Malaria : The organism

Question 1

Which Plasmodium species responsible for more than 95% of cases inSA and has the highest incidence of complications and mortality in non-immune?

Answer 1

Plasmodium falciparum

Question 2

List the 5 Plasmodium species responsible for the transmission of malaria

Answer 2

• P.Falciparum
• P.Ovale
• P.Vivax
• P.Knowlesi

Question 3

How is malaria transmitted to humans?

Answer 3

By the bite of female mosquitoes injecting sporozoites filled saliva into the human bloodstream /needle stick injury /congenital / blood transfusion

Question 4

MOT from humans to mosquitoes

Answer 4

Female mosquitoes are infected by gametocytes in the blood of infected humans

Question 5

Fill in the missing words : Major mosquitoes vectors of malaris in SA are members of ____ species complex especially _______,more recently insecticide-resistant ______has merged in _______

Answer 5

• Anopheles gambiae
• Anopheles arabiesis
• Anopheles Funestus
• KZN

Question 6

List the SA geographical distribution of malaria-endemic regions

9 marks

Answer 6

• Nothern KZN
• Low-veld areas pf MP
• Northern Province of Swaziland
• Zimbabwe
• Botswana
• Namibia
• Mozambique
• Zambia
• Angola

Question 7

T/F: Residents in hyper-endemic regions are semi-immune due to constant exposure and are not clinically ill despite having splenomegaly and parasitemia

Answer 7

True

NB: South Africans living in endemic regions are seasonally exposed they are non-immune / little immune and thus at risk of developing Falciparum malaria

Question 8

After early childhood are not prone to develop complications unless what?

Answer 8

Pregnant / semi-immune status is impaired by inter-concurrent illness eg advanced Aids

Question 9

Pathogenesis of malaria

Answer 9

*Parasite RBC adhere to capillary endothelium by means of sticky knobs involving specific ligands and endothelial cytoreceptors > sequestration of RBC containing matured parasites in vascular beds of internal organs > Infected RBC become less deformable > impaired microcirculation in organs > Release of pro-inflammatory cytokines eg TNF and IL-1 are stimulated by malaria antigens. TNF upregulates endothelial adhesion molecules and stimulates the release of NO.

NO contributes to cerebral malaria by interfering with transmission

Question 10

Clinical presentation of malaria

Answer 10

*P. The falciparum incubation period is 10-14 days and can be reduced to 7 days but can be prolonged by prophylaxis.

Typical symptoms: fever, malaise, headache, anorexia, myalgia, shivering, and hot sweats

Intermittent symptoms: flu-like cough, diarrhea, may mimic viral hepatitis, anemia, pallor, jaundice, hepatomegaly, and change in the level of consciousness

Question 11

The differential diagnosis for malaria

Answer 11

influenza, viral hepatitis, meningitis, septicemia, typhoid, arbovirus infections

Question 12

Riak factors for severe malaria and complications

Answer 12

pregnancy, children <5 years, splenectomy and non-immune

Question 13

List the 13 complications of malaria

Answer 13

1. CNV involvement : cerebral malaria , change in conciouness , convulsions. If neck stiffness occur then bacterial meningitis should be excluded
2. Anemia: common in African children due to hemolysis and dyserythropoietic
   3.Jaundice: from hemolysis and hepatic dysfunction
3. Respiratory dysfunction: Severe anemia causes over-hydration thus IV must be avoided, ARDS especially in pregnant women
   5.Renal failure: tubular necrosis especially in Quartan malaria ( P.malaria ) complicated by necrotic syndrome
   6.Metabolic acidosis and lactatic acidosis
4. Hypoglycaemia: may be mistaken for cerebral malaria thus must always monitor glucose levels of malaria patients and must treat with quinine
   8.Fluid and electrolyte imbalance: Hypovolaemia and dehydration can be corrected but be aware of pulmonary edema
5. Circulatory collapse: Occurs in pulmonary edema ,metabolic acidosis, complicated GNB septicemia or GIT hemorrhage
   10 . Bleeding: thrombocytopenia is common in P.Falciparum, DIC
6. Vomiting and diarrhea
7. Hemoglobinuria and blackwater fever: caused by severe intravascular hemolysis and renal failure

Question 14

How to diagnose malaria

Answer 14

Microscopy of thick and thin blood films ( must be repeated if the initial report is negative ).

• WCC and platelets are low
• Parasitaemia must be quantitative if >5-10 % this indicative of malaria but lowe must exclude malaria
• Rapid antigens tests on blood for P.falciparum detects histidine-rich protein 2