Eperythrozoonosis (ep-pur-rith-ro-zo-on-osis) is the disease produced by the bacterium Mycoplasma ovis, formerly known as Eperythrozoon ovis. M. ovis inhabits red blood cells of sheep and goats and causes their destruction leading to anaemia, jaundice, and in heavy infections, deaths of susceptible animals. Typically, infected animals show signs of weakness and ill-thrift, lag behind the group and collapse if mustered. Older, previously infected animals develop a protective immunity.
Disease may be spread by procedures such as vaccination (re-using the same needle) and ear tagging. When outbreaks occur in sheep they are often 4 to 6 weeks after marking, mulesing and/or shearing. Blood sucking insects and flies feeding on open wounds are also implicated in transfer of parasites.
When sheep and goats are diagnosed with anaemia, and barber’s pole worm and fluke are ruled out as a cause, then blood smears need to be made from a cross-section (about 10–20 sheep or goats confined in the corner of a paddock to avoid mustering stress) of the mob to see if the M. ovis bacterium can be detected. Once sheep or goats are showing signs of anaemia, the parasite is often no longer seen in smears, hence, a number of animals, including those that appear healthy, must be tested.
Treatment using antibiotics is not effective. Management protocols should eliminate the need to yard stock within six weeks of the activities that could spread M. ovis (described above), and also to minimize stress to affected animals from handling during this time.
Outbreaks are sporadic and mostly seen in spring. Some sheep breeds are more affected than other breeds. Further losses occur when infected carcases are condemned at abattoirs because of jaundice.
There are a number of other causes of anaemia, such as copper deficiency and protein/vitamin B12 deficiency, which also should be considered and it is also possible that more than one disease could be occurring at the one time, e.g. both worms and M. ovis.
If your flock or herd is suffering losses with anaemia and you have ruled out worms and fluke by conducting egg counts, seek veterinary advice immediately.