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Three studies, a pilot study with conventional early-weaned pigs and two studies with gnotobiotic pigs were completed. The piolot study indicated that conventional pigs could be challeneged with at least 107 colony forming units (cfu) or Actinobacillus pleuropneumonia (APP) or Actinobacillus suis (A suis) without developing clinical signs. No serological response was detected in these pigs. In the first gnotobiotic study, nine pigs were used: 3 control, 3 APP or 3 A. suis. The two groups of challened pigs failed to respond clinically or serologically to the intial callenege of 106 cfu or either APP or A. suis but the APP pigs did respond clinically and serologically to a second challenge of 107 cfu. A second study with twenty gnotobiotic pigs was completed. Eight pigs were assigned to the Actinobacillus pleuropneumoniae (APP) serotype 5 group; eight pigs were assigned to the Actinobacillus suis (A. suis) group and 4 pigs were assigned to the control group. Each group of gnotobiotic pigs were challenged with 107 colony forming units (cfu) of either APP or A. suis. In both gnotobiotic studies, serological tests indicated that the hemolysin neutralization test (HNT) specificity was poor as it was unable to discriminate between APP or A. suis infections. The HNT test detected more APP positive animals than any other test and detected APP infected animals one-month post challenge. In the first gnotobiotic study, APP infected pigs were detected at one-two weeks post challenge with the APP5 ELISA developed by the University of Montreal (ELISA-M). ELISA-M was a more sensitive test than the APP5 ELISA developed by Oxford Laboratories (ELISA-O). In the second gnotobiotic study, the ELISA-M and ELISA-O failed to detect any APP 5 infected animals. In both gnotobiotic studies, the complement fixation test failed to detect any animals and was insensitive to APP infections.

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South Dakota State University


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