Coxiella burnetii

Monday, January 4, 2021

(New England) A dairy goat herd recently experienced a series of late term abortions in their doelings. These doelings produced brown vaginal discharge several days prior to abortion. Differential diagnoses to consider for caprine abortion include Chlamydophila abortus infection, Campylobacteriosis, Leptospirosis, Coxiella burnetii infection, Toxoplasmosis and selenium deficiency. Other less common pathogens associated with caprine abortions include bovine viral diarrhea virus, Cache valley fever virus, caprine herpesvirus-1, Listeria monocytogenes, and Brucella species. Fetal and placental tissues from this case were submitted for necropsy, which revealed necrotizing placentitis with abundant bacterial colonization of trophoblasts, raising the suspicion for abortion caused by C. burnetii. A diagnosis of C. burnetti was confirmed with a strong PCR positive on placental tissue. Diagnosis of C. burnetti as a cause of abortion in small ruminants can be challenging because the organism can be shed heavily at the time of parturition even under normal circumstances. A diagnosis of Q fever as a cause of abortion requires both a positive PCR on fresh placenta as well as corresponding evidence of infection on histopathological examination.

Coxiella burnetii is a small, pleomorphic, gram negative intracellular bacterium that is ubiquitous in the environment. Young, naïve small ruminants infected with C. burnetii are at higher risk for late term abortions, still-births or birth of weak offspring. This bacterium is the etiologic agent of Query fever in humans, and is a significant public health concern. Ruminants serve as the primary reservoir of human infection with C. burnetii. The organism replicates in trophoblasts of the ruminant placenta, eventually producing a spore-like form called a small cell variant which is easily aerosolized and extremely hardy in the environment. During both abortion and normal parturition, infected animals shed massive numbers of the pathogen in placental membranes, fetuses and uterine fluids which aerosolize and disperse readily in the environment. Humans become infected with C. burnetii via inhalation, which puts farmers and veterinarians working with sheep and goats during kidding and lambing season at a high risk. Personal protective equipment and adherence to good biosecurity practices are recommended to avoid transmission of Query fever to people who work with ruminants. For more information on Coxiella burnetii, please refer to this link.