Difficulties in the prevention, diagnosis, and treatment of imported malaria

Imported malaria is quite common in the United States. Increasing antimalarial drug resistance and changes in travel patterns may have important implications for the prevention, clinical presentation, and management of this disease.

Medical records were reviewed for 121 patients with microscopically confirmed malaria diagnosed at 2 university-affiliated hospitals in San Francisco, Calif, between 1988 and 1997.

Among 57 travelers from the United States, only 13 (23%) had been compliant with an appropriate chemoprophylactic regimen. No patients developed falciparum malaria after consistent chemoprophylactic therapy with mefloquine hydrochloride. However, 12 (19%) of US residents with imported malaria developed Plasmodium vivax or Plasmodium ovale infections despite an appropriate chemoprophylactic regimen, generally with a late onset suggestive of relapsing disease. Clinical presentations were similar between foreign residents and American travelers and between patients with falciparum and nonfalciparum infections; 98% of patients had a history of fever. Sixteen percent of patients had received previous evaluations during which the diagnosis of malaria was not considered. In 9% of patients, there were errors in treatment. Only 1 patient developed severe malaria.

Our results suggest that a standard chemoprophylactic regimen is highly effective in preventing falciparum malaria, but that many American travelers do not receive it. Also, relapsing P vivax or P ovale infection despite appropriate chemoprophylactic therapy was not uncommon among our cases. The presentation of imported malaria is nonspecific, highlighting the need to consider the diagnosis in any febrile patient who has been in a malaria-endemic area. Although errors in diagnosis and treatment were quite common in our study population, patient outcomes were good once the appropriate therapy was initiated.