Pet dogs owned by lupus patients are at a higher risk of developing lupus

The aim of this study is to determine whether pet dogs owned by patients with systemic lupus erythematosus (SLE) are at a higher risk of developing SLE. Diagnosis of canine SLE was mainly based on the 11 diagnostic criteria for human SLE and two marked immunological features of canine SLE. Among 59 pet dogs owned by 37 SLE patients, 11 (18.64%) were ANA positive, and three (5.08%) had SLE. In contrast, of 187 pet dogs owned by non-SLE households, nine (4.81%) were ANA positive, and none (0%) had SLE. Among 650 outpatient dogs registered in the veterinary hospital, 34 (5.23%) were ANA positive, and six (0.92%) had SLE. Frequency of ANA and SLE among pet dogs owned by SLE patients was significantly higher than in pet dogs owned by non-SLE households (P = 0.001 for ANA; P = 0.013 for SLE) and in outpatient dogs (P < 0.001 for ANA; P = 0.032 for SLE). With respect to canine SLE development, the relative risk or risk ratio (R) of human SLE contact varied from 5.5 (compared with outpatient dogs) to near the infinite (compared with dogs owned by non-SLE households). The prevalence of canine SLE among pet dogs of SLE patients was therefore estimated to be 508 per 10 000 [95% confidence interval (95% CI), 0-1068]. In conclusion, pet dogs with human SLE contact were at a higher risk of developing SLE. Our results indicate that a common environmental factor or zoonotic agent may be involved in the development of human and canine SLE.