RVF Vectors RVF virus is primarily spread amongst animals by the bite of infected mosquitoes. In addition, the various vector species play differing roles in sustaining transmission of the virus. This provides a durable mechanism for maintaining the virus in nature, as the eggs of these mosquitoes may survive for periods of up to several years in dry conditions. During periods of inundation of larval habitats by rainfall, for example, in the rainy season, the eggs will hatch, and the mosquito population will increase and spread the virus to the animals on which they feed. Many types of animals may be infected with RVF, and disease may be severe in many domesticated animals including cattle, sheep, camels and goats.
Sheep appear to be more susceptible than cattle and goats are less susceptible.
Exotic breeds, which have been recently introduced into an endemic area, fare worse than breeds long adapted to local conditions. This may signal the start of an epidemic. Transmission to Humans During epizootics, people may become infected with RVF either by being bitten by infected mosquitoes, or through contact with the blood, other body fluids or organs of infected animals. Such contact may occur during the care or slaughtering of infected animals, or possibly from the ingestion of raw milk. The aerosol mode of transmission has also led to infection in laboratory workers.