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Parasite Resistance - IgA

Breeding for Parasite Resistance – Measuring IgA levels in blood serum

Research at Glasgow University has shown the antibody responses against the larval stage of Teladorsagia circumcincta, (an important member of the Strongyles family) can be used as a biological marker for host response to infection.

This potential phenotype provides a new way to identify genetic differences between sheep in their resistance to worm challenge. High levels of IgA have been shown to regulate both worm growth and fecundity – leading to a decrease in egg output.

These differences will be even more useful in a breeding programme, where they can be converted into breeding values.

In 2020, as a one off activity AHDB funded a large project to collect Serum IgA and FEC measurements. From this data SRUC have estimated encouraging heritabilities for Serum IgA (~35%) and in one breed, they also found an encouraging genetic relationship with FEC traits. 

AHDB/SRUC have now been able to incorporate this data into the National breeding programmes for hill and maternal breeds. Breeding values are now available for Serum IgA.

Who provides IgA testing services and what does it cost?

In 2024 IgA testing will be provided by Biobest Labs and the test is priced by Biobest at ~£7/sample.

Please contact Biobest before samples are dispatched as the test is offered on the basis of prior agreement only.

Samples need to be accompanied by a submission form, which can be obtained directly from Biobest - please ensure different management groups are clearly identified on submission forms.

Please contact the team at Biobest via [email protected]  with submission forms or if you have any questions about serum IgA. Alternatively you can contact Rebecca Mearns [email protected] 

Send your samples to:

Biobest Laboratories Ltd
6 Charles Darwin House
The Edinburgh Technopole
Milton Bridge
Nr Penicuik
EH26 0PY

Sampling advice

In order that lambs have a high enough egg count for variation between individual animals to be expressed it is vital that lambs are exposed to a parasite infection.

The lambs being tested need to be under a worm challenge (ideally worm count >300) and a mob FEC sample should be taken to determine this.

Please ensure as far as is practical that all animals included have the same or similar grazing history and management treatments (this will mean that results are more comparable as the animals will have been exposed to the same types and levels of parasitic infection). If lambs are kept in different groups/mobs – please submit samples in separate groups and identify the groups clearly on your submission forms so that this information is clear for the lab on receipt and can be included in the result report.

Submitting data to Biobest

IgA measurements are completed relative to a set of controls, which may vary slightly between tests. So all the samples from a flock that are to be compared together must be run on the same test. This would normally be the case where results come as a single submission, but if the submission is split and posted separately and this is not the case it is important to let Biobest know so they can hold off testing until they have all the samples and can test all the flock samples together. 

On the lamb submission form if all lambs have the same prefix/UK flock number just state this once at the top of the form and then indicate each individual lamb ID (last 4 or 5 digits), age, sex and management group (if different).

Samples need to be submitted in the red topped vacutainer tubes, where possible as these contain no anticoagulant. Please request these from your vet as soon as possible to ensure supply.

Please place tubs in the same order as listed on the submission form to assist the lab with processing. 

Further information on breeding for parasite resistance, breeding for worm resistance -FEC and breeding for worm resistance - technical update