Prevalence of anti-Rift-Valley-fever IgM antibody in abattoir workers in the Nile delta during the 1993 outbreak in Egypt

In the early summer of 1993, an outbreak of Rift Valley fever (RVF) was reported among both humans and animals in Aswan Governorate, Upper Egypt. To determine whether RVF infection had spread to the Nile delta region of the country, we carried out a cross-sectional survey of 1181 occupationally exposed abattoir workers (97% male; age 10-72 years) in 15 governorates of Egypt in November 1993. The overall prevalence of anti-RVF virus IgM antibody was 2% (range: 0% (7 governorates) to 10%). The highest prevalences were in Ismailia (10%) and Shargiya (8%) Governorates. None of the seropositive subjects reported having experienced an episode of fever in the 2 months prior to the study. The prevalence of antibody was significantly higher (P < 0.05) among workers employed in high-risk jobs such as cutting animals' throats (relative risk (RR = 2.24)) and handling animal parts (RR = 2.37). The findings suggest that abattoir workers represent a useful sentinel population for surveillance of RVF.