Investigation into the spread of swine dysentery in 25 herds of East Anglia and assessment of its economic significance in five herds.

Of 25 outbreaks of swine dysentery investigated, 22 were considered to have resulted from the purchase of pigs from farms known to be infected, two from the introduction of Treponema hyodysenteriae on the boots of the stockman, and one from the accidental entry of infected pigs into a 'closed' herd. The hidden costs of swine dysentery in terms of an increased food conversion ratio may be more than four times the cost of medication. A method of halting the spread of disease is described.