Figure 7.

EqPV-H transmission via horse flies could not be demonstrated. Horse flies were fed on EqPV-H viremic horses, dependent on horse fly capture and feeding behaviour. Flies that fed on EqPV-H⁺ donors were immediately transferred to EqPV-H⁻ recipient horses, where they fed to repletion. The estimated number of virions transmitted to each horse was calculated based on donor viremia (GE/ml serum) at the time of each fly bite, 2 nl of blood transfer per bite, and an estimated 40% packed cell volume of the donor (60% serum volume). If horses did not become EqPV-H⁺ by 8 weeks after fly feeding, an additional inoculation was administered, as indicated, to demonstrate susceptibility to infection. GE, genome equivalents.