We present and characterize a multi-host epidemic model of Rift Valley fever (RVF) virus
in East Africa with geographic spread on a network, rule-based mitigation measures, and
mosquito infection and population dynamics. Susceptible populations are depleted by
disease and vaccination and are replenished with the birth of new animals. We observe that
the severity of the epidemics is strongly correlated with the duration of the rainy season
and that even severe epidemics are abruptly terminated when the rain stops. Because
naturally acquired herd immunity is established, total mortality across 25 years is
relatively insensitive to many mitigation approaches. Strong reductions in cattle
mortality are expected, however, with sufficient reduction in population densities of
either vectors or susceptible (ie. unvaccinated) hosts. A better understanding of RVF
epidemiology would result from serology surveys to quantify the importance of herd
immunity in epidemic control, and sequencing of virus from representative animals to
quantify the realative importance of transportation and local reservoirs in nucleating
yearly epidemics. Our results suggest that an effective multi-layered mitigation strategy
would include vector control, movement control, and vaccination of young animals yearly,
even in the absence of expected rainfall.