Of the 11 dogs suspected to be infected, five dogs were diagnosed as having leptospirosis based on clinical symptoms or clinical course (case No. 5, 7, 14, 16, and 17), four dogs were IgM antibody positive (case No. 9, 10, 11, and 12), and two had Leptospira spp. This evidence concerns the gene CD40LG and leptospirosis.