Relationship among transmissible gastroenteritis virus antibody titers in serum, colostrum, and milk from vaccinated sows, and protection in their suckling pigs.

We studied the antibody responses to transmissible gastroenteritis (TGE) in serum, colostrum, and milk from sows vaccinated with 2 attenuated (1 IM and 1 oral-IM) and 1 nonattenuated live vaccines and the relationship of these responses with the survivability of the sow's suckling pigs after challenge exposure with virulent TGE virus. Contrary to previous studies, the anti-TGE virus-neutralizing geometric mean titers (GMT) in the milk of sows vaccinated with attenuated vaccines at 3 and 5 days of lactation were similar to that found in the colostrum. Colostral and serum antibody titers were highest in sows given 2 injections of the IM attenuated vaccine. Half of the sows given the oral-IM attenuated vaccine did not seroconvert after 2 oral doses. Only sows vaccinated with the nonattenuated live vaccine had milk GMT that remained high for 21 days after farrowing. The linear relationship between colostral GMT and percentage of survivability of suckling pigs challenge exposed at 3 days of age was significant (P less than 0.05), although the relationship between serum GMT and percentage of survivability and the relationship between milk GMT and percentage of survivability were not significant (P greater than 0.10). The linear relationship between colostral (P less than 0.10) or pre-challenge exposure milk (P less than 0.05) GMT and percentage of survivability of suckling pigs challenge exposed at 5 days of age was significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Tiamulin in drinking water for treatment and development of immunity to swine dysentery.

The diarrhea of swine dysentery receded in swine treated with 60 or 45 mg of tiamulin/L of drinking water (60 or 45 ppm). However, within 2 to 10 days (average 4.1 days) after drug withdrawal, diarrhea recurred. Tiamulin (22.5 mg/L in drinking water) did not markedly reduce the diarrhea during medication, and tylosin (66 mg/L in the drinking water) was not effective. In swine treated with 120 mg of dimetridazole/L of drinking water, there was no recurrence of diarrhea. After the recurrence of diarrhea in swine, repeated medication with tiamulin in drinking water reduced the severity of diarrhea and prevented deaths. After 1 to 3 retreatments, swine were immune to exposure with swine dysentery inoculum, and there was a significant (P less than 0.05) increase in their serum anti-Treponema hyodysenteriae antibodies. Seemingly, drug withdrawal permitted the occurrence and recurrence of diarrhea that was necessary to stimulate immunity.

Comparison of a new aminoglycoside (G-418) and gentamicin for the treatment of swine dysentery in swine naturally infected with Salmonella choleraesuis.

The addition of the aminoglycosidic antibiotic, G-418, to drinking water at the concentration of 37.5 mg/L for 3 days was effective in treatment of experimentally induced swine dysentery in swine. With this concentration, there was a recession of diarrhea during or immediately after withdrawal of medication. However, the diarrhea recurred approximately 2 weeks after medication was stopped. With the concentration of 12.5 mg of G-418/L given to swine for 3 days, the diarrhea did not recede during or after medication. With the concentration of 12.5 mg of gentamicin/L given to swine for 3 days, the diarrhea receded in some swine during and after medication, but more swine died in the medicated exposed groups than died in the nonmedicated exposed groups. Both drugs appeared to be effective against the concurrent spontaneous infection of Salmonella choleraesuis in the swine used in the study.