Protozoa & Helminths

Question 1

Malaria

Answer 1

– 75% falciparum (mortality 10-20%, 90% cases Africa)

• Incubation period:
– Minimum 6 days
– P. falciparum: up to 6/12
– P. vivax/ovale: up to 1 year+

• History
– Fever chills & sweats - cycle every 3rd or 4th day

-Possible nausea/vomiting; headache; dry cough

• Examination
– Often few signs except fever
(+/- splenomegaly)

• Treatment depends on species

– P. falciparum (‘malignant’)
• Artesunate
• Quinine + doxycycline

– P. vivax, ovale, malariae (‘benign’)

• Chloroquine + primaquine
• Hypnozoites (liver stage)
• Can recur months-years later

Question 2

Shistosomiatis

Answer 2

Fresh water exposure allows the cercarial stage, which reside in and are released from water snails, to penetrate intact skin of swimmers. This often causes a localised reaction at the point of penetration (Swimmer’s Itch). Subsequent Katayama fever is thought to be an immune complex phenomenon, and is a clinical diagnosis. In most cases the illness is self-limiting over a few weeks.

Left untreated, mature adult flukes (schistosomes) end up in the venules of the bladder and bowel and release eggs. An immunological reaction to the eggs may cause fibrosis of liver, bowel and bladder over many years. Chronic schistosomiasis can be diagnosed by finding ova in stool and terminal urine, and by serological testing.

Rarely requires hospital admission. Praziquantel kills immature but not mature schistosomes. Therefore a second dose is required 6-8 weeks after Katayama fever to kill the matured organisms. A short course of oral corticosteroids may help to alleviate acute symptoms.