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Flashcards in Parasitology 2 Deck (63):
1

What is the causative agent of pinworm?

Enterobius vermicularis

2

Describe the transmission of Enterobius vermicularis

ingestion of eggs, direct person to person

3

What is the definitive host of Enterobius vermuclaris

Humans- no intermediate host needed

4

Describe the epidemiology of pinworm

More common in children, daycare
very common worldwide and in the US

5

Describe the lifecycle of Enterobius vermicularis

Gravid female emerges from anus to lay eggs, perianal scratching facilitates transmission and auto-infection
Eggs in clothes, sheets can be transmitted to others
Eggs are swallowed, hatch in intestine, adults mate and migrate to colon

6

Describe immunity to pinworm

None- re-infection is common

7

How is pinworm diagnosed?

Perianal itch, restlessness, insomnia
observation of eggs, scotch tape test

8

What treatments can be used for pinworm?

Pyrantel pamoate, mebendazole, albendazole
Multiple treatment for severe infection, stop reinfection
Thorough housecleaning

9

Trichuris trichiura, or _____, infects humans worldwide and is most common in tropical countries and the poorer communities of the southern US

whipworm

10

What is the definitive host of whipworm?

Humans only, no intermediate

11

How is whipworm transmitted?

Ingestion of embryonated eggs only, no direct person to person

12

Describe the lifecycle of the whipworm (Trichuris trichuria)

Eggs swallowed, hatch in intestine, adults mate and migrate to colon
Adults attach in colon
Eggs passed in feces
Eggs mature 10 days in soil before infectious

13

Pathology of whipworm infection depends on _______

worm burden

14

Describe the pathology of whipworm infection

Low to moderate: usually none; bleeding; bacteremia
High: disrupted colonic mucosa, bloody stool, prolapse, anemia

Heavy burden in children leads to impaired growth cognitive ability

15

Is there any immunity to whipworm infection?

Possibly some- acquired immunity in natural infections

16

How is whipworm diagnosed?

Only by eggs in stool

17

What is the treatment for whipworm?

3 days of ivermectin, mebendazole or albendazole

18

Describe transmission of Ascaris lumbricoides

Ingestion of eggs from soil, no direct person to person

Adult worms localize to upper intestine

19

______ is considered a US neglected disease of poverty and is common in Appalachia and the southern US

Ascariasis
Hookworm- Necator americanus
Strongyloides

20

Describe the lifecycle of ascaris lumbricoides

Females lay eggs that are passed in feces
Eggs mature in soil then are swallowed
Larvae hatch and invade the intestinal mucosa, enter venous circulation to the lungs and are coughed up and swallowed
Mature and mate in small intestine

21

The life cycle of _____ is very unique in that the eggs enter through the GI tract but must travel to the lungs, be coughed up and swallowed in order to return to the intestine

Ascariasis

22

Describe the pathology of Ascariasis

usually none with low to moderate worm burden
Heavy worm loads can lead to intestinal obstruction
Stressed worms migration to nose, ear, peritoneal, thru body wall
Chronic malnutrition leads to poor mental & physical development

23

Describe immunity to ascariasis

Allergic inflammation from larval migration through the lungs

24

How is Ascariasis diagnosed?

Eggs in stool

25

How is Ascariasis treated?

Mebendazole, albendazole or ivermectin

26

Necator americanus and Ancylostoma duodenale are also known as:

hookworms

27

Describe the transmission of hookworms

Invasion of skin in contact with soil
NO direct person to person

28

What is the definitive host of hookworm?

Humans
no animal reservoir

29

Describe the life cycle of hookworm

Filariform larvae invade skin and go into circulation, lodge in lungs
Larvae are coughed up and swallowed and mature into adults in intestine
Eggs in feces mature in the soil to infectious filariformlarvae form

30

List two worm infections that involve invasion of the lungs and coughing to introduce the organism into the GI tract

- Hookworm (Necator americanus, enters bloodstream through invasion of skin--> lung--> GI)
- Ascariasis (enters GI--> lung--> back to GI)

31

Describe the pathology of hookworm

Initial pruritis at penetration sites
Heavy infection, larval migration through lungs can cause bronchitis
Prolonged infection leads to pulmonary symptoms like Ascaris
Exsanguination (0.03 - 0.3 ml blood/worm/day)
Anemia, reduced mental & physical development in children

32

Describe any immunity to hookworm

Asthmatic pathology with repeated infection

33

How is hookworm diagnosed?

Anemia + eggs in stool

34

How is hookworm treated?

Pyrantel pamoate, albendazole & mebendazole

35

Describe transmission of Strongyloies stercoralis

Filariform larvae penetrate
localize to small intestine

36

_______ with strongyloides can result in long term infection

Autoinfection

37

What is the definitive host of strongyloides?

Humans

38

Describe the life cycle of strongyloides

Adult female lays eggs in intestinal mucosa, hatch

1. Direct: larvae are excreted in feces

2. Indirect: sexual reproduction occurs in soil under some conditions (environmental amplification)

3. Autoinfection: larvae mature in the host, enter through colonic mucosa or perianal skin (host amplification)

39

How is strongyloides diagnosed?

- wet mount of stool stained with iodine
- human fecal smear with immunostaining
- agar plate culture for motile larvae
- gram staining of sputum can detect filariform larvae for diagnosing pulmonary strongyloidiasis

40

Gram staining of sputum can detect filariform larvae for diagnosis of _______

pulmonary strongyloidiasis

41

Describe the pathology of strongyloides

Pulmonary manifestations
High burden leads to chronic intestinal malabsorption, dysentery
Rash on buttocks, legs and lower back due to autoinfection
Autoinfection and immunosuppression leads to hyperinfection that can be fatal

42

_______ infection in immune suppressed people can lead to hyperinfection that can be fatal

Stronyloides autoinfection

43

How is strongyloides diagnosed?

Larvae in stool, sputum
eggs NOT seen in fecal specimens
serology

44

How is strongyloides treated?

ivermectin 1st choice, thiabenazole 2nd choice

45

_______ is transmitted by eating raw or undercooked pork containing encysted larvae

Trichinella spiralis (trichinosis)

46

What are the definitive and intermediate hosts of Trichiniella spiralis?

Definitive: bears, swine
Incidental: humans- dead end hosts

47

Describe risk factors for Trichinosis

Home made sausage, hunting, undercooked pork and bear meat

48

Describe the life cycle of Trichinella

Transmitted to humans by eating undercooked meat containing encysted larvae
Larvae are released into GI tract
Adults develop, mate in small intestine, female embeds in mucosa
Live larvae are birthed (no eggs)
Larvae enter lymphatics, blood and encyst in muscle
Larvae develop into an encapsualted spiral which is viable for up to 10 years

49

In ____, the female embeds in the intestinal wall after mating and births live larvae rather than laying eggs

Trichinella spiralis

50

Describe the pathology of Trichinosis

Mild pathology from adult worms= nausea, cramps
Localized inflammation around individual cyst;
degeneration of muscle cell architecture
Severity related to the number of cysts. Severe symptoms: fever, muscle pain, weakness, cardiac and neural dysfunction, conjunctivitis

51

List unique clinical sigs of Trichinosis

eosinophilia, periorbital edema, myositis, fever

52

How is Trichinosis diagnosed

clinical presentation
serologic tests

53

How is Trichinosis treated

Mebendazole or albendazole
corticosteroids for symptoms

54

_______ is transmitted by cats and dogs

Toxocariasis canis/ cati

55

What are the definitive and intermediate hosts of Toxocariasis

Definitive: dogs
Incidental: humans

56

How is toxocariasis transmitted

ingestion of embryonated eggs from soil, no direct person to person

57

Describe the life cycle of Toxocara canis

Sexual cycle in dogs produces eggs in the feces, larvae encyst in tissue and infect puppies in utero
Humans are infected by ingestion of eggs from dogs
In humans larvae burrow through the intestine and migrate for months in any tissue

58

What is visceral larva migrans

Toxocara canis larval migration in a dead end host
in humans- larvae burrow through the intestine and migrate through different tissues

59

Describe the pathology of Toxocariasis

Light infection: self-limiting with little pathology
Heavy worm loads can lead to severe necrosis in any location
Enlarged liver, pulmonary complications, ocular lesion, neurological symptoms all grouped as visceral larva migrans

60

Describe any immunity to toxocariasis

Asthmatic and immune hypersensitivity are common

61

How is toxocariasis diagnosed?

NO eggs in stool because infection does not progress to adults
History of geophagia (eating dirt) and/or exposure to dogs
ELISA for larval antigens, but can cross with Ascaris

62

How is toxocariasis treated?

Albendazole or mebendazole in all cases
Corticosteroids in severe cases

63

How can toxocariasis be prevented?

Properly dispose of dog waste
De-worm dogs