Imported malaria in the UK
Authors: J. N Zuckerman
Journal: BMJ (2008)

Malaria is endemic in more than 105 countries. With travel predicted to grow to nearly 1.6 billion international arrivals by 2020, travellers will be at increased risk of exposure.1 2 The linked observational study by Smith and colleagues substantiates the public health concerns regarding the prevention of malaria in migrant families in the United Kingdom.3 4 The authors report that cases of imported malaria significantly increased between 1987 and 2006, with an increasing proportion attributable to Plasmodium falciparum rather than Plasmodium vivax.

The increase in cases of imported malaria is not unexpected. It reflects the increase in the number of visits abroad by UK residents—70.5 million in 2007—together with a 150% increase in UK residents travelling to malaria endemic areas during the past decade.5 One notable change is that with improved vector control in Asia, most cases are now acquired in Africa. As severe acute respiratory syndrome showed, 21st century threats to global public health and travel are inextricably interlinked, and they present ready opportunities for the rapid spread of infectious disease.6

Although people visiting friends and relatives formed the largest group returning with malaria during 2007, business and holiday travel accounted for 5% and 14% of cases.4 People visiting friends and relatives are at particular risk—despite a 12% fall in the number of malaria cases reported in UK travellers during 2007, 72% of cases were in such people.4 7

European sentinel surveillance data and other studies worldwide have reported up to 10 000 cases of imported malaria in industrialised countries as a result of international travel, with a case fatality of around 1%.8 9 The increase in cases in the UK reported by Smith and colleagues occurred despite the availability for decades of effective methods of malaria prevention.3 People visiting friends and relatives accounted for 64.5% of all reported cases of malaria, and travel to West Africa accounted for 76% of cases in this high risk group.3 Large clusters of P falciparum cases were located in London, mirroring UK migrant demography. The sustained increase in migration to the UK has contributed to the increasing incidence of imported malaria, as more migrant families travel to countries of their ethnic origin, where malaria is endemic. The study probably underestimates the true burden of malaria in UK travellers, and unless migration patterns to the UK change, this can be expected to increase.

Failure to comply with prophylaxis or to seek travel health advice mostly explains the increased risk of exposure and cases of malaria in travellers, particularly those visiting friends and relatives. Historically, the problem for travel health practitioners recommending malaria prophylaxis for travel to Africa and Asia has been the adverse publicity regarding this treatment. In addition, many people visiting friends and relatives underestimate their risk of exposure to travel related illness, especially malaria, despite not having lived in an endemic area for many years.10 This is a dangerous presumption. Other reasons for the reported increase include inaccessibility of travel health advice, over the counter purchase of inappropriate prophylaxis, and purchase of inexpensive (and sometimes counterfeit11) prophylaxis at the destination.

Substantial improvements in malaria prophylaxis have aided compliance greatly. Health Protection Agency figures on stated malaria prophylaxis in imported malaria cases together with prescription data over the same four year period suggests that travellers prescribed atovaquone plus proguanil are less likely to contract malaria than those given mefloquine or doxycycline (JN Zuckerman, unpublished data).

Smith and colleagues report a significant decrease in imported cases of P vivax after travel to the Indian subcontinent, a result of successful vector eradication in many urban areas. Pursuing a similar policy and achieving the millennium goals in Africa may reduce the incidence of malaria in endemic areas and improve the health of populations, while also reducing the risk of malaria to travellers, all of which may negate the necessity for prophylaxis in the future.

What else can we do? Healthcare practitioners involved in advising travellers about preventing malaria should follow the clear and concise guidelines on malaria prevention for UK travellers.12 Studies of people visiting friends and relatives aimed at identifying the pertinent factors such as cultural beliefs, knowledge, and attitude towards malaria prevention would help understand how best to impart health education through targeted communication and the use of innovative techniques.