Coxiella burnetii infection is associated with placentitis in cases of bovine abortion

A positive score on a modified acid-fast (MAF)-stained smear test of fresh placenta was used to identify a group of bovine abortion submissions believ ed to be infected with Coxiella burnetti. Immunohistochemical (IHC) testing for Coxiella and Chlamydia antigens was performed on 14 MAF smear-positive cases as well as 29 MAF smear-negative cases received during the study per iod. Nine MAF smear-positive cases as well as 1 MAF smear-negative case wer e Coxiella-positive via the IHC test. No placentas were positive for Chlamy dia antigen. Various histopathologic features were categorized for all plac entas and the presence or absence of selected risk categories was also grad ed for each case. The results between Coxiella IHC-positive cases and Coxie lla IHC-negative/MAF-negative cases were compared using Fisher's exact test (P value at 95% confidence). Significant associations were found between C oxiella IHC-positive cases and the presence of placental inflammation (P = 0.0027), placental necrosis (P = 0.012), fetal pneumonia (P = 0.0152), and the visibility of Coxiella-like organisms within trophoblasts on hematoxyli n and eosin-stained sections (P < 0.0001). Histopathologic features of Coxi ella IHC-positive placentas included infiltration of the chorionic stroma b y mononuclear cells, necrosis of chorionic trophoblasts, and focal exudatio n of fibrin and neutrophils. The results indicate that MAF smears are a goo d screening tool for the presence of Coxiella in placentas from bovine abor tion cases and that the detection of this pathogen in aborted placentas via traditional staining or IHC methods is usually associated with placentitis .