A small, hardy fly called a biting midge may play an important role in spreading vesicular stomatitis virus (VSV), which infects cattle, horses and swine, according to Agricultural Research Service (ARS) microbiologist Barbara Drolet.
VSV causes significant economic losses to the livestock industry from sickened animals, quarantines and subsequent export/import restrictions.
Drolet, at the ARS Arthropod-Borne Animal Diseases Research Laboratory in Laramie, Wyo., and colleagues now have proof that VSV is capable of surviving and spreading throughout the blood-sucking midge, Culicoides sonorensis. To verify that Culicoides propagated VSV, the scientists had to find a way to show, without killing the midge, that virus ingested in a blood meal could survive the insect's midgut, then replicate and escape from the midgut to infect other organs.
Using an artificial feeding system, Drolet fed midges a viral meal and tracked the ensuing infections over time to show that VSV infects the midge's salivary glands and eggs and is shed in the midge's droppings. Drolet used a genetic technique to verify that the virus is able to replicate within the insect.
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