INFECTIOUS STAGE

Question 1

What is the infective stage of Trichuris trichiura?

Answer 1

Embryonated egg with L2 inside

Requires ~21 days in moist soil to become infective

Question 2

What is the infective stage of Trichinella spiralis?

Answer 2

Encysted L1 juvenile in nurse cell (skeletal muscle)

Acquired by eating undercooked pork or meat

Question 3

What is the infective stage of Ascaris lumbricoides?

Answer 3

Fertilized egg containing L3 juvenile

Juveniles molt twice inside the egg before ingestion

Question 4

What is the infective stage of Strongyloides stercoralis?

Answer 4

Filariform (L3) larva

Penetrates skin (especially bare feet)

Question 5

What is the infective stage of Onchocerca volvulus?

Answer 5

L3 larvae from black fly bite

Fly injects infective stage into subcutaneous tissue

Question 6

What is the infective stage of Dirofilaria immitis?

Answer 6

L3 larvae from mosquito bite

Develops in mosquito’s Malpighian tubules before transmission

Question 7

What is the infective stage of Wuchereria bancrofti?

Answer 7

L3 larvae from mosquito bite

Infective L3 migrates to mosquito proboscis during blood meal