PROTECTING YOURSELF AGAINST
MALARIA IS IMPERATIVE ON A TRIP TO SOUTHERN AFRICA
HERE'S WHAT YOU SHOULD KNOW
by John Langone
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."
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
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
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
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
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.
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
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