Rift Valley Fever As a Biological Weapon
RVF is considered suitable as a biological weapon for the following reasons:
Several genera of mosquitoes found in the United States can serve as vectors for RVF virus (eg, Aedes, Anopheles, Culex); therefore, the disease could become endemic following an intentional release. This pattern recently has been illustrated following the natural introduction of West Nile virus (which also is a mosquito-borne disease) into North America.
RVF virus infects both humans and livestock and could, therefore, cause both economic damage to the livestock industry and human morbidity and mortality.
The disease has been demonstrated to cause severe socioeconomic damage, largely due to the high abortion rate in sheep.
Once introduced into a new area, the disease would be difficult to eradicate.
http://www.cidrap.umn.edu/cidrap/content/biosecurity/ag-biosec/anim-disease/rvf.html#_Rift_Valley_Fever
What I read earlier today on this is that there are 23 different types of mosquitos that can carry this disease and transmit it.
West Nile on the other hand limits the mosquitos that can transmit the disease to just a few.