PROTECTING YOURSELF AGAINST MALARIA IS IMPERATIVE ON A TRIP TO SOUTHERN AFRICA

HERE'S WHAT YOU SHOULD KNOW

by John Langone

Malaria

A dreaded word coined in 1690 by Italian physician Francesco Torti. He based it on the Italian malaria, or bad air - allusion to the belief that noxious marsh gases were behind the often deadly disease.

Today we know that malaria is caused by parasites transmitted by mosquitoes. But anti-malarial drugs are still not 100 percent effective, mosquitoes are becoming increasingly resistant to insect repellents and insecticides, and a malaria vaccine has not yet been developed. Moreover, it's residents of Africa who suffer from malaria the most-90 percent of the annual 2.1 million malaria-induced deaths occur there.

"However, there is not as much malaria in southern Africa because of longstanding programs for hitting mosquito-breeding sites," says Dr. Michele Barry, professor of medicine at the Yale University School of Medicine and a staff member of its Health and International Travelers Clinic. Indeed, the major cities-Harare, Bulawayo, Johannesburg, and Cape Town-are malaria-free. "But there are malaria trouble spots," continues Barry, "including Zimbabwe; the Mozambique border parks, such as Kruger National Park; and around Victoria Falls. In these places you have to be on anti-malarials."

This is also true for some of the other major areas of interest to visitors: Ovamboland and the Caprivi Strip in northern Namibia; the Okavango Delta in northwestern Botswana; the Zambezi River Valley in northern Zimbabwe; and game parks and rural areas in northern, eastern, and western low-altitude areas of Northern Transvaal, Province of Northwest, Gauteng, and Mpumalanga in South Africa. In short, the real risk is in rural regions and game parks.

Peak malaria seasons vary from country to country within southern Africa but are generally highest during and right after the rainy season (November to May, peaking between February and April), as mosquitoes require water to breed. However, it's important to remember that malaria isn't seasonal.

"The prevalence of Anopheles gambiae-the mosquito capable of carrying malaria-depends on local breeding conditions and varies with rainfall," explains Dr. William Trager, a parasitologist at Rockefeller University in New York. "In temperate zones mosquitoes hibernate in winter and transmit actively in warm weather. In the tropics mosquitoes are around most of the time, and so are infected people. Mosquitoes draw blood from them and pass on the infection when they bite someone else. So the potential to pick it up is always there."

The Cause

There are 60-odd types of mosquitoes that can transmit malaria, which is actually caused by parasites carried within the female insect's body. When the mosquito bites, she injects the parasites into the victim's bloodstream. One thing that makes the disease particularly insidious is the fact that the parasites reproduce within the mosquito's body. Thus one mosquito can infect many, many people.

There are four malaria parasites that cause the disease in humans: Plasmodium vivax, P. malariae, P. ovale, and P. falciparum. The last named is the most dangerous and the one you're most likely to encounter during your trip. "Ninety-six percent of the malaria in Africa is Plasmodium falciparum," says Dr. Jay Keystone of the Center for Travel and Tropical Medicine at Toronto General Hospital, "and it's the deadliest."

You're most at risk for malaria-carrying mosquitoes in the evening and at night, which are the only times the female anopheles is normally active. Thus it's important to wear long-sleeved shirts and long pants after dark and to use the mosquito netting that game lodges provide

It's not easy to identify malaria symptoms because they can easily be mistaken for those of other tropical diseases, such as yellow and dengue fevers. In its early stages malaria mimics the flu, causing fever, headache, chills, lethargy, and muscle aches. If the disease persists untreated, non-flu-like symptoms can appear, including mild jaundice and an enlarged liver; hypoglycemia, or decreased blood glucose; and blackwater fever, which generally occurs in patients with chronic falciparum malaria. Eventually malaria can cause anemia, kidney failure, coma, and even death.

Prevention There are some powerful anti-malarial drugs available, all of which must be taken on a strict regimen that begins before travel, continues throughout, and lasts for several weeks after returning home. None of the drugs, however, are 100 percent effective. "There's no question that the drugs lower the risk dramatically," says Dr. Bradley Connor, medical director of Travel Health Services in New York, "but there's also no worldwide consensus as to what's best for malaria prevention." Even worse, the side effects of the drugs can be extremely unpleasant.

Which drug you should take depends largely on which one your body can tolerate. For trips to southern Africa, most doctors prescribe mefloquine, also known as Lariam. Developed by the U.S. Army, it is widely considered the most effective drug against P. falciparum. It is taken once a week on the same day, starting one week before entering the malarious area; while there; and for four weeks after leaving. Some specialists caution that side effects are likely, including gastrointestinal and sleep disturbances, anxiety attacks, irritability, depression, nausea, and dizziness. More severe effects-seizures, hallucinations, and psychosis-are less common but are the reason travelers with a known hypersensitivity to the drug, a history of epilepsy, or psychiatric disorders should not take it. "Only one person in ten to thirteen thousand experiences the most severe side effects," says Dr. Keystone, "and only one in two hundred fifty to five hundred experiences lesser ones. Just three percent of patients stop taking the drug because of them."

For those who can't take , the Centers for Disease Control (CDC) in Atlanta recommends doxycycline, an antibiotic. It is taken every day for the same amount of time as mefloquine. Possible side effects include stomach upset, esophagitis (inflammation of the esophagus), vaginal yeast infection, and skin photosensitivity, which can result in extreme sunburn. The drug cannot be used by pregnant women, children under eight, and travelers with known hypersensitivity.

Chloroquine, the drug which replaced quinine in the 1940s and is now marketed in the United States under the brand name Aralen, is used in some areas of Africa-mainly Egypt and northern Africa-because of its low cost. But it isn't recommended for trips to southern Africa. "Chloroquine just doesn't work against P. falciparum in most parts of Africa," says Dr. Keystone. Dr. Trager concurs: "It doesn't work very much anymore against P. falciparum. Vivax malaria still responds to it, despite some reports of resistance, so there's some value in taking it if you're going to parts of Africa where P. vivax is present." (That means mainly the northeast part of the continent.)

Fansidar, or pyrimethamine sulfadoxine, a drug developed in the 1960s, is also prescribed widely by doctors in Botswana and Namibia because it is inexpensive. The CDC recommends it for self-treatment if medical help is not available. But doctors with whom we spoke say that, in general, self-treatment isn't recommended except in the most dire situations. "If you come down with malaria symptoms and can't get to medical care within forty-eight hours," says Keystone, "a single dose of Fansidar can be taken so that you have time to get to a doctor. But it should not be used as a preventative measure in general." The main risk from a one-time dose of Fansidar is a severe skin reaction, but taking it weekly can be fatal. It also shouldn't be taken by pregnant women or anyone with a sulfur allergy.

Two combinations of anti-malarials are also sometimes prescribed. One is chloroquine taken simultaneously each day with Proguanil, or Paludrine. It isn't available in the United States but is obtainable in Canada, Great Britain, Europe, and many African countries. "Unfortunately there's a schism between British and U.S. recommendations regarding this combination," says Dr. Connor. "The CDC just doesn't believe that it offers adequate protection." But even Dr. Keystone in Toronto is against it. "We advise against this combination," he says. "Sure, it is safer than mefloquine, only it doesn't work."

The other combination sometimes given is Malarone, a mixture of proguanil and atovaquone, which has been licensed in Great Britain. It is expected to be available in the United States and Canada later this year but, according to some authorities, is less effective than mefloquine alone. The real advantages are that side effects are limited to upset stomach, itchiness, and cough and that it must be taken daily for only one or two weeks.

Treatment

A number of drugs are effective in treating malaria among them primaquine, antibiotics, quinine, quinidine, and mefloquine. Chloroquine is also used, but only if the malaria was acquired in locales where parasites aren't resistant to the drug, which excludes southern Africa. "The good thing about falciparum malaria is that once it's been treated it usually never comes back, unless you're reinfected," says Dr. Trager. "With P. vivax this is not true-even after ordinary treatment, it may relapse." An effective malaria vaccine has not yet been developed, mainly because the complex parasite-mosquito relationship makes it difficult for researchers to pinpoint the stage at which a vaccine could intervene. Trager, the first to culture P. falciparum in red blood cells (a key step in vaccine development), says that back in 1976 he believed a vaccine would be available in 10 years. "Here it is 1998," he says, "and it's turned out to be more difficult than we thought."

Recently, however, a couple of promising new advances have surfaced. One of them, the DNA vaccination, involves injecting the DNA coding for a specific component of the malaria parasite into the patient's body through a hypodermic needle or special "gene gun." With the other, mosquitoes rendered genetically incapable of carrying or transmitting malaria parasites would be introduced into the environment to propagate. The problem, according to Dr. Greg Lanzaro, a medical entomologist at the Center for Tropical Diseases of the University of Texas Medical Branch at Galveston, is that little is known about the mating behavior of African mosquitoes.

Because a malaria infection can be life-threatening, the best advice is to seek prompt medical assistance if you develop any flu-like symptoms. "Here in the United States we don't appreciate the magnitude of the disease," says Dr. Connor. "We advise travelers to consider any fever as malaria until proven otherwise."

This is true both during the trip and up to a year or more after returning home. Says Dr. Barry: "Most times malaria doesn't present itself when you're on holiday. It's usually when you're back home. The majority of falciparum cases show up within four months, vivax as much as years later. You really need a blood test to tell." Because of the risk, travelers to malaria-prone regions may not donate blood for three years after returning home.

Dr. Trager learned the hard way. Years ago he caught malaria while in Nigeria. But he didn't come down with symptoms until three years later. "P. vivax has dormant stages that weren't affected by the chloroquine I was taking," he says. "Once they're activated and infect red cells, that stage can be cured with the drug. I think I hold the record for the longest period of latency."

Disease risks and precautions