Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Pathology


Blood neutrophils from 4 pony foals, 3 lactating pony mares, and 3 non-lactating mares were evaluated ultrastructurally and by in vitro function tests. Lower random migration, lower iodination, and lower Staphylococcus aureus ingestion were seen in tests using neutrophils from foals compared to mares. In tests using neutrophils from lactating mares, iodination, antibody dependent cell mediated cytotoxicity (ADCC), and migration were slightly less than in tests using neutrophils from non-lactating mares. Ultrastructurally, neutrophils from foals and from lactating mares had decreased primary granule concentration and increased concentration in flocculent matrix granules, suggesting partial degranulation;The 4 pony foals and the 3 lactating pony mares were inoculated with equine herpesvirus 1 (EHV-1) subtype 2 and neutrophils from each horse group were evaluated. Random migration was significantly increased in neutrophils from foals by 24 hours after inoculation and returned to normal by 72 hours. Severe transient decrease in ADCC was also seen in neutrophils from foals 24 hours after inoculation. In inoculated mares, increase in migration of neutrophils was more severe and lasted longer than in foals. Ultrastructurally, decrease in primary granule concentration was more severe and lasted longer in mares than in foals;After inoculation with EHV-1 subtype 2, foals had 2 fever episodes, one at 12 hours and one at 3 1/2 days and an initial leukopenia followed by leukocytosis. Mares had milder fever and less severe leukopenia than foals after inoculation with EHV-1. A 4-fold increase (4 to 16) in circulating neutralizing antibodies against EHV-1 was seen in 2 of the 3 mares after inoculation but not in the foals;In conclusion, the strain of EHV-1 subtype 2 used in this study appeared to be a mild pathogen for ponies, responsible for mild clinical disease, and elicited a weak circulating antibody response. However, it was associated with altered morphology and function of circulating neutrophils in both inoculated mares and foals. In foals, low migration of neutrophils before inoculation along with decreased ADCC mediation and primary granule concentration of neutrophils after inoculation may account for susceptibility to EHV-1 infections and to other infectious diseases.



Digital Repository @ Iowa State University,

Copyright Owner

Freddy Louis Coignoul



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116 pages