Abstract:
Rift Valley fever (RVF) is endemic in most parts of Africa and has also been reported to occur in the Arabian Peninsula. It is
responsible for significant morbidity and mortality, particularly in livestock, but also in humans. During the last two decades
several outbreaks of RVF have been reported in countries in Southern Africa. In contrast to other countries, no clinical
disease has been reported in Mozambique during this period. In a serological study conducted in 2007 in five districts of
Zambe´zia Province, Mozambique, of a total of 654 small ruminants sampled (277 sheep and 377 goats), 35.8% of sheep sera
and 21.2% of goat sera were positive for RVF virus (RVFV) antibodies in a virus neutralization test (VN) and in an IgG enzymelinked
immunosorbent assay (ELISA). In 2010, a cross-sectional survey was conducted in 313 sheep and 449 goats in two
districts of the same province. This study revealed an overall seropositivity rate of 9.2% in sheep and 11.6% in goat and an
increased likelihood of being seropositive in older animals (OR = 7.3; p,0.001) using an IgG ELISA. 29 out of 240 animals
assessed for RVF specific IgM by ELISA were positive, suggesting recent exposure to RVFV. However, a longitudinal study
carried out between September 2010 and April 2011 in a cohort of 125 of these animals (74 sheep and 51 goats) failed to
demonstrate seroconversion. The results of the study indicate that RVFV circulates sub-clinically in domestic small ruminants
in Zambe´ zia Province.
