Experimental challenge of pregnant cattle with the putative abortifacient Waddlia chondrophila Author List Nicholas Wheelhouse1# & *, Allen Flockhart1# &, Kevin Aitchison1, Morag Livingstone1, Jeanie Finlayson1, Virginie Flachon2, Eric Sellal2, Mark P. Dagleish1 & David Longbottom1 Affiliations 1 Moredun Research Institute, Edinburgh, Midlothian, United Kingdom. 2 Biosellal, 317 Avenue Jean Jaurès, 69007 Lyoncedex, France # Current address: School of Life, Sport and Social Sciences, Edinburgh Napier University, Sighthill Campus, Edinburgh EH11 4BN, United Kingdom *Corresponding author: E:mail:
[email protected] &These authors contributed equally to this manuscript 1 Waddlia chondrophila is a Gram-negative intracellular bacterial organism that is related to classical chlamydial species and has been implicated as a cause of abortion in cattle. Despite an increasing number of observational studies linking W. chondrophila infection to cattle abortion, little direct experimental evidence exists. Given this paucity of direct evidence the current study was carried out to investigate whether experimental challenge of pregnant cattle with W. chondrophila would result in infection and abortion. Nine pregnant Friesian-Holstein heifers received 2 x 108 inclusion forming units (IFU) W. chondrophila intravenously on day 105-110 of pregnancy, while four negative-control animals underwent mock challenge. Only one of the challenged animals showed pathogen-associated lesions, with the organism being detected in the diseased placenta. Importantly,