Week 1 Flashcards
biosystem
two different species interact with each other over a significant period of time or the relationship is essential to at least one partner
symbiotic relationships
commensalism and mutualism
commensalism
“eating with,” one benefits and the other isn’t harmed
commensalism examples
scavengers, phoresis, honey bee mites
mutualism
both benefit
mutualism examples
intestinal lactobacillus and ciliates in rumen of ruminants
parasitism
one benefits and the other is harmed
sensu lato
broad sense, viruses, bacteria, eukaryotes
sensu stricto
strict sense, only eukaryotes, protozoa, metazoa, excluding fungi
parasitoidism
parasitoids spend long time in or on host and then kill it
parasitoids
most parasites avoid killing host because they need the host to survive, parasitoids are designed to kill the host
parasitoid examples
lampreys on freshwater fish as ectoparasitoids and killer wasps on cicadas
infection
active or passive penetration of microorganisms into the body in which they can multiply and cause diseases
infection exemption
it is not considered infection if the host doesn’t support the infectious agent
parasitology
active penetration, diseases, and infected body
parasitology: active penetration
invasion mostly
parasitology: diseases
only pathogenic organisms
parasitology: infected body
host
who is the guest?
parasites
ectoparasites
external parasites including arachnids and insects
ectoparasites: arthropods
extracellular
endoparasites
internal parasites
endoparasites: helminths
extracellular or intracellular, most extracellular
endoparasites: protozoa
extracellular or intracellular
endoparasites: arthropods
extracellular
what is the advantage of being intracellular?
hide from immune system
ectoparasites: arachnids
mites (scabies) and ticks (lone star tick)
ectoparasites: insects
fleas (dog flea), lice (head louse), mosquitoes (anopheles)
endoparasites: helminths (worms)
trematodes (sheep liver fluke), cestodes (fox tapeworm), nematodes (hookworms), acanthocephala (macranthorhynchus)
helminths: trematodes
flukes
helminths: cestodes
tapeworms
helminths: nematodes
roundworms
helminths: acanthocephala
thorny-headed worms
endoparasites: protozoa
amoebae (entamoeba), ciliates (rumen cialiate isotricha), flagellates (trypanosoma), sporozoa (toxoplasma)
Who is the host?
animals and plants
host: animal vertabrates
warmblooded animals, all kinds of parasitic groups
host: animal invertebrates
bee tracheal mites, protozoa vector function (leishmania), entomopathogenic nematodes (heterorhabditidae)
host: plants
pine beetle
potential usage of parasites
medical leeches, population control, hookworms to reduce asthma
parasitism
a form of ecological interactions
parasitism: host organism
variety in invertebrates and vertebrates, many parasites can go through multiple hosts
parasitism: infectious agent
variety of eukaryotes, including protozoa, helminths, and arthropods
comparison of related free living and parasitic species
parasitic forms show genetic reductions, loss of functional organs, new structure or adaptations to parasitic lifestyle
genetic reductions
reduced functions due to readily available resources results in smaller genome size
loss of functional organ/organelle
results in inability for certain processes due to having readily available resources like cholesterol or nucleotides
new structures or adaptations to parasitic lifestyle
enabling immune response evasion, antigenic variety, novel sense organs
free living mite vs parasitic mite
free living mite has longer legs for mobility, thicker exoskeleton for protection, and is smooth. parasitic mite has short legs, spikes to attach, and thin exoskeleton due to protection from host
divergent evolution
evolution of two or more similar species from a common anscestral stock
close taxonomic relationship but may develop different features
divergent evolution
convergent evolution
evolution of two or more similar species from unrelated forms adapted due to the same selection pressures
significant taxonomic distance but develop similar features
convergent evolution
convergent evolution example
wolf and tasmanian wolf, not related but similar features
divergent evolution example
trichomonas found in T. Rex found in several birds and reptiles today
divergent evolution is mainly in parasites
true
the more host species
the more parasite species
the more host diversity
the more parasite diversity
high host specificity / mono/oligoxenic
highly adapted to one host, bound to host survival, specialization on predictable resources to minimize extinction risk
high host specificity cons
if the host evolves and the parasite doesn’t the parasite will die. so dependent on host that if the host dies or goes extinct, the parasite will die
high host specificity pros
so specialized that they interact closely and work with host immune system to reduce harm to the hosts and resources are used more efficiently
low host specificity / polyxenic
wide variety of hosts accepted, generalists that have higher abundance and survival opportunity
low host specificity cons
not as adapted and get less out of resources
low host specificity pros
more available resources and hosts, and harder to eradicate
is host susceptibility reversible?
possible but not relevant because it would take a long time period to discover
monoxenous
high host specificity, one host
polyxenous
low host specificity, many hosts
oligoxenous
intermediate host specificity, few hosts
co-evolved host parasite systems
certain mutual tolerance, compound organism with little damage of each other, destruction of host leads to destruction of parasite
compound organism example
pigeon tick and pigeon
compound organism spread to new hosts
no mutual tolerance, higher pathogenic effects, parasite may be limited for survival and replication, host reacts strongly and doesn’t sustain parasite
antiquity period
Ebers names human endo and ectoparasites visible to naked eye, aristotle identified round worms
middle ages and renaissance
necropsy prohibited, Moufet though that they were beneficial to rid the body of toxic substances
Modern times
pasteur found that spontaneous generation does not exist, texas fever agent found in 1883, parasite related immunity found in 1928, interest after world war 2
Wholistic point of view
1946, many different fields of knowledge, host, environment, migration patterns, and parasite
today
19,000 journal publications, one health, molecular and cell culture tools, modern morphology, close collaboration
parasitism is a ecological interaction
host organism, infectious agent, close interaction and co-evolution
parasitology
relatively young science considering host and parasite aspects contributing to disease mechanisms
long term co-evolution is essential to parasite
trichomonas in T rex and birds
rarely any sudden changes in host spectrum
pigeon ticks
significant structural adaptation
parasitic mites
Hosts in life cycle
number of hosts per cycle, possible transmission to humans, types of hosts
transmission
modes of transmission, endogenous vs exogenous phages
one host
homoxenous, with or without external phase, the host is generally identical to definitive host
what occurs in the definitive host?
sexual replication of the parasite
two or more hosts
heteroxenous, with or without external phase, different types of hosts (definitive and intermediate)
what occurs in the intermediate host?
further development of the parasite or asexual multiplication of the parasite
additional facultative hosts may be included in both kinds of life cycle but are _________ for parasite transmission and multiplication
not essential
which parasites use definitive hosts?
all parasites except for some ectoparasites
which parasites use intermediate hosts?
in heteroxenous parasites and ectoparasites without parasitic adult stages
non-essential host types
paratenic host and accidental host
paratenic host
if developmental stages are transmitted to this organism but do not undergo multiplication or significant morphological changes (transfer host)
why are paratenic hosts useful?
helpful for transmission and protection
paratenic host species
invertebrates and earthworms
accidental host
host who is infected randomly and from which further transmission is impossible (development may occur)
accidental host characteristics
dead end hosts, cause infection, parasite grows but cannot close lifecycle
monoxeny
strict specificity to one single host species
oligoxeny
restriction to few hosts
polyxeny
wide host range
reservoir hosts
harbor main population of parasites, static transmission
parasitic stage: temporary stage
specific stage is only shortly in or on the host
parasitic stage: stationary stage
specific stage is always on the host
parasitic lifecycle: permanent
all stages in or on any host
parasitic lifecycle: periodical
exogenous stages exist
what kind of parasite is an asian tiger mosquito?
temporary/periodical because it is parasitic during adult stages and it comes and goes from its host
what kind of parasite is a human head louse?
stationary/permanent because all stages are blood feeding
what kind of parasite is a roundworm?
stationary/periodic because it has free living stages
horizontal transmission
between hosts of the same species or in populations of different host species
horizontal transmission routes
contact (venereal), oral uptake of long-term stages (exogenous, endogenous), transmission by an (arthropod) vector
vertical transmission
mother organism to offspring
vertical transmission routes
prenatally (intrauterine) or lactogenic to neonates
arthropozoonosis
parasite transmitted from animals to humans, animal = reservoir
zooanthroponosis
transmission from humans to animals, humans = reservoir
zootherionosis
parasite transmitted from wild to domesticated animals, wild animals = reservoir hosts
theriosthitasonosis
transmission from domestic to wild animals, domestic animals = reservoir hosts
how do domestic animals pass parasites to wildlife?
cattle grazing on public lands and manure fertilizer
endogenous infective stages
developmental stages can be infective, persistent stages are infective
exogenous infective stages
persistent stages with developmental stages inside (hatching), adult stages in ectoparasites
infective stage characteristics
endoparasites vs ectoparasites, ingestion or active invasion
parasite survival and distribution
multiplication potential, survival potential, distribution options, and tolerance by host
multiplication potential
fecundity and biotic potential
survival potential
persistence in host and tenacity in the environment
distrubution
usage of reservoir or transfer hosts
tolerance
evolution and co-evolution
multiplication potential variables
duration of one life cycle and number of offspring per lifecycle
multiplication potential limitation
pathogenicity, parasites don’t want to cause death of the host
survival potential strategy: persistence
endogenous stages including immunoevasion and formation of persistent stages
survival potential strategy: tenacity
exogenous stages including starving and resistance towards physical and chemical stress
physical stressors
temperature, UV light, and aridity
chemical stressors
acidic or alkaline media, enzymes, and chemical disinfectants
parasite distribution factors
host radius and relocation habits, host population density, host specificity and switch potential, seasons
parasite distribution: host radius
confinement or globalization of domestic animals
parasite distribution: seasons
environmental conditions and host availability
parasite distribution: fauna, flora, water and environmental conditions
usage of paratenic hosts, mechanical and biologic vectors
mechanical vector
transport parasite stages, does not assist with development and multiplication
biologic vector
transport and support development and multiplication
vector definition
non-essential or optional hosts but helpful for transmission
parasite lifecycle depends on …
multiplication, survival, host spectrum, mode of transmission, and distribution
