Parasitology I Flashcards Preview

FM3_ EB > Parasitology I > Flashcards

Flashcards in Parasitology I Deck (52):
1

Endoparasites are divided into two major groups:

- protozoa (unicellular)
- helminths (multicellular worms)

2

Differentiate between the definitive host and the intermediate host

Definitive: host in which the sexual stage of the life cycle occurs
Intermediate: host in which asexual reproduction or development can occur

3

An ______ host is not an obligate part of a parasite's life cycle

incidental/ accidental

4

What is a reservoir?

Animal host that maintains the natural cycle of infection in the wild, often not harmed by carriage

5

List the 5 CDC neglected parasitic infections in the US

1. Chagas, caused by Trypanasoma cruzi
2. Neurocysticercosis caused by Taenia sp
3. Toxocariasis caused by Toxocara canis/ cati
4. Toxoplasmosis: leading cause of foodborne deaths, congenital infection
5. Trichomoniasis

6

Most protozoan infections elicit a _____ immune response.
Worms generally elicit a ________ immune response

protozoa: Th1
Worms: Th2/ eosinophils

7

Differentiate between: cyst, cysticeri, hyadatid cyst

Cyst: Dormant stage found encysted in host tissue (intermediate or definitive) so can be passed by eating undercooked meat

Cysticerci: Encysted cestode larval forms in tissues of infected intermediate hosts. Example: Humans/pork tapeworm

Cyst, Hydatid: Specialized cysticercal form of the cestode Echinococcus granulosus found in the intermediate host

8

Metacercaria, Miracidium, Microfilariae, Cercaria,
Filariform, Rhabditiform, Schistosomula, Sporocyst are alternate names for:

larvae

9

Class cestoda contains the

tapeworms

10

Class trematoda contains the

flukes

11

_____ have no internal digestive system and absorb nutrients across the cuticle.
_____ have a simple digestive system

Tapeworms- no digestive system
Flukes/ roundworms- have a simple digestive system

12

Describe the lifecycle of Taenia solium

Pork tapeworm

Pigs are the intermediate hosts and get cysticeri in their meat
Humans are the definitive host and shed eggs and proglottids in feces. Pigs do not shed eggs

Pigs become infected when they eat tapeworm eggs or proglottids

Humans become infected when they eat undercooked pork with cysticeri or tapeworm eggs form other humans

13

Only ___ shed eggs of Tania solium

humans

14

Distinguish between taeniasis and cysticercosis

When humans eat undercooked pork they get taeniasis- tapeworm in the intestine
When humans eat tapeworm eggs they get cysticercosis- larva in muscle, eyes, brain

beef tapeworm eggs are NOT infectious to people, only pork tapeworm eggs cause cystircercosis

15

Describe the location of Taenia solium infection

location: adult worms in intestin, cysticerci in any tissue but especially brain

16

What is the definitive host of Taenia solium

Humans

17

What is the intermediate host of Taenia solium

Humans or pigs

18

Describe the pathology of Taenia solium

- Taeniasis is often asymptomatic or causes abdominal discomfort, occasionally nausea, vomiting, diarrhea, weight loss & obstruction

- Cysticercosis cysticerci located in any tissue; in the brain can cause confusion, difficulty with balance, brain swelling, hydrocephalus, seizures, headaches and mortality

19

How is diagnosis of Taenia solium made?

Self or clinical- proglottids in stool
X ray, CT, MRI

20

Describe any immunity to Taenia solium

Humoral response to adults worms, reinfection is possible

21

Describe treatment for Taenia solium

Praziquantel, niclosamide or albendazole, single dose effective for adult worms but prolonged treatment for cysticerci

Dexamethasone added for infection of CNS

22

How can Taenia solium be avoided?

Fully cook pork
Public and personal hygiene

23

Describe the transmission of Diphyllobothrium latum

Fish tapeworm
Ingestion of undercooked fish containing plerocercoid

24

What is the definitive and intermediate host of Diphyllobothrium latum?

Definitive: Humans
Intermediate: copepod that infects fish

25

Where is Diphyllobothrium latum endemic?

Temperate zones, brought to new world by European immigrants

26

Describe the pathology of Diphyllobothrium latum

Like beef tapeworm; adults absorb 80-100% dietary B12 leading to deficiency, anemia, neurologic symptoms

27

Describe immunity to Diphyllobothrium latum

No clinically relevant immunity, reinfection is possible

28

How is Diphyllobothrium latum diagnosed?

Proglottids in stool, distinct from Taenia spp eggs

29

How is Diphyllobothrium latum treated?

praziquantel or niclosamide, single dose

30

How is Diphyllobothrium latum prevented?

Public hygiene, well cooked fish

31

_________ causes hydatid disease

Echinococcus granulosus

32

Ehinococcus granulosus localizes mainly to the:

lung, liver, spleen, kidney, heart, bone, CNS

33

How is Echinococcus graulosus transmitted

Ingestion of eggs from dogs

34

What is the definitive host of Echinococcus granulosus?

Wild and domestic canines

35

What is the intermediate host of Echinococcus granulosus

Wild and domestic ungulates, humans

36

Describe the life cycle of Echinococcus granulosus

- Basic cestode lifecycle; humans as intermediate/ dead end host only
- Requires intimate contact with dogs

37

How are dogs infected with Echinococcosis?

Ingest internal organs of sheep, goats, etc. Pastoral cycle

38

Describe the pathology of Echinococcosis

Hydatid cysts in liver (50-70%) and lungs (20-30%), but also spleen, kidney, bone and CNS
Latent periods up to 20 years
Disease onset when hydatid cysts cause pain or rupture
Cyst rupture can seed new sites by release of protoscolices
Anaphylaxis associated with rupture can be fatal but is rare

39

Describe immunity to Echinococcosis

Circulating antibodes to hyatid cyst antigens, more pathologic than protective

40

How is echinococcosis diagnosed?

Reside in endemic area or animal husbandry/ hunting
CT/ultrasound for cysts
Serology for confirmation

41

How is echinococcosis treated

percutaneous drainage wiht instillation of hypertonic saline, surgical removal, albendazole if not resectable (poor cure rate)

42

Describe measures to prevent echinococcosis

De-worm dogs, don't feed intestines, good hygiene around dogs

43

Describe transmission of schistosomiasis

Invasive, aquatic free living cercaria penetrate skin

44

What are the definitive and intermediate hosts of schistosomiasis?

Definitie: humans, male-female pairings in blood
Intermediate: snails

45

Pathology of schistosomiasis is proportional to ________

worm burden

46

Schisosome _____ eggs are found in the stool and have a ____ spike
Schistosome ____ eggs are found in the urine and have a ____ spike

mansoni in stool, lateral spike
Haematobium in urine, terminal spike

47

Describe the stages of schistosomiasis pathology:

- Early: asymptomatic, rash that subsides and then fever, headache, nausea

-Middle: immune response to eggs, blood in urine/ stool, abdominal pain

-Chronic: eggs lodge in liver and intestine (mansoni, japonicum) or bladder (hematobium) and can lead to fibrosis and cancer

48

What is Katayama syndrome?

Intense reaction in patients infected with schistosomiasis for the first time, fever with onset of oviposition

49

Describe treatment of schistosomiasis

Praziquantel in single (S.m., S.h.) or multiple (S.j.) dose
Potentiates active immune system killing of adult worms

50

Describe the diagnosis of schistosomiasis

observation of eggs in feces, urine
Serology now available

51

Describe prevention measures for schistosomiasis

Treat infected individuals, proper waste disposal, control of intermediate hosts (snails), avoid contact with infected water

52

Describe the association between hepatitis C and schistosomiasis

earlier mass treatment (with tartar emetic) of Schistosomiasis in Egypt used contaminated needles leading to HCV infection.
Chronic inflammation from schistosomiasis exacerbates HCV
Be suspicious in middle aged Egyptian men