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Characterisation of serum IgG(T) responses to potential diagnostic antigens for equine cyathostominosis

Thomas Tzelos, Kathrin K. Geyer, Mairi C. Mitchell, Hamish E.G. McWilliam, Vitaliy O. Kharchenko, Stewart T.G. Burgess, Jacqueline B. Matthews

Abstract

Cyathostomins are ubiquitous parasitic nematodes of horses. These worms spend substantial periods as

intestinal wall stage encysted larvae, which can comprise up to 90% of the total burden. Several million

larvae have been reported in individuals. Emergence of these larvae from the gut wall can lead to

life-threatening colitis. Faecal egg count tests, increasingly used by horse owners to inform anthelmintic

treatments, do not correlate with the intra-host burden of cyathostomins; this represents a key gap in

the diagnostic toolbox. Previously, a cyathostomin Gut Associated Larval Antigen was identified as a

promising marker for the intra-host stages of infection. Here, cyathostomin Gut Associated Larval

Antigen and an additional protein, Cyathostomin Immuno-diagnostic antigen, were investigated to examine

their value in providing information on cyathostomin burden. ELISA analyses examined serum IgG(T)

responses to recombinant proteins derived from individual cyathostomin species. Receiver Operator

Characteristic curve analysis was performed on the ELISA data; proteins with the highest Area Under the

Curve values were selected to test protein combinations to investigate which were the most informative

in identifying the infection status of individuals. Three cocktail combinations were tested, comprising:

(a) Cy-GALA proteins from two species and a Cy-CID protein from a third species (CT3), (b) Cy-GALA proteins

from five species (CT5), and (c) all CT5 components, plus a Cy-CID protein from an additional species (CT6).

The best predictive values for infection were obtained using CT3 and CT6, with similar values achieved for

both. Proteins in CT3 are derived from the most commonly reported species, Cyathostomum catinatum,

Cylicocyclus nassatus and Cylicostephanus longibursatus. This combination was selected for future development

since it represents a more commercially viable format for a diagnostic test.

This research paper describes the development and validation of ADBs commercial small redworm blood test. Since the work described here, the test was optimised for commercial use and further validated with additional samples. The following paragraph is a quote taken from the research paper discussion.

“This serum-based test has subsequently been validated in a commercial setting (Austin Davis Biologics Ltd., UK) and optimised for use in a robotic system. Where matching serum samples could be assessed, outputs were compared with the prototype test described here; significant correlations were demonstrated between the two methods (Matthews et al., unpublished data).

The commercial version of the test was launched in the UK in September 2019
In selecting thresholds for treatment, the requirement for high sensitivity to minimise false negatives was made. The veterinarian’s decision to use the test and apply its outputs to inform the

application of anthelmintic treatment are defined in guidelines developed to be used in interpreting the outputs of the ELISA and are based on the CT3-specific antibody level measured, expressed as a ‘serum score’, taking into account the grazing management and historic parasitological (FEC) parameters of the individual or group being tested.”

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Pre-paid address labels are available here to download and print FOR UK SUBMISSIONS ONLY. Please contact us if you wish to submit from outside of the UK.

To use our Freepost labels your packaging must be no bigger than large letter size and not thicker than 2.5cm. Packages outside of this sizing will incur additional charges.

Samples can be sent in the post without cooling or ice as serum samples are stable for at least 3 weeks. Please  place in a polythene or leakproof bag within an envelope.