Malaria among pilgrims to Makkah, 1998: Is it imported or locally acquired?

Hajj is a religious congregation in Makkah, in the Kingdom of Saudi Arabia (KSA), attended by more than 2 million Muslim religious visitors from all over the world, including those from countries where malaria is endemic. Makkah is a malaria-free city. However, an unusual increase in the number of malaria cases in western and southwestern KSA in the last 2 years has been noted. The pilgrimage season is advancing to coincide with the malaria transmission season in the pilgrimage area, which starts in October and continues through May of the next year. In this study we examine the proportion of locally acquired malaria cases among religious visitors to Makkah (Hajjees).

During the 1998 Hajj season, the 4month-period between Ramadan and Dhul Hijja 1418H, 178 cases of malaria were diagnosed. Saudis made up 126 (70.8%) of the cases; 52 (29.2%) were non-Saudis. The Saudis came to Makkah from other regions of KSA where malaria transmission exists: 81 cases (45.1%) from the southwestern area of Tihama, and 59 cases (33.1%) cases from the valleys around Makkah. Among the non-Saudis, 21 (11.7%) of the malaria cases were diagnosed among recent arrivals from the Indian subcontinent, 16 (9.0%) from East Africa, 13 (7.3%) from Yemen, and 2 (1.2%) from other countries: China and Egypt. Only 15 (8.4%) patients were Hajjees; whereas, 163 (91.6%) were residents of KSA. Of all residents of KSA, 90 (55.2%) were from Makkah (Table 1). The male to female sex ratio was 2:1. The difference between the mean age of male and female cases was not statistically significant (p>0.05).

Some 123 cases (69.1%) were due to P. falciparum, 49 cases (27.5%) were due to P. vivax, and 6 (3.4%) cases (5 Saudis, 1 Sudanese) were mixed infections (P. falciparum and P. vivax). However, malaria cases were predominantly due to P. falciparum except for patients from the Indian subcontinent, where most of the cases were due to P. vivax (Table 1). The majority of malaria cases due to P. vivax 34 (69.4%) came from valleys around the city of Makkah; whereas, the majority of cases of malaria imported from other regions of KSA were due to P. falciparum, 69 (56.1%). The onset of symptoms of 48 (27%) malaria patients started at or before arrival to Makkah. On detailed questioning about travel history, none of the malaria cases could be attributed to local transmission of malaria inside the city of Makkah and associated holy places.

According to the World Health Organization (WHO), malaria is endemic in 91 countries, predominantly in Africa, Asia, and Latin America. About 40% of the whole world population is at risk. It is estimated that 2.1 billion people live in areas of the world affected by malaria [1]. In KSA, about 1 6 million people live in areas where malaria is transmitted. P. falciparum causes over 90% of malaria cases in southwestern Tihama and about 35% of malaria cases in the northwestern regions of KSA. P. vivax is a predominant species in the northwest regions and accounts for over 50% of the malaria cases; whereas, P. malariae is scarce and constitutes 1-2% of all the malaria cases in KSA [2].

The governmental malaria control project in KSA was initiated in 1952 with assistance from WHO, mainly for the protection of the pilgrimage routes. Hajjees are neither screened for malaria at the entry ports of the Kingdom, nor given suppressive doses of anti-malarial treatment. Currently, most areas are virtually free from malaria with the exception of the southwestern areas. Central KSA is non-malarious and only occasional imported cases are reported every year. Transmission of malaria has been halted in the eastern and northern parts of KSA. However, in western KSA, there is low incidence of malaria (1-3 per 1,000 per year) and in Tihama, the coastal plains along the Red Sea in southern and southwestern KSA, medium or high incidence of malaria (more than 3 per 1,000 per year) is reported [2]. The peak of malaria transmission occurs between October and April and coincides with the rainy season (70-550 mm/year). There is a noticeable decline in incidence of malaria during the summer months [2].

All malaria cases diagnosed during the Hajj period admitted recent travel history to, or arrival from malarious areas within KSA in the 2 weeks that preceded the onset of symptoms. The people traveled to malarious areas such as Al-Leith, Al-Gonfedah, or Jizan to visit their relatives during a school vacation or to work in their farms in the affected valleys. This movement of peoples to and from endemic areas poses the threat of imported malaria also in Kuwait [3]. The majority of non-Saudi cases of malaria came from East Africa, the Indian subcontinent and Yemen, where malaria is known to be endemic.

Diagnosis of malaria cases among Hajjees during Hajj season does not imply local transmission of malaria in the city of Makkah and surrounding holy places. Interruption of malaria transmission in these areas could be explained by the intensive environmental malaria control efforts and strict malaria control measures instituted just before Hajj season, in the holy places, along the road, and the adjacent valleys that lie between Jeddah, the main port of entry of pilgrims (Hajjees), and the city of Makkah [4].

Despite successful efforts made to interrupt local malaria transmission during the Hajj season in the city of Makkah and the neighboring holy places, the continuous influx of religious visitors and expatriate workers remains a potential source for introduction of malaria. The role of illegal aliens in reintroducing malaria into this area cannot be ruled out; an influx of a large number of illegal immigrants changed the epidemiology of malaria and other diseases in Kuala Lumpur, Malaysia [5]. It is probable that the unusual heavy and prolonged rainfalls in the last 2 years, during these 4 months, favored increased breeding of the Anopheles vector and greater transmission of the parasite in endemic areas around Makkah.

Table 1: Distribution of malaria cases during Hajj by nationality in Makkah Holy City, 1998