Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Pathology

First Advisor

L. D. Miller

Second Advisor

N. F. Cheville


The placental and fetal lesions of ewes infected with an abortion strain of Chlamydia psittaci in gestation days 85-110 were evaluated. Ewes were examined at selected times 4-60 days post-inoculation. Infection of erythrophagocytic trophoblasts lining placentomal hematomas was identified at 14 days post-inoculation. The infection and associated inflammation quickly spread from the placentomal hematomas to chorioallantoic trophoblasts of the periplacentome and interplacentome. The severity and extent of placental inflammation increased with duration of infection. Severe suppurative placentitis was a consistent finding in fetuses examined 32-60 days post-inoculation. High numbers of chlamydiae were isolated from infected placentas;No significant macroscopic changes were identified in ovine fetuses infected with chlamydiae. Microscopic changes included lymphoid hyperplasia, infiltrates of mononuclear inflammatory cells in portal areas of the liver, and multifocal hepatic necrosis. Fetal tissues contained low numbers of chlamydiae. Spleen, lung, lymph nodes and conjunctival swabs were the best specimens for isolation of chlamydiae;Ultrastructural evaluation of chlamydiae-infected placentas also indicated that chlamydial infection suggested began in erythrophagocytic trophoblasts of placentomal hematomas. Only chorionic trophoblasts contained chlamydiae. Degenerative changes in infected trophoblasts included swelling, vacuolation, loss of organelles and microvilli, and lysis;An avidin-biotin-peroxidase complex immunohistochemical method was developed and evaluated for detection of chlamydial antigen in formalin fixed paraffin embedded tissues. This procedure readily detected chlamydial antigen in the placenta, but not in other fetal tissues;In another study, an indirect microimmunofluorescent (IMIF) procedure was developed and evaluated for detection of chlamydiae-specific antibodies in fetal body fluids and serum. Chlamydiae-specific antibodies and elevated levels of IgG were detected in fluids from infected fetuses examined ≥24 days post-inoculation;Two commercially available ELISA tests that were designed for detection of Chlamydia trachomatis infections in humans, were evaluated for diagnosis of chlamydial infections in ovine placentas and fetal tissues. These tests were less sensitive than chlamydial isolation in cell culture. Cross-reactions with other gram-negative bacteria was a problem of one immunoassay (Chlamydiazyme[superscript] R). In contrast, the solid phase ELISA test (Kodak SureCell[superscript] TM) was highly specific and proved useful for diagnosis of chlamydial infections in sheep.



Digital Repository @ Iowa State University,

Copyright Owner

Thomas Paul Sanderson



Proquest ID


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File Size

272 pages