Malaria

Malaria is a vector-borne disease caused a parasite that is transmitted to individuals via the bite of an infected Anopheles mosquito. There are five parasite species that cause malaria in humans, two of which, P. falciparum and P. vivax, pose the greatest threat and can be fatal. For a more detailed information see: Understanding Malaria.

Malaria occurs globally in over 100 countries in tropical and subtropical regions. It is the most significant parasitic disease in humans. Although malaria can be deadly, both illness and death can be prevented by:

• Individual adherence to mosquito avoidance measures
• Using prophylaxis when indicated:  Refer to CDC
• Recognising the signs of infection and instigating early treatment.

The global burden due to malaria decreased steadily during the years 2000 to 2015 and then stalled. According to the WHO there was an estimated 241 million cases in 2020 and 627,000 deaths. This is considerably down from 500 million cases and 2 million deaths annually at the turn of the century.

Most deaths occur in Africa. COVID-19 disruption contributed to an increased death rate between 2019 and 2020.

High risk countries include Nigeria, Democratic Republic of Congo, Uganda, Mozambique and Angola.  Remarkable gains in malaria elimination have been achieved outside Africa with China declared free of the disease in 2021.

In malaria-endemic regions, transmission patterns can change rapidly due to several factors, such as local weather conditions, mosquito vector density, population density, prevalence of infection, time of year, rainfall patterns, humidity, temperature, environmental factors, drug resistance, etc. In most regions, transmission is seasonal, with peak case numbers during and immediately following the wet season. The optimum conditions for malria transmission are high humidity and a temperature range of 20C to 30C.

Malaria is not a rare disease and it requires special attention if travelling to an area of risk.

Trips can be very different, even if the country is the same. These differences must be considered when advising on whether someone should take prophylaxis. Travel medicine practitioners will never say there is no risk of contracting the disease in a country which is endemic for malaria. It is only possible to give an idea of risk level and leave it up to the traveller to decide whether they want to reduce their risk using prophylaxis or rely on mosquito-avoidance measures only. The latter also helps to reduce the risk of other mosquito-borne disease.

It is important to consider the following and discuss with your travel medicine provider:

Travel itinerary

While a country may be listed as having endemic malaria it doesn’t mean that all the country has the same risk of exposure. Thailand and Indonesia are both listed as endemic for malaria but in recent years the number of reported cases has dramatically decreased, particularly in urban areas where the conditions are often not favourable for the mosquito that transmits malaria. The same applies to many countries with endemic malaria. Altitude also plays a role.

Season of travel

Malaria risk varies according to season of travel. While malaria transmission is consistent for much of the year throughout tropical Africa, it is certainly much less in the cooler months in southern Africa and increases with the wet in Sub-Saharan Africa.  Periodic chemoprophylaxis programs are often used to reduce morbidity and mortality in young children in high transmission months. Transmission is also much reduced in northern India and Pakistan during the cooler, drier months when the conditions become less favourable for breeding. 

Accommodation

Malaria is mostly transmitted by a night-time biting mosquito. The mosquito may be active both outside and inside. Activity may also vary during the night. Some species in Africa are most active in the second half of the night. Staying in well screened accommodation together with air conditioning substantially reduces your risk of exposure. Sleeping under an insecticide impregnated bed net and using knockdown sprays in living areas can also reduce risk.  

Length of stay

Expatriate workers are much more likely to experience a bout of malaria than short term travellers. It is not only due to cumulative risk; many will start out on chemoprophylaxis but cease during their stay.  This can have serious consequences if they have not researched the local support services for their diagnostic capability or the quality of medication. The trans-Africa traveller has a much greater risk of serious disease as they usually have limited knowledge of local services. Carrying Emergency Standby Treatment (EST) and having a good understanding of the signs and symptoms of malaria is very important.

Activities

It is important to consider what activities you might be doing on your trip.  In Asia, many activities are during the day. At night you are often in your accommodation or at a venue.

In Africa, many activities take place early in the early morning or at sunset. During the middle of the day, you retire to your accommodation for rest.

Do Australian travellers contract malaria? 

The answer is yes. Year to date (December 2023), almost 400 cases have been reported to the National Notifiable Diseases Surveillance system.  These are cases reported in Australia and do not include those contracted and treated overseas. 

A detailed report was compiled for the year, 1 July 2014 to 30 June 2015.  This report details country of origin.  There were 260 cases reported in this period.  This was an unusual year against a five-year average of 400. Almost half the cases came from Africa.  The nasty form, P Falciparum, is more likely in Africa.

This report helps us to focus on those most at risk of the disease.  It is likely many of the cases are those visiting friends or relatives in Africa or the Pacific.

A study of imported cases of malaria (8,439) into Switzerland for the period 1990 to 2019 also found that the majority of cases came from Africa with the big contributor being West Africa (39.8%). A number of individual risk factors have been associated with a fatal outcome for malaria.

• Co-morbidities such as HIV and Tuberculosis
• Pregnancy
• Age over 50 years
• P. Falciparum species
• Not using chemoprophylaxis when indicated
• Inappropriate chemoprophylaxis
• No previous immunity
• Delay in seeking diagnosis/ treatment

Many of these risk factors can be addressed in a pre-travel consultation. There is currently no vaccine approved for malaria.

Atovaquone-Proguanil (Malarone)

It is best taken with food or a milky drink at about the same time daily. This drug combination is generally well tolerated. More common side effects are abdominal pain, nausea, vomiting and headache. Other possible side effects include reversible hair loss, scaling of the skin on palms and soles, and mouth ulcers. 

Reasons why you might consider this medication

• Last minute traveller
• Short period of risk (eg Amazonas, game park in Africa, business traveller)
• Very few side effects

The following people should not use Malarone

• Those who have previously had an adverse reaction to either proguanil or atovaquone.
• Those with poor kidney function
• Pregnant or lactating women

Malarone Junior

This has been formulated to give you an easy dose for children from 5kg to 39Kg. It is very well tolerated.

Mefloquine

This drug, a quinine analogue, has been in use for fifteen years. It remains very effective although areas of resistance have appeared in the Thailand - Indo-China region. The malaria prevention dose is 5mg/Kg or one tablet (250mg) once a week, on the same day of the week, for an average size adult. Children under 3 months of age or 5Kg weight should not use mefloquine. After that, the dosage is adjusted according to bodyweight.

The drug has come under attack for unacceptably high rates of side effects including, occasionally, serious neuro-psychiatric problems. Symptoms may include nausea, dizziness, headache, vivid dreams, and in rare cases, disorientation, agitation, and convulsions. Minor side effects, such as nausea, become less obvious with continued use. Another way to take the dose if you are experiencing mild problems, is to halve it and take it on two different days e.g. Sunday and Thursday. Rare, more serious problems will usually be evident by the sixth dose, and gradually resolve after stopping the drug.   Mefloquine is well tolerated by 90% of those who use it and, for that group, it is moderately priced, convenient, and safe to use for long periods. For those who will need to use it for a long time, we strongly recommend a trial period of a month before leaving.

The following individuals are advised to avoid mefloquine:

• Those with a history of epilepsy or significant brain scarring.
• Those with previous or current psychiatric condition such as depression, mania, schizophrenia, panic or anxiety disorder. Individuals with any mood disorder should avoid this medication.
• Those who have not tolerated mefloquine or chloroquine in the past
• Those for whom dizziness would be dangerous eg. mountaineers, scuba divers, pilots, and those working at heights. Side effects may be confused with symptoms of the bends (decompression sickness) in divers.
• Those with heart rhythm abnormalities or on medications to control the heart rhythm.

Might not be suitable for:

• Last minute travellers
• Short trips

The mefloquine tablet should be swallowed after a meal and with a full glass of water.

“Recreational” drugs affecting the brain, including alcohol, should be avoided for 24 hours before and after the dose. If persistent or increasing dizziness, agitation or sleeping difficulties occur, mefloquine should be stopped and an alternative (see below) used if the traveller is still in a high risk area.

Doxycycline

This drug is a tetracycline type of antibiotic. It cannot be used by pregnant women or children under 10 years of age. It is a broad-spectrum antibiotic and is used in general practice to treat respiratory and skin infections. For this reason, and the fact that it is very inexpensive, it is a good choice for those who want to carry a preventive drug in case they suddenly decide to visit a malarial region. For those bad at remembering to take it every day, however, it may not be the best choice. The dose is best taken with a good-sized meal and a large glass of water to avoid nausea.  To avoid “heartburn”, or reflux oesophagitis, it should not be swallowed too close to bedtime or lying down. Doxycycline is commenced just one or two days before entering the malaria area and continued daily until two weeks after leaving it. If many doses have been missed, however, or you have been bitten a lot by mozzies in a high-risk area, it is best to continue it until four weeks after leaving the area. One in ten women reports vaginal itching due to thrush while on this medication and it may reduce the effectiveness of the oral contraceptive pill. One in twenty users may experience sensitivity to sunlight with abnormal redness of exposed skin. Doxycycline should not be used at the same time as Roaccutane or Vitamin A. 

It is the least expensive antimalarial.

Chloroquine Phosphate

This drug has been used for the prevention of malaria for five decades. Unfortunately, P. falciparum  has developed widespread resistance to it. It remains useful for the prevention of malaria in areas such as Central America where the malaria is mostly due to P. vivax...In Indonesia, however, it seems that this species is also becoming resistant. Chloroquine has few side effects and is very inexpensive. This drug can be used if necessary in children and pregnant women. It should not be used by people with a history of epilepsy or widespread psoriasis. If used for more than 5 years, an eye check should be undertaken. Dark skinned people occasionally experience severe itching with this drug. Common minor side effects include nausea, headache and dizziness. If these occur, the dose should be divided in two and taken on two different days e.g. Sunday and Wednesday. The tablets are bitter and need to be swallowed with plenty of water. Children usually need their dose crushed and mixed with something sweet such as jam.

Tafenoquine

This is a newer medication and very effective for the prevention of P. Vivax malaria as well as P. Falciparum.  It is a good choice for last minute travellers and those undertaking short trips.  The drug cannot be used in people who have G6PD deficiency. It cannot be used unless the status is known. It cannot be used in children, if pregnant or breast feeding and in those being treated for psychotic disorders.

Emergency or “standby” treatment options.

For those unwilling to take malaria prevention drugs but nonetheless at some risk of malaria, there is an option to carry drugs for self-treatment. This option may be useful, for example, for a group travelling for a moderate time in areas of low to medium malaria risk. It is desirable to carry a thermometer, to know when to suspect malaria, and to have a well companion to assist. Side effects are usually greater in treatment doses when compared to prevention doses. Medical assistance should be sought when possible. Where it is relatively easy to get to a major centre within 24 hours, it is probably unwarranted to carry such drugs. The other group who may benefit from holding “standby” treatment doses are those at high risk for long periods in remote areas. They may get breakthrough infections despite chemoprophylaxis.

If medical help is difficult to reach, they may use a rapid diagnostic test kit to decide whether or not to self-treat.

• Be Aware of areas where malaria is a risk. Understand how the disease is transmitted and how the illness may present
• Avoid mosquito Bites. If you don’t get bitten you can’t get malaria. Remember peak biting occurs between dusk and dawn
• Chemoprophylaxis (preventive medication) is important in high risk areas. Choose the right medication for you and take it as directed
• Do not delay seeking medical advice and Diagnosis if a fever develops after 5 days from entering a risk area and up to 3 months after leaving. It may still be malaria after this time and you must remember to make any medical attendant aware of recent travel
• Malaria is Easy to diagnose but more than 1 blood slide may be necessary. At least three slides over 48 hrs must be undertaken to exclude the diagnosis

The story of malaria is one of interaction between a tiny blood parasite, a female mosquito that feeds on human to grow her eggs, and humans.

The parasite:

Five species of Plasmodia infect humans. P.falciparum is the most feared because it causes the red blood cells it has invaded to stick to the lining of small blood vessels. Left untreated, broken cells begin to clog up the small blood vessels in vital organs such as the brain and kidneys. Without early diagnosis and treatment, this can kill quickly, especially the very young and older people with no immunity. This species dominates in Africa, Papua New Guinea and the Solomon Islands but also occurs in many other parts of the tropics. The other species P.vivax, P.ovale, and P.malariae, while less likely to kill in the short term, can add to the long term ill-health burden of the poor in these areas. P.vivax was once common all over Europe. It is also able to lie dormant in the liver in a form which is unaffected by most treatment drugs. Relapses due to this form usually occur within 6 months of the original infection. P. knowlesi is a parasite of macaques and found in the Asia Pacific region.

The mosquito:

There are hundreds of species of anopheles mosquitoes, each with their own behaviours. About 20 of these transmit most of the world’s malaria. Their efficiency at transmitting malaria depends on many factors. For example, one species might feed more often than another, or survive better at certain temperatures, or prefer to feed on other animals if they are available. Each species may prefer different types of watery places to breed. In general, the larvae will hatch in their thousands after the rainy season. When a mosquito takes in malaria parasite sexual forms from a human blood meal, the parasites need at least 10 days in the mosquito before they can be transmitted with her bite to another person. At high altitude mosquitos don’t survive long enough for this to occur. Africa has the most efficient malaria transmitting mosquitoes. They live long, feed often, and prefer to feed off people. Most malaria vectors bite late in the evening or in the early hours of the morning.

The human:

When humans from the “Old World” tried to expand their boundaries, for reasons of commerce, religion or war, malaria awaited them. Ross commented that no geographical difficulties were as great as that posed by malaria. The papal conclave in Rome in the summer of 1623 was a disaster, with 6 of the Cardinals dying of malaria. Not long after this, the Jesuits working in Peru identified the bark of the Cinchona or “quina-quina” tree for its medicinal merits in treating some fevers. Its use for both treatment and prevention of malaria spread in Europe. British exploration trips to West Africa in the 1800’s suffered catastrophic malaria death rates.