11 January 2002

Botulism kills stock

BOTULISM, a condition more commonly seen in humans, caused the death of 141 cows in a 164-head English dairy herd in June 2000.

According to Stephen Cobb of the Vet Lab Agency, Sutton Bonnington, Leics, producers must avoid contamination of feed and water with dead birds or mammals to prevent any future outbreaks.

In the past rotting animals have contaminated a single bale of silage or a small area of clamp and infection was seen in a small proportion of stock. But use of mixer wagons may cause a small amount of contaminated material to infected a large proportion of a herd, he and his colleagues report in Vet Record.

"In June 2000, all clinical cases occurred within 17 days, suggesting the herd had been exposed for a short period – possibly a single mix of feed."

Although the infective organism, clostridium botulinum, was not found in silage or water troughs on the farm, purchased concentrate was ruled out as other farms were not infected. He believes the most likely source was a small area of the silage clamp.

The disease was identified by clinical symptoms seen in cows, having ruled out other possibilities. These signs included hindlimb weakness, failure to stand, diabetes and listlessness.

To protect public health, no milk was sold from the herd until 14 days after the last case. &#42