Faecal IgA but not salivary IgA is associated with canine atopic dermatitis

To characterise immunoglobulin A (IgA) levels in the faeces and saliva of dogs with canine atopic dermatitis (CAD) and healthy breed matched controls.

Dogs with canine atopic dermatitis were recruited based on history, clinical examination and diagnostic testing where appropriate. Control dogs were over 4 years of age with no history of skin disease. Saliva samples were obtained using chewable synthetic swabs with saliva extracted by centrifugation. Faecal samples were collected from the ground before homogenisation in phosphate buffered saline and centrifugation to extract faecal supernatant. Total immunoglobulin A in saliva and faecal supernatants was measured using a commercial dog immunoglobulin A ELISA kit. Immunoglobulin A concentration was interpolated from a six-point standard curve. Mann-Whitney tests were performed to compare immunoglobulin A concentrations between cases and controls.

Mean ranked faecal immunoglobulin A was significantly lower in dogs with canine atopic dermatitis than controls (difference between medians 0.803 g/L, 95% CI 0.064 to 1.721). There was no significant difference in mean ranked salivary immunoglobulin A between the groups (difference between medians 0.108 g/L). Faecal immunoglobulin A and salivary immunoglobulin A were not correlated. There were no dogs in either group with both low faecal and low salivary immunoglobulin A suggestive of selective immunoglobulin A deficiency.

This study builds on existing evidence that low immunoglobulin A is associated with canine atopic dermatitis. Further work is required to determine the significance of low faecal immunoglobulin A in the development of tolerance or hypersensitivity to food and environmental allergens which may inform strategies for interventions in high-risk breeds.