Key learning points:
– Imported UK malaria is declining reflecting the global efforts on
– Late diagnosis and treatment can be fatal and obtaining a travel
history is critical for making the diagnosis of malaria
Malaria can be a life-threatening disease caused by the protozoan plasmodium. The parasites are transmitted to humans through the bite of an infected female anopheles mosquito. There are many different plasmodium species, but just five that can potentially infect humans; p. falciparum, p. vivax, p. ovale, p. malariae and p. knowlesi. P. falciparum and p. vivax are the most frequent with p. falciparum infection resulting in the majority of deaths in humans.
It usually takes between seven and 30 days from infection for symptoms to occur. However this can be much longer if the patient is infected with p. vivax that can persist for months in the liver. Relapses then occur and may recur for some time afterwards.
Malaria, although preventable and curable, remains an enormous global public health problem with the World Health Organization (WHO) reporting half a million deaths annually. (1)
Malaria occurs throughout tropical and sub-tropical areas, including many parts of South East Asia, central and South America, sub-Saharan Africa, areas of the middle-east and some pacific islands.
Within malaria endemic countries there can be variable areas of transmission with some areas known as hot spots, where there is a high risk of infection, and many low risk areas – particularly in cities, or at high altitudes and during cold seasons.
The environmental temperature is important in the
malaria cycle as p. falciparum cannot complete its life cycle below 20 degrees, plasmodium vivax and other species can tolerate cooler climates. (2)
The highest prevalence of malaria is near the equator in sub- Saharan Africa, where the risk of transmission is all year round and intense.
What is the current situation?
According to the WHO, since 2000, Malaria mortality rates have fallen by 54% in Africa and globally by 47%.1 Of the 584,000 deaths related to Malaria in 2013, 78% of these were children under five – meaning a rate of more than 1,200 deaths in children under the age of five every single day. (3)
Areas now free or with a markedly reduced risk of malaria have been achieved through successful vector control, diagnosis and treatment. These measures include the combined use of: insecticide treated bed nets (ITN), indoor residual spraying of houses (IRS) effective diagnosis with rapid diagnostic tests (RDT) and treatment of malaria with artemesinin combination therapy (ACT). However, it is important not to become complacent as these gains could be threatened by a future decline in commitment to elimination (financial and political) as well as by resistance and change in the disease itself.
In the UK, the overall numbers of imported malaria cases have fallen over the past decade, with the rates of p. falciparum cases and deaths fluctuating year on year. (4) A total of 184 deaths from malaria were reported between 1987 and 2006 with seven deaths in 2013, mostly from p. falciparum acquired in West or East Africa. (5)
Are cases of Plasmodium Falciparum increasing in the UK?
The UK travel and tourist industry is expanding each year. More and more residents from the UK are travelling abroad as the cost of travel declines. For most years the number of visits abroad made by UK residents has increased. According to the Office for National Statistics (6) most trips abroad are for holidays (4% increase) or for visiting friends and family (5.7% increase). What the epidemiological data reveal is that despite increasing numbers of visits to tropical and other countries, the number of cases of malaria have been declining. Behrens and colleagues described a 2.3 fold increase in visits to West Africa during a 13-year period (1993-2006) but a fall of 9.8% a year in the incidence of malaria over the same period. (3) They showed that the decline was likely to be related to the change in malaria transmission in West Africa and not due to more travellers using malaria chemoprophylaxis.
Who gets malaria?
The majority of imported malaria into the UK is reported in travellers who have been visiting friends and family abroad. Over the past decade more than 80% of the cases of imported malaria to the UK were in travellers visiting family and friends (VFRs). (4) The majority of this group (74%) were of black African ethnicity or African descent. (5)
More than half of the number of imported cases of malaria in the UK are in residents of London. Boroughs in the south east, in particular Southwark and Greenwich, house the majority of cases. This is possibly due to the high numbers of residents being of black African ethnicity.
The number of residents within the UK who were not born here is increasing every year. In 2012 one-in-eight residents (12.4%) were born abroad and one in 13 (7.8%) were of non British nationality. Due to the diverse community that exists within the UK it means there is an increase in the number of people flying home to their country of birth to visit friends and families and then returning to their present home within the UK.
Why do VFRs get Malaria?
One of the key contributing factors that results in VFR is getting malaria is poor compliance to malaria chemoprophylaxis. Only 38% of VFR travellers visiting Nigeria were taking appropriate malaria tablets. (6) Of the malaria cases reported by the Malaria Reference Laboratory, only 7% of VFRs reported having used a recommended anti-malarial regime. (7) Although VFRs do infrequently seek pre-travel advice this is not the only reason for poor compliance to malaria prophylaxis. Cost may contribute to low uptake, but where malaria prophylaxis has been made available for free the uptake by VFRs remains low.
There seems to be no correlation between a traveller’s knowledge about malaria and their use of chemoprophylaxis. Often knowledgeable travellers who have lived in endemic countries believe they can recognise symptoms of malaria and are able to treat themselves. (8)
When travellers seek pre-travel advice, whether in a travel clinic or through their GP practice, the consultation should ensure a thorough risk assessment is undertaken so the traveller is informed of all the health threats and preventative measures necessary for their journey.
The UK guidelines from the Advisory Committee on Malaria Prevention (9) outline the information needed to advise the traveller on how to effectively prevent malaria. These guidelines are based on the acronym ABCD:
– Bite prevention.
Awareness of risk
Travellers need to be both aware that malaria exists where they are going, and that it is a serious disease, which is occasionally fatal. They need to be aware of and compliant with measures to reduce the malaria risk. Health providers need knowledge of well described risk factors including the impact of pre-existing health problems and age (infants and children and the elderly traveller may all have a higher risk of severe malaria).
The health professional should discuss bite avoidance techniques with the traveller.
Female anopheles mosquitoes bite between dusk and dawn.
All travellers to malaria areas should understand the implications of this. The use of bed nets and other means of protecting their sleeping environment, including the use of air conditioning, vaporizing devices and insecticide sprays should be emphasised.
Insect repellent should be used, especially between dusk and dawn, but ideally the traveller should be encouraged to use repellent throughout the day to avoid other insect borne diseases such as dengue fever, yellow fever and chikungunya. A DEET (N,N diethyl-m-toluamide) based insect repellent at concentrations of 20-50% is highly effective in areas where malaria is endemic. A useful guide to repellents has recently been published (10) with the important messages being:
– Always recommend a topically applied repellent with a proven active ingredient such as DEET (20-50%), PMD (30%), or Icaridin (20-50%). IR3535 (20%) is recommended only for areas where vector borne diseases are not present but nuisance biting may occur.
– Re-apply repellents at least every six-to-eight hours if using DEET or IR3535, or every four to six hours for PMD and Icaridin, and sooner if they wear off while swimming or sweating in warm weather.
– DEET can be used on children over eight weeks old, PMD in children over three years.
– DEET can be used in pregnancy and in breast feeding mothers.
Travellers should be encouraged to cover up exposed skin as much as possible where mosquitoes are most attracted.
Chemoprophylaxis should be discussed while taking into consideration a number of factors. The side effects should always be mentioned as around a third of people can have side effects from the medication. (9) Tolerability (side effects) should be carefully explained, i.e. the type of side effects that are associated with the drug and what to do if they occur. The selection of drug regimen should be based on its appropriateness to the region, (9) frequency and duration of side-effects and cost considerations. Cost can be an important deciding factor when someone is travelling for an extended period of time.
Diagnose promptly and treat without delay
At the consultation it is important to determine how much the traveller understands about the risks of malaria. Depending on their depth of knowledge, the health professional should then educate the traveller on the signs of malaria and the importance of early diagnosis and treatment.
Prodromal symptoms for malaria are usually non-specific mimicking many other infectious diseases. Common characteristics include flu-like symptoms, chills, headaches, myalgia, diarrhoea, nausea, vomiting, loss of appetite and fever (with or without rigors). It is, however quite common to see individuals with a normal temperature when they present with malaria.
Where malaria is not diagnosed and treated promptly, p. falciparum infections may progress rapidly to severe disease (coma, renal failure, pulmonary oedema, severe anaemia or metabolic acidosis) and occasionally death. Delayed and missed diagnosis are major contributory factors to developing severe life threatening malaria. (11) The majority of deaths from malaria reported in the UK are due to missed or delayed diagnosis. Malaria should be suspected in all travellers who are unwell. All symptomatic individuals seen by a health professional should always be asked: “Have you travelled abroad recently?”
Treatment of malaria
Modern day chemotherapy of treatment of malaria is based around the artemesinin drugs. For uncomplicated p. falciparum malaria the combination of artemether and lumefantrine (Riamet), piperaquine and artenimol (Euratesim) or atovaquone and proguanil are the choices in oral treatment. For p.vivax malaria chloroquine followed by primaquine are the recommended drugs. For patients with severe or complicated malaria intravenous artesunate is the first line drug treatment.
Global malaria has been successfully tackled by effective interventions based on vector control, diagnosis and new treatments. This success has impacted on imported malaria to the UK. The rates of malaria overall are declining, however malaria remains a problem in travellers visiting friends and relatives. Early diagnosis of an unwell patient depends on a travel history being taken and rapid diagnosis and treatment. Modern drugs are safe and highly effective in eliminating the infection.
1. World Health Organization. World Malaria Report 2014 (summary): World Health Organization; 15448 2012 [updated 2015]. http://apps.who.int/iris/bitstream/10665/160458/1/WHO_HTM_GMP_2015.2_eng... (accessed 29 April).
2. CDC. Health-Related Quality of Life. CDC 24/7: Saving lives. Protecting people. Centers for Disease Control and Prevention [Internet]. 2013. http://www.cdc.gov/hrqol/wellbeing.htm (accessed 29 April).
3. Behrens RH, Carroll B, Smith V, Alexander N. Declining incidence of malaria imported into the UK from West Africa. Malaria Journal 2008;7:235.
4. Behrens RH, Neave PE, Jones CO. Imported malaria among people who travel to visit friends and relatives: is current UK policy effective or does it need a strategic change? Malaria Journal 2015;14(1):149.
5. Agency HP. Migrant Health: Infectious diseases in non-UK born populations in the UK. An update to the baseline report. 2011.
6. Behrens RH, Alexander N. Malaria knowledge and utilisation of chemoprophylaxis in the UK population and UK passengers departing to malaria endemic areas. Malaria Journal. 2013.
7. Smith AD, Bradley DJ, Smith V, Blaze M, Behrens RH, Chiodini PL, et al. Imported malaria and high risk groups: observational study using UK surveillance data 1987-2006. British Medical Journal. 2008;337(7661):103-6.
8. Behrens RH. The Raised Potential for Vector-Borne Diseases in European Travelers Following the EU’s Biocide Directive on DEET Dosing. Journal of Travel Medicine. 2015.
9. Chiodini PL, Field VK, Whitty CJ, Lalloo DG. Guidelines for malaria prevention in travellers from the United Kingdom. 2014. www.gov.uk/government/uploads/system/uploads/attachment_data/file/337761... (accessed 29 April).
10. Stanczyk NM, Behrens RH, Chen-Hussey V, Stewart SA, Logan JG. Mosquito repellents for travellers. British Medical Journal. 2015;350:h99.
11. Checkley AM, Smith A, Smith V, Blaze M, Bradley D, Chiodini PL, et al. Risk factors for mortality from imported falciparum malaria in the United Kingdom over 20 years: an observational study. British Medical Journal. 2012;344:e2116.
12. Lalloo DG, Shingadia D, Pasvol G, Chiodini PL, Whitty CJ, Beeching
NJ, et al. UK malaria treatment guidelines. Journal of Infection 2007;54(2):111-21.
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