الكاتب: Multiple References

Animal virnses may be transmitted by arthropods in two ways, either biologically or mechanically. Many different species of Diptera are implicated ill mechanical transmission, but haematophagous species are the most important. The insects become contaminated with virus during normal feeding behaviour, and virus persists on their mouthparts or body until tile next feed. Some viruses are inactivated rapidly on mouthparts, whereas others survive for manv days or weeks, prolonging the potential period of transmission. Some viruses produce high titres in the skin of the infected vertebrate host, which facilitates transmission, whereas other viruses are transmitted even during relatively low levels of viraemia. Mechanical transmission by arthropods is important in the epidemiology of many animal diseases, and may be the major mode of horizontal transmission. Ill other instances vector spread is merely incidental.