Malaria is one of those diseases that adventurous travelers – and even many who don’t consider themselves to be intrepid explorers – need to be aware of.
Malaria is a disease not uncommon in tropical and subtropical parts of the world, and it’s a “vector-borne” disease. A vector is something that doesn’t actually cause the disease, but spreads it from organism to organism. In the case of malaria, that means mosquitoes – by biting a malaria victim and then biting a healthy person, the mosquito can transfer the malaria parasites to the healthy person and therefore spread the disease without actually causing or having it.
The malaria parasite is well-adapted not just to us, but also to its life in the mosquito. The infection to you is injected along with the saliva from the mosquito, that contains an anti-coagulant to assist the mosquito’s sucking. It is not a matter of injecting you with blood from a previous meal, as the parasite has a special life stage that takes up residence in the mosquito’s salivary glands.
Mechanism of disease. It is a parisite passed through female, night-stalking Anopheles mosquitoes. Malaria-carrying mosquitos make their homes in the damp lowlands of Asia, Africa, and Latin America, and areas in the Pacific and sub-Saharan Africa are typically the most infested. Malaria parasites dwell in mosquito saliva so when it sucks your blood, she’s also leaves behind a few thousand virus particles in exchange.
Malaria is caused by a parasite that lives within red blood cells. It breeds until the cell eventually bursts and the released parasites seek other red blood cells to set up home in and breed further. As the parasite hides within your own cells, it is more difficult for your body’s defenses to get rid of them.
Once the mosquito-human bonding experience is complete, the parasites head toward the liver. After spending one to two weeks building up their red blood cell-attacking army, these parasites re-emerge, causing fever, sweats, chills, muscle soreness, exhaustion, and headaches. Most of the time, people are all right after a few days. However, if the severe form of malaria is left untreated, restricted breathing, coma and even death can result. And while the death rate is relatively low, malaria still kills more than a million people a year, most of them children in sub-Saharan Africa.
The parasite also changes randomly as its generations pass, so that there are likely to be survivors of an onslaught that manage to rebuild the parasite numbers until a fresh assault is mounted, thus the cycles of fever, reduction, and relapse in an exhausting cycle. The fever can be very high (the fever alone can be deadly.
Some symptoms can include high fever, shivering, vomiting, anemia, joint pain, and convulsions. Thanks to all the killed red blood cells, the liver and spleen, overloaded with their recycling task, are likely to become swollen and tender. But no symptom can be absolutely relied upon to be clearly present in a particular case. You need diagnosis by experienced personnel (which may well not include your doctor at home, no disrespect), and a blood test.
There are four different types of bugs, one of which is particularly dangerous – Plasmodium falciparum, that’s responsible for about 80% of all malarial infections, and 90% of malarial deaths.
Incidence. While accurate statistics are hard to come by, since many of the places where malaria is found aren’t well-tracked, it’s safe to say that there are more than 510 million cases of malaria each year and between 1-3 million deaths annually as a result of the disease. And some who don’t die as a direct result of malaria are often so weakened by the parasites that they’re more susceptible to other diseases. Some who survive malaria continue to have poor health for the rest of their lives.
Is malaria infectious? It is not infectious. It is spread by bites from certain species of mosquito. Sharing uncleaned needles might work occasionally but is rare. Blood transfusions would be another unlucky chance.
Drugs to prevent malaria
Called “prophylactic drugs” – they must be taken continually, and they only reduce (not eliminate) the risk of malaria infection. There is no drug that is completely safe and effective either for prevention or for treatment, nor is there a vaccine. The optimum regimen is an attempt to balance the risk of side effects against the risk of disease. You must consider where you are going and when, how you will travel, the types of malaria present, types of drug resistance, the prevalence of risk, how long you will be exposed, and also your personal condition: as with many other drugs, pregnant women are especially constrained, as are young children. And if you’re making a fortnight’s visit to, say, a seaside resort with air-conditioned rooms and dining area, you might well get by with no drugs at all.
Because of the dangers of malaria going untreated, anyone traveling for longer than a week to a malaria-risk area is encouraged to consider bringing and taking anti-malarial drugs. Due to the evolution and mutation of the disease in different parts of the world, treatments have become increasingly complex and should be discussed with a qualified physician. Many of these drugs have rare side effects that include nausea, headaches, disorientation, vomiting and itching, and there is some controversy around taking certain drugs.
Recommendations for drugs to prevent malaria differ by country of travel and can be found in the country-specific tables of the Yellow Book. Recommended drugs for each country are listed in alphabetical order and have comparable efficacy in that country. it can be surprisingly difficult to maintain a regular weekly dose when off travelling, but I choose Sunday.
No antimalarial drug is 100% protective and must be combined with the use of personal protective measures, (i.e., insect repellent, long sleeves, long pants, sleeping in a mosquito-free setting or using an insecticide-treated bednet).
For all medicines, also consider the possibility of drug-drug interactions with other medicines you might be taking as well as other medical contraindications, such as drug allergies.
When several different drugs are recommended for an area, the following might help in the decision process.
1. Atovaquone/Proguanil (Malarone) Combines the two drugs to prevent malaria.
Good for last-minute travelers because the drug is started 1-2 days before traveling to an area where malaria transmission occurs. Some people prefer to take a daily medicine. Good choice for shorter trips because you only have to take the medicine for 7 days after traveling rather than 4 weeks. Very well tolerated medicine – side effects uncommon. Malarone is also the best drug to carry with you when traveling in a malaria risk area – at first symptoms, empirically take 4 tablets once/day X 3 days. Take with food or milk.
Contraindications: Cannot be used by women who are pregnant or breastfeeding a child less than 5 kg. Cannot be taken by people with severe renal impairment. Tends to be more expensive than some of the other options (especially for trips of long duration). Some people (including children) would rather not take a medicine every day
2. Chloroquine (common brand name: Aralen)
Some people would rather take medicine weekly. Good choice for long trips because it is taken only weekly starting one week before arrival and ending one month after departure.
Chloroquine is the cheapest drug available, and the most widely distributed, with rare side effects. Some people are already taking hydroxychloroquine chronically for rheumatologic conditions. In those instances, they may not have to take an additional medicine. Can be used in all trimesters of pregnancy.
Even in areas where chloroquine resistance exists, it is not thereby rendered useless. Even in areas with resistant strains, the high-dose course of chloroquine will cure all but five percent of cases. Thus, if chloroquine is your drug you should not live in daily fear of imminent death (except when on the roads), and note that chloroquine is quite cheaply available throughout malarial areas, much cheaper than in the rich countries though less likely to be coated so as to avoid the bitter taste. Fancier drugs are much less available in poor areas. The unlucky five percent are going to be in trouble, but this is what you have the “stand-by” course of mefloquine for. The local population is unlikely to be able to afford drugs such as mefloquine. In the “Hyperendemic” areas, about 90-100 infected bites a year could be expected, out of 2-300 bites a month if no mosquito-blocking procedures were employed. That means about 3% of mosquitos are infected, but 1% was considered high.
Contraindications: Cannot be used in areas with chloroquine or mefloquine resistance. However, chloroquine is no longer effective in many countries. May exacerbate psoriasis. Some people would rather not take a weekly medication. For trips of short duration, some people would rather not take medication for 4 weeks after travel. Not a good choice for last-minute travelers because drug needs to be started 1-2 weeks prior to travel
3. Doxycycline (common brand names are Doxine 100 or Vibramycin)
It is often prescribed to fight a bacterial infection and for the treatment of acne. If taking doxycycline chronically for prevention of acne, you do not have to take an additional medicine. Doxycycline also can prevent some additional infections (e.g. Rickettsiae and leptospirosis) and so it may be preferred by people planning to do lots of hiking, camping, and wading and swimming in fresh water.
Some people prefer to take a daily medicine. Tends to be the least expensive antimalarial. Good for last-minute travelers because the drug is started 1-2 days before traveling to an area where malaria transmission occurs, it must be taken daily, and continued for a month after leaving the malaria-risk location. Nausea, yeast infections and susceptibility to sunburn are common side affects. As an tetracycline antibiotic, the use of doxycycline diminishes the effectiveness of birth control pills. Another form of birth control should be used.
Contraindications: Cannot be used by pregnant women and children <8 years old. Some people would rather not take a medicine every day. For trips of short duration, some people would rather not take medication for 4 weeks after travel. Women prone to getting vaginal yeast infections when taking antibiotics may prefer taking a different medicine. Persons planning on considerable sun exposure may want to avoid the increased risk of sun sensitivity. Potential of getting an upset stomach from doxycycline.
4. Mefloquine (Lariam)
Some people would rather take medicine weekly. Good choice for long trips because it is taken only weekly. Can be used during pregnancy. is the most widely known malaria drug, due to its ‘vivid dreams’ side effect, and daytime hallucinations that can be disabling. There is a lot of chatter about this amongst travellers. Though some of this is suspected to be self-suggestion and anxiety amongst groups, some people are indeed susceptible. It also promotes confusion and poor coordination, so people intending to drive should avoid it.
Contraindications: Cannot be used in areas with mefloquine resistance. Cannot be used in patients with certain psychiatric conditions as side effects can include hallucinations, anxiety and seizures. The drug must be taken once a week, starting one week before arrival and ending one month after departure. Anyone with a history of epilepsy or mental illness is discouraged from taking Lariam. Not a good choice for last-minute travelers because drug needs to be started at least 2 weeks prior to travel. Some people would rather not take a weekly medication. For trips of short duration, some people would rather not take medication for 4 weeks after travel.
5. Primaquine
It is the most effective medicine for preventing P. vivax and so it is a good choice for travel to places with > 90% P. vivax. Good choice for shorter trips because you only have to take the medicine for 7 days after traveling rather than 4 weeks. Good for last-minute travellers because the drug is started 1-2 days before traveling to an area where malaria transmission occurs. Some people prefer to take a daily medicine
Contraindications: Cannot be used in patients with glucose-6-phosphatase dehydrogenase (G6PD) deficiency and cannot be used in patients who have not been tested for G6PD deficiency. There are costs and delays associated with getting a G6PD test done; however, it only has to be done once. Once a normal G6PD level is verified and documented, the test does not have to be repeated the next time primaquine is considered.
Cannot be used by pregnant women. Cannot be used by women who are breastfeeding unless the infant has also been tested for G6PD deficiency. Some people (including children) would rather not take a medicine every day. It has the potential of causing an upset stomach.
Malaria can be present even though you might not have all the textbook symptoms. To complicate matters it is often ambiguous to start with, and your prophylaxis might be hindering its full expression. Some other disease may be adding its symptoms to confuse you and worse, you may be confused by the disease. Any fever without a definite explanation is suspect until proved otherwise, as by a blood test. Self-diagnosis while you’re ill is not reliable.
Treatment. The best drug to carry with you for emergency treatment – with first symptoms empirically start Malarone 4 tablets once/day X 3 days.
Time Limits on Antimalarial Drugs
None of the anti-malarial drugs can be taken indefinitely. Even for chloroquine, which rarely provokes adverse reactions at prophylactic doses, the World Health Organisation’s recommendation is to limit your lifetime dose to the equivalent of about eight years of consumption, or risk blindness. Thus, if you are living indefinitely in a malarial area, you will only take drugs if you are infected.
The Role of Genetics
Local people generally do not have much of a choice other than to wait for an infection, and hope. A certain amount of resistance may develop with time, but as repeat infections plainly demonstrate, it is not 100% effective. The only effective inbuilt response is the recessive gene amongst certain African populations that in a double dose causes sickle-cell anaemia (and, when left untreated, early death), but its credit is that in a single dose it defends against malaria.
Few travellers catch malaria, and even if you spend a fair while in a bad area, your chances of avoiding malaria are good if you avoid being bitten. But anyone can be unlucky. So go see your doctor, or a specialist travellers’ medical clinic.
Beyond Malaria: Other Problems With Mosquito Bites
Incidentally, aside from malaria, a bite may become infected. It helps not to scratch the bite (and squeezing out some lymph will flush out some of the irritating mosquito saliva), so an anti-histamine ointment will assist those of weaker character. Tincture of iodine will encourage the scratched area to dry (though in hot humid areas, your skin will be slimy with sweat for hours on end) and discourage infection until it heals.
Tropical ulcers typically start from a bug bite, or small scratch. They can be very difficult to get rid of once established, but good nutrition seems to help so eat well. And don’t let an ulcer start. Traditional remedies include raw chili pepper applied to the ulcer, and that has to hurt. Often the most swiftly effective medical treatment is to depart for a cool climate.