The Menace of Malaria
Stay on your toes to keep malaria at arm’s length

By Barbara Barzolaski, RN, MSN
August 12, 2004

Up with your antennae nurses! When parasites like Plasmodium vivax pop up in the suburbs, you need to read the signals. This organism, the culprit in mosquito-transmitted malaria, showed up in patients in Florida last summer and in Virginia in 2002. Such locally acquired cases serve as a reminder that insectborne infections can appear in unexpected places. What’s more, locally acquired cases of malaria have appeared virtually every summer in the U.S. for the past decade, and almost half the people in the world are at risk for the disease.^1,2

Although a few cases of malaria in the United States don’t merit panic, they do remind us that malaria is mobile. With 300 million to 500 million cases diagnosed worldwide every year, the 1,200 that occur on average in the United States every year are mostly in immigrants and travelers from malaria-risk areas.³ However, since 1997, mosquito-transmitted outbreaks of malaria not attributed to travel or other risk factors, such as blood transfusion, organ transplantation, or needle sharing, have been reported in Florida, Virginia, Georgia, and New York.³ There also have been cases of airport malaria in unexpected areas around the world in which mosquitoes arrive via airplane and infect inhabitants on arrival.³

Virginia cases

According to Holly Williams, RN, MN, PhD, an anthropologist / epidemiologist for the Malaria Epidemiology Branch of the Centers for Disease Control and Prevention, the cases in Virginia were probably not caused by an immigrating insect. They occurred too far from the airport. “The flying range [for mosquitoes] is about two to three kilometers from their breeding sites,” she explains. “They found habitats with larva in the area,” Williams notes of the investigation that ensued after the Virginia outbreak was discovered.

On a hot August night in the summer of 2002, three teens happened to be within a block of one another when they were infected. Although it is not known if one mosquito bit all three people, it is possible, according to Williams. “After a mosquito bites, her eggs develop over the course of several days. She’ll lay her eggs, then go off in search of blood once more. However, feeding can be interrupted, causing her to bite a second or third person in a given night,” she explains.

As for how the local mosquito picked up the Plasmodium in the first place, it is highly plausible that it took blood from someone in the vicinity who had acquired malaria overseas. “PCR [polymerase chain reaction] of the three parasites indicates that the parasite most likely came from the New World, the Americas, with a high probability that all three came from the same source,” Williams notes.

The fact that two cases were identified during the summer of 2002, and another much later in March 2003 in Virginia, adds to the intrigue but is not particularly mysterious.² Symptoms of malaria can begin 10 days to four weeks after infection, but can be delayed for a year. Plasmodium vivax, the parasite in this case, can relapse or rest in the liver for four years after a person is bitten by an infectious mosquito.⁴ Although rare, a relapse, or recrudescent malaria, can occur up to 30 years after the initial infection.⁴

Health threat

Malaria occurs mostly in poor tropical and subtropical parts of the world, mainly affecting areas in Asia and Africa south of the Sahara Desert, where an estimated 90% of deaths due to malaria occur.5 Financial constraints in these impoverished areas impede controlling this preventable infection, and the incidence of disease and death appears to be getting worse.

In countries where malaria is not endemic, such as the U.S., malaria also poses a health threat because most people living in nonendemic areas have no protective immunity. When they get malaria they can develop a rapidly severe, even fatal, disease.

To add to the problem, health care providers are unfamiliar with malaria, and this can cause delayed or incorrect diagnosis and treatment. Under certain conditions, people infected with malaria can transmit parasites to local mosquitoes. They can, in turn, infect local residents. Left unchecked, this course of events can reintroduce malaria in a previously malaria-free area such as the United States.

Life cycle

The Anopheles species of mosquito that carries malaria lays its eggs in water and needs blood to develop eggs. Once a mosquito bites an infected human, the sporozoites migrate to the salivary glands of the mosquito where they are passed on to the next human during feeding. The sporozoites travel to the liver and develop for seven to 30 days. Once they complete this asexual development, they rupture from the liver cells and invade the red blood cells of the victim. These blood-stage parasites cause the symptoms of malaria. They grow within the red cells and destroy them, releasing daughter cells (merozoites) that continue the cycle by invading other cells.

Classic attacks last six to 10 hours and occur every second or third day, depending on the strain of malaria infecting a person. As a result, symptoms tend to occur in cycles of attacks.⁴

Malaria presents with a fever; chills, which can be violent and have a sudden onset; headache; muscle aches; and fatigue. Gastrointestinal symptoms also can occur. Because the parasites multiply in the liver cells and enter the red blood cells, anemia and jaundice also may occur.⁴ Within hours, in addition to fever, the patient may develop hot, dry skin and a rapid, bounding pulse. As the patient’s temperature begins to drop, profuse sweating occurs.

This coincides with the rupture of red blood cells and may last up to 10 hours. This cycle of events may recur every several days, with frequency depending on the type of Plasmodium parasite causing the infection.⁴

“Malaria is diagnosed not by blood cultures, but by microscopic examination of a stained blood smear referred to as a ‘blood slide,’” Williams says. “This is the gold standard for diagnosing all four Plasmodium species of human malaria. The blood examination can tell you if the patient is infected, the level of infection, and which is the infecting species.”

Prevention and treatment

There are effective treatments for malaria as well as effective prophylaxis for people living in or traveling to malarious areas. Chemoprophylaxis for malaria is essential for prevention. It must be initiated several weeks before travel and must be continued several weeks after return in order to be effective.⁴

North America and Central America now are the only regions where parasites that carry malaria have not yet developed a resistance to chloroquinine. The alternative chemoprophylaxis for all other areas is mefloquine. For those unable to take mefloquine, atovaquone/proquanil (Malarone) and doxycycline can be used.

A variety of medications are available to treat malaria once a person has become infected. (See “Malaria Medications” sidebar.) Selection is based on the type of Plasmodium parasite, the likelihood of resistance in that region, as well as the severity and relapse rate of the disease.

The best indicator of drug effectiveness is whether the patient experiences a decreased fever. If the patient does not become afebrile, he or she will likely need a different medication.

Many of the medications indicated for malaria may be harmful to pregnant women, so careful assessment is key. Dosages and duration of therapy vary based on the medication, age, and weight of the person.⁴

Malaria is preventable, Williams says. Although the idea of using insect repellents is unwelcome to some, she notes that DEET is the best and most effective method to avoid being bitten by mosquitoes. “Other control measures can include personal protection devices.”

For instance, Anopheles attack in the evening, so screened windows and clothing that covers the skin can offer protection. In endemic areas, the use of insecticide-impregnated bed nets for sleeping is effective.6

Williams notes that the CDC has a great deal of information, including a malaria hotline, (770) 488-7788, with epidemiologists on call 24 hours a day to answer any questions, and a website for professionals and the general public.

The take-home message for nurses is to be on the alert for malaria. For patients who present with flulike symptoms and fever, Williams says to consider malaria as the cause and get a travel history.

“Nurses should understand the transmission patterns for malaria and have a high index of suspicion for persons who present with a fever and a history of international travel to malaria-endemic areas. Other people for whom malaria should be considered would be temporary migrant workers coming from Central or South America,” Williams advises.

At this point, nurses practicing in the United States don’t know if they’ll have to care for a patient with malaria. But knowing about this global health threat can arm them with information that could someday make a difference in preventing unnecessary disease and fatalities.

Barbara Barzoloski-O’Connor, RN, MSN, is a contributing writer for Nursing Spectrum.

References

1. Multifocal autochthonous transmission of malaria —- Florida, 2003. Available at www.cdc.gov/mmwr/preview/mmwrhtml/mm5319a2.htm. Accessed July 27, 2004.

2. Local transmission of Plasmodium vivax malaria –Virginia 2002. Available at www.cdc.gov/mmwr/preview/mmwrhtml/mm5141a1.htm. Accessed July 27, 2004.

3. Malaria on the move: Human population movement and malaria transmission. Available at www.cdc.gov/ncidod/eid/vol6no2/martens.htm. Accessed July 27, 2004.

4. Malaria: topic home. Available at www.cdc.gov/malaria/index.htm. ccessed July 27, 2004.

5. The impact of malaria, a leading cause of death. Available at www.cdc.gov/malaria/impact/index.htm. Accessed July 27, 2004.

6. Parmet S. Malaria. JAMA. 2004, 291:2664. Available at http://jama.ama-assn.org/cgi/content/full/291/21/2664?etoc. Accessed July 2, 2004.