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Clinical Case Study 1

Case 1

A 44-year-old male is seen at a physician's office in the United States, during a week-end, for suspected malaria.

The patient was born in Pakistan but has lived in the US for the past 12 years. He travels frequently back to Pakistan to visit friends and relatives. His last visit there was for two months, returning 11 months before the current episode. He did not take malaria prophylaxis then.

Five weeks ago, he was diagnosed with malaria and treated at a local hospital. The blood smear at that time was reported by the hospital as positive for Plasmodium malariae (schizonts, trophozoites). He was then treated with 2 days of IV fluids (nature unknown) and tablets (nature unknown), and recovered.

The patient now presents with a history of low grade fever for the past few days, with no other symptoms . A blood smear is taken and examined at a hospital laboratory by the technician (no pathologist is available on this week-end). Through a telephone discussion, the technician states that she sees 4 parasites per 1000 red blood cells, with rings, "other forms with up to four nuclei", and that some of the infected red blood cells are enlarged and deformed.

Question 1. What is your most probable diagnosis?

• Not malaria
• Plasmodium falciparum
• Plasmodium vivax
• Plasmodium ovale
• Plasmodium malariae
• Babesia

Question 2. What treatment approach would you recommend, based on this clinical history and on the fact that the microscopy findings will not be confirmed by a pathologist for at least 24 hours?

• Do not start treatment until a formal microscopic diagnosis is made (in 12-24 hours)
• Treat as if chloroquine-sensitive Plasmodium falciparum malaria
• Treat as if chloroquine-resistant Plasmoidum falciparum malaria
• Treat as if Plasmodium vivax malaria

The diagnosis of P. vivax malaria is later confirmed by review of a blood smear available from the first episode (Figure), and by a PCR positive for P. vivax on blood collected during the current episode.

P. vivax schizont	P. vivax gametocyte

The microscopic diagnosis of P. vivax is based on the following: a) the infected red cells are enlarged and deformed; b) the schizont shown contains 20 merozoites (schizonts of P. malariae and P. ovale have fewer merozoites; and in P. falciparum schizonts are not usually seen in the peripheral blood); c) the round gametocyte shown, contained in an enlarged red cell. (In this case, the typical Schüffner's dots were not visible, probably due to staining problems.)

Question 3. To prevent further relapses from dormant liver stages, what would you recommend?

• No further measures needed
• A lab test to determine if the patient has dormant liver stages
• Treatment directly with a drug that kills dormant liver stages
• A lab test, followed by treatment

Question 4. Should this patient have taken preventive measures against malaria for his visit to Pakistan, considering that he was born there, and probably would have visited only cities?

• No
• Yes

Main Points

1. Travelers to Pakistan (including those visiting friends and relatives) need to take prophylaxis (atovaquone-proguanil (Malarone®), doxycycline or mefloquine).
2. Clinical history and travel history, and careful microscopic examination, probably would have directed the diagnosis toward P. vivax during the earlier episode.
3. P. vivax malaria should be treated with chloroquine, except when acquired in Papua New Guinea and Indonesia, areas with high prevalence of chloroquine-resistant P. vivax. After a normal G6PD test, patients should get a radical cure with primaquine (30 mg per day for 14 days).