Endoparasites - Nematodes, T. gondii, Fasciola spp. Flashcards Preview

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Flashcards in Endoparasites - Nematodes, T. gondii, Fasciola spp. Deck (99):
1

What is a parasite?

An organism which is metabolically dependent upon another where one benefits at the expense of another.

 

2

Describe the structure of a nematode.

  1. Cylindrical
  2. Radial symmetry
  3. Can be free-living and parasitic
  4. Dioecious
  5. Vary in size

3

What are the common names for nematode, trematode and cestode?

Round worm, fluke and tapeworm

4

What are the structural features of a trematode

Some free living and parasitic species

Dorso-ventrally flattened

Mainly hermaphrodite

5

What is a platyhelminth?

A flat worm

6

What is the average size of a cyathostomine?

1cm

7

Name the species of stronglyus we concentrate on.

S. VulgarisS. EdentatusS. Equinus

8

  1. How can you differentiate between strongylus species?
  2. Which species is shown here?

Head shape/ mouth piece

Vulgaris - Mickey Mouse mouth piece

Edentus and equinus - no teeth in mouth piece

9

What is meant by a direct parasitic lifecycle?

One where the parasite only infects a single host species

10

Name the order of the cyathostomine lifecycle.

Eggs -- larval 1 -- larval 2 -- early larval 3 -- late larval 3 -- larval 4 -- larval 5 -- eggs

11

Which larval stage is considered the infective stage of development which can cause infection of the horse?

L3

12

How long does it take for cyathostomine eggs to develop into the infective stage?

2+ weeks

13

What are the defining features of cyathostomine eggs?

80 micronsOvalThin shelled Undifferentiated morula

14

What temperature must be exceeded for eggs for cyathostomines to develop?

10 degrees

15

Which larval phase of cyathostomine development matures and mates to form eggs? What is the fate of cyathostomine eggs?

L5They are expelled in the faecal pat

16

What is the average size of an infective L3 cyathostomine?

150 microns

17

What happens to the L3 cyathostomine when they are ingested by the horse?

They loose the L2 sheath which protected them on pasture

18

How long is the lifecycle of cyathostomine within the horse?

6-8 weeks

19

Hypobiosis

Parasite driven arrest in development within the host.

20

Which states of cyathostomine development undergo Hypobiosis?

EL3, LL3

21

What time of year would cyathostominosis occur usually?

Late winter/ spring

22

What is the 80:20 rule of cyathostomines?

Eighty percent of the burden in twenty percent of the population

23

What climatic features are required for parasitic development on pasture?

>10 degrees CelsiusHumidityRainfall which disperses the pat

24

What management protocol can be introduced to reduce cyathostomine present on pasture?

Removing faecesHarrowing, spread around and dry the faecesRotational grazing of the pastureBiological control - nematode trapping fungi

25

Which Anthelmintics are used in the control of cyathostomines?

IvermectinMoxidectinBenzimidazolesPyrantel

26

Which Anthelmintics has/ had the highest efficacy against nematodes?

Ivermectin

27

What characteristic features define Galba Truncatula?

Amphibious, fresh-water snail, feeds on algae, found at the edge of rivers and in puddles

28

What is meant by an indirect parasitic lifestyle?

One in which an immediate host is required before entering the definitive host

29

Which geographical areas are Fasciola Hepatic found?

EuropeAustraliaSouth AmericaHigh altitude tropics

30

Which geographical areas are Fasciola Gigantica found?

Hot, humid tropicsAsia

31

Where are juvenile Fasciola found within the body during a fluke infection?

Liver

32

Where are adult fluke found within the body during a fluke infection?

Bile ducts

33

Which structural component of Fasciola causes inflammation during fluke infections?

Spines on the outer surface

34

Multifocal necrotic/ haemorrhagic tracts in the liver are characteristic of which phase of fluke lifecycle?

Juvenile migration

35

Expulsion of cercaria causes _______ of the intermediate host.

Death

36

Which stage of the fasciola lifecycle is found on grass in the pasture and is considered the infective stage?

Metacercaria

37

How long does it take cercaria to locate substrate for development once they are expelled from the snail?

0-3 hours

38

How many cercaria are produced from one redia?

Hundreds

39

How many redia are produced from one sporocyst?

6-8

40

Name the stages of the Fasciola lifecycle, in order.

Eggs, embrionation, miracidium, sporocyst, redia, cercaria, Metacercaria, juvenile fluke, adult fluke

41

The encystment of Metacercaria is made from what?

Calcerous material

42

Which stages of the fluke lifecycle are found within the snail?

Sporocyst and redia

43

What is the appearance of Fasciola eggs?

Similar to cyathostomines but yellow due to absorbance of bile salts

44

How large are the eggs of Fasciola hepatica

150 micrometers

45

How does the miracidium of fluke hatch out of the embryonic shell?

Through the operlum, a type of lid

46

How long is the embryonic stage of fluke development?

2-4 weeks

47

Through October to January which type of Fasciola disease would be found and why?

Acute

Fluke mature on pasture over the late summer and autumn due to favorable climate and are ingested in large numbers. Migration of juvenile fluke through the liver causes clinical disease.

48

What post mortem features can be found in a sheep with acute Fasciola infection?

Anaemia - pancytopenia? Erythropenia?Necrotic and haemorrhagic tracts in the liverEnlarged liverLiver fibrosis

49

Metacercaria are ingested over a long time - fewer in number with both juvenile and adult fluke being found. This statement characterises which type of Fasciola disease?

Sub-acute

50

Hyperplasia of bile ducts, fibrosis, calcification and cholangitis are characteristic of which type of Fasciola infection?

Chronic

51

Bottle jaw describe which clinical symptom?

Sub-mandibular oedema

52

How many and where are suckers found on the fluke?

2 - oral and ventral

53

What are the function of the suckers found on Fasciola?

Sticking to bile duct wall and feeding on blood

54

A temperature of _____ and _____ time may cause death of eggs on pasture in the fluke.

<0 degrees CelsiusLong

55

How do Fasciola stages survive over winter on pasture?

  1. Fluke in snails during hibernation
  2. Metercercaria
  3. Eggs
  4. Carrier animals

56

Which temperature is vital for snail development?

7-10 degrees

57

Which Anthelmintic is used to treat all stages of the Fasciola lifecycle?

Triclabendazole

58

Closantel is active against which stage of the fluke lifecycle?

Mature and immature fluke

59

Name the three main groups of anthelmintic drugs.

Benzimidiazoles 

Imidathiazoles/ tetrahydropyramidines

Macrocyclic lactones

 

60

Outline the mechanism of action of benzimidazoles.

They bind to beta-tubulin in the parasite and therefore inhibit microtubule mediated transport. Preventing transport and enzyme secretion - nutrition etc

61

Ovicidal

Causes death of eggs.

62

Outline the mechanism of action of 2LEV's 

Act upon nicotinic acetyl choline receptors affecting somatic muscle cells

63

LEV/PYR are mainly effective against which stages of nematode development?

Gut dwelling stages

64

Avermectins and Milbemycins are examples of which class of anthelmintics?`

Macrocyclic Lactones

65

Which class of anthelmintic drugs act upon GABA glutamate-gated chloride channels?

macrocyclic lactones

66

How do macrocyclic lactones affect GluCls?

They cause hyperpolarisation of parasitic cells by potentiating GluCl's - keeping them open for longer.

67

Which stages of nematode development are ML's used against?

Migrating larvae and hypobiosed larvae

68

Praziquantel is a potent drug against which type of helminth? At which life stage?

Cestode - adults

69

Name the three types of "new" anthelmintics.

Amino Acetonitrile

Spironidoles

Depsopeptide

70

What is meant by strategic dosing of anthelmintics?

Treating for the parasite when numbers are highest. This therefore disrupts the seasonal cycle of transmission.

71

"Treating at regular intervals based upon egg reappearance period"

This statment characterises which type of anthelimintic strategy?

Interval dosing

72

Which type of anthelmintic control strategy involves dosing for worms based on specific diagnostic parameters?

Targetted dosing

73

Ivermectin and selamectin are examples of which Macrocyclic lactone?

Avermectins

74

When using pyrantel to treat a cestode infection in the horse how much more would be given than when normally using this drug?

Twice normal dose

75

Which classes of anthelmintic drugs can be used to treat the hypobiosed larval stage of development?

Benzimidazoles

Macrocyclic lactones

76

Name a anthelmintic drug which has residual activity of 2 weeks 

Ivermectin

77

Ivermectin can be toxic to which type of dog and is therefore contraindicated in breeds with this characteristic?

Long nosed dogs

eg Sight hounds

78

What is meant by drug resistance?

A specific drug at a specific dose no longer has its desired effect.

A heritable trait of parasites

79

Fasciola Hepatica have shown resistance to which drug which has been key to their control in the past?

Triclabendazole

80

Which class of anthelmintic has shown to have the most extensive resitance amongst helminths?

BZ's

81

"Resistance is a reversible trait"

True or false?

False - Resistance is non-reversible

82

What is meant by the "in refugia" population of parasites?

Those which have not yet been exposed to the drug and have therefore not developed resistance.

83

How does anthelmintic resitance occur?

Overuse of anthelmintic drugs causes a selection pressure which favours those parasites with resistance genes. There numbers therefore increase until they are the majority strain

84

Draw and label a toxoplasma gondii tachyzoite.

A image thumb
85

Are T.gondii an example of an actively motile or non-motile endoparasite?

Non-motile, they glide around the body.

86

What is the function of the apical complex of T. gondii?

Attachment to and invasion of the host.

87

What are the names of the dense granules found in a T.gondii cell?

Micronemes, rhoptries

88

Outline the lifecycle of T.gondii.

Which lifecycle stage is infectious to the intermediate host?

In which phase can transplacental transmission occur?

Oocyst > sporulated oocyst > sporocyst > sporozoite > ingested sporozoites penetrate cells > tachzoite (rapidly divide in cells) > free tachyzoites > bradyzoite (cysts, slow developing)

 

89

Name the intermediate and definitive host of T.gondii.

Intermediate - Rat, mice (prey species), humans (warm-blooded mammels)

Definitive - cat

90

How do tachzoite and bradyzoite differ?

Tachyzoite - Intracellular, Rapidly dividing, Crescent shaped, 2x6um

Bradyzoite - Found within bradyzoite cyst in muscle or neural tissue, slow growing, persistent

91

How are T. gondii transmitted?

Ingestion of meat infected with tissue cysts. Transplacental trasnmission to the foestus during pregnancy.

92

What effect can T. gondii have on:

a) Immunocompromised patients

b) Pregnant women

c) Sheep ?

a) Toxoplasmic encephalitis (AIDs)

b) Foetal effects: hydrocephalus, retinochorioditis (2-3yrs blindness), convulsions, intracerebral calcification

c) Lambs: mummification in early gestation, abortion, still birth, strawberry lesions on the cotyledons, congenital infection. Ewe: barren, infertile

93

How can an infection of T.gondii be diagnosed in the ewe?

  • Serology detects antibodies - dye test, IFAT, agglutination tests
  • Histology of cotyledons or brain shows non-suppurative inflammation

94

How can T. gondii be controlled in sheep?

Since infection provides strong immunity any potential infection (eg by introduction of new stock) should occur well before tupping. Vaccination program (live, attenuated tachyzoite vaccine using S48 strain which doesn't form cysts)

95

How is T. gondii controlled in humans?

Chemotherapy (using pyrimethamine and sulphonamides), reduing the risk of infection (washing vegetables, making sure meat is cooked properly)

96

Which type of cat is the main reservoir for T.gondii?

Farm and stray cats - those who do more hunting.

97

It is suspected that T. gondii has what effect on behaviour of prey species? How does this affect prevalence?

Individuals infected with T. gondii are less inhibited and fearful regarding preditors, they are therefore more likely to be caught by cats and therefore transmit the parasite.

98

It is predicted that a single cat can have an output of how many oocysts? How many are required to cause abortion in sheep?

10^8

10^3

99

How many sporocysts and sporozoites are contained within an oocyst?

Two sporocysts in each oocyst each containing four sporozoites each.