Field and laboratory investigation of Crimean-Congo haemorrhagic fever virus (Nairovirus, family Bunyaviridae) infection in birds.

In November 1984 a case of Crimean-Congo haemorrhagic fever (CCHF) occurred in a worker who became ill after slaughtering ostriches (Struthio camelus) on a farm near Oudtshoorn in the Cape province of South Africa. The diagnosis was confirmed by isolation of CCHF virus from the patient's serum and by demonstration of a specific antibody response. It was suspected that infection was acquired either by contact with ostrich blood or by inadvertently crushing infected Hyalomma ticks while skinning ostriches. Reversed passive haemagglutination-inhibition antibody to CCHF virus was detected in the sera of 22/92 ostriches from farms in Oudtshoorn district, including 6/9 from the farm where the patient worked, but not in the sera of 460 birds of 37 other species. In pathogenicity studies domestic chickens proved refractory to CCHF infection, but viraemia of low intensity (maximum titre 2.5 log10 mouse ic LD50/ml) followed by a transient antibody response occurred in blue-helmeted guinea fowl (Numidia meleagris). These results offer the first direct evidence that some bird species are susceptible to CCHF virus infection.