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DWT Exam 2 > Parasitology (introduction, nematodes) > Flashcards

Parasitology (introduction, nematodes) Flashcards

1
Q

What is a parasite?

A

An organism that lives in or on another living organism (host), obtaining from it part or all of its nutrients.

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2
Q

What are the 4 main classes of parasites?

A

Protozoa
Arthropods
Platyhelminthes
Nematoda

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3
Q

What are simple (direct) life cycles?

A

Only have one host during its life cycle

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4
Q

What are complex (indirect) life cycle?

A

Have 2 or more hosts during its life cycle

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5
Q

What is a definitive/final host?

A

Host in which sexual reproduction takes place

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6
Q

What is an intermediate host?

A

Host in which only immature stages grow & develop. Asexual reproduction may or may not occur. Blood meal is required from host to develop

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7
Q

What is a paratenic host?

A

Host not required to complete the life cycle but help parasite to get to the host. Blood meal not needed because they are just used as transport

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8
Q

What is considered a normal host?

A

An animal recognized as part of the normal life cycle.

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9
Q

What is considered an abnormal or aberrant host (dead-end)?

A

Animal not normally used as a host
Often associated with disease (not always)
Animal could be an abnormal definitive, intermediate or transport host, depending on which stage of the parasite life cycle or is present

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10
Q

What is considered a reservoir host

A

Host serves as a source of infection for other animals

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11
Q

What is a considered a biological vector?

A

Parasite develops in the vector and transmits infectious disease

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12
Q

What is a considered a mechanical vector?

A

A contaminated instrument that transmits infectious disease

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13
Q

Where’s a endoparasite located in a host and what do they cause?

A

Inside the host
Cause infection

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14
Q

Where’s an ectoparasite located in a host and what do they cause?

A

Outside of the host
Cause infestations

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15
Q

What is the difference between a micro parasite and a macroparasite?

A

Microparasites multiply inside the host while macroparasites don’t multiply at all

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16
Q

What does infectious mean?

A

Caused or capable of being communicated by infection

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17
Q

What does infective mean?

A

Parasite stage capable of infecting the host

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18
Q

What does prepatent period mean?

A

The period from infection until the sexual maturity of the parasite

Mainly associated with macroparasites

Ex: heartworm has a 6 month prepatent period.

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19
Q

What does patency period mean?

A

The complete life span of an adult parasite

It is an ongoing cycle

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20
Q

What determines outcomes of the host-parasite relationship?

A

Infection/infestation
Parasite usually requires appropriate stimulus to recognize potential host
Host immune response

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21
Q

What 3 factors does pathogenesis depend on?

A

1) the status of host defenses
2) number of parasites present (+/- virulence)
3) pathogenicity of those parasites

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22
Q

Pathology from parasitic infection may be the result of what?

A

1) trauma to cells, tissues, &/or organs
2) changes in cellular growth patterns
3) interference with host nutrient acquisition
4) toxins released
5) host immune response to infection

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23
Q

What does it mean when parasite populations in animals are aggregated (over dispersed)?

A

Not each member of a group will be infected equally
Not evenly dispersed through the main group

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24
Q

What is the 70-30 rule?

A

The top 30% of a given group will have 70% of the parasitic infection while the bottom 70% will have 30% of the parasitic infection

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25
How do we diagnose parasites?
Morphologic (microscopic and gross examination of blood, feces, tissue and remains Immunologic assays Molecular tests (PCR)
26
What are the general characteristics of helminths (worms)
Macroparasite Often highly host specific in the definitive host either oviparus or ovoviviparous Fecal oral or environmental-oral
27
What are the two phylum of helminths?
Nematoda & platyhelminthes
28
What are the general characteristics of the phylum nematoda?
Non-segmented, cylindrical, tapered at both ends Most successful parasite of all the worms Many are free living in the soil Major plant and animal parasite Range in size Cuticle present and is flexible but not metabolically active & is a secondary sexual structure Body wall as muscles for movement Can sensing environment Neurotransmitter
29
What are the general characteristics of nematoda digestion?
Buccaneers capsule-oral opening Esophagus Intestine
30
What are the general characteristics of nematoda reproduction?
Sexual dimorphism Males have spicules Females produce eggs or larvae
31
What is the diagnostic stage of most nematodes?
Females producing eggs or larvae
32
Why do nematodes need to molt?
Cuticle restricts growth
33
How many molts do nematodes generally go through?
4
34
What is the L3 rule?
The infective stage for nematodes is almost always L3
35
What are the 4 superfamilies of strongylida?
Trichostrongyles Strongyles Hookworms Metastrongyles
36
What are the characteristics of strongylida?
Bursa Usually found in the GI tract Cause tissue damage Feed on blood or tissue
37
What are the characteristics of strongylida eggs?
Oval, thin shell & contain a morula
38
What are the characteristics of the strongylida L3 larvae?
Retained cutical from L2 as a sheeth Uses nutrients stored from L1 & L2 Need high temperatures and moisture to develop faster
39
What is hypobiosis?
Larvae become dormant in host GI tissue site & the resumes development to adult at a later time It’s an adaptation mechanism for optimizing chances of survival
40
What are the parasites that undergo hypobiosis in the L3 larval stage?
Trichostrongylus Ancylostoma Cyathastominae
41
What are the parasites that undergo hypobiosis in the L4 larval stage?
Ostertagia Teladorsagia Harmon hus
42
What are the 2 common stimuli for arrested development?
Environmental Host immunity
43
What is “periparturition egg-rise”
2 weeks from parturition to 1 week after, immunity in GImtract is decreases due to immunity being focused on baby and this allows the parasite numbers to increase
44
What is the life cycle of Trichostrongyloida?
1) host ingests L3 stage 2) L3 molts to L4 in the GI tract 3) adults feed and reproduce in host 4) parasite exits host 5) larvae grow & molt in environment until L3 and ingested by host
45
Where are trichostrongyles located in the host body and what species do they usually infect?
Abomasum in ruminants
46
What condition do trichostrongyloida induce?
Parasitic gastroenteritis
47
What is the most important helminths in cattle
Ostertagia ostertagi (brown stomach worm)
48
What is the most important helminths in small ruminants?
Haemonchus contortus (Barber’s pole worm)
49
Where do Ostertagia ostertagi go in the body and why?
The L3 larvae enter gastric glands for a couple of days to molt to L4
50
What is the most pathogenic stage of Ostertagia ostertagi and why?
L4 because it emerges from the gastric gland after hypobiosis because it damages the gland
51
What characteristic lesion does Ostertagia ostertagi produce and why is it important?
A lot of small nodules within the abomasum and it causes permanent destruction of gastric glands which fail to activate pepsinogen and the loss of bacteriostatic effects
52
What is the clinical importance of Ostertagia ostertagi?
Mainly affects young cattle Causes diarrhea, weight loss, hypoproteinemia (bottle jaw), and death
53
What parasite is more pathogenic in sheep & goats?
Haemonchus contortus
54
What does Haemonchus contortus cause?
Anemia Anorexia Hypoproteinemia (bottle jaw) Weight loss Death
55
Why does Haemonchus not cause gastroenteritis in ruminants?
It is a blood sucker
56
What is the most pathogenic stage in osteragia?
L4
57
What stimulus has the most influence on the proportion of strongylid worms that become hypobiotic?
Weather conditions and host immune system
58
What are the general characteristics of strongyloidae
Parasite of GI tract Large buccaneers capsule Plug feeders Most important helminths of horses
59
What are the 2 subfamilies of strongyloidae?
Cyathostominae (small strongyles) Strongylinae (large strongyles)
60
Why are they referred to as “small strongyles” & “large strongyles”
Small has a smaller migration within the host Large has a larger migration within the host
61
What is the disease called when there is a strongylidae infection?
Strongylidosis
62
What is the disease called when there is a strongylinae infection?
Strongylinosis
63
Once the cyathostomins L3 larvae has infected the host where does it migrate to?
Goes to the large intestine and penetrates the lumen to mature to L4 (hypobiosis) with a minimum prepatent period of 2-3 months where they will erupt and mature to adults
64
What stage of cyathostomins cause the most harm & what happens?
L4 (not the adult) and they erupt in the spring and cause nodules within the large intestinal lumen causing secondary infections
65
Can treatment of hypobiotic larvae kill them?
No because their metabolism is not active to consume the antihelminthic
66
What are the characteristics of chronic cyathostominosis (type 2)?
Gradual inflammation & thickening of the gut wall Protein losing enteropathy
67
What are the clinical signs of chronic cyathostominosis (type 2)?
Intermittent diarrhea Mild to moderate colic Poor conditions Hypoproteinemia
68
What are the characteristics of acute larval cyathostominosis (type 1)?
Rapid onset Occurs when large number of arrested larvae synchronously emerge
69
What are the clinical signs of chronic cyathostominosis (type 2)?
Fever Diarrhea that leads to dehydration Edema which leads to hypoproteinemia
70
When are horses most susceptible to cyathostomins?
< 3-4 years of age
71
What is the most important parasite of the large strongyles?
Strongyles vulgaris
72
Explaine the larval migration of Strongyles vulgaris.
Following infection by L3, they molt into L4 which migrates through the arteries. Once it reaches junction of cranial mesenteric artery & aorta. They then return to large intestine about 4 months after infection Occ. larvae migrate to other areas.
73
What is the prepatent period of Strongyles vulgaris?
6 months
74
What is the pathogenesis of Strongyles vulgaris/
Cause verminous arthritis/aneurysm Larvae damage arterial vessels leading to thrombus which can reduce blood flow. Portion of thrombus may break off and block blood flow leading to ischemia
75
What are the clinical signs of Strongylus vulgaris and how is it diagnoses
Colic Abdominal pain Death Difficult to diagnose
76
What are the characteristics of Ancylostomatoidae (hookworms)?
Found in the small intestine of many small animals Blood feeders via plug feeding Teeth or cutting plates
77
What is the most important parasite of dogs in this region?
Ancylostomatidae (hookworms) Specifically Ancylostoma caninum
78
Explain the life cycle of Ancylostoma caninum?
External— egg to L3 in soil Dog infected by environment by L3 via skin penetration After skin penetration larvae migrate to heart/lung and then either cough up, swallow, and develop in small intestine OR travel to tissues & become dormant & become active at the end of pregnancy & migrate to the mammary gland Puppy then ingests the L3
79
What is larval leak?
When larvae reactivate from being dormant and go back to the small intestines and go through cycle again.
80
In pregnant female dogs how many pregnancies can hookworms infect for.
Up to 3 separate pregnancies
81
Egg laying hookworms in the intestine can come from where?
Skin penetration Transmammary infection Ingestion of L3
82
What is the pathogenesis of Ancylostoma caninum?
Low worm numbers= asymptomatic Diarrhea Anemia Skin lesions
83
What is the main difference between Ancylostoma tubaeforme and Ancystoma caninum?
Ancylostoma tubaeforme very rarely cause perinatal transmission
84
Why are hookworms a concern for public health?
Larvae can penetrate human skin & cause cutaneous larva migrans
85
What are the characteristics of Metastrongyloidae (Metastrongyles)?
Parasite of lung, blood vessels & other tissues Mostly diagnosed by larvae in feces not by eggs Invertebrate is intermediate host (mollusk) Not a major concern in domestic animals
86
True or false: in order to differentiate small from large strongyles we must measure the eggs in a fecal analysis?
False
87
What is the most important pathogenic mechanism in canine hookworm infection is
Anemia in puppies
88
What are the main characteristics of Ascrids order?
Bigger than most nematodes Robust GI tract Roundworms Direct life cycle in domestic animals Highly successful parasite in all vertebrate classes
89
Where do the adult ascarids live & what do they feed on?
Live in the lumen of the small intestine & feed on lumen contents of host fluids, do not attach to the lumen wall Females very prolific
90
What are the characteristics of Ascarid eggs?
Thick walled Round One cell inside
91
What is the life cycle of Ascarids?
Eggs passed in feces Develop to infective stage (egg to L3) in 2-4 weeks Egg is not infective until it’s is fully developed The infective larva does not hatch until the egg is swallowed by a host MIGHT have a migratory phase in the definitive host
92
What is the patent infection of Ascarids?
Eggs in feces
93
What are the characteristics of Parascaris equorum
Adults in small intestine World wide distribution Males: up to 30 cm Females: up to 50 cm
94
What is the life cycle of equine ascrids?
Eggs passed in manure Larvae hatch in intestine & penetrate wall Hepatotracheal migration Pre-patent period is about 3 months
95
What is hepatotracheal migration?
Parasite carried to liver in blood Enter hepatic portal system Reach lungs about 1 week PI Coughed up & swallowed Return to small intestine
96
What are Parascaris clinical signs?
Common in young horses Adults in small intestine Competition with host for nutrients Poor condition rough hair coat, pot belly Very heavy infection can lead to perforation or impaction In the lungs they can lead to mechanical & inflammatory damage with nasal discharge
97
True or false: Parascaris don’t typically infect adults because they develop immunity?
True
98
What are the 2 ascarid genuses?
Toxocara canis Toxocara cati
99
What are the routes of transmission of T. canis?
Ingestion of infected eggs Transplacental Transmammary infection Paratenic hosts
100
What clinical signs do heavy toxocara canis burdens cause?
Diarrhea/ constipation Colic & pot belly Vomiting Poor hair coat Intestinal obstruction Pneumonia
101
What is the biggest difference in T. cati life cycle compared to T. canis?
There is no transplacental transmission
102
Why are Toxocara of public health importance?
They are ingested and can cause visceral larva migran &/or ocular larva migrans
103
What are the zoonotic ascrids of importance?
Ascaris suus Baylisascaris procyonis T canis T cati

DWT Exam 2 (6 decks)

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