Treating and Preventing Malaria Acquired Abroad

NEW ORLEANS -- Malaria remains a significant presence in many tropical countries, which means travel medicine clinicians in the U.S. and their patients should be aware of preventive steps, and also should be educated on malaria symptoms so they can get timely care, a specialist said here.

Blood work should be undertaken in patients returning from travel to malaria-endemic countries who show fever or flu-like symptoms within the first month back and even as far out as 1 year, said Anne McCarthy, MD, MSc, of the University of Ottawa in Canada, at the American Society of Tropical Medicine and Hygiene (ASTMH) annual meeting.

Local clinicians should receive training on how to treat these febrile traveler patients accordingly, she said.

Previous reports highlighted the prevalence of malaria as having decreased by 41% across the world from 2000 to 2015. However, these declines have come to a halt with 91 countries remaining endemic, an estimated 216 million cases of malaria, and 445,000 malaria-related deaths annually, McCarthy emphasized.

With changes in the parasite, efforts are needed to improve diagnosis and treatment. Plasmodium falciparum parasites are increasingly showing deletions in the histidine-rich protein 2 gene (HRP2), the analyte for some of the most common rapid diagnostic tests, making it harder to effectively diagnosis and manage infected individuals, she continued.

The majority of travel destinations have malaria prevention strategies available for tourists, but in most cases travelers do not adhere to the recommendations, McCarthy noted.

In her presentation, she highlighted that while malaria cases aren't common among patients seen in the U.S., they aren't unknown either.

She cited data appearing recently in Morbidity and Mortality Weekly Report on 1,517 cases of malaria seen in the U.S. in 2015. More than 80% originated in Africa and they involved a mix of P. falciparum, P. vivax, P. ovale, and P. malariae. Just over 120 patients appeared to contract infection in Asia, of which the great majority were P. vivax. There were also 66 cases from the Caribbean and Central America, and a handful from South America.

The data also showed that there were 241 malaria cases in children, mostly non-U.S. residents; 85.4% had gotten malaria in Africa. There were also 32 cases among pregnant women.

Moreover, 95.3% of patients with malaria did not follow CDC guidelines on taking chemoprophylaxis. Only 26.5% of United States residents that had malaria took prophylaxis in 2015, which was an improvement from only 32.5% in 2014.

There were 259 severe malaria cases and 11 deaths. The disease was severe for high-risk populations like children (24.1%) and the elderly (28.4%) as well as 21.3% for foreign residents. Symptoms became evident in 11.3% of cases before entry in the U.S. and 95.7% showed signs within the first month.

In most cases, when the disease was severe or someone died, it was because the traveler did not seek medical attention soon enough, McCarthy noted.

To prevent malaria illness, travelers should take malaria chemoprophylaxis, and in cases when those drugs are ineffective, early diagnosis and treatment are important, McCarthy continued. But she also pointed out that medication-based prophylaxis isn't 100% effective and it may affect how and when a patient presents. She urged practitioners to educate patients on infection prevention (such as minimizing exposure to mosquito bites).

There are a number of drugs that clinicians may prescribe for malaria and they include: atovaquone proguanil, chloroquine, chloroquine plus proguanil, doxycycline, mefloquine, primaquine, and tafenoquine.

Tafenoquine (Krintafel) recently received FDA approval and has not encountered any resistance difficulties yet. It was effective at all stages of parasite development but was contraindicated in G6PD deficiency and pregnancy.

When travelers return from their time abroad and are sick, they should go to the hospital, tell the medical professionals where they have traveled, and demand that they rule out malaria, McCarthy emphasized.

Comment