Haemotrophic Mycoplasmas in Small Ruminants
The large amounts of standing flood water across eastern Australia are resulting in challenges for us all, including our small ruminants (sheep and goats).
Standing water leads to an increase in biting insects like mosquitoes and midges. In high numbers, these insects can be highly irritating and stressful for us, and for goats and sheep.
They also transmit disease, including Mycoplasma ovis between sheep and goats.
Mycoplasma ovis (formerly Eperythrozoon ovis) is a haemotrophic mycoplasma that is widespread in all sheep-raising regions globally (1).
Unlike Mycoplasma ovipneumoniae that lives in the respiratory tract of sheep and goats closely associated with the cells lining the airways, Mycoplasma ovis parasitizes the surface of the red blood cells. The animal’s body reacts by trying to destroy the infected red blood cells. This can lead to anemia, jaundice, and death if left untreated.
Historical surveys have shown that infection with Mycoplasma ovis is common in all sheep-raising regions of Australia. Less is known about infection in Australian goats. A recent molecular survey in South America has found widespread infection with Mycoplasma ovis in goats in Brazil, with anemia a common finding in infected animals (2).
Mycoplasma ovis has not been reported to infect cattle.
Other insects that that transmit Mycoplasma ovis include stable flies and ticks. Infections can also be transmitted by reusing needles during flock/herd vaccination programs and by poor hygiene during marking and shearing. Only a very small amount of blood is sufficient to spread disease. Oral transmission has been shown experimentally.
Signs of Mycoplasma ovis include poor-doers, anemia (pale membranes around the eyes), jaundice (yellow membranes around the eyes), dark red urine and death, particularly after a stressful event like yarding.
Traditionally Mycoplasma ovis was diagnosed by examining blood smears under the microscope. However, this technique lacks sensitivity because by the time the animal is showing clinical signs of infection, the body is destroying the red blood cells. Newer molecular techniques such as PCR (polyermase chain reaction) are now preferred for diagnosis.
When detected early, infections can be treated.
Testing sheep for Mycoplasma ovis can be arranged as part of my on-farm small ruminant disease investigations.
References
Mycoplasma ovis comb. nov. (formerly Eperythrozoon ovis), an epierythrocytic agent of haemolytic anaemia in sheep and goats. Neimark H, Hoff B and Ganter M (2004), International Journal of Systematic and Evolutionary Micorbiology, Vol. 54, pp. 365-371.
Mycoplasma ovis infection in goat farms from northeastern Brazil. Machado CAL et al (2017), Comparative Immunology, Microbiology and Infectious Diseases, Vol. 55, pp. 1-5.