Ovine abortion and stillbirth investigations in Australia

Abstract

Fetal loss and lamb mortality between mid‐pregnancy and weaning are important economic and welfare issues for the Australian sheep industry. The aim of this study was to determine common causes of ovine abortion and stillbirths based on submissions to veterinary laboratories and identify factors that impact the determination of an aetiological diagnosis. Data for 529 investigations on abortion or stillbirth between 2000 and 2018 were retrieved from four state veterinary laboratories in Western Australia, South Australia, Victoria and Tasmania. An aetiological diagnosis was made for 57% of investigations. Investigations that included placental tissue samples were more than twice as likely to have an aetiological diagnosis compared to investigations without placenta (P = 0.017, 95% confidence interval 1.1, 4.5). Of the investigations where an aetiological diagnosis was made, 81% involved infectious abortion, with Campylobacter spp. (32%), Listeria spp. (25%) and Toxoplasma gondii (9%) being the three most common abortigenic pathogens implicated. The remaining 19% of investigations with an aetiological diagnosis included a wide range of infectious and non‐infectious diseases. Diagnoses made varied year to year and between states. No evidence of exotic abortigenic pathogens were reported. Veterinary practitioners can improve the probability of an aetiological diagnosis by emphasising to farmers the importance of collecting any aborted material, especially placenta, and appropriate storage of the tissues until they can be submitted to the laboratory. Some diseases that cause abortion in Australian sheep have zoonotic potential, and veterinary practitioners play an important role in educating clients about appropriate hygiene when handling pregnant and lambing ewes or any aborted material.

Chlamydia pecorum detection in aborted and stillborn lambs from Western Australia

“…Chlamydia pecorum has predominantly been associated with polyarthritis [ 54 – 56 ], keratoconjunctivitis [ 43 ] and asymptomatic gastrointestinal carriage and faecal shedding in Australian sheep [ 57 ]. Abortion due to C. pecorum is sporadic and not commonly reported [ 12 , 18 , 20 ], and the role of C. pecorum as an abortigenic agent is not well defined. Thereby, detection of this organism in aborted and stillborn lambs from multiple farms with no epidemiological or geographical relationship is notable, and C. pecorum should be considered as a differential diagnosis for abortion and perinatal mortality in Australian sheep.…”

“…Determining the aetiology in abortion and perinatal lamb death investigations is inherently challenging [ 12 ], and conclusive diagnosis of disease cannot be made based only on detection of a pathogen in tissue samples. Nevertheless, several observations from this study suggest C. pecorum was a likely aetiological agent associated with abortion and stillbirth on these farms.…”

“…Infectious diseases may contribute to lamb mortality through abortion, stillbirths and birth of weak lambs that are more likely to die soon after birth. Campylobacteriosis, listeriosis and toxoplasmosis were the most common aetiological agents identified in sheep abortion investigations submitted to Australian veterinary diagnostic laboratories between 2006 and 2019 [ 12 , 13 ]. This is consistent with older reports describing these as the most common infectious causes of abortion and perinatal mortality in Australian sheep [ 14 – 17 ].…”

“…This is consistent with older reports describing these as the most common infectious causes of abortion and perinatal mortality in Australian sheep [ 14 – 17 ]. Sporadic abortion associated with Chlamydia pecorum has been reported in sheep from Australia [ 12 , 18 ] and overseas [ 19 , 20 ], but the epidemiology of C. pecorum -associated abortion in sheep remains poorly understood.…”

“…Most recent Australian studies that included lamb necropsies were conducted with multiparous ewes, and cause of death was assigned based on gross post-mortem findings without adjunct laboratory investigation [ 2 , 23 – 27 ]. In general, relatively few investigations for abortion and perinatal lamb death are submitted to veterinary diagnostic laboratories for exclusion of infectious diseases [ 12 ]. Consequently, the role of infectious diseases as a contributor to mortality of lambs born to primiparous ewes are not well described and it is possible that the contribution of infectious disease to perinatal mortality may be underrecognized.…”