The Risk of Malaria for the International Traveller
Where the disease occurs:
For those travelling to many of the warmer regions of our world there may be a risk of contracting malaria. Each year this parasitic disease causes many deaths both in the tropics and among travellers returning to their home countries. Most of the transmission occurs in tropical Africa (approx. 95%), Asia and Central & South America. Travellers need to remember that there is also a mild risk of the disease when visiting parts of North Africa and some parts of the Middle East.
How is the disease transmitted:
In the majority of cases the disease is transmitted to humans through the bite of an infected mosquito. The parasite enters the blood and passes very rapidly into the liver cells. After an incubation period (usually 1 to 4 weeks) the parasite breaks out of the liver and back into the blood stream. At this stage the infected red blood cell begins to break down and only then does the patient start to develop symptoms. [The disease can also be transmitted through blood transfusion, infected needles and from an infected mother to her unborn baby.]
The main symptoms:
Initially the patient may develop an itchy reaction at the site of the mosquito bite. This is not always present – it depends on the individuals allergic reaction to bites. After the liver phase has passed the patient may go on to develop the classical symptoms of malaria. The individual will usually feel they have ‘flu. It will frequently be difficult to convince them that perhaps malaria is a possibility following their journey.
The common symptoms include;
Generalised ‘flu symptoms
The degree of illness within any particular patient depends greatly on the number of parasites within the blood stream. During an initial attack the symptoms are usually very definite and a clinical diagnosis may be quite straightforward so long as a history of international travel is obtained.
All age groups are at risk of malaria.
Changes in clinical symptoms:
In patients on inadequate prophylaxis the symptoms may be altered significantly. Patients may develop milder sweating attacks though usually this is always a significant element of the disease picture. Generalised ‘flu symptoms may also confuse the diagnosis as travellers often experience a ‘cold’ after longhaul flights.
Young children, diabetic patients and the older age groups may also present with changed symptoms which do not fit the ‘classical’ picture. Patients who are pregnant or on other medications (steroids/antibiotics etc.) may not present in a straight forward fashion.
Making a diagnosis:
The only certain way of confirming the diagnosis of malaria is to find the parasite on examination of the patient’s blood. Many laboratories are quite inexperienced in identifying tropical diseases and so delay or a misdiagnosis sometimes occurs. In patients with history of exposure and suggestive clinical symptoms it may be necessary to commence treatment on a presumptive basis before the final results are through. This is often the safest course of action. Remember that following any at-risk travel Fever = Malaria until it is proven otherwise!
Protection against malaria:
It is essential that all travellers recognise that none of the malaria prophylactic tablets are perfect. Each of the drugs used have problems – either with ease of compliance or side effects of varying severity. Avoiding mosquito bites remains the cornerstone of protection against malaria. In most cases the mosquitoes which transmit malaria tend to bite during the evening hours once the intensity of the sun has lessened. At these times (between dusk and dawn) it is essential that travellers cover up well and use adequate insect repellent. AVOIDING INSECT BITES
Specific drugs used for protection:
Various drugs are used to protect against malaria. As mentioned earlier none of these are perfect and they only have their main effect after the liver stage of the life cycle has been completed. In all cases it is necessary to ensure that adequate blood levels of the drugs are maintained during exposure and for a full four weeks at least afterwards. Even still the patient may develop the disease months after they return home.
This drug has been widely used for the past 10 years for travellers from many countries throughout the world. It is taken once a week and provides a high degree of protection against malaria for many of the high risk regions of the world. In the majority of patients the drug is taken without difficulty but in a number of others there are reports of worrying and disturbing possible side effects. It is essential that travellers discuss these issues through with the prescribing doctor. It may be that alcohol consumption may play a significant role in making some of the side effects more noticeable and so in general, it is probably wise to restrict alcohol consumption for 24 hours before and after Mefloquine administration.
Chloroquine & Proguanil
This combination of two drugs still gives adequate protection against malaria for many regions of the world. Nevertheless patients can experience side effects such as mouth ulcers, nausea, hair loss and headaches though these are usually mild. The single biggest difficulty with this combination is ensuring individual compliance with taking drugs on a daily and weekly basis.
This is a potent form of tetracycline and is used for malaria prophylaxis under certain circumstances. As it is an antibiotic, there will be a possibility of thrush in those who are susceptible. Also patients on tetracycline (and certain other drugs) may become more sensitive to the sun.
It is essential that all travellers realise that malaria is a very serious disease. It can kill a patient very rapidly and we have no vaccine against the disease. The primary responsibility for protection against the disease rests firmly with the individual traveller. The prescribed drugs may assist but they do not provide full protection.
If you think you have malaria:
Remember that patients may develop malaria despite having taken all reasonable care with both personal protection against mosquito bites and prophylactic drugs. The disease may present many weeks or months after exposure. Certainly the disease has been initially seen many years after exposure in some patients.
If you feel you may have malaria it is essential that you attend for detailed medical examination just as soon as possible. Ensure that the medical staff realise your history of international travel to an at risk region of the world, either just recently or in the distant past.
Remember that the blood test (especially in inexperienced hands) may not show the parasite despite the fact that the disease may be present in the patient.