Parasitology 🪱 Flashcards

Question

what is the pathogenesis **(clinical picture)** of Enterobius vermicularis?

Answer 1

**Due to migration of the gravid female worm: perianal, perineal and vaginal irritation.** 1) Local irritation and discomfort, with nocturnal itching. 2) Vaginitis and salpingitis. Granulomas are formed around eggs or worms. 3) **Pruritis ani:** due to nocturnal migration of the female worm on the perianal skin with worm like movement, skin sensitization by ruptured worms, striations on the cuticle cause skin irritation and sticky material on the egg causing irritation. 4) Obstructive appendicitis rarely occurs.

Answer 2

1) **Clinical:** Pinworm infection **2) Laboratory:** Detection of adult worms and/or eggs ▪ In stool: (only 5%), when uterus of gravid female ruptures. ▪ In urine of female patients. ▪ On perianal region by swab: this must be done early in the morning before defecation or bathing and should be repeated for several days before the patient is considered free

Answer 3

- Scotch adhesive tape swab - Vaseline swab - National Institute of Health (N.I.H.) swab

Answer 4

- a piece of scotch tape, hold over a tongue depressor is rolled over the perianal skin and removed. - The adhesive tape is put on a slide with a drop of toluene and examined for eggs.

Answer 5

- the perianal skin is swabbed with a piece of cotton soaked in Vaseline and the swab is put in a mixture of ether and water to dissolve the vaseline. - The mixture is centrifuged and the deposit is examined for eggs.

Answer 6

- it is a piece of non-adhesive cellophane fixed to a glass rod. - The glass rod is inserted through a perforated stopper in a test tube. - The perianal skin is swabbed in the morning by the cellophane paper. - The cellophane paper is united, spread between 2 slides with a drop of toluene and examined for eggs.

Answer 7

❖ Mebendazole (Vermox) ❖ Flubendazole (Fluvermol) ❖ Pyrantel pamoate (Combantrin) as a single oral dose and a 2nd dose must be given after 2 weeks to prevent re-infection.

Answer 8

1) Mass treatment of the whole companions of the infected person. 2) Personal cleanliness. 3) Protection of food and drink from contamination by dust and hands of patients.

Answer 9

Small intestine (Jejunum)

Answer 10

sheathed filariform larvae

Answer 11

Egg → rhabditiform larva→ infective filariform larva (IFL) → adult

Answer 12

- Adults live in the small intestine of man attached by the mouth capsule to the mucosa. Immature eggs pass in the feces. - Under favorable environmental conditions in the soil (moist shaded areas, sandy or loose soil, alkaline and free of salinity, suitable temperature and sufficient oxygen), a rhabditiform larva develops and hatches in about 2 days. - It moults again after about 7 days (keeping its skin; ensheathed) to become an infective filariform larva. - Filariform larva penetrates human intact skin or mucous membrane of the mouth. - The filariform larva is attracted to man by histo-tropism and by warmth of the body (positive thermo-tropism). - It shows other tropisms to various factors, e.g. negative geotropism and positive hygro-tropism. - The larvae on reaching the blood are carried to the right side of the heart → the lungs → penetrate the capillaries into the alveoli → pass up the tracheal tree, over the epiglottis → swallowed to reach their final habitat in the small intestine. - During their migration in the lung they moult giving the adult stage in the small intestine.

Answer 13

**1- Ground itch:** local dermatitis caused by FL penetration at the site of entry or contact with soil (feet, buttocks, hands). **2- Cutaneous larvae migrans:** caused by FL migration in the skin. Appear as maculopapular rash and itching (± pustules due to 2ry infection). **3- Verminous pneumonia (Loffler’s syndrome):** caused by FL migration in the lungs. It is presented by fever, cough, dyspnea, haemoptysis and oesinophilia (transient symptoms < 2 weeks). **4- GIT symptoms:** colic, vomiting, diarrhea. **5- Chronic iron-deficiency anaemia** (hypochromic, microcytic ) due to blood loss.

Answer 14

1.Tear by buccal capsule, curved teeth and cutting plates → ulcer → haemorrhage. 2. Anticoagulant secretion by cephalic glands continued bleeding after detachment. 3. Toxic bone marrow depression. 4. Enteritis (due to 2ry infection) decrease absorption of iron.

Answer 15

**1) Clinical:** the clinical picture. **2) Laboratory:** finding the eggs in stool.

Answer 16

1) Mebendazole (Vermox) or Flubendazole. 2) Pyrantel pamoate (combantrin). 3) Supportive treatment: Iron, vitamins and high protein diet.

Answer 17

- Mass treatment of the infected population. - Sanitary disposal of human faeces and not to use them as fertilizer. - Wearing shoes and gloves for people handling mud or working in mines, gardening, poultry and brick-making.

Answer 18

Tropical and subtropical areas.

Answer 19

- Parasitic female: 2.2 **mm** in length with cylindrical oesophagus - Male: 0.7 mm in length with ventrally-curved posterior end - Free-living female: 1.1 mm in length with rhabditiform oesophagus.

Answer 20

- Seldom found in stool; sub-mucosa or in soil hatches after 2 hours. - Size: 55x30 μ - Shape: oval, very thin shell - Colour: translucent - Contents: mature rhabditiform larva.

Answer 21

- 200 μ, non-sheathed with short buccal cavity - **Mature in 2-3 days to filariform larvae.**

Answer 22

- 500 μ, non-sheathed with cylindrical oesophagus (1/2 body length) and notched posterior end.

Answer 23

- Parasitic adults live in the small intestine (Females embedded in the mucosa, and males live in the lumen of the intestine). - Free living adults occur in the soil.

Answer 24

infective filariform larvae.

Answer 25

- Infective filariform larvae **penetrating skin** in contact with infected soil. **------------------** - **Autoinfection** occurs by the infective filariform larvae that develop in the patient intestine **in constipation and intestinal disturbances** 1. Exogenous autoinfection: when infective filariform larvae develop outside the anus and penetrate the perianal skin. 2. Endogenous autoinfection: infective larvae develop in large intestine and penetrate the mucosa of the intestine.

Answer 26

hyper-infection

Answer 27

▪ Are taking corticosteroids (oral or intravenous) ▪ Are infected with the human T-lymphotropic virus type 1 (HTLV-1) ▪ Have hematologic malignancies such as leukemia or lymphoma ▪ Are transplant recipients.

Answer 28

1- **Skin lesions** following larvae penetration resembling the ground itch. 2- Pneumonitis may be produced by migrating larvae **(Lofflers syndrome)** 3- The adult worms in the intestine may cause no symptoms or moderate to severe **diarrhea** (chronic intermittent painless diarrhea). 4- **Malabsorption syndrome with steatorrhea can occur.** 5- Hyper-infection may lead to **severe debilitation or death** and the larvae that are found in virtually all parts of the body may give rise to **ectopic strongyloidiasis (in lung or kidney).**

Answer 29

- Most people do not know when their exposure occurred. - For those who do, a local **rash** can occur **immediately.** - The **cough** usually occurs **several days** later. - **Abdominal symptoms** typically occur approximately **2 weeks later,** and **larvae can be found in the stool** about **3 to 4 weeks later.**

Answer 30

**Stool analysis** - Demonstration of rhabditiform larvae (or occasionally filariform) in freshly passed stool. - Eggs may be seen in the stool rarely after purgation or in severe diarrhea. - Stool culture (to see the larvae and adults). **Duodenal aspiration** - May be done in mild infection (the larvae passed in the stool are few), for detection of eggs and rhabditiform larva. **Blood picture** - May show eosinophilia of 10-40 % **Sputum and bronchoalveolar lavage examination** - Shows the larvae especially if the adults are present in lungs.

Answer 31

1. Thiabendzole is the drug of choice. 2. Mebendazole (vermox) **All therapy must be repeated 2 weeks later**

Answer 32

Cosmopolitan (commonest tapeworm in children).

Answer 33

- 0.5-5 cm (the smallest tapeworm of man). - Globular scolex with 4 suckers and a retractile rostellum with a crown of hooks. - Broad mature segments - **Broader gravid segments full of eggs.**

Answer 34

- Oval, 30X50 μ , colourless, and mature oncosphere, 2 layered shell with bipolar knobs and filaments

Answer 35

- **A bladder-like structure**, 0.5-1 mm in diameter, having double wall, invaginated everted scolex, and tail-like appendage.

Answer 36

The small intestine.

Answer 37

Rodents (rats and mice).

Answer 38

Man, may be insects like flea larva or grain beetles.

Answer 39

Mature eggs and cercocystic cysticercoid.

Answer 40

- Eggs →onchosphere→ cercocystic cysticercoid in (I.H.) → adult in (D. H).

Answer 41

- Swallowing of infected insects or their larvae containing cysticercoid. - Contaminated food, water with eggs. - **Autoinfection:** by ingestion of mature eggs, either from person to person or by external autoinfection or internal autoinfection.

Answer 42

▪ In light infection, usually there are no manifestations. ▪ In heavy infections: ulcerations of the mucosa lead to **enteritis.** There may be **abdominal discomfort, colic and diarrhea with passage of mucus.** ▪ Some patients **especially children** suffer from **dizziness and may be convulsion**, attributed to neurotoxin product of the worms.

Answer 43

Stool examination for the characteristic egg.

Answer 44

- **Niclosamide:** treatment is prolonged or repeated in 3 weeks to kill worms that emerge from cysticercoids in the submucosa. - **Praziquantel:** a single oral dose after breakfast. It acts on both cysticercoid in the villi and the adult in the lumen of small intestine. - All infected members of the family should be treated at the same time.

Answer 45

Common in **Egypt in Nile Delta,** especially around the lakes of Manzala and Borollos, Turkey, and Far East (Japan, China, Korea, Philippine).

Answer 46

✓ 3X 0.5 mm, pear shape with 3 suckers (oral, ventral and larger genital sucker). ✓ Two oval testes, opposite each other and rounded ovary in between.

Answer 47

**Size:** 30xl5 μ. **Shape:** Oval. **Color:** golden yellow. **Shell:** Thick with operculum at one pole and a small Knob at the other. **Contents:** Full mature embryo (miracidium).

Answer 48

Adult lives between the villi of the small intestine.

Answer 49

**DH:** Man **RH:** Cat, dog, and any fish-eating animals. **IH:** - First is a snail, called Pirenella conica. - Second is fish, Tilapia (Bolty) and Mugil (Boury).

Answer 50

Encysted metacercaria in the muscles of the fish (2nd I. H.).

Answer 51

Egg --> miracidium --> sporocyst -->1st and 2nd generation redialophocercus cercaria --> encysted metacercaria --> adult.

Answer 52

**By eating insufficient cooked, roasted or salted fish,** staked less than ten days **(sweet fesekh)**, containing the infective stage (encysted metacercariae).

Answer 53

- In the small intestine the cyst wall is dissolved, the metacercariae embedded between the villi, maturate and the eggs appear in the stool 2-5 weeks after infection - Eggs pass with the stool, to reach to brackish water→ eggs are ingested by the snail (Pirenella conica) → miracidium hatches into a sporocyst, that gives redia then cercaria→ cercaria penetrates the fish muscle (Boury and Bolty) and becomes encysted metacercaria

Answer 54

- Attachment to mucosal membranes causing **inflammation** - **Abdominal colic and discomfort with chronic intermittent diarrhea.** - The egg may reach the general circulation to different organs: ✓ **Parasitic granuloma and fibrosis.** Migration of the eggs to the heart sometimes results in potentially **fatal myocardial and valvular damage.**

Answer 55

Stool examination for the characteristic eggs.

Answer 56

✓ Praziquantel (Biltricid). ✓ Niclosamide (Yomesan).

Answer 57

- Sanitary disposal of feces. - **Avoid eating raw, insufficient cooked fish or salted fish, salted less than 10 days (sweet fessekh), and proper grilling of fish.** - **Fried fish is safe** as temperature needed for frying is high enough to kill metacercariae. - Periodic **examination of fishermen stool** for Heterophyes eggs. - Mass treatment of infected cases.

Answer 58

Worldwide distribution especially in tropical areas and poor communities.

Answer 59

- Trophozoite (Vegetative or growing stage) - precyst - cyst

Answer 60

- Size: 10-60 μ (average 20 μ). - Shape: Irregular outline with finger like pseudopodia. - Cytoplasm: containing nucleus, food vacuoles, erythrocytes (RBCs), occasionally bacteria, and tissue debris.

Answer 61

- It is rounded, 10-15 μ in diameter. - Has smooth refractile cyst wall. - Immature cysts may be mono- or bi-nucleated. - Mature cysts contain 4 nuclei formed by mitotic division.

Answer 62

**Trophozoite:** - Inhabits the wall and lumen of the large intestine, with extra-intestinal metastases (liver, lung and brain, etc.). **Cyst:** - Inhabits the lumen of the large intestine.

Answer 63

Definitive host: Man Intermediate host: Non Reservoir host: Dogs, rats and monkeys.

Answer 64

Mature quadrinucleated cyst.

Answer 65

- Ingestion of mature quadrinucleated E. histolytica cysts in contaminated food or drink, or through infected food handlers. - Mechanical transmission By flies and cockroaches. - Autoinfection by Feco-oral route (hand to mouth contact)

Answer 66

- On ingestion, the **trophozoites disintegrate in the stomach**, while only the **mature cysts resist** the stomach acidity and **pass to the small intestine**. - The **cyst wall is digested By action of trypsin and excystation occurs** in the **proximal small intestine**, where **metacystic stage escapes** and divides into **8 small amoebae**. - These **trophozoites** move down to the **ilio-caecal region**, multiply by binary fission, and then pass to the **lumen of colon**, where they may remain, feeding on starch or mucus and pass in liquid stool, or may **undergo encystation and cysts pass with formed stool.** - Also, **trophozoite may invade the wall of large intestine** by their lytic secretion to invade the host tissues through blood vessels **(extra-intestinal invasion)**.

Answer 67

**E. histolytica lectin:** Attachment to the surface epithelium. **Cytolytic enzymes:** Haemolysins and pore-forming enzymes (amoeba pore). **Flask-shaped or crater-like ulcer:** - Irregular, with undermined edge and necrotic base with yellow purulent membrane covering its base - More common in the ileocecal region followed by the sigmoid-rectal region.

Answer 68

- Intestinal amoebiasis - Hepatic amoebiasis - Pulmonary amoebiasis - Amoebic brain abscess - Cutaneous amoebiasis - Genitourinary amoebiasis

Answer 69

asymptomatic and symptomatic

Answer 70

- These account for the majority of cases (80-90 %). - These patients are cyst passers, and they are called healthy carriers

Answer 71

- Acute intestinal amoebiasis (Amoebic dysentery) - Chronic amoebic colitis (non-dysenteric colitis)

Answer 72

- There is severe dysentery (colic + tenesmus + frequency of defecation + blood + mucus and shreds of necrotic mucosa in stool) and abdominal tenderness. - The patient is usually afebrile and non-toxic.

Answer 73

- Chronic intermittent diarrhea. - Abdominal pain and distension (Uncomfortable belly or growling abdomen). - Weight loss and weakness.

Answer 74

**Fulminant amoebic colitis** - The patient is febrile and toxic. **Amoeboma** - It is palpable, firm, painful, movable, chronic nodular lesion occurring mainly in the caecum, sigmoid colon or rectum. **Thick mega-colon and colonic stricture** - associated with obstructive symptoms. - Appendicitis, intestinal perforation and peritonitis. **Haemorrhage** - Due to erosion of intestinal blood vessels. **Extra intestinal spread** - with manifestations related to the organ affected.

Answer 75

It is a non-specific reaction of liver to the necrotic debris and toxic materials.

Answer 76

- The liver is enlarged and tender with pain in the right hypochondrium. - Temperature is usually elevated.

Answer 77

- The liver is enlarged and tender with pain in the right hypochondrium. - Elevation of the right diaphragm with severe pain referred to the right shoulder. - Fever, chills, toxemia, anorexia with leukocytosis. - Jaundice occurs with multiple lesions or affection of biliary tract. - The abscess may extend through the diaphragm to the lung, pericardium, peritoneal cavity or rupture through the abdominal wall.

Answer 78

It is characterized by chest pain, cough, dyspnea, chills, fever and leukocytosis.

Answer 79

Hepatobronchial fistula is usually associated with expectoration of chocolatebrown sputum.

Answer 80

It acts as a brain tumor (Space-occupying lesion).

Answer 81

It results from fistula formation (intestinal, hepatic, or perineal). Lesions can be highly destructive, simulating epithelioma.

Answer 82

- In females, vulva, vagina or cervix can be affected by spread from perineum or fistula formation. - The destructive lesions resemble carcinoma

Answer 83

clinical & laboratory

Answer 84

**Stool examination:** ▪ Macroscopy. Dysenteric stool (blood & Mucous). ▪ Microscopy: For identification of cysts and or trophozoites ▪ Stool culture: Using **Robinson's medium**, It is a sensitive method for diagnosing chronic and asymptomatic intestinal amoebiasis. ▪ Detection of amoebic **copro-antigens**: By enzyme-linked immunosorbent assay (ELISA). **Sigmoidoscopic examination:** ▪ For detection of trophozoites and associated pathology. **Serodiagnosis** → Antibodies to E. histolytica can be detected by indirect hemagglutination (IHA) test, immunofluorescence assay (IFA) test, and ELISA in invasive intestinal amoebiasis.

Answer 85

- Metronidazole (Flagyl). - Tinidazole (Fasigen).