28 Vector-borne infections - helminths

Question 1

What is life cycle of schistosomiasis?

Answer 1

infected snails release cercariae which penetrate skin

Migrate through bloodstream via lungs/ liver

move to veins of bladder/ bowel, produce eggs

eggs penetrate bladder/ colon, and passed in urine/ faeces

eggs release miracidia which penetrate snail intermediate hosts

Question 2

Where do these species of schistosomes infect?

S. mansoni
S. haematobium
S. japonicum

Answer 2

S. mansoni - colon

S. haematobium - bladder

S. japonicum - colon

Question 3

What are symptoms of schistosomiasis?

Answer 3

dermatitis - swimer’s itch

fever

lymphadenopathy

splenomegaly

diarrhoea

haematuria

hypersensitivity reactions to eggs

Question 4

What is significance of haematemesis in refugee?

Answer 4

Schistosomiasis eggs can block presinusoidal capillaries in liver

portal hypertension develops, resulting collateral blood vessels forming which can rupture

Question 5

How to diagnose schistosomiasis?

Answer 5

visualisation of eggs - microscopy urine/ stool

antibody detection

Question 6

What is treatment of schistosomiasis?

How to prevent?

Answer 6

Praziquantel - kills worms but not eggs, which die naturally in two months

Mass chemotherapy
snail control
improved sanitation
education

Question 7

Filariasis are nematodes which rely on blood-feeding arthropods for transmission

what are most important species?

Answer 7

Invade lymphatics -
Burgia
Wuchereria

Subcutaneous tissues -
Onchocerca

Question 8

What is life cycle of filariasis?

Answer 8

vector picks up microfilaria from blood (Brugia/ Wuchereria) or skin (Onchocerca) of infected human

microfilaria injected into next host. Make way to lymph nodes or remain in skin, become adults worms

Female worms release microfilaria

Question 9

What are symptoms of filariasis?

Answer 9

asymptomatic

fever
rash
eosinophilia
lymphadenitis/ lymphangitis
tropical pulmonary eosinophilia
elephantiasis

Question 10

What are treatment options for filariasis?

Answer 10

Diethylcarbamzin (DEC) useful for Brugia/ Wuchereria. Not used for Onchocerciasis as can cause allergic response when microfilariae killed

Onchocerciasis - ivermectin + doxycycline