An epizootic of Rift Valley fever in Egypt in 1997

An epizootic of Rift Valley fever (RVF) occurred in Egypt between April and August 1997. The signs among infected cattle and sheep were high fever, ic terus, bloody diarrhoea and abortion. Aborted sheep foetuses a nd sera from the affected herds were collected in the Aswan and Assiut Provinces, Upper Egypt, for virological and serological examination. A cytopathic effect wa s detected in Vero cell cultures 48 h after inoculation with the foetal liv er and spleen suspensions. The same suspensions caused paralysis and mortal ities two to three days post intra cerebral injection in mice. The isolated virus was identified using an agar gel precipitation test (AGPT) and a dir ect fluorescent antibody technique. Serological examination revealed that a ll tested sheep (57) and cattle (93) gave positive results to serological t ests, using a complement fixation (CF), serum neutralisation (SN) and indir ect immunofluorescence assay; while only 48 (84.2%) out of 57 sheep sera an d 69 (74.2%) out of 93 cattle sera gave positive results using an AG PT. Ti tration of the serum samples indicated that SN is more sensitive than CF. I mportation of infected ruminants, especially camels from the Sudan, is the principal source of infection. Aswan, the nea rest Egyptian province to the Sudan, is the focus of RVF virus infection in Egypt. As a result of high i nsect populations, the epizootics of RVF have usually occurred during the s ummer in Egypt. Reoccurrence of epizootics from time to time indicates fail ure of the applied RVF vaccination programme in Egypt.