Non-specific markers of inflammation in bare-nosed wombats (Vombatus ursinus) with sarcoptic mange

Abstract

Sarcoptic mange, caused by epidermal infection with Sarcoptes scabiei, negatively impacts the health, welfare, and local abundance of bare-nosed wombats (Vombatus ursinus) in Australia. Improved understanding of the host immune response to disease and its contribution to pathophysiology could be used to inform management actions for this species in and ex situ. To evaluate the immune response of bare-nosed wombats to sarcoptic mange, we validated three assays (haptoglobin, agarose gel electrophoresis, and micro-erythrocyte sedimentation rate) measuring non-specific markers of inflammation using serum samples from free-living wombats from Tasmania (n = 33). We then analysed correlations between the assay results for each non-specific marker of inflammation and wombat's sarcoptic mange scores, and performed histopathological examinations to investigate association of the acute phase response with systemic amyloidosis. We present evidence that haptoglobin and erythrocyte sedimentation rate increased, and albumin decreased, in association with sarcoptic mange scores. This research demonstrates links between the acute phase response and sarcoptic mange severity in bare-nosed wombats, highlighting the utility of non-specific markers of inflammation for aiding assessment of the systemic effects of mange. Showing the value of agarose gel electrophoresis, we also identified specific acute phase proteins warranting future evaluation and found evidence of an immunoglobulin response in mange-affected wombats, revealed by increasing γ-globulins in association with apparent disease severity. Meanwhile, owing to its relatively low resource requirements and rapidity, the erythrocyte sedimentation rate assay may be useful as a point-of-care test to support therapeutic decisions in the field. Our methods and findings are likely to be applicable to a range of other clinical and population health scenarios in captive and free-living wombats, and species impacted by sarcoptic mange globally.

Keywords: Sarcoptes scabiei; acute phase response; agarose gel electrophoresis; assay validation; bare-nosed wombat; erythrocyte sedimentation rate; haptoglobin; sarcoptic mange.

Figure 1

Representative agarose gel protein electrophoretograms of adult bare-nosed wombats (Vombatus ursinus) that were (A) apparently healthy and (B) sarcoptic mange-affected. Vertical lines indicate breaks between (1) albumin, (2) α-1 globulins, (3) α-2 globulins, (4) β-globulins, and (5) γ-globulins.

Figure 2

Associations between average mange scores and seven non-specific markers of inflammation (NSMI): haptoglobin (Hp), albumin, α-1, α-2, β, and γ globulins, and erythrocyte sedimentation rate (ESR). Circles depict observed NSMI values from individual wombats, and colours depict the wombat’s clinical group. The solid black line depicts the predicted mean NSMI value when it is assumed to relate to the average mange score (α2 = 1). The shaded region depicts the 95% credible interval associated with the mean. The average mange score is the average of the 14 body-segment mange scores (each an integer in the range 0–10). Note that the data associated with unhealthy animals due to reasons other than mange (black circles), were not used when fitting as the objective of the analysis is to estimate the impact of mange on each NSMI.