A swine dysentery model for evaluation of drug prophylaxis: efficacy of various drugs in the control of swine dysentery.

A swine dysentery (SD) model that produces consistent, homogeneous, and severe SD was used in 2 experiments to compare the prophylactic effectiveness of 5 commercially available swine feed additive products. Under the conditions of these studies, carbadox and carbadox + sulfamethazine proved to be the most effective agents in preventing SD during the infection + medication and postmedication periods. Olaquindox was effective in preventing SD in the infection + medication period; however, SD recurrence was high during the postmedication period. Nithiamide and chlortetracycline + sulfamethazine + penicillin were least effective in preventing SD during the infection + medication and postmedication periods.

A swine dysentery model for evaluation of drug prophylaxis: development of a model involving oral infection plus pen contamination.

To overcome some of the inadequacies of the classic artificial swine dysentery (SD) model that is frequently used to judge the efficacy of drugs in preventing SD, a model has been developed that produces SD comparable with natural infections that are frequently encountered in commercial pig production facilities. The model is a combination of a single oral infection (OI) plus pen contamination (PC), conducted each night for 25 nights. Results with OI alone, PC alone, and OI + PC have been compared, and the new model (OI + PC) produced consistent, homogeneous, and severe SD with 100% morbidity and 92% mortality.

Efficacy of a long-acting oxytetracycline against chlamydial ovine abortion.

The treatment of ovine abortifacient chlamydias with Terramycin/LA 200 was examined in three successive experiments in which ewes were inoculated intradermally with 6 x 10(5) PFU chlamydia at 80 days of pregnancy. The efficacy of the treatment was estimated by comparing a control group with a treated group for number of live lambs, number of abnormal lambings, length of pregnancy, average weight of lambs at birth and genital excretion of chlamydia at lambing. Sixty to eighty per cent of the ewes in the control group aborted. Under these conditions a single treatment of 20 mg/kg of Terramycin/LA at day 105 of pregnancy, i.e. four weeks after the inoculation, is not effective. On the other hand, a combination of injections, one three weeks and one five weeks after the inoculation, result in longer pregnancies on average, fewer abortions and more liveborn lambs. However, the treatment does not modify either the weight of liveborn lambs or the vaginal excretion of chlamydia at lambing. The adaptation of this treatment to practical conditions and its interest are discussed.

Swine dysentery. Comparison of experimental diseases produced by infection with colonic mucosa or with Treponema hyodysenteriae, French strains, and of "natural" disease.

Oral inoculation of colonic mucosa scrapings and intestinal contents of animals affected with swine dysentery, or of pathogenic strains of Treponemia hyodysenteriae, as well as spontaneous contamination in infected pens caused in average swine dysentery to appear in 359 out of 409 SPF piglets. The morbidity is high irrespective of the method of contamination: after pen contamination, 75 out of 83 piglets were dysenteric; after only one ingestion of contaminated matter, 265 out of 280 animals were ill; and after inoculation of T. hyodysenteriae, 25 out of 35. Mortality in dysentery was always higher than 80%, respectively 48 out of 60 animals, 132 out of 154, and 13 out of 14. Very few animals were self-cured. The average incubation period varied according to the mode of contamination between 9 and 13 days. Animals having contracted an acute form of the disease died 16 to 23 days after contamination, and those with a chronic from 19 days, also after contamination. The increase in the number of Treponema, of Campylobacter and of Balantidium observed after the onset of the disease was approximately equivalent for all three modes of contamination. This disease was characterized by an alternance of dysentery stricto sensu and of mucoid diarrhea, the latter occurring more frequently in cases of self-cure and in chronic forms.