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Parasitology > 2.01 a - Blood and Tissue Nematodes > Flashcards

2.01 a - Blood and Tissue Nematodes Flashcards

1
Q

Members of the superfamily Filarioidea are

A

(the tissue roundworms) – arthropod-transmitted parasites of the circulatory and lymphatic systems.

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2
Q

Common Name of

Wuchureria bancrofti

A

Brancroft’s filaria

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3
Q

Common Name of

Brugia malayi

A

Malayan filaria

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4
Q

Common Name of

Loa loa

A

Eyeworm

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5
Q

Common Name of

Onchocerca volvulus

A

Blinding filaria

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6
Q

General life cycle of Filaroidea

A
  1. fertilized adult female filarae produce micro filariae
  2. migrate to lymphatics, blood or skin
  3. Arthropod (intermediate host) ingests microfilariae from the blood
  4. Larvae molt in the infective stage filariform larvae
  5. arthropod transmits filariform larvae to human (definitive host)
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7
Q

What is the general intermediate host of filiriae?

A

arthropod

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8
Q

What is the infective stage of filariae?

A

filariform larvae

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9
Q

What is the definitive host of filariae?

A

human

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10
Q

What specific is the intermediate host of:

Wuchureria bancrofti

A

Culex, Anopheles (mosquito- nocturnal feeding

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11
Q

What specific is the intermediate host of:

Brugia malayi

A

Mansonia, Anopheles

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12
Q

What specific is the intermediate host of:

Loa loa

A

Chrysops (fly)

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13
Q

What specific is the intermediate host of:

Onchocerca volvulus

A

Simulum (fly)

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14
Q

Which filariae adults are found in lymphatics?

A

Wuchureria bancrofti

Brugia malayi

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15
Q

Which filariae adults are found in blood?

A

Loa loa

Onchocerca volvulus

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16
Q

Which filariae are larger?

Females or Males?

A

females: 30 to 100 mm
males: 20 to 40 mm

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17
Q

What is the diagnostic stage of filiriae?

A

microfiliriae

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18
Q

Microfilirae reside in blood EXCEPT for

A

Onchocerca volvulus

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19
Q

What happens during infective stage of filiriae?

A

develop to infectious stage larvae in arthropod (intermediate host)

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20
Q

Method of Human Infection of filiriae?

A

infective larvae enter skin at arthropod feeding site

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21
Q

Disease caused by

Wuchureria bancrofti

A

invades lymphatics and causes granulomatous lesions, chills, fever, eosinophilia, and eventual elephantiasis

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22
Q

Disease caused by

Brugia malayi

A

invades lymphatics and causes granulomatous lesions, chills, fever, eosinophilia, and eventual elephantiasis

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23
Q

Disease caused by

Loa loa

A

chronic and benign disease; diagnosis: microfiliriae in blood, serology, Calabar swelling (a transient, subcutaneous swelling)

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24
Q

Disease caused by

Onchocerca volvulus

A

chronic and nonfatal; allergy to microfiliriae causes local symptoms-may cause blindness; diagnosis: adults in excised nodules; microfiliriae in skin snips of nodule

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25
Q

What is the migration of filiriae in the arthropod?

A

arthropod takes a blood meal; ingests microfiliriae

microfiliriae shed sheaths, penetrate fly’s midgut, and migrate to thoracic muscles

migrate to head and arthropod’s proboscis

arthropod takes a blood meal and L3 larvae enter bite wound

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26
Q

What techniques is used to diagnose microfilariae?

A

Locate microfilariae in stained blood smear - Knott technique

serology (lacks specificity)

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27
Q

What is the Knott technique?

A

Knott technique – used when filariasis is suspected, to concentrate the blood in order to increase the possibility of finding microfilariae.

 2% formalin is added to 2ml of blood to lyse RBCs, fix blood protozoa, and kill and straighten microfilariae.

 Centrifuge for 5 minutes at 1000 rpm.

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28
Q

Differentiation of Microfilariae in Stained Blood Smear

A

Examine for the presence or absence of sheath (a thin, translucent eggshell remnant covering of the body of the microfilaria and extending past the head and tail.

 Examine the tail area of microfilaria for the presence or absence of cells that exhibit characteristic array of stained nucleus.

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29
Q

Characteristics of

Bancrost’s filaria

A
  • sheathed
  • body gently curved
  • tail is tapered to a point
  • the nuclear column is loosely packed and do not extend to the tip of the tail
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30
Q

Characteristics of

Malayan filaria

A
  • sheathed measuring approximately 170-230mm and have 2 terminal nucleai that are distinctly separated from other nuclei in the tail
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31
Q

Characteristics of

eyeworm

A
  • kinked and sheathed
  • nuclei crowded extending
  • tip of the tail tapers
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32
Q

Characteristics of

blinding filaria

A
  • unsheathed, only about 150-350 um long
  • head is 2x longer than broad
  • no nuclei in tail tip
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33
Q

Disease name of

Wuchereria bancrofti

A

Elephantiasis, Bancroft’s filariasis

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34
Q

Disease name of

Brugia malayi

A

Malayan filariasis

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35
Q

Disease name of

Loa loa

A

Eye worm

36
Q

Disease name of

Onchocerca volvulus

A

Blinding filarial; river blindness

37
Q

What is elephantiasis?

A
  • In the early acute phase, fever and lymphangitis
  • After years of repeated exposure, chronic
    elephantiasis develops due to obstruction of lymphatics, lymph stasis and lymphadematous changes.
  • After death of the adult worm, a surrounding granulomatous thickening the lymphatic walls are formed causing obstruction and resultant enlargement below the blocked area.

aka Bancroft’s Filaria

38
Q

What is Malayan filariasis?

A
  • More often asymptomatic
  • In endemic areas, “filarial fevers” are seen with
    recurrent acute lymphangitis and adenolymphangitis
  • Topical eosinophilia (or Weingarten’s syndrome): resembles asthma with high eosinophilia and no
    microfilariae
39
Q

What is Topical eosinophilia?

A

(or Weingarten’s syndrome): resembles asthma with high eosinophilia and no
microfilariae

40
Q

What is eye worm?

A
  • Localized subcutaneous edema (Calabar swellings), particularly around the eye
  • Caused by microfilariae migration and death in
    capillaries
  • Dying adults induce a granulomatous reaction
  • Proteinuria and endomyocardial fibrosis can also occur
41
Q

What is Blinding Filaria; River Blindness?

A
  • Fibrotic nodules on the skin encapsulate adults
    (Onchocercomas)
  • Progressively severe allergic onchodermatitis (pigmented rash) develops
  • Blindness occurs from the presence of microfilariae
    in all ocular structures
  • Very prevalent in Africa and on central American
    coffee plantations
  • Onchocerciasis is the major cause of blindness in
    Africa; insect control is difficult because Simulium spp breeds in running water.
42
Q

Treatment for

Wuchereria bancrofti

A
  • Diethycarbamazine

- Ivermectin

43
Q

Treatment for

Brugia malayi

A
  • Diethylcarbamazine
44
Q

Treatment for

Loa loa

A
  • Diethylcarbamazine (also prophylactically)
45
Q

Treatment for

Onchocerca volvulus

A
  • Ivermectin
46
Q

Common name of

Trichinella spiralis

A

Trichnia worm

47
Q

What is the smallest human nematode parasite?

A

trichinella spiralis

48
Q

Infective stage of trichinella spiralis?

A

Encysted Larvae

49
Q

What is the habitat of trichinella spiralis?

A

striated muscle tissue

50
Q

What is a nurse cell?

A

trichinella spiralis larva encysted in the muscle cell

Granuloma forms around the nurse cell and becomes calcified over time

51
Q

Mode of transmission of trichinella spiralis?

A

Ingestion of raw/ undercooked contaminated meat

52
Q

How is trichinella spiralis diagnosed?

A

Diagnostic specimen: Skeletal muscle biopsy/ blood (LDH, Aldolase, CPK)

53
Q

Life cycle of trichinella spiralis

A
  • Trichinellosis is acquired by ingesting meat containing cysts (encysted larvae) of Trichinella
  • After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms
  •  After one week, the females release larvae
  •  The larvae migrates to the striated muscles where they encyst

- Encystment is completed in 4 to 5 weeks and the encysted
larvae may remain viable for several years.

- Ingestion of the encysted larvae perpetuates the cycle

54
Q

Host cycle of trichinella spiralis

A
  •  Rats and rodents are primarily responsible for its endemicity 
  • Carnivorous/ omnivorous animals feed on infected rodents 
  • Humans are accidentally infected when eating improperly
    processed meat of these carnivorous animals.
55
Q

Three phases of trichinella spiralis pathology

A

intestinal phase

migration phase

muscular phase

56
Q

Describe intestinal phase of trichinella spiralis pathology

A

shows small intestine edema and inflammation, nausea, vomiting, abdominal pain, diarrhea, headache and fever (1st week after infection)

57
Q

Describe migration phase of trichinella spiralis pathology

A

shows high fever, blurred vision, edema of face and eyes, cough, pleural pains, and eosinophilia lasting 1 month in heavy infection (death can occur during this phase)

58
Q

Describe muscular phase of trichinella spiralis pathology

A

shows acute local inflammation with edema and pain

Larvae encyst in skeletal muscles of limbs, diaphragm, and face

59
Q

Treatment of trichinella spiralis

A
  • Non life-threatening infection (self-limiting): rest, analgesics and antipyretics
  • Life-threatening infection: prednisone; thiabendazole (with caution due to side effects)
  • Cooking meat to 137F or freezing for 20 days at 5F will kill larvae
60
Q

Common name of Toxocara canis

A

Dog roundworm

61
Q

Disease name of Toxocara canis

A

Toxocariasis

62
Q

Mode of transmission of Toxocara canis

A

Puppies usually contract from the mother before birth or from her milk. At 3-4 weeks old, they begin to produce hundred thousands of eggs that contaminate the environment thru their feces.

63
Q

Diagnostic Exam of Toxocara canis

A

Peripheral blood.

Eosinophilia is the most important finding.

Serologic testing (ELISA, immunoblot); serum total IgE markedly increased.

64
Q

What is the most important finding in toxocariasis diagnosis?

A

Eosinophilia is the most important finding.

65
Q

Life Cycle of Toxocara canis

A
  • T. canis accomplishes its life cycle in dogs, with human as accidental hosts
  • Unembryonated eggs are shed in the feces dogs/puppies. Eggs embryonate and become infective in the environment.
  • Following ingestion by dogs, the infective eggs hatch and larvae penetrate the gut wall.
  • In younger dogs, adult worms develop and oviposit in small intestine.
  • In older dogs, larval encystment in tissues, reactivated in female dogs in late pregnancy and
  • Infect their puppies by the transplacental and transmammary routes.
  • T. canis can also be transmitted thru ingestion of paratenic hosts.
  • The life cycle is completed when dogs eat these hosts.
  • Humans are accidental hosts by ingesting infective eggs in
    contaminated soil.
66
Q

Humans are (accidental/definitive) host of t. canis

A

T. canis accomplishes its life cycle in dogs, with human as accidental hosts

67
Q

Where/when does t. canis become infective?

A

Unembryonated eggs are shed in the feces dogs/puppies. Eggs embryonate and become infective in the environment.
Following ingestion by dogs, the infective eggs hatch and larvae penetrate the gut wall.

68
Q

Where does t. canis infect in dogs?

A
  • In younger dogs, adult worms develop and oviposit in small intestine.
  • In older dogs, larval encystment in tissues, reactivated in female dogs in late pregnancy and
  • Infect their puppies by the transplacental and transmammary routes.
69
Q

How do humans become infected with t. canis?

A

Humans are accidental hosts by ingesting infective eggs in

contaminated soil.

70
Q

3 syndrome of toxacara infection (names)

A

Covert toxocariasis

Visceral larva migrans

Ocular larva migrans

71
Q

What is Covert toxocariasis ?

A

– mild, subclinical febrile illness in children. Symptoms include cough, difficulty sleeping, abdominal pain, headaches, behavioral problems.

72
Q

What is Visceral larva migrans?

A

– caused by migration of larva through the internal organs of humans. Symptoms: fatigue, anorexia, weight loss, pneumonia, fever, cough, bronchospasm, abdominal pain, headaches, rashes and
occasionally, seizures.

73
Q

What is Ocular larva migrans?

A

– migration of larva into the
posterior segment of the eye. Sympyoms: decreased vision, red eye, leokokoria (white appearance of pupil), unilateral visual loss, retinal fibrosis and retinal detachment can occur.

74
Q

Treatment of toxocariasis

A
  • In general, blood eosinophilia combined with a positive serologic test result indicates active toxocariasis and requires treatment.
  • Mebendazole or diethylcarbamazine kills the nematode larvae.
  • Prednisone can be used as an adjunct for patients with wheezing or other signs of inflammation.
75
Q

Prevention of toxocariasis

A
  • Dogs should be dewormed. Puppies should be dewormed at 2,4,6, and 8 weeks
  • Sandboxes should be covered when not in use.
  • Dogs feces should be disposed properly.
  • Wash hands before eating.
76
Q

What is scientific name of Rat lung worm?

A

Angiostrongylus cantonensis

77
Q

Rat lung worm is the most common cause of….

A

Most common cause of human eosinophilic meningitis.

78
Q

Final host and intermediate host of a. cantonensis

A
  • Final Host : Rat

- Intermediate Host : Snails & slugs

79
Q

Diagnostic exam for a. cantonensis

A

Diagnostic Exam : CSF examination with moderate to high WBC count; large numbers of Charcot-Leyden crystals in the meninges.

80
Q

Life cycle of a. cantonensis

A
  • Adult worms of A. cantonensis live in the pulmonary arteries of rats.
  • The females lay eggs that hatch, yielding first-stage larvae, in the terminal branches of the pulmonary arteries.
  • The first stage larvae migrate to the pharynx, are swallowed, and passed in the feces.
  • They penetrate or are ingested by an intermediate host (snail or slug).
  • After two molts, third-stage larvae are produced, which are infective to mammalian hosts.
  • When the mollusc is ingested by the definitive host, the 3rd stage larvae migrate to the brain where they develop into young adults.
81
Q

Which stage of a. cantonensis is infective?

A

After two molts, third-stage larvae are produced, which are infective to mammalian hosts.

82
Q

Humans are (definitive/incidental) hosts of a. cantonensis

A

Humans are indidental hosts of a. cantonensis

83
Q

Major pathology of a. cantonensis

A
  • Some infected people don’t have any symptoms – or have only mild symptoms that don’t last very long.
  • Sometimes the infection causes a rare type of meningitis (eosinophilic meningitis). The symptoms can include headache, stiff
    neck, tingling or painful feelings in the skin, low-grade fever, nausea, and vomiting.
84
Q

Treatment of a. cantonensis

A
  • There’s usually none since the parasite dies over time. Even people who develop eosinophilic meningitis usually don’t need antibiotics. Sometimes the symptoms of the infection last for several weeks or months, while the body’s immune system responds to the dying parasites.
    • The most common types of treatment are for the symptoms of the infection, such as pain medication for headache or medications to reduce the body’s reaction to the parasite, rather than for the infection itself. Patients with severe cases of meningitis may benefit from some other types of treatment.
85
Q

Prevention of a. cantonensis

A
  • Don’t eat raw or undercooked snails or slugs, frogs or shrimps, prawns
  • If you handle snails or slugs, wear gloves and wash your hands.
    • Always remember to thoroughly wash fresh produce.
  • When travelling in areas where the parasite is common, avoid
    eating uncooked vegetables.
86
Q

Which parasites affect the eyes?

A
  • Toxocara canis = Ocular larva migrans – migration of larva into the posterior segment of the eye. Sympyoms: decreased vision, red eye, leokokoria (white appearance of pupil), unilateral visual loss, retinal fibrosis and retinal detachment can occur.

Eye Worm (Loa Loa)
- Localized subcutaneous edema (Calabar swellings), particularly around the eye
- Caused by microfilariae migration and death in
capillaries
- Dying adults induce a granulomatous reaction
- Proteinuria and endomyocardial fibrosis can also occur

Blinding Filaria; River Blindness (Onchocerca volvulus)
- Fibrotic nodules on the skin encapsulate adults
(Onchocercomas)
- Progressively severe allergic onchodermatitis
(pigmented rash) develops
- Blindness occurs from the presence of microfilariae
in all ocular structures
- Very prevalent in Africa and on central American
coffee plantations
- Onchocerciasis is the major cause of blindness in
Africa; insect control is difficult because Simulium spp breeds in running water.

87
Q

Diethylcarbamazine is used to treat

A

Wuchereria bancrofti

Brugia malayi

Loa loa (also prophylactically)

Toxocara canis

Parasitology (4 decks)

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