快猫短视频

ANIMALS can harbour viruses and pass on diseases without having detectable
levels of the virus in their blood. The discovery means experts will have to
rethink strategies for controlling mosquito-borne illnesses such as yellow
fever, dengue and Japanese encephalitis.

Knowing which animals can act as reservoirs for pathogens is crucial in the
fight against insect-borne diseases. The WHO says vertebrates can only be
鈥渞eservoir hosts鈥� if you can spot viruses in their blood. But it is becoming
clear that ticks can pick up diseases from animals that don鈥檛 appear to be
infected.

Researchers at the University of Arizona in Tucson have now shown that flies,
which transmit some of the most damaging human pathogens, can do the same.
Daniel Mead and his colleagues investigated the spread of vesicular stomatitis
virus, which causes mouth lesions in livestock. VSV can ruin farmers because the
symptoms mimic foot and mouth disease, and they have to quarantine all infected
animals as a precaution.

How VSV is transmitted is a mystery, however. 鈥淭here鈥檚 a huge amount of
controversy,鈥� says Mead. Because VSV hasn鈥檛 been found in the blood of any
animal host, some researchers think livestock must transmit it to each other
directly. But others suspect insects.

To find out, Mead infected black flies (Simulium vittatum) with VSV,
and let them feed on deer mice (Peromyscus maniculatus). Other flies
that weren鈥檛 infected with the virus fed on the same mice. Although the mice had
no detectable levels of the virus in their blood, a quarter of the non-infected
flies contracted VSV from them.

鈥淐onventional wisdom says there has to be virus in the blood for an insect to
become infected,鈥� says Mead. 鈥淭his gives us a whole new way of looking at
迟丑颈苍驳蝉.鈥�

The virus may pass from one fly to another in the insects鈥� saliva or through
the mouse鈥檚 immune cells, rather than its blood. Either way, it means more
animals could host VSV than previously thought.

Ernie Gould of the Institute of Virology and Environmental Microbiology in
Oxford says the findings may have implications for other diseases. 鈥淚f this is a
mechanism of transmission for mosquito-transmitted diseases, it could
significantly alter our understanding of epidemiology and complicate control
别蹿蹿辞谤迟蝉.鈥�