Wright's stain of peripheral blood. Note early trophozoites seen within red blood cells. Features characteristic of Plasmodium falciparum include double chromatin dots and more than one ring form per red blood cell.
A 19-year-old African-American woman presented to the emergency department with a four-day history of worsening headaches, fever, chills, nausea and vomiting 10 days after a two-week visit to Sierra Leone and Guinea, West Africa. She had not sought prophylaxis or medical advice before her trip.
On admission, vital signs included a temperature of 103°F, blood pressure of 90/50 mmHg, heart rate 108 beats per minute, respiratory rate 24 per minute. She was not acutely distressed, and was well-perfused but slightly dehydrated. The rest of the examination was notable for lack of meningismus, normal cardiac exam, clear breath sounds, mild tenderness to palpation in the umbilical region, no hepatosplenomegaly and clear mental status.
Laboratory studies from admission revealed a positive malaria thin smear (see figure) where Plasmodium falciparum parasitemia was estimated at 3%. White blood cell count was 11,900/mm3, hematocrit 38% and platelet count 104,000/mm3. Blood culture drawn to rule out Salmonella typhi and other pathogens was negative. Urine culture, stool ova and parasite exam, and stool culture were also negative for pathogenic organisms.
She was started promptly on oral quinine sulfate, tetracycline and maintenance intravenous fluids with dextrose upon admission. She remained febrile and her parasite burden peaked at 6% later on her first day of hospitalization -clearance of parasites was not seen until the fourth day after starting antimalarials. Her hematocrit dropped to 27% and her platelet count fell to 79,000/mm3 on the second hospital day. On that same day, a small palpable spleen tip was also felt. Thereafter, her clinical symptoms improved and her laboratory indices slowly recovered. She never developed hypoglycemia, blackwater fever or cerebral malaria. She completed a seven-day regimen of both quinine sulfate and tetracycline as an outpatient. Of interest, the patient did complain of ringing in her ears on therapeutic levels of quinine.
Six months later she was seen in travel clinic for pretravel guidance, vaccinations and chemoprophylaxis before returning to West Africa for another visit with her relatives.
A detailed history can narrow the differential for fever in a returning traveler. igh-yield questions providers may ask of returning travelers include specific navel destinations and length of stay; unusual exposures; and pretravel prophylactic measures taken by the patient.
Malaria is the most common cause of fever in a traveler returning from the tropics. Plasmodium infections account for one-third of all acute febrile illnesses in returning travelers. Febrile travelers returning from areas endemic for malaria should be considered to have malaria until proven otherwise, since P. falciparum malaria can be rapidly fatal, but is curable with prompt, appropriate therapy.
The diagnosis of malaria can be made by an untutored individual. The key to diagnosis lies in having a high index of suspicion for this disease. Such suspicion is required to order the necessary diagnostic test - multiple thin smears (the equivalent of routine Wright's stains of peripheral blood), on blood samples taken at multiple time points. A thick smear in inexperienced hands may not add to diagnosis.
To prevent malaria, as well as other tropical infections, travelers should receive pretravel guidance about chemoprophylaxis and insect precautions. A visit or phone consult with a travel medicine specialist timed six weeks prior to travel abroad would be ideal from the standpoint of anticipatory guidance, vaccinations and prescriptions for the traveler.
Health care providers can use published data and internet resources for up-to-date travel information. Published data include the Centers for Disease Control's Yellow Book, Health Information for International Travel. Internet resources include the CDC Travel Page, http://www.cdc.gov/travel/index.htm, and other commercial websites such as Shoreland's Travel Health Online, at http://www.tripprep.com/index.html.
For more information
- Humar A and Keystone J. Evaluating fever in travellers returning from tropical countries. BMJ. 1996;312:953-6.
- Katherine Hsu, MD, is a fellow in infectious diseases and Elisabeth DiPietro, MD is a senior resident in the combined Boston residency program, Boston Medical Center and Children's Hospital Boston (R.G.) and the Division of Pediatric Infectious Diseases, Boston Medical Center (F.E.B.).
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