Serologic and bacteriologic diagnosis of bovine leptospirosis in Tehran suburb dairy farms

Leptospirosis is a worldwide zoonosis caused by Leptospira interrogans. This study was conducted to
evaluate serologic and bacteriologic findings of leptospirosis in clinically-suspected cows. 380 sera and 33
urine samples were collected from 6 industrial dairy farms in Tehran suburb, from December 2004 to June
2005. The prevalence of disease was determined by microscopic agglutination test (MAT), enzyme-linked
immunosorbent assay (ELISA), direct dark-field microscopic (DFM) examination, indirect fluorescent
antibody test (IFAT), microbiologic cultural isolation technique and polymerase chain reaction (PCR).
Antibodies were detected by MAT at least against one serovar of L. interrogans in 55 sera (14.5%) among
380 samples at a dilution of ≥ 1:100. L. interrogans serovar icterohaemorrhagiae was the most prevalent
serovar. Leptospiral antibodies were detected by ELISA in 85 sera (22.4%) among 380 samples. Four
(12.1%) of 33 urine samples were suspected by DFM examination and no positive sample by IFAT was
observed. Leptospires could be isolated from none of the 33 samples taken from industrial farms. In this
study, positive controls were detected at a dilution of ≥ 2000 leptospires per each ml of urine sample by
PCR. Therefore, no DNA from serum and urine samples were collected from 6 industrial dairy farms could
be detected by this method. It seems that, to increase the accuracy in the diagnosis of the disease, using a
range of reliable techniques and comparing the results is important in reaching final conclusion.