Swine dysentery control in the German Democratic Republic and the suitability of injections of tiamulin for the programme.

In 1977 swine dysentery was made a notifiable disease in the German Democratic Republic, with the intention of eradicating it by the systematic treatment of clinically affected herds using intensive medication and hygiene control programmes. On individual farms the scheme appeared to be successful, but the national incidence of the disease did not decline, owing to the continuous presence of latently infected herds and the movement of carrier pigs to uninfected farms. In 1981 the scheme was re-appraised and a new scheme was introduced in one region where all the breeding herds were screened for the presence of Treponema hyodysenteriae; all positive herds were treated with either metronidazole or tylosin, and the movement of pigs into the region was controlled. This programme effectively eradicated the disease from the region and is being introduced to the rest of the country. Owing to concern about the safety of metronidazole and the development of resistance to tylosin, alternative antimicrobials were examined and tiamulin was selected to assess its suitability for inclusion in the programme. A 560 sow breeding herd and progeny were treated for five days with tiamulin at 10 mg/kg bodyweight. This was coupled with extensive cleaning, disinfection and rodent control programmes. The results of the trial showed that the clinical disease stopped in two days and that no further clinical signs were seen in the subsequent two-and-a-half years. Bacterial monitoring of faeces samples and colonic scrapings from dead pigs failed to identify viable T hyodysenteriae. There was a significant increase of 0.6 piglets weaned per litter and improvements in weaning weights and growth rates. It was concluded that tiamulin was suitable for inclusion in the swine dysentery eradication programme in the GDR.