Nematodes- infective eggs Flashcards Preview

Parasitology > Nematodes- infective eggs > Flashcards

Flashcards in Nematodes- infective eggs Deck (37):
1

What is the distribution of Trichuris species?

worldwide, but especially in tropical areas with poor sanitation, esp in children

2

Is Trichuris an old parasite?

yes, petrified eggs have been found in prehistoric humans

3

What is the name of the human whipworm specie?

Trichuris trichiura

4

What are the species names for cat, pig, mouse, and dog whipworm?

Trichuris campanula, Trichuris suis, Trichuris muris, Trichuris vulpis

5

What are some distinguishing features of whipworm species?

has a narrow anterior end and a wider posterior end
females are always larger than the males

6

Under what conditions will whipworm eggs embryonate?

must be in external environment: high humidity, sandy soil and 20-30 degrees celcius

7

Describe the whipworm egg morphology

barrel-shaped, unembryonated, has bipolar plugs, a smooth shell

8

Where does the first stage larva hatch from the egg?

in the host small intestine and migrate to colon

9

Where do adult whipworms inhabit?

in the cecum and ascending colon, with anterior portions threaded through mucosal layer

10

What is the life span of adult whipworms?

1 year

11

What is the pathology of whipworm infection?

frequently asymptomatic
heavy infections in children can cause abdominal pain, diarrhea and rectal prolapse (caused by weakened ligaments holding rectum), sometimes growth retardation

12

How can a whipworm infection be diagnosed?

microscopic identification of eggs in feces

13

Which drugs can be used to treat whipworm infections?

mebendazole and albendazole

14

What is the distribution of Enterobius vermicularis (pinworm)?

broadest geographic range. most common in temperate regions of Western Europe and North America (rare in the tropics)

15

How are pinworm eggs spread?

oral-fecal route

16

What are the hosts of pinworm?

humans are the only known natural host, no reservoirs

17

Describe the adult pinworm morphology

small, white, threadlike bodies, females are bigger.
females have a long, pin-shaped posterior

18

Where do the adult pinworms reside?

in the cecum. gravid females migrate at night to lay eggs

19

Describe the pinworm egg morphology

flattened asymmetrically on one side, ovoid in shape, embryonate in 6h. viable for 20 days in moist environments

20

What is retro-infection of pinworms?

When the larvae hatch on the anus and crawl back up the intestinal tract to the cecum to mature into adults

21

What is the pathology of pinworms?

usually asymptomatic.
females and eggs may cause irritation of butt hole region.
female migration at night may lead to discomfort and scratching, aiding in the spread of eggs

22

How can pinworm infection be diagnosed?

scotch tape test: cellulose tape is applied to anal area
anal swabs: has adhesive material

23

How are pinworm infections treated?

primarily mebendazole, but also albendazole

24

What is the largest and most common intestinal nematode?

Ascaris lumbricoides (human roundworm)

25

What is the distribution of Ascaris lumbricoides?

worldwide, but mostly in Africa, in the countryside. eggs can remain viable for years in moist environments

26

How are people common infected with Ascaris lumbricoides?

using feces to fertilize soil, children playing in soil

27

What are the hosts of Ascaris lumbricoides?

humans are the only definitive host

28

Describe the morphology of the adult roundworms

adults are the largest nematodes to infect humans
females larger than males
male posterior end is curved due to spicules
three lips at anterior end, lined with miniscule teeth

29

Describe the roundworm egg morphology

unembryonated when passed in the feces, become embryonated in soil, eggs are the infectious stage. thick, rough outer shell

30

Which path do the larva follow in the body?

hatch, burrow in the intestine, through intestinal mucose to blood, reach the lungs and migrate up the respiratory tract so that they can be swallowed. mature into adults in the small intestine

31

What is the pathology of ascariasis from adult worms?

light infection is usually asymptomatic, but can lead to vague abdominal pains
heavy worm burden results in malnutrition
wandering adults can cause blockages resulting in intestinal obstruction, appendicitis, biliary ascariasis, perforation of intestine, pancreatitis, etc

32

What is the pathology of ascariasis from larvae?

larvae can penetrate alveoli, causing plasma to enter them and cause an inflammatory reaction. leads to pneumonia-like symptoms such as low fever, cough, blood in sputum, asthma

33

How is ascariasis diagnosed?

identify egg in feces

34

Which drugs are used to treat roundworm infections?

albendazole in combination with mebendazole. ivermectin can be used alternatively.
this treats adults. no treatment for larvae

35

What is the distribution and host of Baylisascaris procyonis?

it is a raccoon roundworm that does not develop in humans but can cause problems.
common throughout North America

36

What is the pathology of Baylisascaris procyonis?

migration of large larvae through many tissues, including liver, heart, lungs, brain, eyes causes visceral larval migrans or ocular larval migrans symptoms.
symptoms are severe because the larvae are large and move a lot

37

How can Baylisascaris procyonis infection be diagnosed and treated in humans?

rare infection, not often diagnosed. serological test and identification of larvae (biopsy or autopsy).
no drugs are completely effective