Lecture 1 - Principals of Parasitism Flashcards
1
Q
Significant costs of parasitism
A
- lost of agricultral & human productivity
- human/animal suffering & premature mortality
- rational efforts of parasitism control depend on understanding of parasitism
2
Q
Independent evolution is at least _____ times among the nematodes that infect vertebrates
A
4
3
Q
definition of parasite
A
an organism that is metabolically dependent and survives at the expense of another organism
4
Q
commensalism vs. parasitism
A
host not harmed nor helped vs. survives @ expense of host
5
Q
What do parasites depend on the host for
A
Metabolic dependency- sustenance (nutrition), survival, maturation, reproduction
Shelter- stable environment and protection for competition and predation by other organisms
6
Q
What effect can parasites have on the host
A
hematocrit, fecundity, BCS, feed efficiency, time to conception
7
Q
T/F disease resulting from parasitism is secondary
A
TRUE; parasites exist to perpetuate the species
8
Q
How are parasites subject to fitness of evolutionary biology?
A
parasites that kill their host must find way to adapt and overcome the fitness cost
9
Q
Fitness is characterized by parasites ability to
A
- colonize
- ability to resist environmental stresses
- survive host defenses
- reproduce and disseminate its progeny
10
Q
What environmental stressors must parasites overcome
A
drug resistance & seasonal climatic extremes (hard freeze)
11
Q
What host defenses must parasites overcome
A
immunomodulation and immune avoidance
12
Q
Parasites have ability to alter their ____________________ to enhance the odds for survival and reproduction
A
biologic functions
13
Q
Parasite populations are ________and _______
A
plastic and dynamic
14
Q
Parasites have the capacity to respond to a variety of conditions and stimuli
(selection pressures) by ________________
A
permanent alterations of their genetic composition
15
Q
How do parasites respond to selection pressures by alterations of their genetic composition?
A
hypobiosis, vertical transmission of developmental stages, shorter or abbreviated lifecycle development
16
Q
hypobiosis
A
arrested development
17
Q
How are parasite populations dynamic?
A
- permanent alterations of their genetic composition
- drug resistance
- ability to colonize new hosts/sites within hosts
18
Q
Why are puppies born with roundworms?
A
cross placenta @ 42 days gestation
19
Q
Most animals eventually develop some degree of
___________________ to parasitic infections
A
aquired immunity
20
Q
acquired immunity with parasitsm
A
mechanisms to mitigate associated disease
21
Q
Parasitic diseases in domestic livestock and companion animal populations is generally a consequence of __________-
A
management
22
Q
1 cause of death in whitetail deer
A
lead poisoning
23
Q
Parasitic disease is usually related to the
A
number of parasites infecting the host
24
Q
What is it called when their is a large number of parasites in a living/grazing environments
A
hyper-contamination
25
What is it called when the host dies by depletion of host resourses
hyper-infection
26
How we can control parasitism and mitigate disease
1. disrupt transmission between parasites and their host
2. development of host immunity
3. changes in management/modification of environment
27
How can we enhance host immunity?
vaccination and low levels of exposure
28
What is premunition
low levels of exposure
29
How can we disrrupt transmission between parasites and their host population?
breaking the life cycle of infection and reinfection RARELY achieved by meds alone
30
How can we modify environment to mitigate parasites
1. protected environment for neonates
2. reduced environmental contamination with infective stages
3. selective breeding
4. better nutrition
31
How do we create a protected environment for neonates
clean pasture for babies with no established immunity
32
How does better nutrition mitigate parasites
avoid the effects of parasitic disease
33
How can parasites cause disease?
1. suck blood
2. feed on solid tissues directly or after liquifying
3. compete with host for ingested food
4. traumatic injury by mechanical obstructions
5. destroy host cells by growing in them
6. production of toxic substances
7. cause various host reactions
8. stimulate cancerous growth
9. carry additional diseases (parasites, viruses, bacteria)
10. reduce host resistance to other diseases and parasites
34
What parasites suck blood
mosquitos, hookworms
35
What parasites suck lymph
midges
36
What parasites are exudates
lungworms
37
What parasites feed on solid tissues directly
giant kidney worms, liver flukes
38
What parasites feed on solid tissues after lysing and liquifying them
chiggers, amoebas
39
What parasites ingest intestinal contents
ascarids
40
What parasites absorb contens through the body wall
tapeworms
41
What parasites obstruct the intestines
ascarids
42
What parasites obstruct bile ducts
ascarids, fringed tapeworm
43
What parasites obstruct blood vessels
dog heartworm
44
What parasites obstruct lymph channels
filariids
45
What parasites obstruct bronchi
lungworms
46
How do hydatid cysts harm the hosts
pressure atrophy against body organs
47
What parasites destroy host cells by growing in them
coccidia, malaria
48
What toxic substances can parasites produce to aid their ability to enter host tissues, feed, reproduce
hemolysis, histolysins, anticoagulants
49
What host reactions can parasites cause
allergic, inflammatory, hypertrophy, hyperplasia, and nodule formation
50
What parasite stimulates the development of cancerous cell growth
Spirocerca lupi
51
What diseases do the following parasites carry?
Mosquitos
lungworms
flukes
mosquitos- heartworm and malaria, lungworms- swine influenza, flukes- salmon poisoning
52
What is an obligatory parasite
cannot complete its life cycle without spending part of all of its time on or within host
53
What is a facultative parasite
not normally parasitic by become so when eaten or
opportunisitically enter a host through and orifice or
wound
54
Example of facultative parasite
– Naegleria fowleri causative agent of Primary Amoebic
Meningoencephalitis (PAM) “Brain eating amoebae”
– Halicephalobus a causative agent of encephalitis in
horses
55
How does Naegleria fowleri cause disease
warm water->nasal passage->brain
56
Where does Halicephalobus enter
brain and kidney
57
ndoparasite
Organisms living within a host environment
58
Ectoparasite
– Organisms living on host (external environment)
59
Abberant parasite
Organisms found in locations where they do not
normally occur
60
Example of Abberant parasites
“Ectopic infections”
* Toxocara larvae in the eye of its host,
* Dirofilaria immitis in the brain of a tiger
* Paragonimus in the liver
61
How do parasites cause disease in their
host?
They feed on host resources and
impact the host physically and
immunologically
62
Accidental or Incidental parasite
Parasitic organisms that enter or attach to host species that are different from the one(s) with which they are normally associated
63
Why may accidental parasites not be able to survive in host?
often elicits a major pathological response from the host.
64
Repeated successful colonization of an accidental host can cause
host switching, development of new host association
65
Pseudoparasite
Diagnostic parasite stages or other artifacts (plant pollen, fungi,
arthropods) that superficially resemble protozoan cysts or helminth eggs in the feces, blood, or urine of an examined animal
66
Why is pseudoparasite a misnomer
“pseudo‐parasite products” are not associated with
a true host‐parasite association
67
Example of pseudoparasite
Eimeria oocysts passed in dog feces, various pollen mistakenly attributed to parasitic species infecting a host
68
Hyperparasite
When a parasitic organism is host to another parasite species
69
Examples of hyperparasite
-Mosquito that is host to Plasmodium sp. or Dirofilaria immitis
-Flea that is host to Dipylidium caninum
70
Definitive Host
Where a parasite attains reproductive maturity
71
What is definitive host evidenced by
circulation or passage (in feces or other host tissues) of progeny capable of colonizing additional host species
72
Intermediate Host
in which a larval or intermediate stage parasite must
undergo development to become infective for the
“definitive or final host
73
Paratenic Host
A facultative host used by a larval or intermediate stage
parasite to facilitate transmission to the “definitive or final
host, DO NOT undergo development
74
What is the distinguishing factor between paratenic and intermediate hosts?
parasites do not undergo development in paratenic hosts
75
What often bridges an ecological gap between passage of
infective stages and successful transmission and
establishment in a new host for completion of a lifecycle
and perpetuation of the parasite population?
paratenic host
76
reservoir hosts
Maintain a parasite in the population at sufficient levels to
facilitate its transmission between susceptible hosts
77
reservoir host for zoonotic parasites and infectious diseases
animals (Lyme disease deer, white-footed mouse)
78
Reservoir hosts for Dirofilaria immitis
coyotes, and stray/unprotected canines
79
Reservoir hosts may be .....
1. definitive (adult parasites)
2. intermediate (obligate developmental stages)
3. Paratentic (facultative developmental stages)
80
Reservoir hosts are a _________ parameter rather than a _________ parameter
population; individual
81
vectors
Organisms that facilitate transmission of infective
parasite stages between different individuals of a
host population
82
Biological Vectors assume the existence of an
___________________________ for successful transmission and
maintenance of the parasite species in the host
population
obligate relationship
83
vectors often also play a role as _____________
intermediate/paratenic hosts
84
Which vectors have an obligate relationship
biological
85
2 types of vectors
biological and mechanical
86
example of mechanical vectors
flying syringe, transport on feet
87
Direct life cycle
parasites infect host directly
88
Direct Lifecycle
– Parasites infect host directly
– Stages passed from host in
feces/other tissues
– Infective to another “Definitive
host” (dog to dog)
– May require period of
development to infective stage
* Larval development ____________
* Free living larval stages in
_____
1. w/in eggs
2. environment
89
obligate indirect life cycle require intervention of an
intermediate host
90
obligate indirect life cycle is infective to the
intermediate host
91
obligate indirect life cycle have obligate requirement for development to
infective stage
92
obligate indirect life cycle have indirect transmission to
definitive host
93
obligate indirect life cycle may involve
paratenic host
94
facultative indirect lifecycle indirect transmission to
definitive host
95
facultative indirect lifecycle optional intervention of an
intermediate or paratenic host
96
facultative indirect lifecycle stages passed from host in
feces/other tissues
97
facultative indirect lifecycle infective to
definitive host or the "optional host"
98
horizontal transmission
-Parasites colonize susceptible individuals by usual routes
– Infection across different generations of host population not required
99
vertical transmission
-Transmission of parasites from mother to offspring by transplacental or lactogenic routes
– Trans‐generational requirement
– Prenatal or perinatal
100
2 types of host specificity
monospecific and heterospecific
101
monospecfic host
* limited number of hosts capable of completing lifecycle
* Pinworms in primate hosts
102
heterospecific
* wide variety of species capable of hosting parasite
* Typical of intermediate and paratentic hosts
* Toxoplasma gondii, Baylisascaris procyonis
103
zoonotic
animal to human
104
anthroponotic
human to animal
105
endemic (enzootic)
The normal or usual distribution of parasites in a host population or
geographic area (Eimeria sp. is endemic in Tennessee cattle)
106
Epidemic (epizootic)
* An excess number of parasite cases, far exceeding the normal or usual distribution in a host population
* Temporal and Spatial characteristics
* “ 50% of last years kid crop were aborted in an epizootic of
toxoplasmosis “
107
prevalance
The occurrence of a parasite in a population defined by time &
space
108
Incidence
The rate at which new cases are added to a host population defined
by time & space
