Nematodes- tissue nematodes

Question 1

Which three species of nematodes cause lymphatic filariasis?

Answer 1

Wucheria bancrofti, Brugia mlayai, Brugia timori

Question 2

What condition does lymphatic filariasis develop into?

Answer 2

when it is chronic, it becomes elephantiasis

Question 3

What is the distribution of Wucheria bancrofti?

Answer 3

primarily in Africa, South America, and other tropical and sub-tropical countries

Question 4

What is the vector for Wucheria bancrofti?

Answer 4

mosquitoes that feed at night

Question 5

When do the Wucheria bancrofti microfilariae appear in the peripheral circulation?

Answer 5

at night. they are nocturnal

Question 6

Where are adult Wucheria bancrofti found in the body?

Answer 6

in the lumen of the lymphatic vessels. have been found in all lymphatic tissue, including adjacent subcutaneous tissues

Question 7

Which sex of Wucheria bancrofti is bigger?

Answer 7

the female

Question 8

Define ovoviviparous

Answer 8

when embryos develop inside the egg and are retained in the mother’s body until they are ready to hatch

Question 9

In which parts of the body are Wucheria bancrofti more common?

Answer 9

in the upper and lower extremities and the male genitalia

Question 10

What are the Wucheria microfilariae ensheathed in?

Answer 10

a sheath of chitin that may be a remnant of the egg

Question 11

Describe the path taken by the microfilariae

Answer 11

1. migrate between the lymphatic system and the bloodstream. during the day the aggregate in the lung capillaries.
2. when ingested by a mosquito, they penetrate the stomach and move to the flight muscles.
3. undergo 3 molts into L3 larvae
4. move to the mosquito mouth parts

Question 12

Why is it hypothesized that not all patients have the same symptoms to elephantiasis?

Answer 12

they think it is because different people have a different chance of activating their Th1 or Th2 response

Question 13

What is the asymptomatic phase of W. bancrofti infection?

Answer 13

marked by a high microfiliarae infection but is asymptomatic

Question 14

What is the inflammatory/acute phase of W. bancrofti infection?

Answer 14

female worm Ags elicit an inflammatory response. Worms block lymph. symptoms include fever, chills, skin infections, painful lymph nodes, tender skin

Question 15

What is the obstructive/chronic phase of W. bancrofti infection?

Answer 15

marked by elephantiasis.
lymphatic dysfunction causing lymphedema and elephantiasis
scarring of affected areas occurs, as well as thickening of the skin

Question 16

How can Wucheria bancrofti infection be diagnosed?

Answer 16

a blood smear taken from when the jevenile worms are in the periphery of the blood circulation
PCR is also effective

Question 17

How can Wucheria bancrofti infection be treated?

Answer 17

severe symptoms can be avoided by cleansing the skin, surgery, or drugs (diethylcarbamazine, ivermectin, or albendazole). diethylcarbamazine is the drug of choice
no vaccines developed

Question 18

How can Wucheria bancrofti infection be controlled?

Answer 18

mosquito control.

mosquitoe vector has a preference for human blood, W. bancrofti has no known reservoir

Question 19

Which parasite causes river blindness?

Answer 19

Onchocerca volvulus

Question 20

Which parasite species cause subcutaneous filariasis?

Answer 20

Onchocerca volvulus
Drancunculus medinensis
Loa loa
Mansonella streptocerca

Question 21

What are the hosts of Onchocerca volvulus?

Answer 21

only known to affect humans, no reservoir host.

Question 22

How is Onchocerca volvulus spread and in which niches?

Answer 22

transmitted through black fly (Simulium species), which are predominantly found near rivers

Question 23

What problems does Onchocerca volvulus infection lead to?

Answer 23

fourth leading cause of blindness, worst disfiguring dermatitis second to polio

Question 24

What has greatly reduced the occurrence of Onchocerca volvulus infection in endemic areas?

Answer 24

ivermectin program. one dose given to everyone each year, donated by Merck

Question 25

Which parasites are ovoviviparous?

Answer 25

Wucheria bancrofti, Onchocerca volvulus, and Dracunculus medinensis

Question 26

Describe the male and female worm association in Onchocerca volvulus infection

Answer 26

the female is much longer, and the two are often found intertwined

Question 27

Where are the microfiliarae found in the body?

Answer 27

produced in the nodules and migrate throughout subcutaneous tissue

Question 28

Describe the pathology of Onchocerca volvulus infection

Answer 28

• dead microfiliarae cause inflammatory reactions. Live worms cause dermatitis, eye lesions, and onchocercomas.
• lesions are due to immune system attacking worm Ag
• the higher the infection, the worse the symptoms are
• lesions on the cornea= keratitis

Question 29

How can Onchocerca volvulus infection be diagnosed?

Answer 29

take skin from affected region

serological tests measure IgG. it is sensitive but not very specific

Question 30

How can Onchocerca volvulus infection be treated?

Answer 30

ivermectin blocks the release of microfiliarae from the females, but does not kill adults. need to keep giving ivermectin to stop infection (live 10-15 years)

Question 31

How can Onchocerca volvulus infection be controlled?

Answer 31

giving ivermectin once a year for 10-15 years

controlling black fly population

Question 32

Which worm species is the longest nematode and also causes Guinea worm disease?

Answer 32

Drancunculus medinensis

Question 33

How is Drancunculus medinensis transmitted?

Answer 33

through the cyclops (crustacean) in infected waters

Question 34

Where does Guinea worm disease (drancunculiasis) occur?

Answer 34

only in Africa, a few villages in the Rajastan desert of India, and Yemen

Question 35

Where do the female and male Dracunculus medinensis worms reside in the body?

Answer 35

in subcutaneous tissue, usually in the lower extremities. both have curved tails to anchor them to tissues

Question 36

Describe the Dracunculus medinensis life cycle

Answer 36

1. female adult releases microfiliarae into water.
2. the copepods ingest the microfiliarae, which develop into L3 larvae
3. humans eat infected copepods
4. larvae penetrate wall of small intestine and migrate through connective tissue.
5. two more molts until adult stage
6. gravid females migrate through subcutaneous tissue to extremeties, causing ulcers
7. ulcers burst when in contact with water, releasing microfiliarae

Question 37

What is the pathology of Dracunculus medinensis infection?

Answer 37

multiple cutaneous blisters and ulcers
allergic rxns occur before ulcer bursts or when trying to remove worm
secondary bacterial infections from ulcers if untreated (tetanus, gangrene, death)

Question 38

How can Dracunculus medinensis infection be diagnosed?

Answer 38

locating the head of the adult worm in the skin

identify larvae that are released in the water

Question 39

How can Dracunculus medinensis infection be treated?

Answer 39

need to wind the worm on a stick very slowly, over days, to remove it without breaking it
sometimes surgical removal is possible

Question 40

How are most Dracunculus medinensis infections prevented?

Answer 40

transmission is seasonal, cases are easily detected, methods of control (water purification) are very simple