inhibitory effect was shown to be caused by MxA preventing the transport of the THOV genome into the nucleus. As orthomyxoviruses do not encode a capping enzyme, initiation of transcription involves the virus cutting the cap off the 5′-end of host mRNAs, so that the mRNA is recognised by the host translation machinery. A similar "cap snatching" process is used by other orthomyxoviruses, but a much longer host RNA sequence is cleaved along with the cap and incorporated into the viral mRNA. The virus assembles by the cell membrane and leaves the cell by budding. For THOV grown in baby hamster kidney cells, virus particles start to be released 6–8 hours after infection, with substantial quantities still being produced 24 hours after infection. This growth rate is slower than that of influenza viruses, and is more similar to Quaranfil virus. Epidemiology Most thogotoviruses have been shown to infect arthropods, generally hard or soft ticks, which are arachnids, but in one case mosquitoes, which are insects. Members also infect birds and a wide range of wild and domestic mammals, including marsupials, rodents, hares, mongoose, horses, camels, goats, sheep and cattle. Three types – THOV, DHOV and Bourbon virus – have been shown to infect humans. They have a wide geographical range. Transmission to vertebrates usually occurs via a tick vector. THOV persists in the tick, remaining in the organism as it goes through its developmental stages; this is called transstadial transmission. The virus can be transmitted to another host within a day of attachment to the host. THOV can be transmitted between ticks when they feed simultaneously on apparently uninfected guinea pigs, in the absence of a detectable level of virus in the blood. Such nonviraemic transmission has also been observed with other predominantly tick-transmitted RNA viruses, including bluetongue, Crimean–Congo haemorrhagic fever, louping ill, tick-borne encephalitis, vesicular stomatitis virus and West Nile virus viruses. Transmission of DHOV by respiratory aerosol has also been observed. Host interaction and disease Ticks No major pathological changes are observed in Rhipicephalus appendiculatus ticks infected with THOV. The virus is concentrated in the synganglion (the tick brain) early on in the blood-feeding process, with the proportion of virus located in the salivary glands increasing during the late phase of blood-feeding. Lower levels of virus are found in the trachea, digestive tract and female sex organs, but not in the male sex organs or the excretory system.