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Rhodococcus equi foal pneumonia: Protective effects of immune plasma in experimentally infected foals
Author(s) -
MARTENS R. J.,
MARTENS JUDY G.,
FISKE R. A.,
HIETALA SHARON K.
Publication year - 1989
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1989.tb02161.x
Subject(s) - foal , rhodococcus equi , medicine , immune system , horse , pony , fibrinogen , pneumonia , haptoglobin , antibody , immunology , gastroenterology , biology , paleontology , biochemistry , genetics , virulence , gene
Summary The immunoprophylactic capacity of specific immune plasma was evaluated in pony foals infected experimentally with Rhodococcus equi. Immune plasma, produced by repeated parenteral administration of viable R. equi to adult horses, was harvested and frozen. Group I (six control foals) and Group II (six principal foals) received lactated Ringers solution and immune plasma respectively at three and five days of age. R. equi were aerosolised into a caudal lung lobe of all foals at seven days of age. Clinical signs, haematological alterations, immune responses, thoracic radiographs and technetium 99m pulmonary perfusion scans were monitored. All foals were destroyed and complete post mortem examinations performed. All foals developed pneumonia as evidenced by clinical, radiographic and perfusion alterations, but the survival rate of principal foals was significantly (P < 0.01) greater than that of control foals. Five control foals developed terminal disease, whereas all principal foals recovered. There was no significant (P>0.05) difference in temperature response, or peripheral blood leucocyte, neutrophil or fibrinogen concentrations between groups. ELISA values for R. equi antibody were significantly (P<0.001) greater in principal foals following treatment, but there was no significant (P>0.05) difference in IgG or IgM concentrations between groups. Results of the haemolysis inhibition assay indicated that equi factor neutralising antibodies were transferred by immune plasma to the principal foals. Post mortem examinations of five control foals destroyed at approximately three weeks post infection because of terminal disease, revealed severe pyogranulomatous pneumonia. One control and all principal foals were either free of lesions or had resolving lesions and/or minimal scar formation at three months post infection. The results of this investigation document the importance of humoral factors in controlling the disease process, and the capacity of humoral immunoprophylaxis to alter the clinical progression of R. equi pneumonia.