A review of 13 North American and European clinical studies highlighted differences between children and adults in the presenting signs and symptoms of malaria. The majority of children had fever in excess of 40°C, compared with just a quarter of adults. The same was true of hepatosplenomegaly and anemia. Nausea, vomiting, and diarrhea were very common in children, whereas the most common nonspecific symptoms in adults were headache and myalgia. Thrombocytopenia was extremely common in both groups (Lancet Infect. Dis. 2007;7:349-57).
Every medical student has to learn the four human malaria parasites: P. falciparum, vivax, malariae, and ovale. Recently a fifth has been identified: Plasmodium knowlesi. And it’s a pip.
Dr. Jay Keystone
"It’s a monkey malaria that’s now in the human population. Knowlesi is found mainly in Southeast Asia, especially in the border areas of Thailand. It is one of the fatal malarias. It looks benign and like [Plasmodium] malariae under the microscope, but it kills like P. falciparum. So if you see someone from Southeast Asia who’s very sick and it looks like malariae, think about knowlesi," Dr. Keystone urged.
Two very good medications are available in the United States for treatment of malaria. For patients with heavy parasitemia or severe malaria as defined by cerebral, respiratory, or renal manifestations or severe anemia, intravenous artemether/lumefantrine (Coartem) is the treatment of choice because it’s faster acting, with an average parasite clearance time of 2 days, compared to 4 days with atovaquone/proguanil (Malarone). However, atovaquone/proguanil is better tolerated and thus a good choice in patients with less than 5% parasitemia who don’t have severe disease, he said.
For more information on travel medicine, Dr. Keystone recommends the following resources:
• Text: "Control of Communicable Diseases Manual," 19th Edition, edited by Dr. David L. Heymann. An official report of the American Public Health Association. Available in paperback at Amazon.com for about $23.
"It’s a brilliant book," Dr. Keystone said. "The beauty of this book is it doesn’t just give you the epidemiology and incubation, it gives you the period of communicability, and it’s all laid out in easy form. I would highly advise you that if you don’t have one of these in the office, it’s definitely worth having."
• Web: Every infectious diseases program should have a subscription to Gideon, Dr. Keystone said. Plug in the pertinent facts regarding a case and Gideon spits out the complete differential diagnosis, with the possibilities rank-ordered and accompanying treatment recommendations. Physicians can obtain a free 15-day trial through the website.
"Gideon is probably the best geographic, computer-based, online program for infectious diseases that I know of. You don’t have to be smart to know everything about tropical medicine. If you’re looking for something to help you diagnose tropical diseases, this would be the one," he said.
• Phone: 770-488-7788 connects you to the CDC’s malaria branch.
Dr. Keystone disclosed that he is a consultant to Gideon.