30 Parasitology 2: Tissue nematodes

Question 1

What types of hypersensitivity does larva migrans (e.g. Toxocara canis, Ancylostoma brazilense) cause?

Answer 1

I and IV

Question 2

T/F- clinical features of visceral Toxocara disease (larva migrans) include allergic manifestations, granulomas, and possibly death due to effects on the heart, lungs, and brain

Answer 2

true

Question 3

Trichinella spiralis causes 100,000 cases of trichinosis in the US/year. What is the life cycle of this organism?

Answer 3

• animals ingest encysted larvae from striated muscle
• excystment occurs leading to adults in the large intestine
• mate and release larvae where they penetrate into tissues and encyst in striated muscle

Question 4

Although trichinosis is mostly subclinical, what are some possible clinical features?

Answer 4

muscle weakness, fever, nausea, diarrhea, myositis, granulomas, sudden death

Question 5

How is trichinosis diagnosed and treated?

Answer 5

• Dx: eosinophilia and remarkable history of eating undercooked meat, serologic tests for antibodies, biopsy.
• Tx: corticosteroids, mebendazole (prevents new larvae production)

Question 6

T/F- filaria are adults and give rise to microfliaria in the blood which are embryos and eaten by a vector where they develop into infective larvae, which are transmitted to humans

Answer 6

true

Question 7

How is non-optimal antibiotic therapy harmful in filarial disease?

Answer 7

can drive microfilaria into tissues causing sudden death

Question 8

What causes elephantiasis? How are these transmitted?

Answer 8

Wuchereria bancrofti and Brugia malayi

Transmitted by mosquitos

Question 9

How would you treat elephantiasis or filarial fever?

Answer 9

antihistamines, corticosteroids, diethylcarbamazine, surgery

Question 10

Where is Loa loa found? How is it transmitted? What swellings are characteristic of this infection? How is it treated?

Answer 10

• West africa
• transmitted by deer fly
• Calabar swellings (type I hypersensitivity)
• surgical removal and diethylcarbamizine

Question 11

What condition does Onchocerca volvulus cause? How is it transmitted? How is it treated?

Answer 11

• River blindness in tropical areas (4th leading cause of blindness)
• Transmitted by Simulium
• Ivermectin is drug of choice, or diethylcarbamazine + corticosteroids

Question 12

T/F- Dracunculus medinensis is Guinuea worm in equatorial africa, very long (up to 100 cm), acquired from drinking water where “cyclops” is infected with larvae and causes type I hypersensitivity reactions and increases risk of tetanus

Answer 12

true

Question 13

Cestodes are commonly known as what?

Answer 13

tapeworms

Question 14

What does infections with cestodes often cause when the encysted larvae develop in tissues?

Answer 14

cysticercoids

Question 15

Are these matched correctly?
Taenia saginata-pork tapeworm
Taenia solium- beef tapeworm

Answer 15

No, those are backwards

Question 16

What’s the most common cause of acquired epilepsy in the world?

Answer 16

cysticercosis (tapeworm infection)

Question 17

How is a tapeworm infection treated?

Answer 17

niclosamide (inhibits energy production), praziquantel (spastic paralysis in worm), albendazole (inhibits microtubule synthesis)

Question 18

Does Schistosoma mansoni cause intestinal or urinary schistosomiasis? How about S. japonicum? How about haematobium?

Answer 18

• S. mansoni: intestinal
• S. japonicum: intestinal
• S. haematobium: urinary

Question 19

Describe the blood fluke life cycle

Answer 19

• eggs hatch and release ciliated miracidia (larvae) that infect snails
• snail releases circariae that invade human skin
• migrate to lungs, acquire antigen coat
• mature, migrate to liver, mate
• release 3,000 eggs/day

Question 20

Clinical features of blood flukes?

Answer 20

• Katayama fever (acute): malaise, fever, hives, abdominal pain, hepatic tenderness, CNS effects, immune complex disease
• chronic granuloma formation (hepatic), GI symptoms, painful urination, baldder cancer, anemia, pulmonary dysfunction

Question 21

What is swimmers itch? how is it treated?

Answer 21

US form of schistosomiasis in which larvae that cannot develop in humans burrow into subQ areas and cause rash, fever, malaise, and hives
Tx: corticosteroids

Question 22

How is schistosomiasis treated and diagnosed?

Answer 22

Dx: based on symptoms, looking for eggs
Tx: praziquantel

Question 23

A 30 yr old man is windsurfing, he walks along the edge of the lake to his car. 2 days later he has intense itching lesions on both legs and is diagnosed with swimmers itch caused by bird schistosomes. What is he given to clear this infection?

Answer 23

topical cortisone cream

Question 24

What type of hypersensitivity do blood flukes cause after they invade the human skin and lose their tails, forming metacercariae or schistosomulas?

Answer 24

type I

Question 25

What type of hypersensitivity do blood flukes cause after they migrate to the liver, feed and mate there?

Answer 25

type III aka “katayama fever”

Question 26

What type of hypersensitivity do blood flukes cause after they release (about 300) eggs per day?

Answer 26

type 4 hypersensivitiy (granulomas)