lymph, chyle, tissuefluids.
4. Transmission effect
Blood sucking ectoparasites bring about spreadof infections and parasitic diseases among thecommunity. They are known as vectors (flee, louse,mosquito etc).
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VI. EFFCTS OF THE PARASITE ON
THE HOST
5. Sensitization
Majority of parasites have sensitizing effect.
Although that there is a variety of effects of
the parasite on the host the latter remainsalive. System host-parasite keeps up
dynamic balance.
Definition of Sensitization- non-associative learning process
in which repeated administrations of a stimulus results in the
progressive amplification of a response.
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VII. EFFECTS OF THE HOST ON
THE PARASITE
The genetic constitution of the host may profoundlyinfluence the host-parasite relationship. It is now well known thatthere are racial variations in resistance to Plasmodium vivax,which are related to the presence or absence of the Duffy bloodgroup. The sickle cell trait is also associated with increased
resistance to infection with the malarial parasite Plasmodiumfalciparum.
Now we know that every species of animas is naturally resistantto infection by many organisms that parasitize different species.Acquired immunity can be demonstrated in many parasitic
diseases, and it is generally found to be at a lower level thanthat produced by bacteria and viruses.
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VII. EFFECTS OF THE HOST ON
THE PARASITE
The host reacts against parasite by two types of reactions:
1) Cellular and tissue reaction
2) Humoral reaction.
The character of these reactions depends on the species of theparasite, age and the nutritional status of the host, environmental
conditions, etc.
1) Cell and tissue reactions
the changes of the cells size; for ex. red blood cells, infected byPlasmodium vivax become enlarged and pale
Red blood cell with multiple
trophozoites of Plasmodium vivax
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VII. EFFECTS OF THE HOST ON
THE PARASITE
Eosinophils kill some parasites; Macrophages secrete somecytokines
Inflammatory reaction - multiplying of reticuloendothelial cellsend histiocytes, which pile up and lying down tissue fibers
surrounding parasites, thus isolate it somehow from the host;for ex. Trichinella spiralis, Echinococcus
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VII. EFFECTS OF THE HOST ON
THE PARASITE
2) Cells humoral reaction
- it is including phagocytosis
3) Akin to other infectious agents,parasites also elicit immuneresponsesin the host, humoral
as well as cellular butimmunological protection is far lessthan compared to that of bacteriaor virus.
Immune response involvesproduction of specific antibodies byB lymphocyteshumoralimmune response.
- Cell - mediated immune responseinvolves the set of T lymphocytes.
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VIII. DISEASES CAUSED BY
PARASITES
The parasite has to leave the host and gain
entry into other hosts to either complete its
live cycle or to progress its transmission.
Once the parasite overcomes the defenses ofthe host, a certain specific pattern of disease
evolves - parasitic diseases.
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VIII. DISEASES CAUSED BY
PARASITES
Some parasitic diseases
are belong to the so-
called transmissive
diseases (they aretransmitted by vectors -
some blood-sucking
insects and ticks; for
exp. Malaria - P.malariae - mosquito)
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VIII. DISEASES CAUSED BY
PARASITES
Transmissive diseases can be two types:
Obligate(they can be transmitted only by specific vectors; exp.Trypanosoma)
Facultative (they can be transmitted by both; vectors and bywater, food, air; for ex. intestinal infection)
There are also nonspecific mechanical vectors (for ex.
cockroaches or beetles). Some vectors may exist as reservoirs.For ex. ticks can keep the infection decades.
Important for these is the transmission of infection by the eggsto their progenytransovarialtransmission.
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VIII. DISEASES CAUSED BY
PARASITES
The man become infected by sometransmissive diseases if he live in certainarea the so-called seat, focus. They hadbeen by arisen by nature and no matter if
there are human beings or no. The infectionis transmitted from the sick animals intohealth ones by the vectors or predator(Leishmania, Plague, Trichinella spiralis etc.)
The man becomes infected after biting by thespecific vector or when enter into the focus asa hunter, tourist, visitors for a job, etc.
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VIII. DISEASES CAUSED BY
PARASITES
Depending on the life cycle ofthe parasitic helminths(worms) they are classified asfollow:
Biohelminths (they requirenot only definitive butintermediate host as well;Schistosoma)
Geohelminths(a part of their
life cycle takes place in thesoil; Ascaris, Trichiuris ), thereis no need of intermediatehost
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IX. Parasites names (Nomenclature)
Binomial Nomenclature
Scientific system of naming plants and animals
Genus: surname
Species: first name
Strain: second name
Underlined or i tal ic
To simplify the taxonomy, the major divisions
involved in medical parasitology-specifically,
intestinal and urogenital protozoa, blood and
tissue protozoa, nematodes, trematodes, and
cestodes have been addressed.
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The parasites of humans are classified within the kingdomAnimaliaand are separated into two subkingdoms, Protozoa
and Metazoa.
Parasite classification takes into account the morphology ofintracytoplasmic structures, such as the nucleus, the type of
locomotive organelles, and the mode of reproduction.
The Protozoaare animals whose life functions occur in a
single cell.
The Metazoaare multicellular animals in which life functions
occur in cellular structures organized as tissue and organ systems
IX.Parasite classification and structure
Flagellates
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Parasites
Protozoa
Metazoa
Sarcomastigophora
Amoebae
Flagellates
Ciliophora
Apicomplexa or Sporozoa
Microspora
Helminths
Arthropods
Platyhelminths
Nemathelminths Nematodes
Cestodes
Trematodes
Chilopoda
Pentastomida
Crustacea
Insecta
Arachnida
Subkingdo
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Medically
Important
Parasites
(Kingdom
Animalia)
Subkingdo
m Phylum Organisms
Protozoa Sarcomasti
gophora
Ameba, flagellates
Ciliophora Ciliates
Apicomple
xa
Sporozoa, Coccidia
Microspora Microsporidia
Metazoa Nematoda Roundworms
Platyhelmi
nthes
Flatworms
Trematod
es
Flukes
Cestodes Tapeworms
Arthropoda
Chilopoda Centipedes
Pentastom
ida
Tongue worms
Crustacea Crabs, crayfish, shrimp, copepods
Arachnida Mites, ticks, spiders, scorpions
Insecta Mosquitoes, flies, lice, fleas, wasps, ants,beetles, moths, roaches, true bugs
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Protozoa are simple microorganisms that range in sizefrom 2 to
100 m.
Their protoplasm is enclosed by a cell membrane and contains
numerous organelles, including a membrane-bound nucleus, an
endoplasmic reticulum, food-storage granules, and contractileand digestive vacuoles. The nucleus contains clumped or
dispersed chromatin and a central karyosome.
Organelles of motilityvary from simple cytoplasmic
extrusions or pseudopods to more complex structures, such as
flagella and cilia.
Protozoa
Bi l i M h l i d Ph i l i
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Biologic, Morphologic, and Physiologic
Characteristics of Pathogenic Parasites
Organism Class Morphology Reproduction
Organelles of
Locomotion Respiration Nutrition
Protozoa
Amoeba Unicellular; cyst and
trophozoite forms
Binary fission Pseudopods Facultative anaerobe Assimilation by
pinocytosis or
phagocytosis
Flagellates Unicellular; cyst and
trophozoite forms;
possibly intracellular
Binary fission Flagella Facultative anaerobe Simple diffusion or
ingestion via cytostome,
pinocytosis, or
phagocytosis
Ciliates Unicellular; cysts and
trophozoite
Binary fission or
conjugation
Cilia Facultative anaerobe Ingestion via cytostome,
food vacuole
Coccidia Unicellular, frequently
intracellular; multiple
forms, including
trophozoites, sporozoites,
cysts (oocysts), gametes
Schizogony and
sporogony
None Facultative anaerobe Simple diffusion
Microsporidia Obligate intracellular
forms; small, simple cellsand spores
Binary fission,
schizogony andsporogony
None Facultative anaerobe Simple diffusion
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Biologic Morphologic and Physiologic
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Helminths
Nematodes Multicellular; round,
smooth, spindle shaped,
tubular alimentary tract;
possibility of teeth or
plates for attachment
Separate sexes No single organelle;
active muscular motility
Adults: usually
anaerobic; larvae:
possibly aerobic
Ingestion or absorption of
body fluids, tissue, or
digestive contents
Trematodes Multicellular; leaf shapedwith oral and ventral
suckers; blind alimentary
tract
Hermaphroditic(Schistosoma group has separate
sexes)
No single organelle;muscle-directed motility
Adults: usually anaerobic Ingestion or absorption ofbody fluids, tissue, or
digestive contents
Cestodes Multicellular; head with
segmented body
(proglottids); lack of
alimentary tract; head
equipped with hooks
and/or suckers forattachment
Hermaphroditic No single organelle;
usually, attachment to
mucosa, possible
muscular motility
(proglottids)
Adults: usually anaerobic Absorption of nutrients
from intestine
Organism Class Morphology Reproduction
Organelles of
Locomotion Respiration Nutrition
Biologic, Morphologic, and Physiologic
Characteristics of PathogenicHelminths
Organelles of
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Arthropods
Chilopoda Elongated; many legs;
distinctive head and
trunk; poisoning claws
on first segment
Separate sexes Legs Aerobic Carnivore
Pentastomida Wormlike; cylindrical,
or flattened; two distinct
body regions; digestive
and reproductive organs;
lack of circulatory and
respiratory systems
Separate sexes Muscle-directed motility Aerobic Ingestion of body fluids
and tissue
Crustacea Hard external carapace;
one pair of maxillae;
five pairs of biramous
legs
Separate sexes Legs Aerobic Ingestion of body fluids
and tissue, carnivorous
Arachnida Body divided into
cephalothorax and
abdomen; eight legs and
poisoning fangs
Separate sexes Legs Aerobic Carnivore
Insecta Body: head, thorax, and
abdomen; one pair of
antennae; three pairs of
appendages, up to two
pairs of wings
Separate sexes Legs, wings Aerobic Ingestion of fluids and
tissues
Organism Class Morphology Reproduction
Organelles of
Locomotion Respiration Nutrition
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Additional slides for self reading!
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2- CILIOPHORA
Phylum Ciliophora consists of the ciliates, which include a variety offree-living and symbiotic species.
Ciliate locomotion involves the coordinated movement of rows of
hairlike structures, or cilia.
Cilia are structurally similar to flagella but are usually shorter and
more numerous. Some ciliates are multinucleate.
The only ciliate parasite of humans, Balantidium coli ,contains two
nuclei: a large macronucleus and a small micronucleus.
Protozoa
P
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3- APICOMPLEXA
Phylum Apicomplexa organisms are often referred to as Sporozoa orCoccidia. These unicellular organisms have a system of organelles at
their apical end that produces substances to help the organism
penetrate host cells and thus become an intracellular parasite.
4- MICROSPORA
The Microspora are small intracellular parasites that differ
significantly in structure from the Apicomplexa organisms.
These parasites are characterized by the structure of their spores,
which have a complex, tubular extrusion mechanism (polar tubule)
used to inject the infective material (sporoplasm) into host cells.
Protozoa
Metazoa
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The protective covering of flatworms is known as a tegument.
Often, helminths possess elaborate attachment structures such ashooks, suckers, teeth, or plates.
These structures are usually located anteriorly and may be useful in
classifying and identifying the organisms.
Helminths typically have primitive nervous and excretory systems.
Some have alimentary tracts; however, none have a circulatory
system.
The helminths are separated into two phyla, the Nematoda and the
Platyhelminthes.
Metazoa
Metazoa
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1-HELMINTHSA- Nematoda
Phylum Nematoda consists of the roundworms, which have
cylindrical bodies.
The sexes of roundworm are separate, and these organisms have a
complete digestive system. The nematodes may be intestinal
parasites or may infect the blood and tissue.
Metazoa
Metazoa
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1-HELMINTHS
B-PlatyhelminthesPhylum Platyhelminthes consists of the flatworms, which have
flattened bodies that are leaflike or resemble ribbon segments.
Platyhelminthes can be further separated into trematodes and
cestodes.
B-1-Trematodes, or flukes, have leaf-shaped bodies.
Most are hermaphroditic, with male and female sex organs in asingle body. Their digestive systems are incomplete and only have
saclike tubes. Their life cycle is complex; snails serve as first
intermediate hosts, and other aquatic animals or plants serve as
second intermediate hosts.
Metazoa
Metazoa
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1-HELMINTHS
B-PlatyhelminthesB-2- Cestodes, or tapeworms, have bodies composed of ribbons of
proglottids, or segments.
All are hermaphroditic, and all lack digestive systems, with nutrition
being absorbed through the body walls.
The life cycles of some cestodes are simple and direct, whereas those
of others are complex and require one or more intermediate hosts.
Metazoa
Metazoa
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In addition, envenomization by biting and stinging arthropods can
result in adverse reactions in humans that range from local allergic
and hypersensitivity reactions to severe anaphylactic shock and
death. There are five major classes of arthropods.
Metazoa
Metazoa
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2-ARTHROPODS
2-A-ChilopodaClass Chilopoda consists of terrestrial forms, such as centipedes.
These organisms are of medical importance because of their
poisoning claws, which may produce a painful "bite."
2-B-Pentastomida
The pentastomids, or tongue worms, are bloodsucking endoparasites
of reptiles, birds, and mammals. Adult pentastomids are white and
cylindrical or flattened parasites that possess two distinct body
regions: an anterior cephalothorax and an abdomen. Humans may
serve as intermediate hosts for these parasites.
Metazoa
2-ARTHROPODS
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2-C-Crustacea
Class Crustacea consists of familiar aquatic forms, such as crabs,
crayfish, shrimp, and copepods.
Several are involved as intermediate hosts in life cycles of various
intestinal or blood and tissue helminths.
2-D-ArachnidaClass Arachnida consists of familiar terrestrial forms, such as mites,
ticks, spiders, and scorpions.
Unlike insects, these animals have no wings or antennae, and adults
have four pairs of legs, as opposed to three pairs for insects.
Of medical importance are those serving as vectors for microbial
diseases (mites and ticks) or as venomous animals that bite (spiders)
or sting (scorpions).
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2-ARTHROPODS
2-E-Insecta
Class Insecta consists of familiar aquatic and terrestrial forms, suchas mosquitoes, flies, midges, fleas, lice, bugs, wasps, and ants.
Wings and antennae are present, and adult forms have three pairs of
legs.
Of medical importance are the many insects that serve as vectors for
microbial diseases (mosquitoes, fleas, flies, lice, and bugs) or as
venomous animals that sting (bees, wasps, and ants).
Metazoa
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Medical parasitology is the study of invertebrate animals capable of
causing disease in humans and other animals.
The global impact of parasitic infections and the number of parasite-
associated deaths is staggering and must be of concern to all health
care workers.
Increasingly, tourists, missionaries, Peace Corps volunteers, and
others are visiting and working for extended periods in exotic,
remote parts of the world.
Importance of parasites
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Another source of infected patients is the ever-increasing number of
refugees from developing countries.
Finally, the profound immunosuppression problems that accompany
advances in medical therapy (e.g., organ transplantation), as well as
those associated with persons infected with humanimmunodeficiency virus (HIV), place a growing number of
individuals at risk for developing infections caused by certain
parasites.
Given these considerations, clinicians and laboratory workers should
be aware of the possibility of parasitic disease and should be trained
in ordering, performing, and interpreting the appropriate
laboratory tests to aid in the diagnosis and therapy.
Importance of parasites