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Abstract

Background: Rift Valley Fever virus (RVFV) causes certain type of hemorrhagic fever. In Egypt, during September 2017, RVFV was detected in samples from imported cattle (country of origin: the Sudan). Samples were collected from imported cattle from different localities in Cairo during October, November, December 2017.
Material and methods: RVFV isolation in Swiss mice (6 days old) was by intra-peritoneal inoculation (I/P) with tissue homogenates, positive results were seen in second passages. Detection of RVFV antigen in samples was done by Agar Gel Precipitation test (AGPT) and the Immunofluorescence Technique (IF). However; reverse transcription real time polymerase chain reaction (RT-PCR) was applied and showed negative results for both samples and positive control Egyptian strain (Menya /Sheep/258) indicating non indicative information (false negative). IF tests were applied on paraffin sections and tissues impressions.
Results: The pathological investigations showed chronic infection in the form of necrotic foci (necrogranulomas) and IF test was showing RVFV antigen in hepatocytes, lymphocytes, Kupffer cells (histiocytes of liver), polymorphnuclear cells and in macrophages. RVFV is necrotizing virus that use histiocytes to produce its destructive effects on infected tissues (hepatocytes eating virus), it has its specific and unique pathologic profile inside hepatic tissues. The infected cells produce the virus in large number which leaves cells in groups of millions of viral particles enclosed in certain type of capsule or membrane. The severity of RVFV infections of the liver indicates the virulence status of the virus.
Conclusion: The pathologic changes indicate chronic disease. This study proves that RVFV causes chronic diseases and carriers are present in the endemic areas.

Keywords: Rift valley fever; Rift valley fever virus; Liver infections