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Open Access Research article

Effect of haemolysis and repeated freeze-thawing cycles on wild boar serum antibody testing by ELISA

Mariana Boadella* and Christian Gortázar

Author Affiliations

IREC (CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain

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BMC Research Notes 2011, 4:498  doi:10.1186/1756-0500-4-498

Published: 16 November 2011

Abstract

Background

Monitoring wildlife diseases is needed to identify changes in disease occurrence. Wildlife blood samples are valuable for this purpose but are often gathered haemolysed. To maximise information, sera often go through repeated analysis and freeze-thaw cycles. Herein, we used samples of clean and haemolysed Eurasian wild boar (Sus scrofa) serum stored at -20°C and thawed up to five times to study the effects of both treatments on the outcome of a commercial ELISA test for the detection of antibodies against Suid Herpesvirus 1 (ADV).

Results

The estimated prevalence of antibodies against ADV was 50-53% for clean and haemolysed sera. Hence, haemolysis did not reduce the mean observed serum antibody prevalence. However, 10 samples changed their classification after repeated freeze-thawing. This included 3 (15%) of the clean sera and 7 (41%) of the haemolysed sera.

Conclusions

We recommend (1) establishing more restrictive cut-off values when testing wildlife sera, (2) recording serum quality prior to sample banking, (3) recording the number of freezing-thawing cycles and (4) store sera in various aliquots to reduce repeated usage. For instance, sera with more than 3 freeze-thaw cycles and a haemolysis of over 3 on a scale of 4 should better be discarded for serum antibody monitoring. Even clean (almost not haemolysed) sera should not go through more than 5 freeze-thaw cycles.

Keywords:
Aujeszky's disease; Blood sample mishandling; Serological surveillance; Wildlife disease monitoring