Question 25

College Answer

a) Describe the laboratory confirmation of this condition
Thick and thin blood smears (give diagnosis and parasite load)
Rapid diagnostic tests utilising malarial antigens (dependents on specific test)

b) List 2 firstline drugs from different classes given parenterally in the treatment of the severe form of this disease
Cinchona alkaloids (quinine and quinidine)
Artemisinin derivatives (artesunate, artemether).

c) List the acute complications of this disease
• Cerebral Involvement with or without convulsions
• Respiratory Failure - acute respiratory distress syndrome (ARDS)
• Circulatory collapse
• Renal failure, hemoglobinuria ("black water fever")
• Hepatic failure
• Haematological
• Disseminated intravascular coagulation
• Severe anemia secondary to Haemaolysis
• Thrombocytopenia
• Metabolic
• Hypoglycemia
• Severe Acidosis
• Hyponatraemia
• Splenic Rupture

Discussion

This question dips into one's general knowlege of infectious diseases.

Obviously, unless specifically schooled in the infectious arts, the candiate would not be able to regurgitate a very large amount of information regarding this disease. For such candidates, I have compiled a brief summary of malaria in the Required Reading section.

a) Describe the laboratory confirmation of this condition

• Thick and thin films
• Rapid diagnostic tests (RDTs) looking for parasite antigens such as parasite-specific lactate dehydrogenase (pLDH), or aldolase.

Usually thick and thin films are enough. Oh's Manual describes them as the gold standard. The thin films help the parasitologist identify the parasite species because they are visible within the red cells. The thick films have a layer of lysed red cells and with the parasites floating free one can do a head-count and estimate the parasite load. The American CDC has a wonderful set of cartoonish guides to help a semi-skilled practitioner to correctly prepare the thick and thin slides. This is a labour-intensive technique; in contrast, the rapid antigen tests can give an answer within 20 minutes, but does not give a parasite count (and so cannot be used to monitor the effects of therapy)

b) List 2 firstline drugs from different classes given parenterally in the treatment of the severe form of this disease
The college answer lists cinchona alkaloids (eg. chloroquine) and artemisinin derivatives (eg. artemethrin).

From the two-line answer, it would seem that a detailed understanding of the pharmacotherapy of malaria is not required. A certain CDC document can shed some light on the alternative drugs, without being excessively detailed. According to the CDC, in addition to the cinchona drugs and artemisinin family, one could also add tetracyclines (eg doxycycline), napthoquinones (eg. atovaquone) and lincosamides (eg. clindamycin).

The WHO has released a set of guidelines in 2010 which make recommendations of first and second line agents. This boc

c) List the acute complications of this disease
The college answer lists complications in no specific order. I would like to organise my answer according to a puerile alphabetic template.

• A) - ...nothing much happens to the airway in malaria, provided one's brain is not swarming with parasites.
• B) - ARDS
• C) - Shock, circulatory collapse (and maybe a ruptured spleen)
• D) - Encephalitis, maybe with seziures and decreased level of consciousness (swarming, parasites, etc)
• E) - Severe metabolic acidosis, hyperkalemia, hyponatremia
• F) - Hemoglobinuria, leading to acute tubular necrosis and acute renal failure
• G) - Acute hepatitis and syntheic liver failure; hypoglycaemia
• H) - Haemolysis, thrombocytopenia, DIC
• I) - High fever and rhabdomyolysis die to rigors

The Required Reading entry on malaria contains this table, which is a more comprehensive answer:

World Health Organization. Guidelines for the treatment of malaria. World Health Organization, 2006.

We dont have a CDC here in Australia, and so I link to the CDC site for details about standardised diagnosis and treatment of malaria. This page has links to downloadable PDF documents with decisionmaking flowcharts et cetera. One particularly useful document is this set of Guidelines for Clinicians.

WHO. Guidelines for the treatment of malaria. 2nd ed. Geneva: WHO; 2010. Online.