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Surveillance Report

27 July 2011

Malaria cases in Scotland and the UK: 2006-2010

Introduction

Malaria remains a risk to those large numbers of UK travellers1 venturing into malaria endemic areas or to areas where epidemics may occur. Malaria affects sub-Saharan Africa, Asia, including the Indian Sub-Continent, and the Southern and Central Americas. While affected celebrities may raise the profile of malaria in the media and therefore among the general public,2-4 travellers are better served by access to pre-travel advice from health professionals and by targeted campaigns such as 8 weeks to go* which encourage travellers to seek appropriate advice in order to reduce risk of malaria and other diseases.

Appropriate advice on malaria risk is available to both travellers and health professionals advising travellers via websites such as fitfortravel** and TRAVAX*** as well as the UK Guidelines for Malaria Prevention in Travellers.5 Health Protection Scotland reviews and synthesises the data on epidemiological trends,outbreaks and resistance patterns to produce tools such as TRAVAX malaria advice and maps which help the health professional and traveller decide on the appropriate prevention according to risk.6-13

Surveillance of malaria cases imported into the UK is an important component of the data which is reviewed, and provides information on geography, demographics and behaviours which contribute to a travelling individual being infected.9,14,15 Here we report on surveillance data on malaria episodes reported in the UK to the HPA Malaria Reference Laboratory in 2010.

* http://www.8weekstogo.co.uk/

** http://www.fitfortravel.nhs.uk/

*** http://www.travax.nhs.uk/

Methods

The HPA Malaria Reference Laboratory (MRL) tests for and collates data on malaria isolates imported into the UK, this data being supplemented by data from HPS on isolates imported to Scotland. The MRL dataset including the HPS data for the period 2006-2010 was analysed using Microsoft Excel.

Results

UK data:

In 2010 the MRL recorded 1761 episodes of malaria (Figure 1), an increase of 18% from 2009 (N=1495) and a 29% increase from 2008 (N=1370). However, the numbers are similar to those observed in 2005 (1754) and 2006 (1758). The majority of episodes were reported in males (65%, 1138), compared with females (32%, 569); 54 (3%) having no gender reported.

Of 1761 episodes reported in 2010, 1275 (72%) were found to be infected with P. falciparum. In 2010 seven deaths were reported among the 1761 episodes (0.4%), six due to falciparum malaria and one as a result of vivax malaria.

In terms of age distribution, cases increased towards 20-24 years and then decreased again after 50-54 years (Figure 2). There was no significant difference observed in age comparing males and females with both having a mean age of 36 years (t-test, p=0.33), as in 2009.

Of the 1761 episodes 17% (N=299) were unknown for country of transmission (Figure 3). For the remaining 1462 episodes, the major regions where transmission occurred were West Africa (61%, N=886), Asia (not South East or Far East) (19%, 276) and East Africa (10%, 148). Within each of these regions, the countries providing the largest proportion of imported cases were, for West Africa - Nigeria (50%, 447) and Ghana (25%, 224), for Asia - India (71%, 195) and Pakistan (28%, 78) and for East Africa - Uganda (61%, 91) and Kenya (12%, 18).

In the context of country of origin it is worth noting a large rise in the number of episodes identified as having arisen from the Indian subcontinent. Episodes from India rose by 97% from 99 in 2009 to 195 in 2010, while those from Pakistan rose by 63% from 48 in 2009 to 78 in 2010.

With respect to reason for travel (Table 1, Figure 4), for 641 (36%), no reason for travel was given. Of the remaining 1120 episodes the most common reason given was visiting friends and family abroad (VFR) which accounted for 61% (679)of episodes with a reason for travel, with little change from previous years. This was followed by foreign visitors to the UK (11%, 125), UK holiday makers (7%, 83) and new entrants to the UK (7%, 80). The increase in episodes among travellers to the Indian subcontinent was seen across the different traveller types (data not presented).

2010 Scottish data

Of the 1761 UK episodes reported in 2010, 54 (3%) were imported into Scotland (Figure 1). Of these 33 (61%) were associated with falciparum malaria with no deaths reported. The 54 episodes in 2010 represented a 46% increase compared with 2008 (37) but a 11% decrease from 2004 (61).

2006-2010 Scottish data

Over the five year period from 2006-2010, 246 cases of malaria were reported for Scotland. Of these 69% (169) were associated with P. falciparum isolates while P. vivax was isolated in 21% (51) of cases.

With respect to geography (Table 2, Figure 5), of the 246 Scottish episodes, in 37% (N=91) the country in which infection occurred was not known. Of the remaining 155 episodes West Africa (46%, 71), Asia (not Far East/South East) (23%, 36) and East Africa (12%, 19) contributed the largest proportions of cases. For West Africa Nigeria (46%; 33) and Ghana (32%; 23) contributed the most episodes , while for Asia India contributed 83% (30) episodes. Within East Africa Uganda contributed the largest proportion of episodes (58%, 11).

Of the 169 episodes of falciparum malaria 68 were unknown for country of transmission. Of the remaining 101 the largest proportions came from West (61%, 62) and East (13%, 13) Africa. For the 51 episodes of vivax malaria, 14 were unknown with respect to origin, and of the remainder Asia contributed 70% (26).

Conclusions

While the number of UK episodes of malaria increased for a second year running in 2010, a rise of 18% compared to 2009 and 29% over 2008, this observation should be interpreted with caution. As stated previously continued surveillance will reveal whether this increase is due to underlying risk factors or due to random causes.16

Similarly the increase in cases from the Indian subcontinent also requires further monitoring for trends. Access to timely and accurate denominator data is problematic. The observed increase may be due to increased travel associated with the 2010 Commonwealth Games held in India. While recent data from the Office of National Statistics suggests decreased travel to the Indian subcontinent up until 2009,1 we await data from 2010 to see if the occasion of the Games resulted in increased travel to India which may account for some of the observed increase. If increased travel to India has resulted in increased numbers of episodes then it may be that the UK will see increased cases again in 2012 and 2014 as visitors from abroad attend for the London Olympic and Glasgow Commonwealth Games, respectively.

While falciparum malaria remains the most severe form of the disease there was a single death due to vivax malaria observed in 2010, the first since 2005. Like falciparum malaria, vivax malaria can result in severe complications, including death.17, 18 The reasons for increased risk of severe vivax malaria are not fully understood and may include age and genetic factors as well as co-morbidities.19 It is worth noting that both Plasmodium vivax and P. ovale develop hypnozoites as part of their life cycles.20 The prevention of relapse due to activation of these forms of malaria can be achieved by using primaquine as a chemoprophylaxis during travel (but this carries other risks and is only rarely recommended) or by presumptive treatment with primaquine on return from travel.21 Testing for G6PD is required before prescribing primaquine.

As in previous years the quality of the data requires improvement. With evidence of under-reporting from Scotland22 and from England,23 and a large proportions of episodes not having accompanying data on country of origin and reason for travel, particularly in the case of the Scottish data, there remains an urgent requirement to improve the quality of data for the Scottish episodes in particular. Despite this the observation that VFRs remain the largest group among the different traveller types, and therefore may be a higher risk for malaria, is supported by other evidence.25-27 Their increased risk is related to being less likely to take pre-travel advice and appropriate measures during and after travel. Improving data quality and reporting will allow a greater understanding of risk to other traveller types and allow greater confidence in discussing observed trends.

Acknowledgements

We wish to thank the HPA Malaria Reference Laboratory for collating and supplying data, and the various laboratories in Scotland who supplied data to HPS.

References

  1. National Statistics. Travel Trends 2009: Data and commentary from the International Passenger Survey. London: ONS, 2010.
  2. Cheryl Cole being treated for malaria in hospital. BBC News 2010; http://www.bbc.co.uk/news/10520189 Accessed 20th July 2010.
  3. Malaria: a major global killer. BBC News 2010; http://www.bbc.co.uk/news/10520289 Accessed 20th July 2010.
  4. Anti-malarial pills didn't stop me getting the disease. BBC News 2010; http://www.bbc.co.uk/news/10522909 Accessed 20th July 2010.
  5. Chiodini P, Hill D, Lalloo D, Lea G, Walker E, Whitty C, et al. Guidelines for malaria prevention in travellers from the United Kingdom 2007. London: Health Protection Agency, 2007.
  6. Boyne L, Genasi F, Redman C, Sutton H, Smith C, White M. Reviewing the evidence for malaria advice and maps for TRAVAX® and Fitfortravel® - update. HPS Weekly Report 2009;45(2011/03):33-5.
  7. Snow RW, Hay SI. Comparing methods of estimating the global morbidity burden from Plasmodium falciparum malaria.[comment]. American Journal of Tropical Medicine & Hygiene 2006;74(2):189-90.
  8. Peterson AT. Shifting suitability for malaria vectors across Africa with warming climates. BMC Infectious Diseases 2009;9(59).
  9. Anon. Cluster of malaria cases from northern Goa. HPS Weekly Report 2007;41(1).
  10. Greenwood BM, Fidock DA, Kyle DE, Kappe SH, Alonso PL, Collins FH, et al. Malaria: progress, perils, and prospects for eradication. Journal of Clinical Investigation 2008;118(4):1266-76.
  11. Sutherland CJ, Haustein T, Gadalla N, Armstrong M, Doherty JF, Chiodini PL. Chloroquine-resistant Plasmodium falciparum infections among UK travellers returning with malaria after chloroquine prophylaxis. Journal of Antimicrobial Chemotherapy 2007;59(6):1197-9.
  12. Chen LH, Wilson ME, Schlagenhauf P. Prevention of malaria in long-term travelers. JAMA 2006;296(18):2234-44.
  13. Spira AM. Preparing the traveller. Lancet 2003;361(9366):1368-81.
  14. Anon. Malaria imported into the United Kingdom in 2008; implications for those advising travellers. Health Protection Report 2009;3(16).
  15. Williams CJ, Jones J, Chiodini P. High case-fatality from falciparum malaria in UK travellers returning from The Gambia: a case series. Travel Medicine & Infectious Disease 2007;5(5):295-300.
  16. Redman C, Smith V. Travel medicine: Malaria cases in Scotland and the UK: 2004-2008. HPS Weekly Report 2009;43(2009/46):426-8.
  17. Barcus M, Basri H, Picarima H, Manyakori C, Sekartuti, Elyazar I, et al. Demographic Risk Factors for Severe and Fatal Vivax and Falciparum Malaria Among Hospital Admissions in Northeastern Indonesian Papua. Am J Trop Med Hyg 2007;77(5):984-991.
  18. Singh H, Parakha A, Basua S, Ratha B. Plasmodium vivax malaria: Is it actually benign? Journal of Infection and Public Health 2011;4(2):91-95.
  19. Anstey N, Russell B, Yeo T, Price R. The pathophysiology of vivax malaria. Trends in Parasitology 2009;25(5):220-227.
  20. Elliott J, O'Brien D, Leder K, Kitchener S, Schwartz E, Weld L, et al. Imported Plasmodium vivax malaria: demographic and clinical features in nonimmune travelers. Journal of Travel Medicine 2004;11:213-217.
  21. Schlagenhauf P, Petersen E. Malaria Chemoprophylaxis: Strategies for Risk Groups. Clinical Microbiology Reviews 2008;21(3):466-472.
  22. Tolkamp E, Unger H, Jones M. Malaria Reporting in Scotland. 11th Conference of the International Society of Travel Medicine. Budapest, Hungary: ISTM, 2009.
  23. Cathcart S, Lawrence J, Grant A, Quinn D, Whitty C, Jones J, et al. Estimating unreported malaria cases in England: a capture-recapture study. Epidemiol Infect. 2009;Nov 18:1-7.
  24. Public Health etc. (Scotland) Act, 2008.
  25. Fenner L, Weber R, Steffen R, Schlagenhauf P. Imported infectious disease and purpose of travel, Switzerland. Emerging Infectious Diseases 2007;13(2):217-22.
  26. Angell SYC, M. Health Disparities among Travelers Visiting Friends and Relatives Abroad. Annals of Internal Medicine 2005;142(1):67-72.
  27. Pistone T, Guibert P, Gay F, Malvy D, Ezzedine K, Receveur MC, et al. Malaria risk perception, knowledge and prophylaxis practices among travellers of African ethnicity living in Paris and visiting their country of origin in sub-Saharan Africa. Transactions of the Royal Society of Tropical Medicine & Hygiene 2007;101(10):990-5.

Note: It is customary for the travel Health Team to produce a Table of Laboratory Confirmed 'Imported Infections'. Due to changes in data collection by HPS we are in the process of validating these changes to ensure consistency. A table will be produced once this validation process is complete.

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Author(s): Prepared by: Chris Redman & Valerie Smith Vol: 45 No: 30 Year: 2011 Page:

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