Chapter 32: Helminths

Question 1

Which nematodes are acquired by ingesting their eggs?

Answer 1

Ascaris, lumbricoides, Trichuris trichiura, and Enterobius vermicularis

Question 2

What two nematodes are acquired by breaking through the skin?

Answer 2

Necator americanus and Strongyloides stercoralis = penetrates the feet.

Question 3

What nematodes is acquired by ingesting larvae?

Answer 3

Trichinella spiralis = found in undercooked pork

Question 4

What do Ascaris lumbricoides, Necator americanus, and Strongyloides stercoralis have in common?

Answer 4

They all pass into the lungs as one point in time through their life cycle before being coughed up and swallowed to mature within the intestines.

Question 5

Describe the Ascaris lumbricoides life cycle?

Answer 5

Ascaris egg is ingested
larvae emerge in small intestines
Larvae penetrate intestine wall and travel to lung
Larvae grow in lung, then coughed up and swallowed
Larvae in intestines for second time
Larvae fully mature to adults and get excreted

Question 6

Describe the Necator americanus life cycle?

Answer 6

Soil eggs hatch and release larvae > filariform larvae
Flariform penetrate between toes of human
Flariform travels directly to lung
Lung larvae grow and are coughed up and swallowed
Larvae reach intestine for first time
Larvae mature to adults and get excreted

Question 7

What are the possible Strongyloides stercoralis life cycles?

Answer 7

There are three possible cycles = autoinfection, direct and indirect
Direct = flariform larvae penetrate human foot
flariform larvae travels to lung
lung larvae grow and are coughed up and swallowed
Larvea reach intestine for first time
Larvae mature into adults and produce larvae, not eggs
Then the larvae pass out in stool
Indirect = Same uptake but leads to eventual sexual reproduction of adults after development to produce eggs that will mature to flariform larvae
Autoinfection = does NOT have uptake from foot
A current infection pass larvae from lungs to intestines
The larvae then reinvades the intestinal walls
They do not leave out in stool

Question 8

Ascaris lumbricoides have a range of severity from asymptomatic to a severe infection. As the worm grows it can block different passages. What can it block and what can it lead to?

Answer 8

These worms can invade the bile ducts, gallbladder, appendix, and liver. The more obvious infection of the intestines can easily lead to blockage of the food from passing through the GI tract. Due to the inhabitation of the intestines diagnosis is based on eggs in stool.

Question 9

What are the main differences between Necator americanus and Ancylostoma duodenale?

Answer 9

They are both hook worms that enter the body but,

Necator moves directly from foot to lung and Ancylostoma moves to intestines before lung.

Question 10

Hook worms present like many intestinal worms but can develop iron deficiency anemia. What is the cause of the loss of iron in infections with this type of organism?

Answer 10

Hook works tend to feed on the blood of the host causing a blood loss = iron loss.

Question 11

What are some symptoms a host presents due to a hook worm going through its cell cycle?

Answer 11

The site of entry for a hook worm = itchy rash = foot
intestines = diarrhea and ab pain
lungs = cough and infiltrates
eosinophilia

Question 12

Strongyloides stercolarlis present like many worms except for the fact that it causes vomiting and abdominal bloating not just pain. Why should you not this patient some sort of prednisone?

Answer 12

Prednisone is an immunosuppresive drug and any drugs like that can cause the worm to spread and invade during filariform larvae stage. The worms can pass back into intestinal walls, lungs, or other organs. This can lead to pneumonia, COPD, ARDS, and multi-organ failure.

Question 13

Unlike other worms, Trichinella spiralis moves from intestines to what types of tissue?

Answer 13

After maturation in the intestines the worms tend to invade muscle tissue. This includes skeletal muscles causing muscle aches and fever. The worms can even invade areas like the heart and brain which are usually fatal.

Question 14

What is usually found high in serum with a Trichinella spiralis infection?

Answer 14

Eosinophils and creatinine phosphokinase a skeletal muscle enzyme released with their degradation.

Question 15

Eating what tasty treat causes Trichinella spiralis?

Answer 15

BACON and other pork products that are not cooked properly

Question 16

What are some characteristics that set Trichuris trichiura and Enterobius vermicularis apart from the other worms that infect the intestines and cause diarrhea?

Answer 16

These two worms are not “hookworms” and do not have a filariform larvae stage. The Worms actually don’t leave the intestines at all like the other worms meaning there is no invasion on the lungs to cause cough or infiltrates. Also because there is no leaving the intestines, the eosinophil level is held normal.

Question 17

What is the general life cycle of Trichuris trichiura and Enterobius vermicularis?

Answer 17

Eggs incubate in moist soil and cover whats in the soil
Humans ingest a food that is contaminated w/ eggs
Eggs hatch in the GI and migrate to cecum/ascending
The larvae mature to adults and lay eggs
they produce 1000s a day.
Trichuris passes them in stool to be incubated in soil
Enterobius eggs are placed on the perinium to hatch
this causes itching which reinfects host or others

Question 18

What is the scotch tape test?

Answer 18

Gross. That’s what it is.
It is when a person takes a piece of tape and places it over the perianal area and microscopically can see eggs of Enterobius vermicularis.

Question 19

How are blood and tissue nematodes transmitted to a human host?

Answer 19

They require an arthropod vector and when the animal bites the human it transmit the worm.

Question 20

Describe some major differences between life cycle of the intestinal worms and blood and tissue worms?

Answer 20

The intestinal worms all required of their cycles to be in the intestines and in the lungs. The blood and tissue worms are found as adults in the lymph tissue and have live births of offspring that burrow through tissue into the blood stream and other organs.
These blood and tissue words are from the family Filarioidae = filariae with offspring called microfilariae

Question 21

What bacteria live within the filarioidae worms to aid in their infectivity?

Answer 21

Wolbachia is the bacteria that lives within these worms and they are similar to Rickettsia. Killing these bacteria can actually lead destruction of the worms.
This bacteria from the dead worms + microfilariae cause allergic reactions inside infected patients.

Question 22

Describe the species, vector and associated symptoms of the colloquial “river blindness”.

Answer 22

This is an infection of Onchocerca volvulus passed by black flies especially where they breed near water in Africa and Central and South America. This infection leads to microfilariae that migrate through dermis and connective tissue to create pruritic skin rashes with darkened pigmentation. Thin can thicken to create intraepithelial granulomas = lizard skin.
The reason for blindness is due to invasion of the cornea which can be seen with a lamp examination.

Question 23

What are the two organisms associated with Elephantiasis and how does it occur?

Answer 23

Wachereria bancrofti (pacific islands and africa) and Brugia malayi (SE Asia) are known to cause this disease by clogging up the lymphatic system with dead worms. The worms are injected by mosquitos that lead to microfilariae and adult filariae in the lymph vessels and nodes. This can cause febrile events and enlarged lymph nodes that can have fibrous tissue form around the dead worms. The fibrous tissue leads to swelling of lymph nodes of the lower extremities, legs and genitals. This will also be paired with thickening and scaly skin production over the areas of swelling.

Question 24

How and when do you tests for elephantiasis?

Answer 24

The main test is to look at blood draws at night time for the presence of worms in the sample. For an unknown reason the worms tend to be mobile in the blood stream at this time.

Question 25

How does Dracunculus medinensis differ from the other blood and tissue nematodes?

Answer 25

This nematode is swallowed from dirty water before entering into the subcutaneous tissue.

Question 26

Describe the species, vector, and associated symptoms of a Guinae worm infection.

Answer 26

This is Dracunculus medinensis which is spread from water that contain copepods which harbor the worms in Africa = Ghana and the Sudan. The worm enters the intestines and burrows to subcutaneous tissue and mate. The females then grow in the tissue up to 100 cm
The female will pock out the uterus out of the skin to deposit young into water when bathing.
While infected the individual will have allergic reactions to the worm = nausea, vomiting, hives, and shortness of breath especially during larval release.
They take them out by slowly wrapping the end of the worm around a stick. More gross…

Question 27

What are cutaneous larval migrans and are they an organism?

Answer 27

Larval migrans are cutaneous reactions to hookworms that have spread from hookworms from dogs and cats when they affect a human. The movement of the larvae in the epidermis causes an allergic reaction that result in red, raised skin in the path of the hookworm.
The migrans are not an organism. They are simply a manifestation of a reaction to an organism.
Dog hookworm = Ancylostoma braziliense
this can also be seen in Necator americanus and Strongyloides stercoralis.

Question 28

What are the two major Platyhelminths?

Answer 28

Trematodes = flukes = schistosomes
Cestodes = tapeworms

Question 29

What is the life cycle of Shistosoma?

Answer 29

The life starts at eggs in freshwater which are taken up by snails = matures within the snail
The larvae formed are released into freshwater
These tadpole like worms infect humans = open skin
Travels to intrahepatic portion of portal venous system
They mature and mate then move to different area
japonicum/mansoni = intestines Haem = bladder
Can move into lumen and release eggs in feces or urine
The eggs do not hatch inside the body = need water
There is no immune response to adults due to possible mimicry, but eggs and mature larvae are attacked.

Question 30

What are the associated symptoms of blood flukes and in what specific order do they occur?

Answer 30

1. Dermatitis at penetration site.
   itchy skin
2. Katayama fever during egg laying 4-8 weeks
   fever, hives, headache, weight loss, and cough
3. Chronic fibrosis
   the eggs released in the veins go to brain, liver, lungs and cause granulomas = fibrosis of sites of egg implantation.

Question 31

What are the disorders that can occur with fibrosis of blood vessels due to egg implantation?

Answer 31

Fibrosis can lead to blockage of the portal venous system and cause portal hypertension causing increased pressure on the spleen.
Any blood vessel can be blocked and affected = inflammation and ulcers
May also develop hematuria, ab pain, diarrhea, brain and spinal injury, and pulmonary artery hypertension.

Question 32

What stage of Schistosoma is known to have eosinophilia?

Answer 32

Katayama fever due to egg presence.

Question 33

What are the anatomical features of the tape worm?

Answer 33

The head has hooks, suckers and is called a scolex
Immature proglottids > mature proglottids
Mature = hermaphroditic organs
Gravid = uterus full of fertilized egg and genital pore
The ends can break off and pass in feces

Question 34

How do tape worms feed?

Answer 34

They do not have a developed digestive tract and must use a host to extract nutrients that have already been partially digested.

Question 35

What nematodes are associated with pork and beef tapeworms and what is the normal cycle and infection?

Answer 35

Pork tapeworm = Taenia solium = like sodium = bacon
Beef tapeworm = Taenia saginata = sagittarius = taurus
Eggs are ingested by pigs from human feces.
Egg hatches in pig moves through intestines/muscle
Undercooked meat = larvae = cysticercus
Larvae matures to adult tapeworm and continues cycle
This doesn’t usually cause problem just eggs in stool

Question 36

What is Cysticercosis?

Answer 36

Taenia solium eggs are ingested by human not the intermediate animal, the pig.
The larvae then invade the brain and skeletal muscles.
Brain = Neurocysticercosis = cysts of brain that leads to seizures, hydrocephalus and focal neuro deficits.
The worms can continue to grow for years and die
Death leads to fluid leakage and causes inflammation
Seizures, meningitis, hydrocephalus and focal deficits
Many areas = the most common cause of seizures
Revealed with calcified cysticerci and up eosinophils

Question 37

What is the fish tapeworm and how does it differ from his quadroped friends?

Answer 37

Diphllobothrium latum is large growing tapeworm that has two intermediate hosts before infecting a human.
Eggs from humans to water > convert to motile
Motile ingested by crustaceans > ingested by fish
Fish is ingested by humans
this can cause a few ab problems > absorbs B12
Causes anemia

Question 38

What is Hyenolepis nana?

Answer 38

This is the dward tapeworm and is the smallest tapeworm to affect humans and does not have an intermediate host.

Question 39

Which life cycle does Echinococcus granulosus most closely resemble?

Answer 39

Taenia solium when humans ingest the eggs not the larvae.
The exception is when the eggs invade they form hydatid cysts in Echinococcus = budding cysts in the liver, lungs and brain.

Question 40

What problems occur with hydatid cycts?

Answer 40

The cysts can compress on the lungs, liver and brain causing problems with them
Worse off = bursting of a cyst
this contains fluid that is creates an extreme allergic reaction = fatal many times.
they can also be mistaken for malignancies