Seroprevalence of Leptospira infection in occupational risk groups in North Khorasan province, Iran by Hashemi, Seyed Mohammad, Arzamani, Kourosh, Abdollahpour, Gholamreza, Beheshti, Nazanin, Alavinia, Mohammad, Azimian, Amir, Neela, Vasantha Kumari, Van Belkum, Alex, Ghasemzadeh-Moghaddam, Hamed