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Y1B4 (RESP & RAU) 📙 > Parasitology 🪱 > Flashcards

Parasitology 🪱 Flashcards

1
Q

What is the geographical distribution of echinococcus granuloses?

A
  • Cosmopolitan, more in cattle raising countries.
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2
Q

what is Hyadatid cyst?

A
  • It is a cyst caused by the larval stage of Echinococcus granulosus cestode
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3
Q

What is a complex cyst composed of?

A
  • A complex cyst composed of daughter (and even grand-daughter cysts) inside and may be outside the mother cyst and contains several scolices.
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4
Q

What is the commonest type of hyadatid cysts?

A

uni-locular cyst.

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5
Q

What is hydatid disease (hydatidosis)?

A
  • It is the presence of hydatid cyst, larval stage of E. granulosus.
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6
Q

What are the commonest organs affected by hydatid disease?

A
  • The liver is the commonest organ affected (70%) followed by the lungs (20%), then the brain and other organs (10%).
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7
Q

What are the methods of infection of humans by hydatid disease?

A
  • Ingestion of eggs of Echinococcus species by the following ways:

✓ Ingestion of water or vegetable polluted by infected dog’s faeces.

✓ Handling infected dogs where hair is usually contaminated with eggs.

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8
Q

What is the morphology of unilocular hydatid cyst?

A
  • It is the larval stage of E. granulosus.
  • Size: 1-10 cm.
  • Shape: spherical enclosed in a fibrous capsule produced by the host.
  • The wall of the cyst has 2 layers:
    ✓ Outer laminated non-cellular layer.

✓ Inner cellular germinal layer which secretes the laminated layer and produces scolices, brood capsules and daughter cysts.

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9
Q

What are the contents of hydatid cyst?

A
  • Individual scolices (microscopic). “Forms the head after being ingested by dogs”
  • Brood capsules: Cysts formed by invagination of the germinal layer from which scolices develop.
  • Daughter cysts: Cysts formed of the 2 layers of the mother cyst, giving rise to scolices, brood capsules and even granddaughter cysts.
  • Hydatid fluid.
  • Hydatid sand: “all contents”
  • Detached scolices, brood capsules and daughter cysts that fall in the hydatid fluid are called hydatid sand.
  • Exogenous daughter cysts:
  • A daughter cyst is produced outside the mother cyst by herniation through the fibrous capsule, and may separate from it.
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10
Q

What is a sterile hydatid cyst?

A
  • The germinal layer fails to produce scolices, brood capsules or daughter cysts
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11
Q

What is an osseuse hydatid cyst?

A
  • Growth of hydatid cyst in bones is along the medullary cavity with erosion of osseous tissue.
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12
Q

What is alveolar or multilocular hydatid cyst?

A
  • It is the larval stage of another species Echinococcus multilocularis or Alveococcus multilocularis.
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13
Q

What are the characteristics of alveolar or multilocular hydatid cyst?

A
  • There is no laminated layer, hence the cyst has no regular shape and not defined from the surrounding tissue.
  • The germinal layer infiltrates the tissue.
  • There is no free fluid, but a jelly-like substance in irregular cavities separated by fibrous strands.
  • The central area of the cyst undergoes necrosis while growth continues at the periphery
  • Growth is neoplastic and metastasis occurs.
  • In man the cyst is usually sterile or produces only few scolices and brood capsules.
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14
Q

What does the pathogenicity of hydatid disease depend on?

A
  • Depend on the size of the cyst, the number and the organ affected
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15
Q

what is the clinical picture of hydatid disease?

A
  • Hepatic hydatid cyst:
    ✓ Indigestion, jaundice and discomfort in the right hypochondrium.
  • Pulmonary hydatid cyst:
    ✓ Dyspnea, cough, chest pain and hemoptysis
  • Cerebral hydatid cyst:
    ✓ Symptoms of increased intracranial tension and epilepsy.
  • Osseous hydatid cyst:
    ✓ Erosion and spontaneous pathological fracture of long bones.
  • Rupture of the cyst results in anaphylactic shock and transplantation of the germinal layer in other tissues producing secondary cysts.
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16
Q

How is hydatid disease diagnosed?

A

Clinical and laboratory diagnosis

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17
Q

What is the clinical diagnosis of hydatid cyst?

A
  • Slowly growing cyst with hydatid thrill in case of large abdominal cyst. “By palpation”
  • History of contact with dogs.
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18
Q

What is the laboratory diagnosis of hydatid Cyst?

A

Direct:
- Puncture and aspiration to demonstrate hydatid cyst (may lead to leakage of fluid and the risk of anaphylactic shock).

  • Radiological: X-ray, ultrasonography (U.S.), C.T. scans.
  • Blood examination reveals eosinophilia in 20-25% of cases.

Indirect:
- Serological methods: using hydatid fluid antigen for detection of antibodies by:

  • Precipitin reaction: equal parts of hydatid fluid and patient’s serum incubated at 37°C for 1 hour show flocculation in 36 hours.
  • ELISA and IHA.
  • Complement fixation test (CFT).
  • Latex agglutination test (LA).
  • Indirect fluorescent antibody test (IFA).
  • Immuno-electrophoresis test (IEP).
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19
Q

how is hydatid disease prevented and controlled?

A
  • Hydatid cysts found in slaughtered animals should be destroyed.
  • Pet dogs should be examined and dewormed periodically.
  • Avoid close contact and playing with stray dogs.
  • Avoid contamination of hands, food and drink with dog’s faeces.
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20
Q

How is hydatid disease treated?

A
  • Surgical treatment: Is recommended for unilocular cysts in accessible sites with pre- operative administration of Mebendazole. “First choice”

Sterilization: Some of hydatid fluid is replaced by 10% formalin for 5 minutes then the content is aspirated and repeatedly washed with saline or ethanol to kill the germinal layer and scolices causing cyst collapse.

Medical treatment:
- When surgical interference is impossible or contraindicated

  • Mebendazole can be used in high dose and for a long period (about 3 months up to one year), as the drug stop proliferation and spread of the cysts.
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21
Q

What is geographical distribution of Entamoeba histolytica?

A
  • Worldwide especially in tropical and poor communities.
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22
Q

What is the morphology of Entamoeba histolytica?

A

Three stages: ✓ Trophozoite ✓ Precyst ✓ Cyst

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23
Q

What are the diseases caused by Entamoeba histolytica?

A

Amoebiasis, Amoebic dysentery.

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24
Q

What is the definitive host of entamoeba histolyca?

A

Man

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25
Q

What is the reservoir host of Entamoeba histolytica?

A

Dog, rat, monkey

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26
Q

What is the habitat of Entamoeba histolytica?

A

Large intestine, especially caecum “Connection between a small and large intestine”

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27
Q

What are the stages of Entamoeba histolytica?

A
  • Entamoeba histolytica trophozoites
  • Entamoeba histolytica cysts
  • Entamoeba histolytica mature qudrinucleated cysts
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28
Q

What is the mode of infection with Entamoeba histolytica?

A
  • Ingestion of mature Entamoeba histolytica qudrinucleated cysts
  • Ingestion of cysts in
    ✓ Contaminated food or water.
    ✓ Flies and food handlers
    ✓ Faeco-oral.
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29
Q

What is the lifecycle of Entamoeba histolytica?

A
  • Trophozoites are found in the liquid stool as in diarrhea, or may undergo encystations
  • Cysts pass with faeces (never within the tissues).
  • Also trophozoite may invade the wall of large intestine by their lytic secretion to invade the host tissues through blood vessels (extra intestinal invasion as liver, lung, brain or skin, abscess formation).
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30
Q

What are the factors affecting the establishment of Entamoeba histolytica in the epithelium?

A
  • Number of organisms (↑ with large number)
  • Volume of the food (↓ with large volume)
    -Motility of the intestine (↓ with hypermotility)
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31
Q

What is the nature of entamoeba histolyca?

A
  • E. histolytica live in the large intestine usually as a commensal without producing any clinical manifestation but sometimes they change into pathogenic and attack the mucosa.
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32
Q

What do the pathogenic activities of Entamoeba histolytica depend on?

“The attacker, defender and the arena”

A
  • Resistance of the host (immunity status).
  • Virulence of amoeba (strain-number).
  • Local conditions of intestinal tract: physical or chemical injury of mucosa, carbohydrate diet, constipation “prolong its duration” and type of bacterial flora. “Interactions with parasitic infections”
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33
Q

What is the pathogenicity of entameoba histolytica?

A

Pathogenecity:

 Entamoeba trophozoites attach themselves to surface epithelium aided by E. histolytica lectin enzyme then start crawling over the mucosa.

 Depletion of mucus layer leads to contact between trophozoites and epithelial cells.

 Trophozoites secret proteolytic enzymes as amoeba pore leading to necrosis of epithelial cells

 Trophozoites enter the submucosa through the hole (pore), producing area of necrosis or nodular elevation with minute opening.

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34
Q

What is the outcome of infection entameoba histolytica?

A
  • Asymptomatic Cyst passer “mild”
  • Intestinal [Ulcer - Complications] “moderate”
  • Extraintestinal dissemination “severe”
35
Q

What are the types of extra-intestinal dissemination pathogenicity of Entamoeba histolytica?

“Kinda like hyadatd”

A
  • Amoebic liver affection: destruction of hepatocytes by trophozoites →abscess containing lysed hepatocytes, erythrocytes, bile and fat → yellowish to reddish colour (anchovy-sauce).
  • Pulmonary infection: direct extension from the liver or hematogenous.
  • Cerebral Abscess
  • Cutaneous lesions may be formed as a result of intestinal or hepatic fistula. (2ry bacterial invasion may complicate the picture of amoebiasis)
36
Q

What is the clinical picture of infection with amoeba? (Ameobiasis)

A

 Asymptomatic infections

 Symptomatic infections:

  • Intestinal amoebiasis:
    1. Acute (amoebic dysentery)
    2. Chronic colitis
    3. Amoebic granuloma (amoeboma)
  • Extra intestinal amoebiasis
    1. Complications of intestinal amoebiasis
37
Q

What are the characteristics of asymptomatic infection of entameoba histolyca? And what do the infected people represent?

A
  • Majority of cases, they complain of vague abdominal discomfort, constipation alternating with mild diarrhea.
  • These patients are cyst passers (Healthy carriers) and constitute a potential danger to others especially if they are food handlers.
38
Q

What is the clinical picture of extra intestinal amoebiases?

“But they are all kinda like hyadatid”

A
  • Depends on the site of infection
39
Q

What is the clinical picture of hepatic amoebiasis?

A

✓ Diffuse amoebic hepatitis or liver abscess

✓ Liver is enlarged, pain in upper right hypochondrium - - ->radiate to right shoulder

✓ Fever

40
Q

What is the clinical picture of pulmonary amoebiasis?

A

✓ Chest pain
✓ Cough
✓ Fever
✓ Chills
✓ Pulmonary consolidation

41
Q

What is the clinical picture of amoebic brain abscess?

A

✓ As brain tumour i.e. C/P of space-occupying lesions.

42
Q

What is the clinical picture of cutaneous amoebiasis?

A

✓ Direct invasion of genitalia.

43
Q

What does cutaneous amoebiasis results from?

A
  • Result from fistula formation (intestinal, hepatic or perineal lesions)
44
Q

How is extra intestinal amoebiasis diagnosed?

A

Clinical: According to the affected organs.

Laboratory:
- Examination of aspirate from abscess.
- The specimen must be taken from its border for detection of trophozoite stage.
- Leucocytosis: due to 2nd bacterial infection.

Radiology: Ultrasonography, CT & MRI.

Serologic tests:For detection of antibodies.

45
Q

How is infection with Entamoeba histolytica prevented and controlled?

A

☺ Health education.
☺ Safe water supply.
☺ Proper sewage disposal.
☺ Treatment of cases
☺ Repeated examinations of food handlers.
☺ Insect control.

46
Q

How is extra-intestinal ameobiasis treated?

A
  • Metronidazole followed by Diloxanide furoate as before plus Chloroquine phosphate (Resochin) for small abscesses.
  • Large abscesses require medical treatment and closed aspiration or surgical drainage.
47
Q

what is the geographical distribution of shistosoma hematobium?

A

Africa and Middle East, few cases reported in France.

“Bad hygiene in France?”

48
Q

What are the three main species of Schistosoma that infect human beings?

A
  1. Schistosoma haematobium: causing urinary schistosomiasis (present in Egypt).
  2. Schistosoma mansoni: causing intestinal schistosomiasis (present in Egypt).
  3. Schistosoma japonicum: causing oriental “‏شرق آسيا” schistosomiasis (not present in Egypt).
49
Q

What is the size, shape, tegument, genital system of the male of Schistosoma hematobium?

“‏خشن”

A
  • Size: 1 -2cm x l mm
  • Shape: Flattened, lateral margins are folded ventrally to form the gynaecophoric canal

Tegument: Provided with fine tubercles on the dorsal surface

Genital system: testes

50
Q

What is the size, shape, tegument, genital system of the female of Schistosoma hematobium?

A

Size: Longer (2 - 2.5 cm x0.25mm)

Shape: Cylindrical

Tegument: Smooth

Genital system: Ovaries and uterus

51
Q

What is the habitat of Schistosoma hematobium?

A

Habitat: Schistosoma haematobium adults live in the vesical and pelvic venous plexuses in man surrounding the kidney, pelvis, urinary bladder, urethra, prostate, seminal vesicles, lower 1/3 of uterus and vagina.

52
Q

What is the definitive host, intermediate host, reservoir host of Schistosoma hematobium?

A

-Definitive host: man.
-Intermediate host: snail “in water”
-Reservoir host: no reservoir host.

53
Q

What are the stages of the lifecycle of Schistosoma hematobium and what is infectious stage?

A

-Stages in life cycle: egg →miracidium→ sporocyst→ furcocercous cercaria→adult.

-Infective stage: furcocercus cercaria.

54
Q

Where is the egg of Schistosoma hematobium found?

A

Eggs sweep out in urine and rarely with feces.

55
Q

What are the characteristics of Schistosoma hematobium egg?

A

Size: 120 x 60 μ
Shape: Oval
Colour: Translucent
Shell: Thin with terminal spine
Contents: Mature miracidium

56
Q

What are the characteristics of the miracedium?

A
  • It hatches in fresh water
  • It is distributed homogeneously in water
57
Q

What are the steps of changing of miraciduim into cercaria?

A
  • It penetrates the soft tissue of the snail intermediate host, where it develops into first and second generation sporocysts, then cercariae that escape into water. Each miracidium gives rise to 250.000 cercariae. “Too much”
58
Q

what is the shape of furcocercus cercaria?

A

a. Body: 200 u in length with 2 suckers, primitive gut and penetration glands.

b. Tail: 300 μ in length, bifid or bi-forked. Forked cercaria is the infective stage.

59
Q

How much does the cycle of cercaria in the snail take?

A
  • The cycle inside the snail takes 1-2 months.

“Makes sense as it produces too many cercaria”

60
Q

For how long does cercaria survive in canal water and how is it attracted to the body of humans?

A
  • It survives in canal water for 48 hours and is attracted to man by the body temperature.

“Cercaria are in a timed Mission”
“They seek heat”

61
Q

What is the mood of infection by Schistosoma hematobium?

A
  • Infection occurs by skin penetration within minutes up to half an hour as water begins to dry, after bathing, washing or playing in infected canals. “Drying yourself very quickly is key”
  • Drinking water leads to infection when cercaria penetrates the mucous membrane above the gastric acidity that kills it. “Rare”
62
Q

What helps in penetration of skin by Schistosoma hematobium?

A
  • Penetration is helped by the penetration glands and mechanically by the tail activity.
63
Q

What happens to cercaria after it penetrates the skin?

A
  • The body “main” of cercaria enters the skin or mucous membrane leaving the tail (schistosomulum). It is carried by the blood→left side of the heart→ systemic circulation→intestinal capillary bed→intra-hepatic “first home” branches of the portal vein where it matures in 7 weeks.
  • Then male carries the female in the gynaecophoric canal and migrates out of the liver in the portal vein against the blood stream to reach the vesical and pelvic plexuses to deposit the eggs. “Against circumstances”
  • Eggs appear in urine 10 weeks after infection.
    “3 weeks after reaching vésical venous plexuses”
64
Q

What is the disease caused by Schistosoma hematobium?

A
  • schistosomiasis haematobium, vesical or urinary bilharziasis
65
Q

What are the stages of schistosomiasis hematobium?

A
  1. Invasion
  2. Migration
  3. Egg deposition and extrusion (early-acute stage)
  4. Tissue proliferation, repair and fibrosis (chronic-late stage)
66
Q

What is the cause of stage of invasion?

A

cercarial penetration

67
Q

What are the characteristics of stage of invasion?

A
  • Skin reaction in the form of local dermatitis, itching (bather’s itch), irritation and papular rash.
68
Q

What causes the stage of migration?

A

circulating schistosomules

69
Q

What are the characteristics of stage of migration?

“Still circulating”
“‏بكح بلغم ودم وباين عليه أعراض عامة”

A

a- Lung: verminous pneumonitis (small patches of inflammation) & hemorrhage, with cough, sputum & heamoptysis.

b- Liver and spleen: hepatosplenomegaly.

c- Metabolic products of maturing parasites “living” →toxic and allergic manifestations e.g. urticaria, fever, headache, cough, wheezes, muscle pain, leucocytosis & eosinophilia.

70
Q

What causes the stage of egg deposition and extrusion?

“الم ودم في البول”

A
  • active egg deposition with escape of eggs in urine→tissue damage and hemorrhage
71
Q

What are the characteristics of stage of egg deposition and extrusion?

A

a- Terminal haematuria (blood in the last part of micturation) which is due to increased contraction of bladder → injury of venules by egg spine→drops of blood in urine.

b- Frequency of micturation.

c- Dysuria (burning pain during micturation).

72
Q

What causes the stage of tissue proliferation, repair and fibrosis?

A
  • Eggs trapped in the wall of blood vessels stimulate both humoral and cellular immune response to miracidial antigen→aggregation of inflammatory cells around eggs (granulomas) and fibrosis with the formation of sandy patches, bilharzial nodules, papillomata which may ulcerate.
73
Q

What are the characteristics of stage of tissue proliferation, repair and the fibrosis?

“Complications”

A
  1. Inflammatory reaction heals by fibrosis :

a- Urinary bladder: polyps, ulcers, cystitis, contracted bladder, calcified bladder, malignancy (due to parasite toxic secretions).

b- Ureters: stricture, hydroureter.

c-Kidneys: hydronephrosis, 2ry infection (pyonephrosis) & renal failure.

d-Urethra: stricture, fistula.

e-Genital organs: pseudo-elephantiasis of the penis, granuloma in prostate, seminal vesicle, spermatic cord, ovaries, uterus and vagina.

  1. Embolic lesions: Schistosoma eggs are swept by blood to reach various organs (liver, lungs, brain or other organs).
  • Eggs swept from the pelvic and vesical plexuses→pulmonary artery branches produce granulomas and fibrosis with obliteration of blood flow→pulmonary hypertension, right ventricular hypertrophy and right sided heart failure (Bilharzial cor-Pulmonale).
74
Q

How is Schistosoma hematobium diagnosed?

“ELISA ——> In early acute infection”

A
  1. Clinically: history of terminal haematuria & dysuria in endemic area is suggestive. In mild infection, haematuria manifests only after muscular activity. Infection of seminal vesicle manifests by blood in seminal fluid.

“Infection in seminal vesicles = blood in semen”

  1. Laboratory:
  • Direct: Detection of eggs in urine, Cystoscopy, ELISA for circulating antigens & PCR
  • Indirect
75
Q

How are eggs of shishtosoma Hematobium detected in urine?

A
  • microscopic examination of last drop of urine sample for the eggs after sedimentation or centrifugation (concentration method). In 5% of cases, eggs can be detected in stool.
76
Q

When is cystoscopy done for Schistosoma Hematobium?

A
  • in chronic cases when eggs cannot be detected in urine, for histopathological lesions as well as eggs.
77
Q

What happens after detection of eggs of Schistosoma Hematobium?

A
  • Eggs should be examined for viability by the hatching test to differentiate between living and dead eggs: fresh water is added to the urine sediment and examined after 30 minutes by a hand lens to demonstrate swimming miracidia.
78
Q

What are the characteristics of living egg of Schistosoma hematobium?

A
  • Translucent
  • Intact moving miracidium, contracting and relaxing.
  • Surrounded by R.B.Cs.
  • Hatches in fresh water (Positive hatching test)
79
Q

What are the characteristics of dead egg of Schistosoma hematobium?

A
  • Opaque
  • Dead miracidium (not motile or silent)
  • No R.B.Cs
  • Does not hatch (Negative hatching test)
80
Q

What are the indirect methods done for the diagnosis of Schistosoma Hematobium?

A
  • Serological tests for detection of antigen antibody reaction.
  1. Indirect haemagglutination test (IHA).
  2. Indirect fluorescent antibody test (IFA).
  3. Enzyme-linked immunosorbent assay (ELISA): for antibodies detection. “Direct and indirect”
81
Q

How is shidtosoma hematobium treated?

A

Praziquantel (Biltricide or Distocide).

82
Q

How is schistosoma hematobium prevented and controlled?

A

(1) Protection (prophylaxis from infection)
(2) Treatment of cases: mass treatment by Praziquantel.
(3) Snail control

83
Q

How is prophylaxis from infection by Schistosoma Hematobium done?

A

A) Health education
-Should be directed mainly for school children. -Prevention of urination in or near water streams.

B) Personal prophylaxis
- By wearing boots and gloves, use of repellents e.g. dimethyl phthalate.

C) Quick and thorough drying of exposed wet skin

D) Pure water supply and sanitary disposal of excreta

E) Treatment of canals water to become safe
e.g. storage more than 48 hours, boiling or
addition of chemicals like chlorine to render it free from living cercariae.

Y1B4 (RESP & RAU) 📙 (8 decks)

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