Experimental studies on serum treatment and vaccination against Cl. perfringens type C infection in piglets.

Subcutaneous administration of serum to piglets just after birth resulted in serum titres of 9-18 I.U. beta-antitoxin per ml in the first three days of life. At the ages of 7, 14, and 28 days the titres had dropped to about 5-9, 2 and 1 I.U. per ml, respectively. Oral administration of the same dose of serum resulted in serum titres of about half of those found after s.c. administration. In infected herds a significant protective effect after both s.c. and oral administration of serum was found to be dependent on the time of treatment but independent of the route of administration. After vaccination a correlation was noted between the levels of beta-antitoxin in colostral whey and specific mortality in the litters. An initial beta-antitoxin concentration of about 10 I.U. per ml whey seems to be sufficient to secure effective prevention. By vaccination once during gestation the beta-antitoxin levels in colostral whey were all less than 10 I.U. per ml. Two vaccinations during gestation resulted in whey titres greater than 10 I.U. per ml in 12 of 20 dams. By revaccinating once only during the following gestation effective beta-antitoxin levels in colostral whey were secured regardless of whether the vaccination had been performed once or twice during the previous gestation : the mean was 87.4 I.U. beta-antitoxin per ml; three of 20 dams had titres less than 10 I.U. per ml whey. From mortality studies including 63 liters in three infected herds specific mortalities of 17.3% and 4.6% were found after one and two vaccinations respectively, as compared with 36.6% in the control group. After revaccination during the ensuing gestation the figures were 1.4%, 0.0% and 32.2% named in the same order. 2 ml serum given as soon as possible after birth or 5 ml vaccine injected twice during gestation followed by one revaccination during subsequent gestations effectively protect piglets against infection with Cl. perfringens type C.