Parasitology

Question 1

Dracunculus medinensis

Answer 1

→ Guinea worm.
→ habitat- subcutaneous tissues
→ DH- humans
→ IMH- cyclops
→ MOI- ingestion of water with cyclops ( L3 larva)

Question 2

Wuchereria bancrofti

Answer 2

→ habitat- lymphatics, lymph nodes ( inguinal, scrotal, abdominal)
→ DH- humans
→ IMH- culex quinquefasciateus, Aedes & anopheles.
→ infective form- L3 larva.
→ MOI - blood sucking arthropods

Question 3

Ascaris lumbricoides.

Answer 3

→ Mc helmintic infection worldwide.
→ longest nematode in human intestine
→ host- Human
→ habitat- small intestine especially jejunum.
→ moi- ingestion of eggs which have rhabditiform larva.

Question 4

Ancylostoma duodenal.( nematode)

Answer 4

→ old world hook worm.
→2nd most common helminthic disease in the world.
→ females longer than males.
→ females have tapering end & males have coiled/ spicules in posterior end.
→ has teeth
→habitat-small intestine esp. Jejunum.
→ host-human.
→ MOI- skin penetration.
→ infective form - filariform larvae
→causes hookworm disease characterised by anaemia
→cause 3 types of lesions:
1. Ancylostoma dermatitis or ground itch.
2. Creeping eruption or cutaneous larva migrans.
3. Lesions in the lungs.
→lab diagnosis:
1. Direct methods- stool examination for worms & eggs, duodenal contents.
2. Indirect methods- blood examination: microcytic, hypochromic anaemia & eosinophilia. Stool examination: occult blood & Charcot- Leyden crystals.
→ eggs: 60 um, thin transparent shell, 4-8 blastomers, non bile stained.

Question 5

Strongyloides stercoralis.

Answer 5

→smallest round worm found in intestine.
→ adults are free living in soil
→ females- parthenogenic & ovo-viviparous.
→ immunodeficient- autoinfection→ hyper infection & disseminated disease.
→ habitat- duodenum & upper jejunum.
→ host - Human.
→ MOI - skin penetration.
→ infective form-filariform larva

Question 6

Trichuris trichiura.

Answer 6

→ whipworm
→ males shorter than females.
→ Males home coiled posterior ends.
→ females have tapering ends.
→ 30-45 mm long.
→ habitat- Human
→ MOI- ingestion of eggs ( larvae produced in soil so no autoinfection)

Question 7

Enterobius vermicularis.

Answer 7

→ pin worm/ thread worm/ seat worm.
→ common infection worldwide.
→ 2-13 mm long
→ female longer than males.
→ Male worms have curved posterior end containing spicules.
→ host-human
→ habitat- caecum & ascending colon.
→ MOI-
• ingestion of eggs ( contains larvae) → autoinfection
• retroinfection→ female lay eggs on perianal skin → larvae emerge & crawl back to GIT
• fomites → contaminated taps, handles, bed linens.

Question 8

Hymenolepis Nana

Answer 8

→ dwarf tapeworm - smallest tape worm
→ 4-5 cm long, 200 proglottids.
→ can complete life cycle in one host.
→ host- humans, rodents.
→ IMH- insects ( beetles, moths) occasionally
→moi- ingestion of eggs by faeces contaminated food/water. Internal/ external auto infection.

Question 9

Echinococcus Granulosus

Answer 9

→ dog tape worm.
→ has only 3 segments
→ DH- dog.
→ IMH- sheep, goats, humans.
→ MOI- ingestion of eggs in dog feces contaminated food / water, direct infection while handling dogs.
→ Hydatid just in liver
→ Man is dead end host.

Question 10

Taenia solium

Answer 10

→pork tape worm
→ armed tape worm- has rostellum with hooks on scolex.
→ 2-3 m long, 800-1000 segments.
→ DH- human
→ IMH- pigs.
→ sometimes man is IMH. This disease is called as cysticercosis
→ MOI- cysticercus cellulosae in poorly cooked pork. Also by ingestion of eggs in food / auto infection.

Question 11

Taenia saginata.

Answer 11

→ beef tape worm, unarmed tapeworm- no Rostellum & hooks.
→ 4-6 m long, 1000-2000 segments.
→ dh- Human ( small intestine lumen)
→ imh- cows
→ infective form-cysticercus bovis in poorly cooked meat.

Question 12

Paragonimus westermani.

Answer 12

→ lung fluke
→ 1st imh- snail (molluscs)
→ 2nd imh- crabs/ cray fish ( crustaceans)
→ infective form- metacercariae

Question 13

Liver flukes.

Answer 13

1. Fasciola hepatica
    → sheep liver fluke
    → 1st imh- snail
    → 2nd imh- fresh water plants
    → 3c's - cholangitis, cholelithiasis, cholecystitis
2. Fasciola gigantica
     → giant liver fluke
     → 1st imh- snail
    → 2nd imh- fresh water plants
    → 3c's - cholangitis, cholelithiasis, cholecystitis
3. Clonorchis sinensis
     → Chinese liver fluke
     → 1st imh- snail
    → 2nd imh- fresh water fish
    → 3c's - cholangitis, cholelithiasis, cholecystitis + cholangio carcinoma
4. Opisthorchus viverenii
     → southeast Asian liver fluke
     → 1st imh- snail
    → 2nd imh- fresh water fish
    → 3c's - cholangitis, cholelithiasis, cholecystitis + cholangio carcinoma
5. Opisthorchus felineus
     → cat liver fluke
     → 1st imh- snail
    → 2nd imh- fresh water fish
    → 3c's - cholangitis, cholelithiasis, cholecystitis

Question 14

Schistosoma haematobium

Answer 14

→ blood fluke
→ dh- mammals
→ imh- snail.
→ moi- cercariae penetrating skin.
→ habitat- vesical plexus.

Question 15

Plasmodium

Answer 15

→ p. falciparum, p. vivax, p. malariae, p. ovale, p. knowlesi
→ dh- female anopheles mosquito as sexual replication occurring in mosquito.
→ imh-humans.
→ moi- sporozoites

Question 16

Toxoplasma gondii.( sporozoa)

Answer 16

→ dh-cat
→ imh- rodent, sheep, pig, man.
→ man is dead end host.
→ moi
1. Ingestion- tissue cyst in poorly cooked meat, sporulated oocyst in contaminated food & water & while cleaning cat litter boxes
2. Blood /organ transplantation.
3. Transplacental.

Question 17

Cryptosporidium parvum

Answer 17

→ mcc of Diarrhea in HIV patients.
→ only zoonotic
→ small infective dose ( 10-100 sporutated oocysts)
→ Traveller’s Diarrhea
→ Oocysts in stool are infectious causing autoinfection.
→ Category B bioterrorism agent.
→ habitat - small intestinal mucosal cells
→ host- only humans
→ moi- Feco oral.
→ infective form- sporulated oocyst.

Question 18

Leishmania donovani.

Answer 18

→ Kala Azar
→ habitat- Reficulo endothelial system.
→ dh- humans
→ vector- sandfly. ( Phlebotomus argentipes)
→ moi-
1. Bite of sandfly - inoculation of infective form → promastigote
2. Mother to fetus
3. Blood transfusion
4. Sharing of needs in iv drug users.
→ reservoir- rodents, dogs, wolves

Question 19

Naeglaria fowleri

Answer 19

→ free living amoeba.
→ aka ameboflagellate
→ Brain eating amoeba
→ in countries with temperate climates.
→ habitat- soil & warm fresh water.
→ host- man is an accidental & dead end host.
→moi- swimming in contaminated water
→ causes 1° amoebic meningo encephalitis.

Question 20

Entamoeba Histolytica.

Answer 20

→cyst can survive routine chlorination of water.
→ small infective dose ( 10-100 cysts)
→ Traveller’s Diarrhea.
→ 2nd mc protozoan causing death. ( 1st malaria)
→ habitat - caecum & ascending colon.
→ host- strict human pathogen.
→ infective form- quadrinucleate cyst.

Question 21

Parasites causing anaemia.

Answer 21

1. Plasmodium sp.
2. Leishmania donovani
3. Ancylostoma duodenale.
4. Necator americanus.
5. Schistosoma haematobium.