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Wednesday, February 19, 2014
Cache Valley Virus Showing Up in Ohio Sheep
Nancy Hannaway, USDA Aphis
Cache Valley virus is a
virus that causes infertility, abortions and congenital abnormalities in sheep.
Sheep producers during lambing season should be aware of the potential for
Cache Valley virus, or CVV, to potentially affect their lambing crop. This year
there has been an increase in the number of cases diagnosed and reported by sheep
producers in Ohio.
The virus is spread by
mosquitoes during early breeding season, generally August through September. The virus is not spread from ewe to ewe only
through mosquitos. Abnormalities in
lambs may include crooked joints, deformities of the skeleton, twisted necks or
spines, weak muscles or an uncoordinated gait. Most lambs born with severe defects are
usually stillborn, yet CVV can cause the birth of lambs that act drowsy, weak,
or unsteady and typically all lambs within a set of twins or triplets are
affected.
If the infection occurs at
less than 28 days gestation, the embryos usually die and are reabsorbed. If it
occurs between 28 and 45 days of gestation, the fetuses usually develop the
“A_H syndrome” resulting in various congenital abnormalities affecting the
central nervous system. Infections after 45 days of pregnancy usually produce
no adverse effects. Ewes exposed to the virus that have developed immunity before
the breeding season are protected from reinfection and fetal infections.
Sheep producers suspecting
CVV should contact their veterinarian in order to rule out other causes of
birth defects, miscarriages or infertility. Diagnosis is sometimes difficult because
the virus is usually gone by the time of the abortion or birth however it can
be made in the laboratory by submitting blood, body fluids or brain tissue from
the lamb or blood from the ewe.
The virus is found throughout
the U.S., Canada, and Mexico. There is no vaccine and there is no known
treatment available. The most effective method of protecting ewes from the
Cache Valley virus is to minimize their exposure to mosquito-infested areas during
and shortly after the breeding season.
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