Malaria Information Page

Malaria is a serious and sometimes fatal disease which is widespread in many tropical and subtropical countries. It is caught by being bitten by an infected mosquito that is carrying the malaria parasites in its saliva.

The malaria parasite is a microscopic organism called a Plasmodium and it belongs to the group of tiny organisms known as protozoans. There are four types of plasmodium: P. falciparum (the most dangerous), P. vivax, P. ovale and P. malariae. The species of mosquito that carries the malaria parasites is the Anopheles mosquito.

These parasites enter the host's bloodstream when bitten by an infected mosquito and then migrate to the liver where they multiply before returning back into the bloodstream to invade the red blood cells. The parasites continue to multiply inside the red cells until they burst releasing large numbers of free parasites into the blood plasma causing the characteristic fever associated with the disease. This phase of the disease occurs in cycles of approximately 48 hours.

The free parasites are then able to infect any mosquito that feeds on the host's blood during this phase. The cycle then continues as the parasites multiply inside the mosquito and eventually invade its salivary glands. (see the plasmodium life cycle below).

Malaria occurs in over 100 countries and more than 40% of the people in the world are at risk. Large areas of Central and South America, Hispaniola (Haiti and the Dominican Republic), Africa, the Middle East, the Indian subcontinent, Southeast Asia, and Oceania are considered malaria-risk areas.

The World Health Organization estimates that each year 300-500 million cases of malaria occur worldwide and more than two million people die of malaria.

Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhoea may also occur. Malaria may cause anaemia and jaundice (yellow colouring of the skin and eyes) because of the loss of red blood cells. Infection with one type of malaria, P. falciparum, if not promptly treated, may cause kidney failure, seizures, mental confusion, coma, and death.

For most people, symptoms begin 10 days to 4 weeks after infection, although a person may feel ill as early as 8 days or up to 1 year later. Two kinds of malaria, P. vivax and P. ovale, can relapse; some parasites can rest in the liver for several months up to 4 years after a person is bitten by an infected mosquito . When these parasites come out of hibernation and begin invading red blood cells, the person will become sick.

Any traveller who becomes ill with a fever or flu-like illness while travelling and up to one year after returning home should immediately seek professional medical care. You should tell your GP that you have been travelling in a malaria-risk area.

Malaria can be cured with prescription drugs. The type of drugs and length of treatment depend on which kind of malaria is diagnosed, where the patient was infected, the age of the patient, and how severely ill the patient was at start of treatment.

Anybody travelling to an area where malaria is endemic is at risk of catching the disease. Lately there has been an increase in the cases of malaria reported in the UK - in 1993 there were 1922 reported cases in the UK, including five deaths. All caught the disease abroad and almost all cases could have been prevented.

Be aware of the fact that adventure travellers are usually more exposed to malaria than ordinary travellers due to the nature of their activities and the fact that they travel to the more remote locations.

The Malaria Cycle (Plasmodium life cycle)

Ruptured blood cells release free parasites (gametocytes) into the host's bloodstream.

The human host shows the classic malaria symptoms at this stage.

The gametocytes are sucked up by a feeding mosquito and the cycle begins again.

The Prevention and Treatment of Malaria

Malaria is a preventable infection that can be fatal if left untreated.

You cannot be vaccinated against malaria, but you can protect yourself.

Avoidance of Bites

Mosquitoes cause much inconvenience because of local reactions to the bites themselves and from the infections they transmit. Mosquito bites spread other diseases such as yellow fever, dengue fever and Japanese B encephalitis.

Mosquitoes bite at any time of day but the anopheles bites in the night with most activity at dawn and dusk. If you are out at night wear long-sleeved clothing and long trousers.

Mosquitoes may bite through thin clothing, so spray an insecticide or repellent on them. Insect repellents should also be used on exposed skin.

Spraying insecticides in the room, burning pyrethroid coils and heating insecticide impregnated tablets all help to control mosquitoes. If you are sleeping in an unscreened room a mosquito net (which should be impregnated with insecticide) is a sensible precaution. If sleeping out of doors it is essential. Portable, lightweight nets are available.

NOTE: Things like Garlic, Vitamin B and ultrasound devices do not prevent mosquito bites.

Taking Antimalaria Tablets

It should be noted that no prophylactic regimen is 100% effective and advice on malaria prophylaxis changes frequently. There are currently five prophylactic regimens used (A, B, C, D & E), due to the differing resistance that exists by the malaria parasites to the various drugs used. (See the above map of Malaria Endemic Areas).

The tablets you require depend on the country to which you are travelling (see the table page). Start taking the tablets before travel take them absolutely regularly during your stay, preferably with or after a meal and continue to take them after you have returned. This is extremely important to cover the incubation period of the disease.

Prompt Treatment

If you develop a fever between one week after first exposure and up to two years after your return, you should seek medical attention and inform the doctor that you have been in a malarious area.

Anyone with suspected malaria should be treated under medical supervision as soon as possible. If malaria is diagnosed then treatment is a matter of urgency. Treatment should not normally be carried out by unqualified persons.

The drug treatment of malaria depends on the type and severity of the attack. Typically, Quinine Sulphate tablets are used and the normal adult dosage is 600mg every twelve hours which can also be given by intravenous infusion if the illness is severe.

Remember: Prevention is better than cure and over two million people die from malaria every year. It is a very serious illness!

Side Effects of Antimalarials

Like all medicines, antimalarials can sometimes cause side-effects:

Proguanil (Paludrine) can cause nausea and simple mouth ulcers.

Chloroquine (Nivaquine or Avloclor) can cause nausea, temporary blurred vision and rashes.

Patients with a history of psychiatric disturbances (including depression) should not take mefloquine as it may precipitate these conditions. It is now advised that mefloquine be started two and a half weeks before travel.

Doxycycline does carry some risk of photosensitization i.e. can make you prone to sunburn.

Malarone is a relatively new treatment and is virtually free of side effects. It is licensed for use in stays of up to 28 days but there is now experience of it being taken safely for up to three months.

No other tablets are required with mefloquine or doxycycline or Malarone.

Drug Resistance

It is the plasmodia that cause malaria that develop resistance to antimalarial drugs not the mosquitoes that transmit the disease.

Resistance to antimalarial drugs is proving to be a challenging problem in malaria control in most parts of the world. Since the early 60s the sensitivity of the parasites to chloroquine, the best and most widely used drug for treating malaria, has been on the decline.

Drug resistance is the ability of a parasite species to survive and multiply despite the administration of a drug in doses equal to or higher than those usually recommended but within the limit of tolerance.

Newer antimalarials have been developed in an effort to tackle this problem, but all these drugs are either expensive or have undesirable side effects.

The discovery of chloroquine revolutionized the treatment of malaria, pushing quinine to the sidelines.

However, after a variable length of time, the parasites, especially the falciparum species, have started showing resistance to these new drugs.

Resistance is most commonly seen in P. falciparum whereas only sporadic cases of resistance have been reported in P. vivax malaria.

Resistance to chloroquine is most prevalent, while resistance to most other antimalarials has also been reported.

Resistance to chloroquine began from two epicenters; Colombia (South America) and Thailand (South East Asia) in the early 1960s. Since then, resistance has been spreading world wide.

Recently, cases of mefloquine resistance have been reported from areas of Thailand bordering with Burma and Cambodia (see map above). Travellers to Thailand are therefore advised to avoid using mefloquine when travelling to these risk areas.

Because mefloquine is structurally similar to chloroquine, cross resistance is possible due to the prolonged half life of mefloquine.