Ovine Observer

Sheep abortion and stillbirth investigations at Australian veterinary laboratories

Tom Clune and Caroline Jacobson, Murdoch University WA; Sue Beetson, Clinipath Consulting; Shane Besier, Department of Primary Industries and Regional Development WA; Graeme Knowles, Department of Primary Industries, Parks, Water and Environment TAS; Roger Paskin, OMNI Animal Health Consulting SA; Grant Rawlin and Robert Suter, Department of Jobs, Precincts & Regions VIC; Gordon Refshauge, Department of Primary Industries, NSW; Marta Hernandez-Jover, Charles Sturt University VIC.

Author correspondence:


Abortion (loss of the foetus during pregnancy) and stillbirths in sheep have the potential to cause significant production and economic losses for Australian sheep producers. Infectious diseases are considered the most common cause of sheep abortion. Some of these diseases can also result in lambs that survive the duration of pregnancy but are weak and die during or soon after birth.

Identifying the cause of abortion outbreaks using disease investigation can inform strategies for preventing future losses and monitoring for zoonoses (diseases that may also infect humans).

Here we show collated data summarising sheep abortion investigations submitted to state veterinary laboratories from major sheep producing states in Australia.

Key Findings

  • Veterinary laboratories were able to identify cause of abortion in about half of investigations.
  • Of the 419 investigations where a diagnosis was made, 79% involved an infectious disease.
  • Infections with Campylobacter (32%), Listeria (24%) and Toxoplasma (10%) were the most common infectious causes of abortion identified in investigations. These diseases were diagnosed in all states, but the frequency fluctuated between years.
  • Nutritional deficiencies and ‘maternal illness’ were the most common non-infectious causes identified, but these were less frequently diagnosed than infectious causes of abortion.
  • Investigations that include submission of placenta were more than two times more likely to have a cause of disease identified compared to investigations where placenta was not available.
  • There are several important diseases that cause sheep abortions overseas. No exotic diseases were identified in any of the investigations as part of surveillance.

Materials and methods

Data for sheep abortion and stillbirth investigations submitted by government and private veterinarians between 2000 and 2018 were obtained from state veterinary laboratories in Western Australia, South Australia, Tasmania, Victoria and New South Wales.  

Diagnostic tests performed included necropsy (post-mortem examination), histopathology (examination of tissues using microscope), microbial culture (growth of bacteria or viruses), molecular diagnostic tests (for example PCR for bacteria, virus or parasites), and serology (blood tests to detect antibodies).

The time period and level of detail available for each investigation varied between states due to constraints in retrieving results from the different databases.

We used statistical tests to investigate associations between type of sample submitted and success in identifying the cause of disease, including two-tailed two-sample z-test for significance, odds ratio and relative risk with a 95% confidence interval. Characteristics of the type of sample submitted included whether placenta tissue was available for testing, and whether there was evidence of autolytic changes (deterioration, decomposition or ‘spoilage’ of samples).


Data for 854 sheep abortion or stillbirth investigations were available from state veterinary laboratories in Western Australia, South Australia, New South Wales, Victoria and Tasmania. 

An aetiological diagnosis (cause of disease) was identified in 49% of investigations.

The diagnoses made for investigations are shown in Table 1. An infectious cause was identified in 79% investigations where a diagnosis was made. Infections with Campylobacter (32%), Listeria (24%) and Toxoplasma (10%) were the most common infectious causes of abortion identified.

Table 1 – Diagnoses made for abortion and stillborn lamb disease investigations


Diagnoses by state (n)









% investigations with diagnosis

Campylobacter spp.








Listeria spp.








Toxoplasma gondii








Other infectious diagnoses








TOTAL infectious diagnoses








TOTAL non-infectious diagnoses








WA – Western Australia; SA - South Australia; NSW – New South Wales; VIC – Victoria; TAS – Tasmania

# Total number of investigations with diagnoses (investigations with more than one infectious cause are only counted once)

abc Values for diagnosis category (total Campylobacter, Listeria, Toxoplasma, other) with different superscripts are significantly different (P<0.05) using 2-tailed 2-sample z-test

There were several less common diseases that were identified including infections with Leptospira (not diagnosed in WA), Chlamydia, Yersinia, Salmonella, Q-fever, Border Disease, Brucella ovis (brucellosis) and opportunistic bacterial infections.

Non-infectious diseases included nutritional deficiencies (such as iodine, causing goitre) and maternal (ewe) illness. Some investigations identified more than one disease in the same foetus or across different foetuses in same investigation.

No exotic diseases were detected.

Investigations that include a sample of placenta were 2.3 times more likely to have a cause identified compared investigations with no placenta available (Table 2). Autolytic changes (deterioration of samples) were common (50% of investigations), but the laboratories were still able to identify a diagnosis for 57% of those investigations.

Table 2 – Association between submission of placenta samples and diagnostic success (% investigations with aetiological diagnosis) in sheep abortion investigations


Submissions (n)

Aetiological diagnosis made

No aetiological diagnosis

Placenta available


48 (62%)

29 (38%)

Placenta not available


26 (42%)

36 (58%)


Campylobacteriosis, listeriosis and toxoplasmosis were the most commonly diagnosed causes of sheep abortion and stillbirths. However, a large number of other infectious and non-infectious diseases are sporadically associated with sheep abortion outbreaks on Australian farms.

Farmers and vets should be aware of sampling protocols that can support successful laboratory investigation. If producers identify an aborted lamb or placenta, these should be collected in a clean container or bag and kept chilled or refrigerated prior to submission to the vet or lab. Finding and submitting a placenta or foetal membranes will improve the chance that the laboratory can identify the likely cause of abortions. Tissues should be collected even if they appear dirty, deteriorated or partly predated by foxes or birds as there are some tests that can be used with deteriorated tissues that assist with making a diagnosis. The laboratory may ask that tissues are frozen if there is likely to be a delay receiving samples. Molecular diagnostics can still be performed on frozen tissue, but other tests may not be available if samples are frozen. In many cases, subsidised testing is available for veterinary investigation of abortions and stillbirths.

Some diseases that cause abortion are zoonotic and can infect people. Appropriate hygiene should be used when handling aborted lambs, placenta and affected ewes. This includes using gloves and mask where possible, and washing hands and changing clothes after handling sheep or aborted lambs.


Infections with Campylobacter, Listeria and Toxoplasma were the most commonly identified cause of abortion for investigations submitted to Australian veterinary diagnostic laboratories, but there are a wide range of less common infectious and non-infectious diseases identified on Australian farms. If producers suspect that sheep abortions are occurring, they should contact their vet for advice. Collecting dead lambs and placenta and storing these appropriately will increase the probability that the cause can be identified.

Many of the diseases that cause abortion and stillborn lambs in Australian sheep have zoonotic potential, therefore appropriate hygiene should be used when handling pregnant and lambing ewes, as well as aborted lambs or placenta.

Further information

Project final report:

Scientific paper (WA, SA, VIC and TAS):

DPIRD Sheep Abortion Surveillance Scheme:


This work was funded by Meat and Livestock Australia. The publications from which this data is derived were approved for publication by the Chief Veterinary Officers for each state included in this study. Tom Clune received a Sheep Industry Business and Innovation scholarship (Department of Primary Industries and Regional Development, Western Australia) and Postgraduate Study Award (Meat and Livestock Australia). We thank the many producers, veterinarians and pathologists who were involved in collecting, submitting and investigating case material used for this report, and for assistance retrieving data.

Adapted for Ovine Observer with assistance of Sofia Testa (Murdoch University Bachelor of Agricultural Science student).