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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
Q

How do we diagnose parasites?

A

Morphologic (microscopic and gross examination of blood, feces, tissue and remains

Immunologic assays

Molecular tests (PCR)

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26
Q

What are the general characteristics of helminths (worms)

A

Macroparasite

Often highly host specific in the definitive host either oviparus or ovoviviparous

Fecal oral or environmental-oral

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27
Q

What are the two phylum of helminths?

A

Nematoda & platyhelminthes

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28
Q

What are the general characteristics of the phylum nematoda?

A

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

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29
Q

What are the general characteristics of nematoda digestion?

A

Buccaneers capsule-oral opening
Esophagus
Intestine

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30
Q

What are the general characteristics of nematoda reproduction?

A

Sexual dimorphism
Males have spicules
Females produce eggs or larvae

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31
Q

What is the diagnostic stage of most nematodes?

A

Females producing eggs or larvae

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32
Q

Why do nematodes need to molt?

A

Cuticle restricts growth

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33
Q

How many molts do nematodes generally go through?

A

4

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34
Q

What is the L3 rule?

A

The infective stage for nematodes is almost always L3

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35
Q

What are the 4 superfamilies of strongylida?

A

Trichostrongyles
Strongyles
Hookworms
Metastrongyles

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36
Q

What are the characteristics of strongylida?

A

Bursa
Usually found in the GI tract
Cause tissue damage
Feed on blood or tissue

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37
Q

What are the characteristics of strongylida eggs?

A

Oval, thin shell & contain a morula

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38
Q

What are the characteristics of the strongylida L3 larvae?

A

Retained cutical from L2 as a sheeth
Uses nutrients stored from L1 & L2
Need high temperatures and moisture to develop faster

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39
Q

What is hypobiosis?

A

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

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40
Q

What are the parasites that undergo hypobiosis in the L3 larval stage?

A

Trichostrongylus
Ancylostoma
Cyathastominae

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41
Q

What are the parasites that undergo hypobiosis in the L4 larval stage?

A

Ostertagia
Teladorsagia
Harmon hus

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42
Q

What are the 2 common stimuli for arrested development?

A

Environmental
Host immunity

43
Q

What is “periparturition egg-rise”

A

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
Q

What is the life cycle of Trichostrongyloida?

A

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
Q

Where are trichostrongyles located in the host body and what species do they usually infect?

A

Abomasum in ruminants

46
Q

What condition do trichostrongyloida induce?

A

Parasitic gastroenteritis

47
Q

What is the most important helminths in cattle

A

Ostertagia ostertagi (brown stomach worm)

48
Q

What is the most important helminths in small ruminants?

A

Haemonchus contortus (Barber’s pole worm)

49
Q

Where do Ostertagia ostertagi go in the body and why?

A

The L3 larvae enter gastric glands for a couple of days to molt to L4

50
Q

What is the most pathogenic stage of Ostertagia ostertagi and why?

A

L4 because it emerges from the gastric gland after hypobiosis because it damages the gland

51
Q

What characteristic lesion does Ostertagia ostertagi produce and why is it important?

A

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
Q

What is the clinical importance of Ostertagia ostertagi?

A

Mainly affects young cattle
Causes diarrhea, weight loss, hypoproteinemia (bottle jaw), and death

53
Q

What parasite is more pathogenic in sheep & goats?

A

Haemonchus contortus

54
Q

What does Haemonchus contortus cause?

A

Anemia
Anorexia
Hypoproteinemia (bottle jaw)
Weight loss
Death

55
Q

Why does Haemonchus not cause gastroenteritis in ruminants?

A

It is a blood sucker

56
Q

What is the most pathogenic stage in osteragia?

A

L4

57
Q

What stimulus has the most influence on the proportion of strongylid worms that become hypobiotic?

A

Weather conditions and host immune system

58
Q

What are the general characteristics of strongyloidae

A

Parasite of GI tract
Large buccaneers capsule
Plug feeders
Most important helminths of horses

59
Q

What are the 2 subfamilies of strongyloidae?

A

Cyathostominae (small strongyles)
Strongylinae (large strongyles)

60
Q

Why are they referred to as “small strongyles” & “large strongyles”

A

Small has a smaller migration within the host

Large has a larger migration within the host

61
Q

What is the disease called when there is a strongylidae infection?

A

Strongylidosis

62
Q

What is the disease called when there is a strongylinae infection?

A

Strongylinosis

63
Q

Once the cyathostomins L3 larvae has infected the host where does it migrate to?

A

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
Q

What stage of cyathostomins cause the most harm & what happens?

A

L4 (not the adult) and they erupt in the spring and cause nodules within the large intestinal lumen causing secondary infections

65
Q

Can treatment of hypobiotic larvae kill them?

A

No because their metabolism is not active to consume the antihelminthic

66
Q

What are the characteristics of chronic cyathostominosis (type 2)?

A

Gradual inflammation & thickening of the gut wall
Protein losing enteropathy

67
Q

What are the clinical signs of chronic cyathostominosis (type 2)?

A

Intermittent diarrhea
Mild to moderate colic
Poor conditions
Hypoproteinemia

68
Q

What are the characteristics of acute larval cyathostominosis (type 1)?

A

Rapid onset
Occurs when large number of arrested larvae synchronously emerge

69
Q

What are the clinical signs of chronic cyathostominosis (type 2)?

A

Fever
Diarrhea that leads to dehydration
Edema which leads to hypoproteinemia

70
Q

When are horses most susceptible to cyathostomins?

A

< 3-4 years of age

71
Q

What is the most important parasite of the large strongyles?

A

Strongyles vulgaris

72
Q

Explaine the larval migration of Strongyles vulgaris.

A

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
Q

What is the prepatent period of Strongyles vulgaris?

A

6 months

74
Q

What is the pathogenesis of Strongyles vulgaris/

A

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
Q

What are the clinical signs of Strongylus vulgaris and how is it diagnoses

A

Colic
Abdominal pain
Death
Difficult to diagnose

76
Q

What are the characteristics of Ancylostomatoidae (hookworms)?

A

Found in the small intestine of many small animals
Blood feeders via plug feeding
Teeth or cutting plates

77
Q

What is the most important parasite of dogs in this region?

A

Ancylostomatidae (hookworms)

Specifically Ancylostoma caninum

78
Q

Explain the life cycle of Ancylostoma caninum?

A

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
Q

What is larval leak?

A

When larvae reactivate from being dormant and go back to the small intestines and go through cycle again.

80
Q

In pregnant female dogs how many pregnancies can hookworms infect for.

A

Up to 3 separate pregnancies

81
Q

Egg laying hookworms in the intestine can come from where?

A

Skin penetration
Transmammary infection
Ingestion of L3

82
Q

What is the pathogenesis of Ancylostoma caninum?

A

Low worm numbers= asymptomatic
Diarrhea
Anemia
Skin lesions

83
Q

What is the main difference between Ancylostoma tubaeforme and Ancystoma caninum?

A

Ancylostoma tubaeforme very rarely cause perinatal transmission

84
Q

Why are hookworms a concern for public health?

A

Larvae can penetrate human skin & cause cutaneous larva migrans

85
Q

What are the characteristics of Metastrongyloidae (Metastrongyles)?

A

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
Q

True or false: in order to differentiate small from large strongyles we must measure the eggs in a fecal analysis?

A

False

87
Q

What is the most important pathogenic mechanism in canine hookworm infection is

A

Anemia in puppies

88
Q

What are the main characteristics of Ascrids order?

A

Bigger than most nematodes
Robust
GI tract
Roundworms
Direct life cycle in domestic animals
Highly successful parasite in all vertebrate classes

89
Q

Where do the adult ascarids live & what do they feed on?

A

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
Q

What are the characteristics of Ascarid eggs?

A

Thick walled
Round
One cell inside

91
Q

What is the life cycle of Ascarids?

A

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
Q

What is the patent infection of Ascarids?

A

Eggs in feces

93
Q

What are the characteristics of Parascaris equorum

A

Adults in small intestine
World wide distribution
Males: up to 30 cm
Females: up to 50 cm

94
Q

What is the life cycle of equine ascrids?

A

Eggs passed in manure
Larvae hatch in intestine & penetrate wall
Hepatotracheal migration
Pre-patent period is about 3 months

95
Q

What is hepatotracheal migration?

A

Parasite carried to liver in blood
Enter hepatic portal system
Reach lungs about 1 week PI
Coughed up & swallowed
Return to small intestine

96
Q

What are Parascaris clinical signs?

A

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
Q

True or false: Parascaris don’t typically infect adults because they develop immunity?

A

True

98
Q

What are the 2 ascarid genuses?

A

Toxocara canis
Toxocara cati

99
Q

What are the routes of transmission of T. canis?

A

Ingestion of infected eggs
Transplacental
Transmammary infection
Paratenic hosts

100
Q

What clinical signs do heavy toxocara canis burdens cause?

A

Diarrhea/ constipation
Colic & pot belly
Vomiting
Poor hair coat
Intestinal obstruction
Pneumonia

101
Q

What is the biggest difference in T. cati life cycle compared to T. canis?

A

There is no transplacental transmission

102
Q

Why are Toxocara of public health importance?

A

They are ingested and can cause visceral larva migran &/or ocular larva migrans

103
Q

What are the zoonotic ascrids of importance?

A

Ascaris suus
Baylisascaris procyonis
T canis
T cati

DWT Exam 2 (6 decks)

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