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Ability to detect antibodies to beak and feather disease virus in blood on filter paper decreases with duration of storage

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posted on 2021-01-01, 00:00 authored by B Blanch-Lázaro, Raoul RibotRaoul Ribot, Mathew BergMathew Berg, Soren AlexandersenSoren Alexandersen, Andy Bennett

Background
Beak and feather disease virus (BFDV) is a circovirus that infects captive and wild psittacine birds, and is of conservation concern. The haemagglutination inhibition (HI) assay is used to determine antibody titres against BFDV, and the use of dried blood spots (DBS) on filter paper stored at room temperature has been suggested to be an equally valid technique to the use of frozen serum. However, research on other pathogens has found variable results when investigating the longevity of antibodies stored on DBS at room temperature. Consequently, we aimed to test the temporal stability of antibodies to BFDV in DBS samples stored long-term at room temperature. A further goal was to add to the current knowledge of antibody response to naturally acquired BFDV infection in crimson rosellas (Platycercus elegans).


Methods
Blood was collected from wild P. elegans in Victoria, Australia, that had been live-trapped (n = 9) or necropsied (n = 11). BFDV virus load data were obtained from blood stored in ethanol by real-time quantitative PCR (qPCR); antibody titres were obtained by HI assay from either DBS or serum samples, which had been collected concurrently. All HI assays were performed commercially by the Veterinary Diagnostic Laboratory (VDL) in Charles Sturt University, Australia, who were blind to BFDV blood status.


Results
HI titres from DBS stored at room temperature declined significantly over time (~80 weeks). By contrast, frozen serum samples assayed after 80 weeks in storage all had high HI titres, only varying up to one dilution step from the initial HI titres obtained from DBS at 3–6 weeks after sampling. Weak HI titres from DBS samples all came back negative when the test was repeated only nine weeks later. Novel high HI titres were reported in P. elegans, and while most birds with high antibody titres had corresponding negative qPCR results, a single subadult presented with high HI titres and virus load simultaneously.


Conclusion
Detection of antibodies on filter paper stored at room temperature decreases over time, increasing the chances of false negatives in these samples, and in repeated testing of samples with weak HI titres. Consequently, serum should be the preferred sample type to use for seroepidemiological studies on BFDV in parrots and other bird species. When not possible, it may help to store DBS on filter paper at −20 °C or lower. However, prompt testing of DBS samples (e.g., <6 weeks in storage) is recommended pending further research on antibody temporal stability. We also show that P. elegans, especially adults, can produce high antibody titres against BFDV, which may help them resist infection.

History

Journal

PeerJ

Volume

9

Article number

e12642

Pagination

1 - 15

Publisher

Peerj Inc

Location

Corte Madera Calif.

ISSN

2167-8359

eISSN

2167-8359

Language

English

Publication classification

C1 Refereed article in a scholarly journal