Epidemiology of Imported Malaria in Qatar

Authors


Mohamed Ghaith Al-Kuwari, MBBS, ABCM, FPHM, Department of Public Health, National Health Authority, PO Box 5054, Doha, Qatar. E-mail: drmgalkuwari@hotmail.com, drmgalkuwari@gmail.com

Abstract

Objective This study estimated the annual incidence of imported malaria in Qatar from 1997 to 2006 and described the epidemiological features of malaria from 2004 to 2006.

Methods A retrospective review was conducted of the imported malaria cases in Qatar reported by the malaria surveillance program during the period 1997 to 2006 to estimate annual incidence. Data on 438 malaria cases reported during 2004 to 2006 were analyzed to describe the epidemiological features of imported malaria in Qatar.

Results The incidence of malaria in 1997 was 58.6/100,000, and since then, it has shown a consistent decline to reach the lowest rate of 9.5/100,000 in 2004. After that the incidence of malaria has increased by more than two times in 2005 and 2006. All 438 malaria cases were contracted as a result of travel to endemic countries, namely India, Pakistan, and Sudan. The majority of cases were male, non-Qatari, and aged 15 years and older. Plasmodium vivax was the main etiologic agent in 40% of cases and most occurred between August and October.

Conclusions Imported malaria reported in Qatar has shown an increase in the past 2 years after a long period of constant reduction, and the people most affected were adult male migrants from endemic countries. This group should be targeted by malaria prevention programs.

Although most malaria morbidity and mortality are reported in endemic areas like Africa, Southeast Asia, and the Western Pacific,1 thousands of imported malaria cases are reported annually in nonendemic countries due to international travel.2–4 Malaria poses threats to both tourists and visitors of friends and relatives (VFRs). However, in many countries, an increasing proportion of imported cases are seen in migrants and VFRs in endemic countries.5

In the World Health Organization Eastern Mediterranean Region, 48% of the regional population (approximately 248 million people) reside in areas at risk of both Plasmodium falciparum and Plasmodium vivax malaria, and an additional 15% are at risk of P. vivax malaria alone.6,7 Reported malaria cases (about 6.1 million in 2000, 4.5 million in 2003, and 2.7 million in 2005) represent only a fraction of the true incidence. It is estimated that about 10.5 million malaria episodes and 49,000 malaria-related deaths occur every year in the region.7

Qatar is a small country located in the Arabian Peninsula, with a total population of 838,000 estimated in 2006; more than 75% of these are expatriates from the Middle East and Indian subcontinent.8 It is one of nine countries in the Middle East that have eliminated indigenous malaria transmission since the 1970s.7 However, the risk of imported malaria still exists due to the large number of immigrant workers from malaria-endemic countries like Sudan, Pakistan, and India.

This study estimated the annual incidence of imported malaria in Qatar from 1997 to 2006 and described the epidemiological features of imported malaria cases from 2004 to 2006.

Methods

We conducted a retrospective review of all reported malaria cases in Qatar that have been reported to the malaria surveillance system in the Department of Public Health, National Health Authority, during the period 1997 to 2006. The case of malaria was confirmed by a positive thin or thick, or both, blood film.

To describe the epidemiological features of imported malaria in Qatar, data on 438 confirmed cases reported during 2004 to 2006 were collected using a checklist that included the following information: patient demographics such as age, gender, nationality (either Qatari, or migrant expatriates who have lived in Qatar for at least 1 y); travel history; time of malaria reporting; and Plasmodium species (P falciparum, P vivax, Plasmodium malariae, and Plasmodium ovale).

The incidence of malaria was calculated for each year from 1997 to 2006, and the number of imported cases of malaria reported each year was divided by the total population at risk, that is, the estimated population living in Qatar in the same year.

Data were entered into the SPSS for windows version 11.00 and descriptive statistics were used for data analysis.

Results

Over the 10 years from 1997 to 2006, 1,799 cases of malaria were reported in Qatar. All were imported from endemic countries. Table 1 shows the number of reported malaria cases, population at risk, as well as the annual incidence for each year. The incidence of malaria in 1997 was 58.6/100,000, which was the highest during the study period. Since then, the incidence of malaria has shown a consistent decline to reach the lowest rate of 9.5/100,000 in 2004. After that, the incidence of malaria increased by more than two times in 2005 and 2006 to a rate of 21.1 and 23.6/100,000, respectively. Figure 1 illustrates that the incidence of P vivax showed a greater than threefold increase in the past 2 years from 3 to 10/100,000, while the incidence of P falciparum did not show the same increase.

Table 1.  Yearly number of cases and the estimated incidence of imported malaria, Qatar, 1997–2006
 1997199819992000200120022003200420052006
Number of malaria cases3682652431401141389372168198
Population per 100,000628.4643.3560.7578.5595.3616.1724.1755.1796.1838.0
Estimated incidence per 100,00058.641.243.324.219.122.412.89.521.123.6
Figure 1.

Annual incidence of imported malaria species per 100,000, Qatar, 2002–2006.

Table 2 describes the epidemiological pattern of 438 cases of malaria reported between 2004 and 2006. The majority of cases were male (84%), non-Qatari (99.1%), and aged 15 years and older (90.8%). All 438 cases were contracted as a result of travel to or previous domicile in malaria-endemic countries, namely India, Pakistan, and Sudan. About 47.9% of patients with malaria have a history of travel to India, while 29.2% and 8.5% of cases were imported from Pakistan and Sudan, respectively. In addition to these three countries, 14.4% of cases were imported from different endemic countries such as Sri Lanka, Bangladesh, Yemen, and Philippines.

Table 2.  Distribution of imported malaria cases in Qatar 2004–2006 according to demographic variables, malaria species, and country of travel
Variablen%
Gender
 Male36884
 Female7016
Age group (y)
 <15409.1
 15–2911325.8
 30–4414232.4
 >4414332.6
Nationality
 Qatari40.9
 Non-Qatari43499.1
Country of travel
 India21047.9
 Pakistan12829.2
 Sudan378.5
 Others6314.4
Malaria species
 Falciparum6013.7
 Vivax17540
 Unknown20346.3

Plasmodium vivax was the main etiologic agent in 40% of the 438 reported malaria cases in 2004 to 2006 compared with 13.7% cases being infected with P falciparum. Nearly half of the cases (46.3%) were reported without identifying the malaria species. Table 3 shows that the majority of patients with P vivax infection (64.6%) had a history of travel to India compared with 29.2% and 2.9% of cases that came from Pakistan and Sudan, respectively. On the other hand, 40% of patients infected with P falciparum had a history of travel to Pakistan compared with 23.3% and 16.7% of cases that came from Sudan and India, respectively. This difference was statistically significant (p < 0.001).

Table 3.  Distribution of imported malaria cases in Qatar 2004–2006 according to country of travel and y species
Country of travelPlasmodium falciparumPlasmodium vivaxUnknownTotal N
n%n%n%
Sudan1423.352.9188.937
Pakistan24403922.36532128
India1016.711364.68742.9210
Others12201810.33316.363

In relation to time of reporting of malaria, Figure 2 shows the peak of the reported malaria cases occurred between August and October. About 18.5% of cases were reported in October, 17.8% in September, and 14.8% in August. The lowest percentage of cases was reported in January and February, with 3.7% in each month.

Figure 2.

Monthly distribution of imported malaria cases, Qatar, 2004–2006.

Discussion

The study showed a downward yearly trend of reported malaria cases during the period 1997 to 2004. This can be attributed to the efforts of health authorities in the country to reduce importation of malaria; an awareness campaign was established for all travelers visiting malaria-endemic areas, and the travel clinic of the department of public health, which was established in 2000, provided free malaria prophylaxis. However, this service is used more by Arabic-speaking travelers from Qatar and Sudan, compared with India and Pakistan, as most of the health education campaigns are conducted in Arabic. The recorded increase in 2005 and 2006 can be attributed to other factors, such as the high influx of expatriate workers, especially from Asia, to help with the construction of sports facilities in Doha for the 2006 Asian Games. This is supported by the demography of VFRs in this study who were mainly young adult men from Asia. Another possible explanation is overreporting of malaria without laboratory confirmation. Malaria surveillance in Qatar has shown increased reporting in the past 3 years, and a large percentage of these reports have not been confirmed in the laboratory.

The present study showed that the epidemiological features of imported malaria in Qatar were no different from those reported in nonendemic countries in the Arabian Gulf, such as Kuwait and Bahrain.9–10 In Qatar, male expatriates were more affected by malaria than females. This was probably due to the movement of large numbers of single male expatriates to work in Qatar, mainly from endemic areas in the Indian subcontinent, as the most affected age group was adults aged 30 years and older, which represents the age of the labor force. This sex and age pattern has also been described in previous epidemiological studies from Qatar, Saudi Arabia, United Arab Emirates, and Kuwait.9,11–13 Even in Western countries, male gender has been identified as a risk factor for imported malaria. For example, a Swedish study has shown that male travelers have a higher risk of being reported with malaria (OR = 1.7) than women.14 This can be attributed to the poor compliance of young adult male travelers to chemoprophylaxis and other preventive measures.15

The low percentage of Qatari nationals among malaria patients (<1%) cannot be attributed to the improvement of health awareness alone, but also because malaria-endemic countries are not a favorite destination for Qatari travelers. However, we could not establish whether these expatriates had recently come to the country or were older migrants visiting their families, as there was no information about the purpose of travel in the notifications. Such information is extremely valuable for controlling this infection because it gives a clear picture about the affected population and whether they are new immigrants or VFRs. In particular, the population affected in this study was consistent with the characteristics of VFRs in Western countries, as they were middle-aged men who originated from endemic countries.16–18

In relation to the time of imported malaria in Qatar, more than half of the cases were reported during August, September, and October, which correlated with the return of migrants living in Qatar from their home countries in the summer. This trend was similar to that reported in other neighboring countries in the Arabian Gulf.9,10,12

In addition, the study showed that P vivax was more commonly found among patients from India and P falciparum was more common among those who traveled to Sudan and Pakistan. This finding is consistent with other studies from neighboring countries in the region, such as Kuwait, Bahrain, and Saudi Arabia.9,10,12,19,20 It is well documented that P vivax is responsible for 60% to 65% of malaria infections in India, whereas P falciparum is predominant in Sudan.7,21

One of the most important pieces of information that should be collected in such a study is the history of chemoprophylaxis before and after travel. Such information can illustrate whether the imported malaria is due to poor patient compliance or drug resistance, especially because P vivax is becoming increasingly resistant to antimalarial drugs in some areas.22 Unfortunately, this information is not collected in the current malaria surveillance in Qatar.

The present study showed that the information collected for malaria surveillance in Qatar was inadequate to give a clear epidemiological picture to develop a national strategy to control importation of malaria. Information about pretravel chemoprophylaxis and laboratory results should be collected in the future by public health officers, as it is usually missed by attending physicians.

In conclusion, imported malaria is still reported in Qatar, and it has shown an increase in the past 2 years after a long period of constant reduction. Plasmodium vivax is an important cause of imported malaria in Qatar, and the most affected people were adult male migrants from the Indian subcontinent and other endemic areas with a history of travel to their home countries during the summer season in particular. This group should be targeted by malaria prevention programs through health education campaigns in their native languages and by increasing the accessibility to chemoprophylaxis through drop-in clinics at their work place, as part of occupational health services, especially before travel in the summer season.

Declaration of Interests

The author states that he has no conflicts of interest.

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