Small strongyles (cyathostomin) infection in equines can cause clinical symptoms such as lethargy, sudden weight loss, debilitation, and diarrhoea. The encysted stages of cyathostomin can enter a dormancy stage called hypobiosis, which are not detected with a standard faecal egg count (FEC). Although a commercialised IgG(T) sera test identifying encysted larvae is available, the requirement for blood samples impedes its wide scale adoption. The aim of the current study was to investigate whether saliva can be used as an alternative to blood to detect antibodies against encysted and adult stage larvae.
Saliva blood and faeces were collected at three timepoints (Spring, Autumn, and Winter) from horses (n=27) in regional Victoria, Australia. Blood was processed for IgG(T) antibodies against encysted stage larvae, the Mini-FLOTAC method was used to calculate FEC, and an IgA/IgG(T) ELISA was optimised for saliva. A positive correlation between sera and saliva IgG(T) in Autumn and Winter was found against late encysted and adult stage larvae (r=0.55, P=0.003; r=0.50, P= 0.018). A positive correlation between sera and IgA in Winter was found against early encysted larvae (r=0.51, P=0.014; r=0.422, P=0.045). No correlations were observed with FEC for either blood or saliva. These results demonstrate antibodies to encysted and adult stage larvae antigens used in the commercial test are also present in saliva and may have potential as an alternative test to detect encysted stage of cyathostomin infection in equines.