Global infections

Question 1

Which parasitic species can infect humans with malaria?

Answer 1

Plasmodium falciparum (most common and dangerous)
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi

Question 2

Which people are more at risk of severe malaria?

Answer 2

Pregnant women, extremes of age, asplenic patients

Question 3

Describe the life cycle of malaria

Answer 3

1. BLOOD MEAL - Mosquito bites human and injects sporozoites in the saliva, which are taken up by the liver
2. Vivax and ovale lie dormant as hypnozoites here
3. Hypnozoites awake after months and become merozoites
4. Merozoites invade and develop in RBCs (trophozoite, schizont) until the RBC bursts
5. Those that multiply lead to clinical illness. Those that don’t become gametocytes to be taken up by mosquitos and passed on.

Question 4

What is the ABCD of prevention in malaria?

Answer 4

Awareness of risk
Bite prevention (DEET based)
Chemoprophylaxis
Diagnosis

Question 5

What are the optimum conditions for malaria transmission?

Answer 5

Temperature 20-30C
Altitude <2000m
High humidity
Rural areas

Question 6

What are the different types of chemoprophylaxis?

Answer 6

Causal - directed at the liver phase of the parasite life cycle
Suppressive - directed at the red blood cell stage of the parasite life cycle

Question 7

What is the incubation period of P.falciparum?

Answer 7

7-14 days (this can be longer in cases of partial immunity or antimalarial medication)

Question 8

What is the incubation period of P.vivax and P.ovale?

Answer 8

12-18 days (this can be months or years due to hypnozoites)

Question 9

What are the symptoms of malaria?

Answer 9

FEVER, rigors, malaise, abdo pain, headache, fatigue, myalgia

Question 10

Name some complications of malaria

Answer 10

Kidney failure, low iron levels, low blood sugar, uncontrollable bleeding, low blood pressure, pulmonary oedema, coma, death

Question 11

How is malaria diagnosed?

Answer 11

Take an EDTA-anticoagulated venous blood sample and do thick and thin blood smears.
Re-examine the smears every 12 to 24 hours for 3 days

Question 12

How is malaria treated?

Answer 12

Oral quinine sulphate 600mg/8h for 5-7 days PLUS doxycycline 200mg daily for 7 days (or clindamycin 450mg if pregnant)

Atovaquone proguanil (malarone) - 4 tablets daily for 3 days

Coartem (Riamet) 4 tablets each at 0, 8, 24, 36, 48, 60 hours

Question 13

What is typhoid and what are the symptoms?

Answer 13

A bacterial infection caused by salmonella typhi, causing fever, malaise, bradycardia, headache and constipation/diarrhoea

Question 14

What are the signs of typhoid?

Answer 14

Rose spots on trunk
Hepatomegaly
Epistaxis
Bruising

Question 15

What is the treatment for typhoid?

Answer 15

IV fluids, CIPROFLOXACIN

Question 16

How is typhoid investigated?

Answer 16

Blood, bone marrow and stool samples
Widal test (looks at antibodies)

Question 17

How is typhoid prevented?

Answer 17

Two live vaccines (not routine, given before travelling to endemic area)

Question 18

What pathogen causes dengue fever?

Answer 18

Flavaviridae ssRNA

Question 19

What vector carries dengue?

Answer 19

Mosquito - Aedes (A.aegypti)

Question 20

What are the symptoms of dengue?

Answer 20

OFTEN ASYMPTOMATIC

Febrile phase –> headache, rash, malaise, fever, arthralgia

Critical phase –> abdo pain, vomiting, lethargy, hepatomegaly, sepsis

Question 21

How is dengue managed?

Answer 21

No antiviral

Give fluids and oral rehydration therapy

Question 22

What are some DDs for dengue, and how would you differentiate?

Answer 22

Chikunyunga - back pain

Zika - conjunctivitis