Introduction to Helminths Flashcards

(60 cards)

1
Q

What kind of organisms are helminths?

A

Worms

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2
Q

Are most helminths parasitic?

A

No, they are free-living in the environment and only a minority are parasitic.

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3
Q

A very significant proportion of expenditure on veterinary medicine is spent on what?

A

Anthelminthic drugs

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4
Q

Parasite control programs for helminth diseases are based on what?

A
  • Drugs
  • Management measures such as keeping stocking densities down and understanding life cycles
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5
Q

What are the categories of parasitic helminths?

A
  • Nematodes (roundworms)
  • Platyhelminthes (flatworms)
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6
Q

What was the first complex organism to have its genome sequenced?

A

Cenorhabitis elegans

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7
Q

Is C. elegans a parasitic helminth?

A

No

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8
Q

What are the uses for Cenorhabditis elegans as a model helminth?

A
  • Used in a wide variety of broad biological studies, including studies on developing new anthelminthic drugs
  • Has 302 neurons and therefore used extensively in studies of neural networks
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9
Q

How many hosts do parasitic nematodes have?

A

One host (definitive)

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10
Q

Name 4 key facts about parasictic nematodes

A

1) They have separate sexes (di-ecious)
2) Females are often bigger
3) One egg = One adult
4) Organized body structure with cavities.

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11
Q

How are infective larvae of parasitic nematodes are spread?

A

Via grass and plant material, which is contaminated by eggs in host species

More animal feces = more contamination.

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12
Q

True or false: Infection by parasitic nematodes generally is only significant about a certain level.

A

True

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13
Q

Control of parasitic nematodes works best by reducing _________ numbers.

A

Host; you have to break the cycle of infection.

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14
Q

What are the 2 groups of flatworms?

A
  • Trematodes (flukes)
  • Cestodes (tapeworms)
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15
Q

What are the major differences between nematodes and platyhelminthes?

A
  • Nematodes: organs in the coelom, protective cuticle
  • Platyhelminthes: organs in parenchyma, metabolically active tegument
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16
Q

How many hosts do flatworms have?

A

At least 2 or more are needed to complete their life cycle.

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17
Q

Flatworms body structure is more ________ than nematodes.

A

Primitive

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18
Q

Which classification of helminths are often hermaphrodites?

A

Flatworms

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19
Q

Describe the reproduction of flatworms.

A

Can be asexual or sexual, so one egg produces many adults.

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20
Q

Taenia solium is what kind of helminth?

A

Flatworm

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21
Q

What is the scientific name for the liver fluke?

A

Fasciola hepatica, which is a flatworm.

They live in the bile ducts of ruminant and other mammalian hosts

Anemia is a common sign of infection.

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22
Q

What is the Life Cycle of Fasciola hepatica?

A

1) Adult liver flukes produce fertilizd eggs that leave the host via the common bile duct (CBD)iand intestinal tract feces.
2) If eggs fall into water, a ciliated miracidium develops over weeks or months depending on water temperature.
3) On hatching, they seek** lymnaeid snails** to develop 1 generation of sporocysts and 2 generations of rediae. No snail within 24 hrs = it dies.
4) It reproduces in the snail to become cercaria, tadpole-like larva and migrate above water level.
5) Cercaria mature, lose tadpole tail, become **metacercaria and climb up plants. **
6) **Metacercaria are infective to sheep and other grazing animals. **

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23
Q

In Life Cycle Terminology, define a helminth definitive host.

A

Helminth reproductive stages in the host.

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24
Q

In Life Cycle Terminology, define a helminth intermediate host.

A

Immature helminth stages occur here.

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25
In Life Cycle Terminology, define a paratenic host?
Optional extra host that is not required for life cycle completion.
26
What is an example of a helminth organism with a paratenic host?
Toxocara cati
27
In Life Cycle Terminology, define a direct life cycle?
Life cycle with only one required host.
28
In Life Cycle Terminology, define an indirect life cycle?
Life cycle with more than one required host.
29
How do helminths affect the immune response of their host?
Often 'dampen' it; which can be either bad or good. | dampen could mean "extra burden"
30
What is the hygiene hypothesis?
The hypothesis that early exposure of a child/immature animal to particular microorganisms such as helminths protects against allergies by properly tuning the immune system.
31
What is the "old friends" hypothesis?
Observations of the potentially important role that helminth-driven suppression of our immune system responses has played in preventing or lessening our development of allergies and autoimmune diseases.
32
What are the major clinical issues associated with helminths in general?
- Very limited number of drugs available - Few new drugs in development - Drug resistance has become a major problem; in Australia and NZ, some sheep roundworms are resistant to all available drugs.
33
What are the aspects of future helminth control?
- New drug development - Development of vaccines - Anthelmintic stewardship - Prescriptions for food animals in EU
34
In what kinds of animals are parasitic helminths found?
- All grazing animals - Cats, dogs, wildlife, and exotic pets
35
What % of drug expenditures are spent on parasiticides?
23%
36
Describe the importance of veterinary involvement in the control of helminth diseases.
Vets play a crucial role in the prevention measures, specifically those that do not involve the use of drugs, so as to minimize the rising levels of resistance.
37
What 6 things make an animal at risk for a parasite?
1. age 2. immune status 3. genetics 4. nutritional status 5. pregnancy 6. hyperbiosis (ability of parasite to stay dorment inside the host, arrested development), common in livestock
38
What 4 things make an environment at risk for a parasite?
1. parasite type 2. temperature 3. moisture 4. pasture composition
39
What 5 things make an environment at risk for a parasite?
1. Grazing system 2. Housing system 3. Co-grazing 4. Alternate grazing 5. Anthelmintic regime
40
Control is based on _____?
risk
41
In the principles of parasite control, describe the susceptibiltiy of adults, compromised adults, and young stock.
1) Adults are mostly fine the majority of the time - Low susceptibility. 2) Compromised adults are pregnant, immunosupressed, or aged. Moderate susceptibility. 3) Young stock - Immature immune system. Highest susceptibility.
42
Which grazing animals are at risk, high to low?
1) sheep **HIGH** 2) spring dairy cows 3) autumn dairy cows 4) beef calves **LOW**
43
What 4 things to consider with pasture managment?
Avoid overuse of pastures and decrease pasture burden 1) Stocking densities - taking into account risk of stock 2) Mixed grazing -parasite cross over 3) Rotational grazing -between age cohorts (biological hoover) 4) Young stock pasture - turn out onto least contaminated pastures
44
What is the 80/20 rule regarding parasites?
Most of the Parasites are in a minority of the population.
45
Describe Ostertagia ostertagii.
- Anterior end has a mouth opening that feeds on the gut contents of the host - Lives in the abomasum of cows - Burrows into the mucosa of abomasum - Late summer and autumn
46
What aspect of the posterior end of Ostertagia organisms was used to identify the organism prior to molecular ID?
Presence of 2 spicules.
47
Describe Toxocara canis.
- Ascarid worm; long, spaghetti-like - Usually found in young animals - Live in small intestine - Produce very distinct eggs - Can survive a very long time in the environment - Infectious once larvae develop within the host.
48
Describe cyathostomins.
- 'Small redworms' - Mostly white - Live in large intestine - Ubiquitous.
49
True or false: Nematodes have separate sexes.
True; they are di-ecious.
50
Which sex of nematodes are often bigger?
Females.
51
One nematode egg gives rise to how many adults?
One.
52
Describe the body structure of nematodes.
Organized with cavities.
53
What allows nematodes to survive environmental conditions?
Cuticle.
54
What allows nematodes to move?
Muscle layer.
55
What kind of life cycle do flatworms have?
Indirect.
56
Flatworms are what kind of parasite?
Obligate parasites.
57
How do flatworms move?
Spikes on outside of tegument.
58
Describe Taenia solium.
- 'Pork tapeworm' - Humans are definitive host, pigs are intermediate host - Causes space occupying lesions and epilepsy.
59
Describe Fasciola hepatica.
- Mammalian species are definitive host - Intermediate host is very specific to snails - Causes serious economic losses in ruminants - Zoonotic.
60
Describe the life cycle of Toxocara cati.
- Definitive host is cats - Paratenic host is rodents and birds.