Abstract
A cross-sectional and longitudinal serological study was conducted on domestic ruminants in Al-Hasa Oasis to clarify the presence, prevalence and distribution of Rift Valley Fever (RVF). A total of 598 serum samples were collected from sheep, goats, cattle and camel during the year 2007. Enzyme Linked Immuno-Sorbent Assay (ELISA) was used to detect the presence of anti-RVF IgG and IgM antibodies in sheep, goats and cattle sera. Camel sera were tested by isotype-nonspecific inhibition ELISA. Two out of 225 sheep sera were IgG, but not IgM, seropositive, other sera were IgG and IgM seronegative. In a single sentinel herd of 40 sheep, which was established in the oasis, no seroconversion was detected during the period from July 2005 to May 2008. The low intra-herd prevalence, the scattered distribution of the two seropositives, the absence anti-RVF IgM antibody and the absence of RVF-incidence in the sentinel herd, all suggest that the seropositive animals were introduced from outside of the oasis rather than infected inside the oasis. The prospective study shows that readiness of the region to RVF outbreak is possible.