A Serological Survey on Leptospiral Infection Among Wild Rats (Rattus rattus) of Ahvaz District, Southwest of Iran: A Preliminary Study

Background: Leptospirosis is an important zoonotic disease caused by pathogenic Leptospira which can infect both humans and animals. This disease is caused by various serovars of Leptospira interrogans sensu lato infection. Rats are known to be one of the most important reservoirs and transmission sources of leptospirosis. However, the status of leptospirosis in wild rats has been unknown in many areas of Iran. Objectives: This study was conducted to evaluate the seroprevalence of leptospiral infection in wild rats (Rattus rattus) in Ahvaz district (southwest of Iran) from October 2009 to November 2011. Materials and Methods: Rats were trapped alive, anaesthetized, and blood-extracted by cardiac puncture. Serum samples were collected from 120 wild rats and screened for different leptospiral serovars using the microscopic agglutination test (MAT). The rats were classified according to sex, season and region of capture. The results were analyzed by Chi-square analysis and Fisher’s exact test. Results: From a total of 120 rats, 4 (3.33%) were serologically positive for the L. gryppotyphosa serovar. All positive titers were detected at 1:100 dilutions. Antibodies against more than one serovar were not detected in any sample. The prevalence of leptospiral infection was 2.5% and 0.83% in male and female rats, respectively. There was no significant difference in positive titer prevalence between different sexes, seasons and areas (P > 0.05). Conclusions: This survey indicated that serovars of L. gripotyphosa are prevalent in the rats population of this area and can be a source of infection for humans. The results of the present study provide useful information on the epidemiology of leptospirosis in this species, which was not well studied before.