Enzootic Pneumonia of Pigs: Immunization Attempts Inoculating Mycoplasma Suipneumoniae Antigen by Various Routes and with Different Adjuvants

Abstract

SUMMARY Attempts were made to immunize naturally-born pigs from an enzootic-pneumonia-free herd against enzootic pneumonia, the challenge being a single, intranasal dose of a suspension of consolidated lung lesions from cases of enzootic pneumonia. The pigs were vaccinated with concentrated suspensions of Mycoplasma suipneumoniae antigen, both untreated and after treatment with formaldehyde. Complete Freund’s, Bayol and Arlacel, Cosbiol and Arlacel, and Alhydrogel were used as adjuvants, and in one experiment the mycoplasma was also given without adjuvant. The injection routes were intradermal (followed by intravenous), double intramuscular, single subcutaneous, and double subcutaneous. The effect of challenging at different times after vaccination was also observed. Significant protection was achieved with antigen and either complete Freund’s adjuvant or Bayol and Arlacel given intramuscularly, although both these adjuvants would be excluded from general use owing to the severity of the local reactions induced. Antigen without adjuvant was of no value. Subcutaneous injections produced less local damage, and one single subcutaneous injection proved more effective than a double injection. Cosbiol and Arlacel, and Alhydrogel, produced more acceptable local reactions than Bayol and Arlacel. In general, the assessment of the experiments was made more difficult by the variable susceptibility of naturally-born pigs to the method of challenge used.