37 - Parasitic Roundworm Infections of the GI Tract Flashcards
1
Q
What are helminths?
A
Worms
2
Q
What are Nematodes?
A
Round worms
- Non-segmented bodies
- Separate sexes
- Complete digestive systems
3
Q
What are Cestodes?
A
Tapeworms
- Segmented bodies
- Hermaphroditic
- Absorb nutrients
4
Q
What are Trematodes?
A
Flukes
- Non-segmented (leaf)
- Hermaphroditic
- Primitive gut
5
Q
What is the most common type of parasitic helminth in the US and the world?
A
Nematodes
6
Q
Are nematodes typically fatal?
A
No, however they do contribute to malnutrition and a diminished work capacity
7
Q
Where do we most commonly see Nematodes?
A
- Areas of poor sanitation
- Developing countries
- Tropics
8
Q
What population is most likely to develop a symptomatic nematode infection?
A
Children
9
Q
What is disease typically caused by?
A
The presence of adult forms of the worms in the GI tract
10
Q
Are these infections common in the US?
A
Yes, relatively common
11
Q
What stages does the life cycle of a nematode consist of?
A
- Egg
- Multiple larval
- Adult stages
12
Q
Are there different sexes in nematodes?
A
Yes - the female is usually larger than the male
13
Q
What needs to happen in order for an individual to be shedding INFECTIOUS eggs?
A
There needs to be a male and a female, 2 or more worms
A female alone can shed eggs, but not fertilized, infectious eggs
14
Q
Do adult worms replicate themselves in humans?
A
No - worms lay eggs, but the adult worms do NOT replicate
15
Q
How do we identify and diagnost nematodes?
A
They are identified by the characteristic morphology of their EGGS
KNOW YOUR EGGS!
16
Q
Some GI nematodes pass through other tissues. What other tissues can be infected during development?
A
Lungs and skin
17
Q
What is a good laboratory clue that your patient is infected with a nematode?
A
Increased levels of eosinophils
They are an immune response that fight off helminth infections
18
Q
What is the most comon helminthic infection encountered in the US?
A
Pinworm or Enterobius vermicularis
19
Q
What types of nematode infections fall in the category of Geohelminths?
A
- Nemotode infections that are acquired through contact with infected soil
- Larvae or eggs require a period of time to develop in warm, moist soil
20
Q
There are two groups of geohelminths. What are they?
A
Ingestion of an infectious egg
- Ascaris
- Trichuris
Penetration of the skin by an infectious larvae found in the soil
- Strongyloides
- Hookworms
21
Q
How do these helminths get in the soil?
A
Inadequate disposal of human waste, contamination of water supplies with sewage or the use of human waste as fertilizer
22
Q
What is the life cycle of a Pinworm or Enterobius vermicularis?
A
1 - Ingestion of an embryonated egg in the infective stage
2 - Egg hatches in the small intestine and the larva moves to the large intestine
3 - The larva penetrates the mucosa and develops there
4 - They mature to adults within 2-6 weeks
5 - Females migrate to the perianal region to lay eggs at night
6 - Males live in the cecum of the lumen
7 - Eggs are laid on the perianal folds, allowing for diagnosis of the infection
23
Q
How is a Pinworm or Enterobius vermicularis infection transmitted?
A
Fecal-oral route
- By the ingestion of eggs
24
Q
Why is reinfection common?
A
It can be easily transmitted within families
25
Can pinworms of other animals (the family dog) infect humans?
No
26
Are most Pinworm or Enterobius vermicularis symptomatic or asymptomatic?
Asymptomatic
27
When you do have a symptomatic infection, what will you see?
- Perianal itching
- Possibly a secondary bacterial infection from a lesion
- Some studies show appendicities (possible)
28
How do you diagnose a Pinworm or Enterobius vermicularis infection?
Identification of eggs or the appearance of adult worms in the perianal region
29
What does an egg from a Pinworm or Enterobius vermicularis infection look like?
Flat sided eggs
30
How can you see the eggs?
The scotch tape prep
View with microscope
31
How do you control and prevent a Pinworm or Enterobius vermicularis infection?
- Several anti-helminthic compounds
- Usually a single dose, repeated again 2 weeks later
- Good hygiene and housekeeping
32
What drugs can you use to treat a Pinworm or Enterobius vermicularis infection?
- Mebendazole
| - Pyrantel pamoate
33
Should you treat all household members?
Used to be the recommendation, not really anymore
34
The pinworm poem...
The pinworm is a parasite
That makes a journey every night,
From the intestine where it resides
To lay its eggs on the outside.
The usual symptom is an itchy bottom
Though in the appendix it can cause a problem.
It generally resides in tiny tots,
But can infect both moms and pops.
Its thin walled eggs float in the air
So they can end up anywhere.
So if tonight you start to squirm,
remember it might be this worm.
But, this nematode’s easy to diagnose
By affixing scotch tape to the host;
Then examining the microscopic slide
For eggs that are flatter on one side.
So if you have him, don’t be embarrassed
Anyone can have Enterobius vermicularis.
35
What is the trichuris trichiura parasite commonly called?
Whipworm because of its "whip-like" appearance
36
How much of the world's population is infected with whipworm or trichuris trichiura?
One quarter (25%)
37
What regions in the US do we see whipworm or trichuris trichiura infections?
Mostly tropical - found in Southeast US
38
How do you transmit whipworm or trichuris trichiura?
The fecal-oral route
- Contaminated soil
- Warm, moist soil promotes the development of eggs
39
What percent of infections of whipworm or trichuris trichiura are asymptomatic?
90%
40
What do you see in a symptomatic infection of whipworm or trichuris trichiura?
- Heavy worm burden (more than 200 worms in the body)
- Bloody, mucus containing diarrhea
- Frequent stools
- Rectal prolapse in children
- May contribute to growth retardation and anemia in children
41
How do you diagnose whipworm or trichuris trichiura?
Identification of eggs in the stool
42
How do you control or prevent whipworm or trichuris trichiura?
Proper sanitation and personal hygiene
43
What is ascaris lumbricoides commonly called?
Ascariasis
44
What is the life cycle of ascariasis or ascaris lumbricoides like?
Complicated
- Ingestion of eggs that have developed in the external environment over the course of 10-14 days
- The ingested eggs are in the infective stage
- They live in the lungs for 10-14 days
- They are coughed up and swallowed
- Adult ascariasis worms develop in the lumen of the small intestine
- Adults begin producing eggs
- Unfertilized eggs are found in feces and used for diagnosis
- The egg becomes fertilized in the environment, forms a two cell-stage, then undergoes advanced cleavage before being ingested in the infective stage
45
What is a key feature of a ascariasis or ascaris lumbricoides infection?
They are the largest, longest type of roundworm
You can actually see them and they're big
46
How many people in the world are infected?
1 billion
Including a few million Americans in the Southeast
47
How are ascariasis or ascaris lumbricoides transmitted?
Via the fecal-oral route
- Contaminated human feces
- Eggs need to develop in the soil before they are infective
48
Are humans the only reservoir for ascariasis or ascaris lumbricoides?
YES
The pig form rarely infects humans
49
Are most ascariasis or ascaris lumbricoides infections symptomatic or asymptomatic?
Asymptomatic
50
What will you see in the symptomatic disease?
A range from abdominal discomfort to death (rare)
51
What intestinal disease will you see with ascariasis or ascaris lumbricoides?
- The physical presence of adult worms in the small intestine
- Abdominal pain, indigestion, loss of appetite, vomiting, diarrhea
52
What will heavy ascariasis or ascaris lumbricoides infections cause?
A physical obstruction
53
What is the main concern when children have a ascariasis or ascaris lumbricoides infection?
Nutritional deficiency and growth retardation
54
What pulmonary disease will ascariasis or ascaris lumbricoides cause?
A combination of the physical presence and the immune response to the worms results in the following symptoms:
- Mild cough
- Pneumonitis (inflammation of the alveoli)
55
Why will we see these pulmonary symptoms?
Because parasite antigens are highly allergenic
Repeated exposure can cause an asthmatic attack
56
What is another clinical diagnostic test you can use to help with identification?
Eosinophilia is common
57
How do you diagnose ascariasis or ascaris lumbricoides specifically?
- Eggs found in stool
| - Larvae or eosinophils found in the sputum
58
How do you control and prevent ascariasis or ascaris lumbricoides infections?
Sanitation and hygiene
59
What do we commonly call a Necator americanus or Ancylostoma duodenale infection?
Hookworm
60
How many people in the world are infected with hookworm?
1 billion
61
What is hookworm (Necator americanus or Ancylostoma duodenale) a major contributor to?
Anemia in children and pregnant women
62
Where is Necator americanus found?
Southeast US
63
How is hookworm (Necator americanus or Ancylostoma duodenale) transmitted?
Larvae from fecal contamination of soil that are able to penetrate intact skin
64
Are there any animal reservoirs for human hookworms?
NO
65
What causes the anemia in hookworm?
Iron-deficiency anemia due to blood loss from hookworm feeding. If infection is severe enough this can result in fatigue, exertional dyspnea, koilonychias (brittle, spoon shaped nails), pale sclera, and heart murmurs.
66
What can happen to children infected with hookworm?
Children with severe infection can become protein malnourished due to blood loss.
67
What is "ground itch"?
Penetration of the skin - moderate dermatitis (“ground itch”).
68
What are two diseases that may accompany the larval passage though the lungs in a hookworm infection?
Pneumonia and eosinophilia
69
Which form of hookworm (Ancyclostoma or Necator) is more pathogenic?
Ancyclostoma
Ancylostoma consumes more blood than Necator; therefore it is usually considered more pathogenic.
70
How do you diagnose hookworm?
Presence of egg in the stool
71
How do you distinguish between Necator and Ancylostoma?
Distinguishing between Necator and Ancylostoma requires and examination of adult worms or larvae.
72
How do you prevent hookworm?
Sanitation and wearing shoes!
73
What do we commonly call a Strongyloides stercoralis infection?
Strongyloidiasis
74
What is the patient shedding in the stool?
Actual larvae
They will develop into free living eggs in the SOIL, not in your intestine
75
How big is a Strongyloidiasis or Strongyloides stercoralis worm?
It is the smallest of all nematodes (1-2 mm)
76
How many people world wide are infected with Strongyloidiasis or Strongyloides stercoralis?
50-100 million people
Mostly in the Southeast US and appalachia regions
77
What is a UNIQUE feature of Strongyloidiasis or Strongyloides stercoralis?
It can multiply in the host and in the environment
It is FREE living
78
How is a Strongyloidiasis or Strongyloides stercoralis infection transmitted?
Penetration of the skin by infectious larvae
79
What is meant by auto-infection or re-initiate infection of Strongyloidiasis or Strongyloides stercoralis?
***Infectious form larvae can develop in the intestine, penetrate the intestine, enter the bloodstream, and re-initiate infection (auto-infection).***
80
Are the symptoms of Strongyloidiasis or Strongyloides stercoralis typically severe?
No
There is a low worm burden, resulting in little symptomology
81
What are they symptoms of Strongyloidiasis or Strongyloides stercoralis if they arise?
Non-specific symptoms
- Epigastric pain and tenderness
- Bloating
- Heartburn
82
What will you see in the pulmonary stage of infection in Strongyloidiasis or Strongyloides stercoralis?
Pulmonary inflammation (eosinophilia)
83
What results in a hyperinfection from Strongyloidiasis?
Abrogation of the immune defenses
84
What is the process of abrogation of the immune defense?
increased numbers of filariform larvae leave the intestine resulting in a worsening of intestinal (diarrhea) as well as pulmonary symptoms.
85
What will result when a hyperinfection leads to a disseminated infection?
hyperinfection can develop into disseminated infection, resulting in the migration of larvae not only to the lungs and GI tract, but also the CNS, peritoneum, liver and kidney.
86
What populations do we see a disseminated strogyloidiasis infection in?
Individuals undergoing immunosuppressive therapy (glucocorticoides)
87
How do you diagnose strongyloidiasis infections?
Detection of LARVAE in the stool... Not eggs
** This is UNIQUE **
88
How do you prevent a strongyloidiasis infection?
Sanitation
Hygiene
Wear shoes
89
What type of infection will present with eggs that are flat on one side?
Pinworm
Enterobius vermicularis
90
What type of infection will present with eggs that are lemon or barrel shaped?
Trichuris trichiura
91
What type of infection will present with lumpy, bumpy eggs?
Ascaris lumbricoides (fertile)
92
What type of infection will present with boring/plain eggs?
Hookworm
93
A 36-year-old woman with a history of travel to Puerto Rico submitted a routine stool specimen. The images below were captured during wet mount examination of the concentrate from a stool specimen. The images are not on the same scale (see below). What is your diagnosis? Based on what criteria?
Ascaris and Trichuris
94
A 30-year-old woman discovered a worm in her stool (Figure A). She took the specimen to her doctor, reporting no symptoms or international travel. The specimen was preserved in 10% formalin and sent to CDC for identification.
Long, big worm
Ascaris
95
A concentrate (formalin-ethyl acetate technique) of a stool specimen was preserved in formalin. Figures A and B show a bright-field examination of the wet mount. The objects measured approximately 300 micrometers in length. What is your diagnosis? Based on what criteria?
Strongyloides
larvae, NOT eggs
