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News Archives 8 December 2005

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Archives | News Archives 2006: Page 1| News Archives 2005 Page 2 | News 8 December 2005

News Archives: | 2006 | 2005 | 2004 | 2003

• Malaria deaths in travellers returning from The Gambia
  
• An outbreak of cryptosporidiosis in north west Wales
  
• Outbreak of Salmonella Goldcoast infection in tourists returning from Mallorca – final summary

Malaria deaths in travellers returning from The Gambia

A series of six falciparum malaria cases have occurred in travellers recently returned from The Gambia. Two cases are known to have died, and a further two are seriously ill. The cases, aged between 31 and 61 years, all returned to the United Kingdom (UK) and became ill in the second half of November 2005. Five had been on holidays of one to two weeks, all in resorts within 20km of the Atlantic coast, with some cases having been on fishing or bird-watching excursions. The sixth case had visited the Gambia several times on business and had travelled a little further inland than the other cases. All of the cases had taken either no or inadequate chemoprophylaxis.

The Gambia is a popular ‘winter sun’ destination for UK travellers, who account for nearly half of all tourist visits (1) (around 30,000 last year). It is also a country where malaria is highly endemic, with year-round transmission and over 100,000 cases reported annually in residents (2).

Plasmodium falciparum is the commonest type of malaria seen in The Gambia, and accounts for over 90% of cases in returning travellers. Falciparum malaria is the most severe form of the disease, and can rapidly progress to serious illness and death. Nearly 4/100 cases of falciparum malaria in travellers returning from the Gambia (between 2000 and 2004) were fatal (HPA Malaria Reference Laboratory, unpublished data).

Over the last six years, the annual number of cases in travellers returning from The Gambia has decreased, but the case fatality rate has increased. Table 1 shows the total numbers of cases of malaria from The Gambia reported to the Malaria Reference Laboratory, in relation to cases from other areas.

Table 1 Cases of Plasmodium falciparum malaria reported to the Malaria Reference Laboratory, 2000 to 2005* (these figures do not include the current case series)

* Unpublished data supplied by the HPA Malaria Reference Laboratory, December 2005.
† The denominator is all falciparum case reports from The Gambia, including those where prophylaxis status was unknown.
‡ To end August 2005; note that the main holiday season to the Gambia from the UK is over the UK Winter.

Most cases of P. falciparum malaria did not take chemoprophylaxis. The overall percentage of travellers who take adequate chemoprophylaxis is not known.

Travellers to The Gambia and other malarious countries should seek medical advice on appropriate measures before travelling. The risk of malaria can be reduced by taking appropriate chemoprophylaxis, and by bite avoidance through suitable clothing, insect repellents and bed-nets (3).

There is significant resistance to chloroquine in The Gambia, so this treatment, available over the counter in some pharmacies, is not recommended as chemoprophylaxis (4). Instead, travellers should use either atovaquone/proguanil (Malarone), doxycycline or mefloquine (Lariam). These regimes are only available on prescription, and the latter two need to be started at least one week before travelling. Full details are available in the 2003 UK malaria guidelines (5), and the National Travel Health Network and Centre (www.nathnac.org) can provide up-to-date advice to clinicians on travellers with complex medical needs or travel itineraries.

Organising preventive measures, medical advice and prescriptions may be difficult where holidays are booked at short notice; a cluster of cases were reported in December 2003 associated with late bookings to The Gambia (6). Late booking holidays are increasingly available through travel companies via the Internet.

The Federation of Tour Operators and Association of British Travel Agents have been informed about these cases. They are taking steps to alert their members about this issue, and the need to remind travellers to malarious areas to seek medical advice prior to departure.

This series of cases in people returning from The Gambia is associated predominantly with tourism. Most malaria cases in the UK however occur in former residents of malaria-endemic countries, mainly in west Africa, who return home to visit friends or family (7). Most have not taken appropriate chemoprophylaxis All travellers to such areas, irrespective of where they were born, should take medical advice and appropriate preventive measures to reduce their risk of malaria.

Travellers who fall ill following a visit to a malarious area should seek prompt medical attention, and be aware that malaria can present up to a year or more after return (7). Healthcare professionals should always take a travel history from anyone with a fever/flu-like illness, and be aware that absence of fever in an ill patient does not exclude the diagnosis of malaria. If the travel history includes travel to a malarious area in the past year, blood film examination should be performed without delay.

Malaria is a notifiable disease. All malaria cases should also be reported to the HPA Malaria Reference Laboratory, with reporting forms available by downloading from the MRL website http://www.malaria-reference.co.uk, or from Marie Blaze at Marie.Blaze@lshtm.ac.uk.

References

1. World Tourism Organization (WTO). Yearbook of tourism statistics. 2002. Madrid: WTO; 2002.

2. Malaria country profiles: The Gambia. In: World Health Organization Regional Office for Africa website [online] 2004 [cited 8 December 2005] Available at <http://www.afro.who.int/malaria/country-profile/gambia.pdf>.

3. National Travel Health Network and Centre. Travel Health information sheets: Insect bite avoidance. In: Nathnac website [online] [cited 8 December 2005]. Available at <http://www.nathnac.org/pro/factsheets/iba.htm>

4. Moore DAJ, Grant AD, Armstrong M, Stümpfle R, Behrens R. Risk factors for malaria in UK travellers. Trans R Soc Trop Med Hyg 2004; 98: 55-63.

5. Bradley DJ, Bannister B, on behalf of the Health Protection Agency Advisory Committee on Malaria Prevention for UK Travellers. Guidelines for malaria prevention in travellers from the United Kingdom for 2003. Commun Dis Public Health 2003; 6(3): 180-99. Available at <http://www.hpa.org.uk/cdph/issues/CDPHvol6/No3/6(3)p180-99.pdf> .

6. Health Protection Agency. Consequences of failure to use malaria prophylaxis in The Gambia. Commun Dis Rep CDR Wkly [serial online] 2003 [cited 8 December 2005]; 13 (49): news. Available at <http://www.hpa.org.uk/cdr/archives/2003/cdr4903.pdf>.

7. Health Protection Agency. Foreign travel-associated illness. England, Wales, and Northern Ireland – Annual Report 2005. London: Health Protection Agency Centre for Infections; 2005. Available at <http://www.hpa.org.uk/publications/PublicationDisplay.asp?PublicationID=2>

An outbreak of cryptosporidiosis in north west Wales

In early November 2005, the Health Protection Team in north Wales noted an increase in cases of cryptosporidiosis in Gwynedd and Anglesey. Initial investigations indicated that cases were concentrated on either side of the Menai Straits and were mostly in young adults, with a predominance of women. Several cases reported drinking a lot of tap water. The UK Cryptosporidium Reference Unit confirmed that all isolates were Cryptosporidium hominis, indicating a human origin.

The affected area is supplied with drinking water from several sources. Lake Cwellyn is an upland reservoir (Cwellyn) serviced by a water treatment works that provides microstraining, pressurized sand filtration, and chlorination. A resident population of 70,000 people (approximately one third of the population of the two counties) receives water from Lake Cwellyn, either exclusively or blended 80:20 with water from source B, a blend of water derived from two high upland lakes. Cumulative attack rates from 1 September were 90 per 100,000 population supplied from lake Cwellyn compared to 13 case per 100,000 supplied from other sources in North West Wales.

The initial incident management team instituted further investigations including a case-control study, and testing of raw and treated water samples for cryptosporidium oocysts. The water company had been undertaking continuous monitoring at Cwellyn since 2 November. General practitioners and consultants in northwest Wales were asked to issue advice on boiling water to patients with impaired T cell immunity.

Cases were defined as people living in Gwynedd or Anglesey with onset of diarrhoea after 1 September 2005 and the presence of C. hominis oocysts in a faecal sample. Travel related cases and secondary cases were excluded. Telephone interviews were conducted with 45 cases and 37 unmatched controls. Cases had an odds ratio of 9.5 (95%CI 2.1 to 41.0) for drinking unboiled tap water, together with a dose response.

Monitoring by the water company has shown oocysts in both raw and treated water. Levels in treated water were, however, always below the treatment standard of one oocyst per 10 litres of water.
By 27 November there were 100 cases that met the case definition (figure 1). A boil water notice was issued on the 29 of November to all residents of the area supplied by Lake Cwellyn.

Figure1 Cryptosporidiosis cases by date of onset and source of water supply: 1 September to 27 November 2005

Investigations are continuing into the source of cryptosporidium oocysts in the water from Source A. The reservoir catchment includes a small village with a sewage treatment facility, and several properties with septic tanks. There was very heavy rainfall in northwest Wales during the two weeks preceding the outbreak. The hypothesis that the reservoir may have been contaminated by oocysts in sewage run-off is therefore being explored.

Outbreak of Salmonella Goldcoast infection in tourists returning from Mallorca – final summary

An international Outbreak Control Team (OCT) led by Health Protection Scotland has investigated an outbreak of Salmonella Goldcoast infections in tourists returning from Mallorca (1,2). The case definition was agreed as ‘a case of gastroenteritis caused by Salmonella Goldcoast visiting Mallorca one week prior to the onset of symptoms, onset being between 20 September and 19 October’. One hundred and forty-eight cases of S. Goldcoast meeting the outbreak case definition were reported from around Europe between 1 October and 1 December 2005: England and Wales (66), Scotland (28), Germany (17), Sweden (12), Norway (8), Ireland (6), Denmark (4), Finland (4), and Mallorca (3). The last onset date reported was 19 October 2005.

United Kingdom

The Health Protection Agency Centre for Infections reported 116 confirmed cases of S. Goldcoast in England and Wales between 1 October and 1 December 2005, compared to four in the same time period in 2004.

Follow-up information was available for 112 cases (97%). Eighty-three cases (74%) reported recent foreign travel and of these, 73 (88%) reported Mallorca as their destination. One case reported visiting Mallorca as part of a cruise. During investigations five cases were deemed to be secondary cases and were excluded leaving sixty-six primary cases which met the case definition . Of the sixty-six primary cases, all age groups were affected although almost half (33/66) of cases were aged under 5 years (age range: 0 to 76 years). Males were over-represented (55%) compared to females (45%). Onset dates ranging between 26 September and 19 October 2005 were available for 64 cases (figure 1). Five cases were admitted to hospital.

Figure 1 Epidemic curve by country: UK cases of S. Goldcoast with history of travel to Mallorca: 20 September to 19 October 2005 (n=91)

The Scottish Salmonella Reference Laboratory (SSRL) has reported 40 isolates of S. Goldcoast between 1 October and 1 December 2005 of which 28 fitted the outbreak case definition. One case reported visiting Mallorca as part of a cruise. Cases ranged in age from 0 to 80 years. Sixty-one per cent of the cases were aged 5 years or under. Onset dates ranging between 27 September and the 11 October 2005 were available for 27 cases (figure 1).

All United Kingdom isolates tested were fully sensitive to antibiotics and all have the same Pulsed Field Gel Electrophoresis (PFGE) profile GldX2 (SSRL designation).

To generate hypotheses for disease transmission, seventeen cases resident in various parts of England, Wales, and Scotland were interviewed at length using a detailed standardised trawling questionnaire. Analysis of data from the trawling questionnaires did not generate a testable hypothesis about foods, outlets, or other potential sources of infection. The international outbreak control team was reconvened on 1 December 2005 and the outbreak was declared over. Members agreed that no further environmental or epidemiological investigations were warranted.

References

1. Outbreak of Salmonella Goldcoast infections in tourists returning from Mallorca
Commun Dis Rep CDR Weekly [serial online] 2005 [cited 3 November 2005]; 15(44): News. Available at <http://www.hpa.org.uk/cdr/archives/2005/cdr4405.pdf>.

2. Update: outbreak of Salmonella Goldcoast infection in tourists returning from Mallorca – United Kingdom update. Commun Dis Rep CDR Weekly [serial online] 2005 [cited 10 November 2005]; 15(45): News. Available at <http://www.hpa.org.uk/cdr/archives/2005/cdr4505.pdf>.