Introductory Concepts of Parasitology Flashcards
living together of unlike organisms.
Symbiosis
a symbiotic relationship in
which two species live together and one species benefits from the relationship without harming or benefiting the other
Commensalism
Entamoeba coli in the intestinal lumen
Types of Symbiosis
Commensalism
Shape of Entamoeba coli
Round
Several nuclei – can reach 8
Entamoeba coli
meaning residing in intestine especially in large intestine/colon
Enta
Means that we eat something fecally contaminated, could be from eating raw vegetables
Entamoeba coli in the intestinal lumen
a symbiosis in which two organisms mutually benefit from each other
Mutualism
Termites and Flagellates in their digestive system, which aids in breakdown of ingested wood by
synthesizing cellulase
Types of Symbiosis
Mutualism
symbiotic relationship (one-sided) where one organism, the parasite, lives in or on another, depending on the latter for its survival and usually at the expense of the
host.
Parasitism
Entamoeba histolytica
Type of Symbiosis
Parasitism
means it lyses the tissue through producing enzymes such as cysteine proteinase (this is the reason why there is a blood in stool sample indicating ulceration – dysentery
Histolytica
derives nutrition from the human host and causes amebic dysentery
Entamoeba histolytica
stool samples contains blood and mucus
Dysentery
Shape of Entamoeba histolytica cyst
circular
Entamoeba histolytica
contains maximum of __ nuclei (mature)
4
Entamoeba histolytica Infection of it occurs when its _______ is ingested
matured cyst
Prior to ingestion – Entamoeba histolytica cyst will become trophozoite in the intestine which will develop extension called ____________, enabling its movement
pseudopod (false feet)
area of biology concerned with the phenomenon of dependence of one living organism on another
Parasitology
concerned primarily with parasites of humans and their medical significance, as well as their importance in human communities
Medical Parasitology
inside (Infection)
Types of Parasites (According to Habitat)
Endoparasite
outside
(Infestation)
Types of Parasites (According to Habitat)
Ectoparasite
parasite found in an organ which is not its usual habitat
Types of Parasites (According to Habitat)
Erratic
parasite that requires host, otherwise, it dies
Obligate parasite
a nematode (roundworm) and is an endoparasite which can move out of the intestinal lining to other organs like lungs. You can get infected by this through ingestion of embryonated eggs
Ascaris lumbricoides
Parasite that cannot survive outsided
the intestine
Ascaris Lumbricoides
may exist in a free-living state or
may become parasitic when the need arises
Facultative parasite
A nematode; Facultative parasite
Strongyloides stercoralis (Threadworm)
a parasite that establishes itself in a host in which it does not usually live
Accidental/ incidental parasite
remains on or in the body of the host
for its entire life
Types of Parasites (According to time)
Permanent Parasite
lives on the host only for a short
period of time
Types of Parasites (According to time)
Temporary parasite
a free-living organism that passes through the digestive tract without infecting the host
Types of Parasites (According to time)
Spurious parasite
Sexual or Adult/Final stages
Types of Hosts
Definitive / Final host
one in which the parasite does not develop further to later stages but remains alive and can infect other hosts. Harbors the infective stage of the parasite
Paratenic host
Asexual or larval stage
Intermediate host
allow the parasite’s life cycle to continue and become additional sources of human infection
Reservoir host
Presence of the __________ makes the total eradication of the parasite difficult because these are sources of possible infections
reservoir host
parasite where cattle are the reservoir host
Balantidium coli
Responsible for transmission
Vectors
humans are intermediate host
Types of vector
Biologic vector
do not participate
intrinsically
Types of vector
Mechanical / Phoretic vector
Malarial parasite, Mosquito acts as definitive host
Types of vector
Biologic vector
Not that important in the life cycle of
parasite, are only carriers
Types of vector
Mechanical / Phoretic vector
Fly, Cockroaches, what type of vector
Mechanical / Phoretic vector
(Known mechanical
vector of Ascaris)
Most common source of infection
Modes of Transmission
Oral
Ingestion of contaminated food & water
Modes of Transmission
Oral
Examples of parasites of Oral Transmission
- Taenia solium
- Taenia saginata
- Dibothriocephalus latus
- Entamoeba histolytica and Giardia duodenalis (G. lambia)
- Clonorchis, Opistorchis, and Haplorchis
(raw pork tapeworm)
Taenia solium
(raw beef tapeworm)
Taenia saginata
formerly Diphyllobothrium latum
Dibothriocephalus latus
found in raw fish causing anemia
Dibothriocephalus latus
infective
stage of Taenia saginata
Cystecercus larva
infective stage of Dibothriocephalus latus
Plerocercoid larvae
Examples of parasites of Oral Transmission by Ingestion of Cysts
- Entamoeba histolytica
- Giardia duodenalis (G. lambia)
Examples of parasites of Oral Transmission flukes
- Clonorchis
- Opistorchis
- Haplorchis
Infective stage of Clonorchis, Opistorchis, and Haplorchis
Modes of Transmission
Metacercaria
Parasites that uses Skin penetration
- Hookworms
- Strongyloides
- Schistosoma sp.
Hookworms and Strongyloides infective stage
Filariform
larvae
enter skin via water, bathing in rivers and lakes
Schistosoma sp.
Infective stage of Schistosoma sp.
Cercariae
Arthropod bites (Vector-borne) parasites:
- Mosquito
- fly
- tick
- bug (Reduviid)
Disease associated with mosquito
- Malaria
- Filariasis
Infective stage of Malaria
Sporozoite
Infective stage of Filariasis
L3 Larva
Disease associated with Fly
- Leishmaniasis
- African trypanosomiasis
- Onchocercosis
- Loiasis
Infective stage of Leishmaniasis
Promastigotes
Infective stage of African trypanosomiasis
Trypomastigotes
Infective stage of Onchocercosis
L3 larva
Infective stage of Loiasis
L3 larva
Disease associated with Tick
Babesiosis
Infective stage of Babesiosis
Sporozoite
Disease associated with Bug (Reduviid)
Chagas’ Disease
Infective stage of Chagas’ Disease
Trypomastigotes
_________ bite you near your
mouth, thus the “kissing bug”
Reduviid bugs
in Chagas’ Disease, not through biting, infective
stage of parasite is transferred
through the _________
feces of the bug
refers to the transmission of infections, diseases, or other agents from a pregnant mother to her developing fetus during pregnancy, childbirth, or shortly after birth
Congenital transmission
Example of Congenital Transmission
Toxoplasma gondi
Definitive hosts are cats (reason for keeping pregnant mothers away from cats)
Toxoplasma gondi
refers to the transmission of infections or other agents from a mother to her offspring through breastfeeding or the mammary glands.
Transmammary
Example of Transmammary parasites
- Ancylostoma - hookworms
- Strongyloides – similar in terms of life cycle
Example of Inhalation of Airborne parasite
Enterobius vermicularis (pinworm)
a nematode; infective
stage is eggs; inhalation of airborne eggs
Enterobius vermicularis (pinworm)
Example of Sexual Intercourse parasite that infects both male and female
Trichomonas vaginalis
possibility of infection when one partner is the only one treated, not both (reason for treating both)
Ping-pong phenomenon
redness and
inflammation of cervix
Strawberry cervix
study of patterns, distribution, and occurrence of disease
Epidemiology
new cases
Incidence
old and new cases
Prevalence
– refers to burden of infection which is related to the number of worms per infected person
Intensity of Infection / Worm Burden
refers to the state of being diseased or the prevalence of disease within a population.
Morbidity
refers to the occurrence of death within a population.
Mortality
the use of anthelminthic drugs in an individual or a public health program
Deworming
permanent reduction to zero of the worldwide incidences of infection caused by a specific agent, as a result of deliberate efforts
Disease Eradication
reduction to zero of the incidences of a specified disease in a defined geographic area as a result of deliberate efforts
Disease elimination
disease that occurs infrequently and irregularly
Sporadic
– refers to constant presence and/or prevalence
of a disease or an infectious agent in the population within
a geographic area
Endemic
refers to an increase, often sudden, in the number of cases of a disease often above normal
expectancy in the population of an area
Epidemic
refers to an epidemic that has spread over
several countries or continents
Pandemic
Mechanisms by which parasites cause injury:
Effects of Parasites on Hosts
- Creation of enzymes
- Invasion and destruction of host tissue
- Depriving the host of essential nutrients and substances
What enzyme does E. histolytica release?
cysteine
proteinase
What enzyme does Balantidium coli release?
hyaluronidase
Several Factors that affect outcome of Infection in the host
Effects of Host on the Parasites
- Genetic make-up of the host
- Nutritional Status of the host
- Immunity of the host
Possible outcomes of parasite to host interactions:
Immunology of Parasitic Infections
- Parasite fails to become established in the host.
- Parasite becomes established and the host eliminates the
infection. - Parasite becomes established, and the host begins to
overcome the infection but is not totally successful. - Parasite becomes established and the host, in trying to
eliminate the organism, becomes damaged itself. - Parasite becomes established and kills the host.
Physical barriers (1st line of defense against pathogens)
Host Parasite Interactions
- Skin
- Mucous membranes
- Components of body fluids
- Physiologic functions of the body
Example of Physiologic functions of the body
Physical barriers (1st line of defense against pathogens)
Elevation of temperature
Body detects and eliminates pathogens
through non-specific mechanisms
Host Immune Response
Innate immune response
Ex: Phagocytosis by macrophage (Not guaranteed protection) and dendritic cells
Host Immune Response
Innate immune response
parasites that multiply
in Macrophages
Leishmania
Hemoflagellates:
transmitted by sand fly
Leishmania
Infective stage of Leishmania
promastigotes
Macrophages eat them
promastigotes
But promastigotes transform to _________ (tissue forms) – they are multiplicative, so they are not killed by macrophages
amastigotes
host exposed to the parasite antigens > stimulate an
immune response
Host Immune Response
Acquired immune response
Example of Acquired immune respone
T and B cells (Lymphoctes)
cell mediated
immunity
T-cells
humoral
immunity (antibody)
B-cells
Permits survival of parasites upon
entering blood and tissues
Parasite Evasion Mechanism
Resistance to infection
Cuticle and integument (refer to skin of
parasites) > resist macrophage
Parasite Evasion Mechanism
Resistance to infection
Parasites can reduce immune function of macrophages > lower action of macrophages and defecting processing of
antigen
Parasite Evasion Mechanism
Immune suppression
Parasites have antigenic variation capability resulting to difficulty in creation of vaccines against them
Parasite Evasion Mechanism
Antigen Variation
parasite that uses Variant surface glycoproteins
(VSG)
Parasite Evasion Mechanism
Trypanosoma brucei infection
Antigenic diversity
Parasite Evasion Mechanism
Plasmodium
Body could not differentiate self from non-self (WBCs cannot see parasites as foreign)
Parasite Evasion Mechanism
Host Mimicry
Parasites that uses antigen variation
Parasite Evasion Mechanism
- Trypanosoma brucei
- Plasmodium
Parasites that uses Host Mimicry
Parasite Evasion Mechanism
- Echinococcus granulosus
- Schistosoma sp
Parasite that larval stages carry P blood group antigens
Parasite Evasion Mechanism
Echinococcus granulosus
Tapeworm in dog
Parasite Evasion Mechanism
Echinococcus granulosus
can acquire antigenic
molecules from host
Parasite Evasion Mechanism
Schistosoma sp.
Parasites that uses Intracellular Sequestration
Parasite Evasion Mechanism
- Leishmania
- Plasmodium
2 important genera of hemoflagellates
Parasite Evasion Mechanism
Trypanosoma and Leishmania
Dysfunction of any of the host defense systems
can result in damage to host tissue and produce
clinical disease
Adverse Effects of Immune Response on the Host
Types of Reaction:
Adverse Effects of Immune
Response on the Host
- Type 1 (Immediate type hypersensitivity)
- Type 2 (Immune complex formation)
- Type 3 (Cytotoxic reactions of antibody)
- Type 4 (Delayed-type hypersensitivity).
unicellular eukaryotic organisms
Taxonomy (Classification) of Medically Important
Parasites
Protozoans
Define nucleus
Eukaryote
Types of Protozoans
- Phylum Sarcomastigophora
- Phylum Ciliophora
- Phylum Apicomplexa
Examples of Phylum Sarcomastigophora
- Ameba
- Atrial
- Flagellates
- Hemoflagellates
Examples of Phylum Ciliophora
Ciliates
Examples of Phylum Apicomplexa
- Plasmodium
- Babesia
- Intestinal Coccidians
- Tissue Coccidians
now under Fungi
Microspora
“worms”; metazoan parasites
Helminthes
Examples of Helminthes
- Nematodes (Roundworms)
- Cestodes (Tapeworms)
- Trematodes (Flukes)
Have defined locomotor apparatus
Phylum Sarcomastigophora and Ciliophora
locomotor apparatus of Amoeba
pseudopod
locomotor apparatus of Flagellate
flagella
locomotor apparatus of Ciliate
cilia
2 diagnostic stages of Phylum Sarcomastigophora and Ciliophora
Trophozoite and Cyst
motile stage of Phylum Sarcomastigophora and Ciliophora
Trophozoite
usually infective stage and
non-motile of Phylum Sarcomastigophora and Ciliophora
Cyst
Stages of Phylum Apicomplexa
- Schizogony
- Sporogony
- Gametogony
asexual
stage of Phylum Apicomplexa
Schizogony
Sexual stage of Phylum Apicomplexa
Sporogony
process of
forming gametes in Phylum Apicomplexa’s stage
Gametogony
confused with
Plasmodium falciparum
Babesiosus
Cysts with tri-layered structure
Nematodes (Roundworms)
- Ribbon-like
- Can extend up to 25m
Cestodes (Tapeworms)
liver flukes
Fasciola
Leaf-like (adult stages)
Trematodes (Flukes)
2 blood-flukes (copulation of male and female; appear elongated and cylindrical)
Schistosoma -
Infective stage of Schistosoma
Cercarian
seen together
(male and female) in one body
Hermaphrodite / Monoecious
separated reproductive organs
Non-Hermaphrodite / Dioecious
Parasites occur in two distinct forms
Protozoa and Helminths
For medical purposes, protozoa are classified according to their most important site of infection,
namely:
- intestinal protozoa
- urogenital protozoa
- blood protozoa
- tissue protozoa
what kind of protozoa according to site of infection is Giardia
intestinal protozoa
what kind of protozoa according to site of infection is Trichomonas
urogenital protozoa
what kind of protozoa according to site of infection is Plasmodium
blood protozoa
what kind of protozoa according to site of infection is Toxoplasma
tissue protozoa
In some contexts, the protozoa are classified into four groups:
o Sarcodina (amebas),
o Sporozoa (sporozoans),
o Mastigophora (flagellates),
o Ciliata (ciliates)
Metazoa are subdivided into two phyla:
- Platyhelminthes (flatworms)
- Nemathelminthes (roundworms,
nematodes)
the tapeworm that causes
cysticercosis
Taenia solium
The phylum Platyhelminthes
contains two medically important
classes:
- Cestoda (tapeworms)
- Trematoda (flukes).
the fluke that causes
schistosomiasis.
Schistosoma
mansoni
Medically important roundworms
(nematodes) include the:
- pinworm (Enterobius)
- the hookworms
(Ancylostoma and Necator) - the threadworm (Strongyloides)
- Trichinella
flagellated forms of Leishmania and Trypanosoma
promastigotes or
trypomastigotes
non-flagellated forms of Leishmania and Trypanosoma
amastigotes
type of hosts where the larval form in the human is not transmitted to other humans or animals
dead-end hosts
Humans are dead-end hosts for:
- Taenia solium (cysticercosis)
- Echinococcus (hydatid cyst disease)
- Trichinella (trichinosis)
one or more whip-like flagella and, in some cases, an undulating membrane (eg, trypanosomes)
Flagellates
use pseudopodia or protoplasmic flow to
move
Amebae
undergo a complex life cycle with alternating sexual and asexual reproductive phases
Sporozoa
complex protozoa bearing cilia
distributed in rows or patches, with two kinds of nuclei in each individual
Ciliates
elongated and tapered at both ends, round in crosssection, and unsegmented
Phylum Nemathelminthes
set of longitudinal muscles, which allows them to move
in a whip-like, penetrating fashion
Phylum Nemathelminthes
complete digestive system that is well adapted for
ingestion of the host’s gut contents, cells, blood, or
cellular breakdown products
Phylum Nemathelminthes
highly developed separate-sexed reproductive
system
Phylum Nemathelminthes
shed their tough cuticles (molt) as they undergo
development from larvae to adults
Phylum Nemathelminthes
eggs and larval stages are well suited for survival in
the external environment. infections are usually
acquired by ingestion of the infective egg (Ascaris lumbricoides) or larval stage (Trichinella spiralis),
but can also be vector transmitted (Wuchereria
bancrofti) or via skin penetration (Necator americanus)
Phylum Nemathelminthes
hermaphroditic, with a few exceptions (Schistosoma sp.)
Phylum Platyhelminths
flatworms that are dorsoventrally flattened in crosssection
Phylum Platyhelminths
flattened and leaf shaped with two muscular
suckers (oral and ventral)
Trematode
bifurcated gut and possess both circular and
longitudinal muscles
Trematode
lack the cuticle but has syncytial epithelium
Trematode
hermaphroditic, except for the schistosomes
(blood flukes), which have male and female worms
that exist coupled together within small blood
vessels of their hosts
Trematode
Life cycle of Trematode
Eggs – Larva: [Miracidium, Sporocyst, Redia, Cercaria, Metacercaria] – Adult
Most fluke infections are acquired by ingestion of
the __________
metacercariae
The ________ of schistosomes, however, directly penetrate the skin of their hosts and do not encyst as metacercariae.
cercariae
flat and have a ribbon-like chain of segments (proglottids) containing male and female reproductive structures
Cestode
can reach lengths of 10 m and have hundreds of
segments, with each segment releasing thousands
of eggs
Cestode
Adult tapeworms have no mouth or gut and absorb
their nutrients directly from their host through
their ____________.
integument
At the anterior end of an adult tapeworm is the
______, which is often elaborated with muscular
suckers, hooks, or structures that aid in its ability
to attach to the intestinal wall
scolex
