Fever in the returning traveller

Question 1

What is the organism that transmits malaria?

Answer 1

Female anopheles mosquito

Question 2

What are the 5 main species of malaria?

Answer 2

Plasmodium:
falciparum (most common, most likely to kill)
vivax
ovale
malariae
knowlesi

Question 3

What is the most common and most likely to kill malaria?

Answer 3

Falciparum

Question 4

What is the plasmodium life cycle?

Answer 4

• Mosquito bites human and sporozoite transferred into blood - travels to hepatocytes, invades + replicates to produce 1000s of merozoites
• In falciparum merozoites quickly enter blood and infect blood cells to cause haemolysis; in non-falciparum merozoites remain in hepatocytes in a hypnozoite phase (primaquine targets this stage) before being released
• Some merozoites release gametocytes that stay in the blood. Mosquito biting infected person takes up gametocytes - mature in mosquito gut to sporozoites

Question 5

Plasmodium different stages

Answer 5

Sporozoites transferred into blood and invade hepatocytes
Merozoites produced from replication in hepatocytes
Hypnozoites in non-falciparum in hepatocytes
Gametocytes produced by merozoites in blood

Question 6

What is a key difference between falciparum and non-falciparum malaria? How does this affect treatment?

Answer 6

In falciparum merozoites are instantly released from hepatocytes into blood
In non-falciparum merozoites remain in hepatocytes for a while (‘hypnozoites’) before being released into the blood
Primaquine targets the hypnozoites (Tx for non-falciparum)

Question 7

What are the features of malaria?

Answer 7

Cyclical fevers with spikes when merozoites released from liver
Haemolysis = dark urine

Question 8

What are the two main cell types affected by malaria?

Answer 8

Hepatocytes

Red blood cells

Question 9

Ix suspected malaria

Answer 9

3x thick and thin blood films (thick identifies Plasmodium parasite, thin identifies Plasmodium type)
Malaria antigen detection tests (antigens = LDH, HRP-III)
Haemolytic anaemia on bloods

Question 10

Tx Non-falciparum

Answer 10

Chloroquinine 3d
Primaquine 2w (targets hypnozoite stage)

Question 11

Tx Falciparum

Answer 11

Depends on severity:
MILD (not vomiting, parasitaemia <2%) = oral malarone (4 tablets daily for 3d)
SEVERE (unstable, parasitaemia >2%) - A-E approach with IV artesunate

Question 12

Man returns from Sierra Leone with cyclical fever

Answer 12

Malaria

Question 13

Man returns from Thailand with a fever, retro-orbital headache, blanching rash + joint pains

Answer 13

Dengue

Question 14

Tx severe malaria

Answer 14

A-E approach

IV artesunate

Question 15

Tx mild malaria

Answer 15

Oral malarone

Question 16

What can Dengue progress to?

Answer 16

Dengue haemorrhagic fever - bleeding and shock

Question 17

Tx Dengue

Answer 17

Supportive

Question 18

What is Dengue?

Answer 18

Flavivirus transmitted by Aedes mosquito

Question 19

Rose spots + fever + abdominal pain + dry cough + constipation
India

Answer 19

Enteric fever
(Salmonella enteri)
(Tx = Ceftriaxone then Azithromycin)

Question 20

Eschar (dark scabs)

Returned from Africa

Answer 20

Rickettsia

Tx = doxycycline