Anaemia in Lambs Caused by Mycoplasma ovis: Global and Australian Perspectives.

Abstract

Simple SummaryMycoplasma ovis (formerly Eperythrozoon ovis) inhabits red blood cells and may cause their destruction, leading to anaemia, jaundice and death mainly in lambs, and condemnation of jaundiced carcases at abattoirs. Mycoplasmosis is spread during high-risk procedures that expose or share blood, especially when blood sucking flies and other insects are present on wounds that transfer infection. High-risk procedures include vaccination (re-use of needles), ear-tagging (ineffective disinfection), surgical castration and mulesing (in Australia), and potentially crutching and shearing, with outbreaks usually occurring up to 6 weeks later. Affected animals are weak, lagging in the ‘tail of the mob’ and collapsing when mustered. The investigation of other causes of anaemia and jaundice is required, particularly haemonchosis (Barbers pole worms) and malnutrition. The diagnosis involves the demonstration of M. ovis in blood smears and/or by PCR, although the absence of the parasite in smears from affected animals requires the examination of in-contact healthy animals. Treatment with antibiotics is ineffective. For its control, it is required that risky procedures are avoided during high insect activity and the yarding of stock within the next 6 weeks is minimised. Recent anecdotal observations suggest that improved farm practices, including fly control and pain/antiseptic wound dressing may potentially decrease M. ovis risk on some farms in some areas of Australia.Mycoplasma ovis (formerly Eperythrozoon ovis) is a haemotropic parasitic bacterium found within erythrocytes and distributed widely in global sheep and goat production regions. M. ovis is transmitted by biting flies and by contaminated instruments, causing morbidity and mortalities from anaemia, usually within 6 weeks following blood-exposure procedures, particularly vaccination, castration, ear tagging, mulesing, and occasionally crutching and shearing. Affected animals develop haemolytic anaemia and may have jaundice, causing abattoir condemnations. The typical history, clinical and pathological findings, display of M. ovis in blood smears and/or by PCR is diagnostic, although immune responses deplete M. ovis from smears; hence, in-contact healthy animals should be examined. Differential diagnoses include haemonchosis, fasciolosis, malnutrition (copper or vitamin B12 deficiency), and plant toxicities. M. ovis parasitaemia may persist, with recrudescence following stressful events, although most older sheep remain immune. Human infections have been reported. Inadequate socioeconomic data present difficulties in assessing the impact of M. ovis on production and as antimicrobial therapy is ineffective, its control requires management practices that minimize the impact of invasive procedures in periods when risks of M. ovis transmission are more likely. Although considered an emerging pathogen, recent improvements in welfare attitudes and husbandry practices on Australian sheep farms may potentially limit the transmission of M. ovis.