The biggest danger to cattle is becoming dehydrated or starving if the disease lasts long enough. The treatment is basically to ensure the affected cattle get water and feed. Disease outbreaks are scattered geographically and appear sporadically. The disease is most likely to be diagnosed in late summer and early fall, coinciding with peak populations of the gnat that transmits the disease. The insect that transmits EHD is generally active when the weather is warm, humid and calm.
Moist soil is necessary for reproduction to occur.
Optimal breeding grounds for the gnat are wet, low-lying areas such as valleys, along rivers and creeks, or marshland. These insects transmit EHD to susceptible animals via bloodmeals. Historically, the animals at greatest risk are the older ones in the herd. The rate of illness declines sharply following the first frost, which removes the insect carrier. EHD and bluetongue can be diagnosed by blood tests.