•  Cholera

Malaria is a tropical disease that strikes up to 500 million people and causes 1 million deaths worldwide every year. It is caused by a type of single-celled parasite (protozoa) called plasmodium. Four species of plasmodium cause malaria; the most common is Plasmodium falciparum. The parasite is carried by anopheles mosquitoes. There are about 400 types of anopheles mosquitoes, but only about 30 can spread malaria.

Scientists believe the parasite has been around for at least as long as humans have. It probably originated in central and east Africa, and spread all over the globe during human migration. As a disease, malaria has probably been known to man for about 5,000 years, and it continues to be one of the deadliest infectious diseases in the world. But it doesn't have to be -- malaria is both preventable and curable.

Malaria is endemic in tropical areas throughout the world, from jungles of Southeast Asia and South America to tropical islands of the South Pacific. As recently as 1935, malaria caused about 4,000 deaths in the United States annually,but it is not commonly found anymore in the United States, Canada, and Western Europe. However, due to climate change and other factors, isolated outbreaks have been reported again in Florida, New Jersey, New York, and Texas.

The real danger zone is Africa. According to the WHO, about 90 percent of malaria cases occur here. The continent can be a dangerous place not only for residents, but also for travelers. About two-thirds of Americans who contract malaria overseas had spent some time in Africa.

Some places are more mosquito-friendly than others. The insects thrive in warm, moist climates. They are more common in rural areas (which may have more standing water, where mosquitoes lay eggs), but they can also be found in cities. The insects are not as common at higher altitudes because they can't survive at low humidity or temperatures.

Anopheles mosquitoes feed on blood. Depending on the region, they may feed exclusively on human blood, or they may include other animals in the mix. If a carrier mosquito bites a person, the parasite can enter the bloodstream. Mosquitoes can also pick up the parasite by biting infected humans, allowing the disease to spread from person to person.

Malaria can also spread from one person to another through blood transfusions, which is why people in the United States are prohibited from donating blood for at least a year after visiting malarial countries. Sometimes the plasmodium parasite can lie dormant in the liver -- even if a traveler has taken antimalarial drugs -- and then become active months later.

Once inside the body, the parasite enters red blood cells, where it multiplies. After 48 to 72 hours, the red blood cells burst and release more parasites, which infect other red blood cells. Some enter liver cells.

Malaria is marked by flu-like symptoms including fever, shaking chills, heavy sweating when the fever falls, severe lack of energy, headaches, body aches, nausea and vomiting, and jaundice (yellowing of the skin). The symptoms can come and go every 2 to 3 days.

Advanced symptoms may include mental confusion, kidney failure, seizures, and coma. Without effective treatment, the disease can be fatal.

Symptoms usually start within one week to one month after infection, but the onset could be delayed if, for example, a person took antimalarial pills before becoming infected and the parasite silently resided in the liver. In some people, these dormant parasites can cause relapses months or even years after the first attack.

If you're feeling ill with a fever or flu-like symptoms, let your doctor know if you traveled to a malaria zone within the last year. Your doctor can use a microscope to check for signs of the plasmodium parasite in your blood. And if you have symptoms while you're traveling, don't wait until you get home to get checked out -- see a doctor right away.

The sooner you can be diagnosed and treated, the better. Prompt treatment with antimalarial drugs can shorten the duration of the disease and help prevent complications. Several different medications are used to attack the parasite and speed recovery, including chloroquine, mefloquine, and doxycycline. Even with treatment, you may feel tired and weak for a few weeks.

The earliest treatment for malaria was the drug quinine, extracted from the bark of the Peruvian Cinchona tree. Later, more effective synthetic drugs such as chloroquine became standard treatment for decades. But just as bacteria can build up resistance to antibiotics, malaria parasites in most parts of the world no longer respond to chloroquine. In some regions, there is resistance emerging to other drugs, such as sulfadoxine-pyrimethamine and mefloquine. In Africa, where drug-resistant malaria is especially widespread, doctors are now treating the disease with combinations of drugs.

If you're visiting a malaria-infected area, do everything you can to protect yourself. There's no vaccine against malaria, so your top priority should be keeping mosquitoes away, especially in the evening and at night when mosquitoes come out to feed. It's wise to be careful during the day too: Mosquitoes that are active during the day may be carrying yellow fever or other diseases.

Here are some tips:

•Stay indoors whenever possible.

•Wear long sleeves and long pants to cover as much skin as you can. Keep in mind that mosquitoes can bite through very thin material.

•Spray your clothing with insect repellent. Brands containing the insecticide DEET are the most effective. The spray will last until you wash your clothes. Once you're out of the malaria zone, wash your clothes before wearing them again. (If you're pregnant, DEET appears to be safe but it's still a good idea to limit your exposure.)

•Consider wearing insect-repellent sprays or lotions on exposed skin. When using DEET sprays, lotions, or wipes, follow all directions and minimize your contact. Don't use on broken skin, near the mouth or eyes, or on infants under two months of age. After you come back inside, wash off the sprayed areas with soap and water. DEET isn't meant for long-term use, as it can cause agitation, disorientation, unsteady gait, seizures, and coma. The risk may be higher for children.

•(If you'd rather not use chemical sprays, there are natural options available made from citronella, rosemary, and other insect-repellent essential oils. However, these are not as effective and wear off faster.)

•When possible, sleep only in places that are air-conditioned, or at least breezy and well-screened from the outside.

•Cover your bed with mosquito netting. You can also spray the netting with DEET or permethrin for added protection.

•In many parts of the world it's common to burn incense-like coils of mosquito repellent containing citronella, but beware -- many brands contain toxic, cancer-causing chemicals banned in the United States.

You can get extra protection by taking doxycycline, atovaquone/proguanil (Malarone), or another antimalarial drug before you arrive in a malaria region. If possible, visit a travel-health physician for your prescription because a specialist will have the most up-to-date information on regional differences in drug resistance. But be careful with these drugs -- one common malaria medicine, mefloquine (Larium), can cause seizures, psychosis, heart problems, and other side effects.

The CDC also advises preventive antimalarial drugs for children visiting malaria areas, but the dosage must be carefully calculated for their weight because overdoses can be fatal. If you're pregnant, the CDC advises that you avoid traveling to malaria regions. The disease can be severe during pregnancy and can result in prematurity, miscarriage, or stillbirth. If you must travel, it's essential to take antimalarial pills.

For best results, start taking the antimalarial pills days or weeks before arriving in the region, and up to a month after you leave; exactly how before or after depends on the particular drug.

It's important to buy your pills before you leave the United States to get the best possible drug for you and make sure it's high-quality medication. Also, scam artists in malaria-ridden countries often sell fake or inferior "malaria pills" to unsuspecting travelers.

Chris Woolston, MS, is a contributing editor to Consumer Health Interactive. A former staff writer for Hippocrates magazine, he has written for Health, Prevention, and other journals. He writes The Healthy Skeptic, a biweekly column in the Los Angeles Times. He is also the co-author of Generation Extra Large: Rescuing Our Children from the Epidemic of Obesity (Perseus paperback, 2006).

Further Resources

The Centers for Disease Control and Prevention Malaria Risk Map. http://www.cdc.gov/malaria/risk_map/

References

First published June 16, 2008
Copyright © 2008 Consumer Health Interactive

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