Leptospirosis in Zakarpattia Oblast (2005-2015)

Background: Leptospirosis occurs sporadically and as outbreaks throughout Ukraine and is a nationally reportable disease. Zakarpattia oblast, in the southwestern region of the country, is endemic for disease. This study examines changes in epidemic patterns from 2005 to 2015. Materials and Methods: Suspected cases from health care services were identified based on clinical presentation and serological samples were collected. Patient sera were tested by microscopic agglutination test (MAT) against serovars of Leptospira spp. belonging to 13 serogroups. Small mammals were also collected, sampled, and tested near locations of suspected exposures. Changes in leptospirosis incidence in Zakarpattia oblast were characterized over an 11-year period. Results: A total of 420/2079 possible human cases were identified as having leptospirosis and 401/420 were confirmed by MAT. There was no annual trend in prevalence. Incidence increased from 2005 to 2009, peaked in 2010 (6.24 cases/100,000), and by 2015, there were only sporadic cases (0.88/100,000). The predominant serogroups were Icterohaemorrhagiae, Hebdomadis, and Grippotyphosa of Leptospira spp. The dominant serogroups shifted during the study from predominantly Icterohaemorrhagiae to Grippotyphosa in later years. A total of 2820 small mammals were assayed for Leptospira spp. Apodemus agrarius, Rattus norvegicus, and Mus musculus were the most common species sampled (76.1% of all captures). Among small mammals, antibodies were found mostly for Icterohaemorrhagiae, Pomona, and Grippotyphosa serogroups, and were detected in 276 samples (9.79% +/- 0.56%). The dominant serogroups of Leptospira spp. isolated from mammals and patients changed cyclically, but the common human serogroups tended to differ from that seen in the concurrent mammal populations. Conclusions: Patients with leptospirosis in this endemic region decreased more than fivefold during the past decade. Leptospira infections in small mammals remained common across multiple species ranging from 5% to 14%.