Screening for OPA using transthoracic ultrasound
Our in-house vet, Rachel Marshall has taken a look at OPA scanning for our latest article. Using information available from the Moredun Research Institute she explains how ultrasound can reduce the risk of OPA spreading throughout sheep flocks.
Ovine pulmonary adenocarcinoma (OPA) is one of a number of respiratory diseases prevalent in the UK sheep population. It is a disease that can cause significant annual losses to flocks; can be as much as 4-5%.
A small (1-2cm) pulmonary lesion, with loss of the hyperechoic white line (white arrow) and a well-demarcated area of pathology associated with OPA (yellow arrows) in this case. Note the depth setting here is merely 4cm.
Image courtesy of Dr. Phil Scott
The specificity and sensitivity of ultrasound scanning for OPA is generally very good (Cousens & Scott, 2015), however false positives can occur and it must be remembered that scanning cannot guarantee a sheep to be free from disease as the very smallest tumours will go undetected. There is currently no treatment for the disease, therefore early detection and isolation from the flock are imperative for control of the disease within the flock.
The forelimb is extended and held by the imager, exposing the 5th to 7th intercostal spaces.
Image courtesy of Dr. Chris Cousens
All in all, a quick and easy technique that could help to save many farms from sizeable losses related to OPA, but can also differentiate other lung pathologies (e.g. pulmonary abscess) that may require alternative treatment.
You can access the full article HERE.
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