Farmers have spent the past 12 months looking for nasal
discharges and runny eyes as classic bluetongue symptoms, but they
are also key indicators for
malignant catarrhal fever(MCF) and farmers
could be unwittingly spreading it.
Housing sheep and cattle together in close proximity is a major
risk factor in the spread of MCF but, for a disease that is largely
unheard of, farmers should think twice before mixing animals.
With sheep as natural carriers and shedders of MCF, there is a
risk of inter-species disease spread. But because cases are rare,
the practicalities and economics of shared housing outweigh the
risk of MCF, says VLA
vet investigation officer Roger Daniel.
"With just 82 cases of MCF reported by the VLA last year
compared to 95 in 2007 and 125 in 2006, cases are rare and
sporadic. This is a fatal disease affecting all ages of cattle, but
these statistics demonstrate cattle are fairly resistant to the
disease," he says.
Juvenile lambs between the ages of two and nine months are
thought to be the main factor in the spread of the ovine herpes
virus 2 strain of MCF, with all ages of sheep thought to be
carriers. And although it is uncertain why certain sheep shed the
virus, it is thought transmission to cattle is via aerosols, with
mixed housing at winter a prime time for infection.
"MCF is a differential diagnosis for bluetongue and any
suspected cases must be seen by a vet because of the similarity of
symptoms," says Mr Daniel. "Following exposure, symptoms normally
occur rapidly, with cows exhibiting symptoms such as severe nasal
discharge and glazed-over and sometimes runny eyes. Fatal dysentery
was also seen in MCF animals last year, which resulted in high
mortality," he says.
