Crimean-Congo haemorrhagic fever virus infection in the Western Province of Saudi Arabia

In 1990, an outbreak of suspected viral haemorrhagic fever involving 7 individuals occurred in Mecca in the Western Province of Saudi Arabia. Congo-Crimean haemorrhagic fever (CCHF), not previously known to be present in Saudi Arabia, was incriminated. A study of the epidemiology of this virus was therefore carried out in Mecca, and in nearby Jeddah and Taif in 1991-1993; 13 species of ixodid ticks (5 Hyalomma spp., 5 Rhipicephalus spp., 2 Amblyomma spp., 1 Boophilus sp.) were collected from livestock (camels, cattle, sheep, goats), and of these 10 were capable of transmitting CCHF. Camels had the highest rate of tick infestation (97%), and H. dromedarii was the commonest tick (70%). Attempts to isolate virus from pools of H. dromedarii and H. anatolicum anatolicum were unsuccessful. The source of infection in 3 confirmed cases of CCHF was contact with fresh mutton and, in a suspected case, slaughtering sheep. An investigation in Mecca, which included a serological survey of abattoir workers, identified 40 human cases of confirmed or suspected CCHF between 1989 and 1990, with 12 fatalities. Significant risk factors included exposure to animal blood or tissue in abattoirs, but not tick bites. It is suspected that the CCHF virus may have been introduced to Saudi Arabia by infected ticks on imported sheep arriving at Jeddah seaport, and that it is now endemic in the Western Province.