Identification of canine saliva using mRNA-based assay

A dog saliva analysis in addition to a bite-mark analysis may be important for evidence when a crime involves a dog bite. In this study, the utility of detecting canine saliva-specific mRNAs to identify canine saliva was evaluated. Canine saliva swabs (n = 20), urine swabs (n = 20), body surface swabs (n = 20), whole blood samples (n = 10), human saliva (n = 20), human skin surface swabs (n = 20), and human whole blood (n = 20) were tested. The saliva-specific genes encoding statherin (STATH), carbonic anhydrase VI (CA-VI), and dog allergens (Canf1 and Canf2) were analyzed as candidate genes. Moreover, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as confirmation of canine mRNA extraction. STATH, CA-VI, Canf1, Canf2, and GAPDH mRNAs were detected in 19/20, 1/20, 11/20, 4/20, and 20/20 saliva samples, respectively. The STATH, CA-VI, Canf1, Canf2, and GAPDH mRNAs did not exhibit cross-reactivity with samples of human origin. This mRNA-based assay was also able to detect canine saliva in mock forensic samples. The results of this study indicated that the detection of STATH mRNA is useful for the identification of canine saliva, and GAPDH is a suitable marker for canine mRNA extraction.