Summary Serum haptoglobin (Hp) concentrations were measured in swine that were naturally or experimentally infected with Actinobacillus pleuropneumoniae . In swine from a specific-pathogen-free herd, mean serum concentration of Hp (± SD ) was 5.79 ± 1.06 mg of cyanmethemoglobin-binding capacity ( CHBC /dl. Serum Hp concentrations in paired samples were measured at 7-day intervals in 40 swine randomly selected from a conventional herd that was experiencing an acute episode of pneumonia and deaths caused by A pleuropneumoniae serotype-5 infection. Day-0 and -7 serum Hp concentrations were 24.58 ± 1.38 and 23.10 ± 1.12 mg of CHBC /dl, respectively, with no significant difference between these measurements. In a second conventional herd with a history of chronic infection with A pleuropneumoniae serotype 5, serum concentrations of Hp measured in paired samples obtained 6 days apart were 12.36 ± 0.81 and 18.63 ± 0.76 mg of CHBC /dl, respectively, and were significantly ( P < 0.05) different from each other. Twenty-nine 12-week-old conventional swine were challenged intranasally with A pleuropneumoniae serotype 1 (n = 19) and serotype 5 (n = 10). Serum Hp concentration increased from prechallenge concentrations of 7.49 ± 1.38 and 15.10 ± 1.22 mg of CHBC /dl, respectively, to 41.01 ± 1.35 and 22.37 ± 1.78 mg of CHBC /dl, respectively, 72 hours after challenge. For these 29 swine, serum Hp concentration was positively correlated with rectal temperature (r = 0.34; P < 0.001) during the immediate postchallenge period.
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Hall et al. (1992) studied this question.