762 AJVR, Vol 66, No. 5, May 2005 L eptospirosis is a worldwide zoonotic disease caused by spirochetes of the genus Leptospira. Leptospires infect all species of mammals, including humans. Among domesticated animals, cattle, dogs, and pigs are the species most commonly infected. 1-4 Clinically, lep- tospirosis may be mild, which is difficult to diagnose, or the disease may prove fatal. 5 Animals infected with host-adapted serovars of Leptospira spp become main- tenance hosts. Examples of leptospires that adapt to the hosts and cause those animals to become mainte- nance hosts are Leptospira interrogans serovar hardjo (bovine), L interrogans serovar bratislava (swine), and L interrogans serovar australis (ovine). 6-11 Certain lep- tospires, such as L interrogans serovar pomona and L interrogans serovar icterohaemorrhagiae, are not host-adapted to cattle and pigs and cause illness in these animals accompanied by signs of severe clinical disease that sometimes results in death. 10-12 Host-adapt- ed serovars have not been implicated in infections in humans, but there are variations in virulence among the serovars that infect humans. 13 Most cattle develop chronic leptospirosis after infection; they become carriers and shed Leptospira organisms in their urine. 14 Only rarely do animals devel- op acute illness, which can be fatal (especially in young animals). 5,15 In these instances, clinical signs include abortion, stillbirths, weak newborns, decrease in milk yield, mastitis, icterus, and hemoglobinuria. 11,15-17 Differential diagnoses for leptospirosis in cattle include babesiosis, anaplasmosis, toxicosis attributable to the ingestion of rape or kale, postpartum hemoglobinuria, acute hemolytic anemia (in calves), other causes of abortion, agalactia, brucellosis, and infection with Coxiella burnetii (ie, Q fever). 5 The most widely accepted serologic test for diag- nosis of leptospirosis is the microscopic agglutination test (MAT). 18 A 4-fold increase in the MAT titer in paired sera or a single MAT titer of ≥ 1:400 is diagnos- tic of leptospirosis in humans, 18 whereas a titer of ≥ 1:100 is evidence of past exposure. 19 In cattle, how- ever, the minimum MAT titers for Leptospira infection in several studies 11,20-22 have varied from 1:10 to 1:40. The direct and definite means of diagnosing lep- tospirosis is by documentation of the organisms in samples. 11,18,19 Microbial culture, dark-field microscopy Received June 7, 2004. Accepted October 14, 2004. From the Departments of Microbiology and Immunology (Suwimonteerabutr, Chongsa-nguan, Kalambaheti) and Social Medicine and Environment (Ramasoota), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand 10400; the Department of Medical Technology, Faculty of Allied Health Sciences, Thammasat University, Rangsit Center, Pathum-thani, Thailand 12121 (Chaicumpa, Tapchaisri, Sakolvaree); the Department of Pathology, Faculty of Medicine, Srinakharinwirot University, Bangkok, Thailand 10110 (Saengjaruk); and the Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Chulalongkorn University, Bangkok, Thailand 10300 (Virakul). Supported by The Thailand Research Fund. The authors thank Mathukorn Na Ubol and Drs. Mark Roselieb and William Ba-Thein for technical assistance. Address correspondence to Dr. Chaicumpa. Evaluation of a monoclonal antibody–based dot-blot ELISA for detection of Leptospira spp in bovine urine samples Junpen Suwimonteerabutr, MS; Wanpen Chaicumpa, DVM, PhD; Patcharin Saengjaruk, PhD; Pramuan Tapchaisri, PhD; Manas Chongsa-nguan, MPH, PhD; Thareerat Kalambaheti, PhD; Pongrama Ramasoota, DVM, PhD; Yuwaporn Sakolvaree, MS;Prachin Virakul, DVM, PhD Objective—To evaluate the efficacy of a novel mono- clonal antibody (MAb)–based dot-blot ELISA for detection of Leptospira antigens in urine samples of cattle. Sample Population—Blood and urine samples of 45 test cattle from 5 farms in Chonburi province and 20 control cattle from 2 farms in Khon Kaen province in Thailand. Procedure—Blood and urine samples were assayed (microscopic agglutination test and urine antigen test) for Leptospira infection by use of an MAb–based dot- blot ELISA, and results for the ELISA were compared with those for dark-field microscopy (DFM), microbial culture, and a polymerase chain reaction (PCR) assay. Results—All urine samples with positive results for DFM, microbial culture, PCR assay, or > 1 of these tests also had positive results when tested by use of the MAb–based dot-blot ELISA, except for 1 sample that had positive results only for the PCR assay. Detection limits of the dot-blot ELISA were 10 3 lep- tospires/mL of urine and 9.3 ng of Leptospira homogenate. Comparison revealed that the diagnos- tic sensitivity, specificity, efficacy (accuracy), positive predictive value, and negative predictive value for the ELISA were in agreement with results for DFM (100%, 72.72%, 80%, 57.14%, and 100%, respec- tively), microbial culture (100%, 61.54%, 66.62%, 28.57%, and 100%, respectively), and PCR assay (95.45%, 100%, 91.77%, 100%, and 95.83%, respec- tively). Conclusions and Clinical Relevance—The MAb–based dot-blot ELISA is suitable as a tool for detecting leptospires in urine samples of cattle. (Am J Vet Res 2005;66:762–766) Unauthenticated | Downloaded 08/14/22 02:58 PM UTC