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Flashcards in Parasites 101 Deck (56):
1

As organisms get closer to the species in similarity that they are infecting...

it makes them harder to kill.
*Cancer is the hardest to kill!

2

Parasites are composed of..

Internal and external parasites.

3

What are internal parasites?

Protozoa (unicellular) and Helminths (composed of cestodes, trematodes and nematodes).

4

What are protozoa?

Internal unicellular parasite organisms

5

What are Helminths?

Internal parasites:
Cestodes (tapeworms), Trematodes (flukes), Nematodes (roundworms).

6

What are cestodes?

Tapeworms

7

What are trematodes?

Flukes

8

What are nematodes?

Roundworms

9

What are external parasites?

Insects and Arthropods

10

What are three types of insects?

Flies, fleas and lice.

11

What are two types of arthropods?

Ticks and mites.

12

What types of parasites are localized to the skin?

External: Insects and Arthropods
Insects: Flies, Fleas, Lice
Arthropods: Ticks and Mites.

13

Anti-parasite drugs;
Neurotoxins treat:

Helminths and external parasites.

14

Anti-parasite drugs;
DNA inhibitors treat:

Protozoa

15

Anti-parasite drugs;
Metabolic Inhibitor treat:

Helminths and Protozoa

16

Anti-parasite drugs;
Protein Synthesis Inhibitors treat:

Protozoa

17

Anti-parasite drugs;
Membrane inhibitors treat:

Protozoa

18

Anti-parasite drugs;
Development inhibitors treat:

External parasites

19

What drugs treat..
Helminths: Tapeworms (Cestodes), Trematodes (Flukes) and Nematodes (Roundworm)

Metabolic Inhibitor and Neurotoxins.

20

What drugs treat..
External parasites?
External: Insects and Arthropods
Insects: Flies, Fleas, Lice
Arthropods: Ticks and Mites.

Neurotoxins and Development inhibitors.

21

What drugs treat protozoa? (unicellular organisms)

DNA inhibitors, metabolic inhibitors, protein synthesis inhibitors and protein synthesis inhibitors.

22

What drugs treat cestodes?
Tapeworms (Cestodes)

Isoquinolones

23

What do Isoquinolones treat?

Only one that treats tapeworms

24

What are the rice granules observed in pet feces?

Proglottids are the reproductive sections of the tapeworms.

25

What is the Taenia speices lifecycle (tapeworm)?

1) Eggs or gravid proglottides in feces and passed into environment.
T. saginata & T. solium.
*Diagnostic stage
2) Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contained by eggs or gravid proglottides.
3) Oncospheres hatch, penetrate intestinal wall and circulate to musculature.
4) (Infective stage) Oncospheres develop into cysticeri in muscle. Humans infected by ingesting raw or undercooked infected meat.
5) Scolex attaches to intestine.
6) Adults in small intestine; eggs or gravid proglottides in feces and passed into environment.

26

Praziquantel
Indications

-All tapeworms in dogs, cats and horses (extra-label)
-Doses may vary based on age and species of the cestodes.
-Not approved for use in food animals (due to resistance risks)

27

******Praziquantel
Pharmacodynamics:

*****Altered intracellular calcium homeostasis, leading to..
Direct and indirect disruption of cellular metabolism, leading to, tetanic paralysis and tegumentrary break down, leading to host immune response leading to..
Dead tapeworms.
*Same for epsiprantel

*Needs to be absorbed from the GI tract of the host, taken up by the worms blood meal

28

Praziquantel
Pharmacokinetics
Absorption:

Formulated for administration by PO, IM and SC routes.
Completely absorbed by PO route.
Poor oral bioavailability due to extensive first pass metabolism by liver

29

Praziquantel
Pharmacokinetics
Distribution

Throughout the body, including the CNS.

30

Praziquantel
Pharmacokinetics
Metabolism

Metabolites produced by dogs are biologically active

31

Praziquantel
Pharmacokinetics
Elimination

Metabolite excreted in the urine t1/2 ~ 3 hours (dogs)

32

Praziquantel
Adverse effects;

None are documented at any dose tested, up to 5x the highest treatment dose.

33

Epsiprantel
Indications for use

Labeled for use in DOGS and CATS
Dogs: Dipylidium canium and Taenia pisiformis
Cats: Dipylidium canium and Taenia taeniaeformis
*NOT approved for use in food animals*

34

Epsiprantel
Pharmacokinetics

PO administration
Very poor absorption from the GI tract.
Not distributed or metabolized.
Eliminated in the feces.

35

Since epsiprantel is NOT absorbed into the body...

****Its effects on cestodes are due to direct uptake of the drug by the parasites. It is not by transport of the drug by the host to the parasite.

36

Only drug that is effective against echinococcosis species:

Epsiprantel

37

What trematodes/flukes have the biggest impact on livestock.

Fascioldae (hepatica and gigantica) from snails.

38

What is the life cycle of fasciola hepatica? Treamatode/fluke

Sheep and Cows shed unembroynated egg capsules > embryonated egg capsules > miracidium > snail host > gymnocephalus cercaria > metacercaria on vegetation > eaten by sheep and cows.
*Three stage lifecycle.

39

What is the first stage of the lifecycle of Fasciola hepatica pathology..

Metecercariae
Immature flukes: penetrates GI and traverses the peritoneum to the liver; 4 days
migrates through and feed on liver tissue causing damage
-may disseminate clostridium novyi throughout the liver and peritoneum
-at ~8 weeks, penetrate main bile ducts.

40

What is the second stage of the lifecycle of Fasciola hepatica pathology..

Flukes mature (~10 to 12 weeks)
-Feeds on blood
-Causes biliary hyperplasia and progressive occlusion.

41

What are the indications for use of Clorsulon?

Fasciola spp in cattle (labled)
Sheep (extra-label)
*****-Not effective for flukes BEFORE 8 weeks post infection.
-Ivomec Plus contains both clorsulon and ivermectin (so it also covers nematodes)

42

What are the pharmacodynamics for use of Clorsulon?

Stops glycolysis by inhibiting phosphoglyceromutatse and phosphoglycerate kinase.
Stops glycolysis of the fluke!

43

Clorsulon
Absorption:

Formulated for PO administration
Oral bioavailability is 55 to 60% in sheep and goats.

44

Clorsulon
Distribution:

Ingestion of blood containing the drug is the route of administration to flukes.
Administered dose in livestock is just above the dose that saturates the blood concentration in rats.
Unmetablolized parent drug is eliminated in the urine 1/2 - 48 hours.

45

Clorsulon
Adverse effects:

None!
LD50 in mice is 10kg/kg PO or 761 mg/kg IP

46

What are benzimidazoles?

Albendazole
Febendazole

47

*****Albendazole is effective against ..

F. hepatica in cattle at labeled dose.
-12 weeks post infection
-Comparable to clorsulon (70-99%)

48

Fenbendazole is effective against ..

95% effective against F. gigantica in sheep at the labeled dose.

49

What are the cestocides/isoquinolone drugs?

Praziquantel
Epsiprantel

50

What are the flukicidies?

Clorsulon
Benzimidazoles
-Albendazole
-Fenbendazole

51

Altered intracellular calcium homeostasis, leading to..
Direct and indirect disruption of cellular metabolism, leading to, tetanic paralysis and tegumentrary break down, leading to host immune response leading to..
Dead tapeworms.

Acts DIRECTLY on the worm while the worm is in the GI

Epsiprantel

*Acts directly on the worm while the worm is in the GI

Does NOT get taken up with a blood meal like Praziquantel.

52

******Clorsulon is not effective on flukes..

*****Not effective for flukes BEFORE 8 weeks post infection.
Advantageous because even though flukes are developing, they are still maturing not causing occlusion of the bile ducts or biliary hyperplasia at this state.

53

******Benzimidazoles
-Albendazole
-Fenbendazole

Used against fasicola hepatica in cows, these flukes are mature..
Doesn't work until 2 weeks post infection..

*These flukes are mature, causing much more significant liver damage! Need to provide earlier protection.

54

******Comparing Clorsulon to Benzimidazoles for treatment of flukes..

Clorsulon is effective earlier, but Benzimidazoles have a broader spectrum!

55

******What drugs can be used in a horse?

Piperizine***

56

**** What drug treats fleas and nematodes?

Macrocyclic lactone**
Avermectin, milemycin and spinosyns.