Leptospirosis Statistics in the Pacific Northwest
January through December, 2018
This report summarizes leptospirosis titer testing submitted through Phoenix Lab using the microscopic agglutination test (MAT) at the Washington Animal Disease Diagnostic Laboratory (WADDL) at Washington State University. We also report on the result of Leptospira PCR (polymerase chain reaction) testing on urine and whole blood through the Michigan State University Veterinary Diagnostic Laboratory.
A total of 151 samples were submitted for leptospirosis titers – from 144 dogs, six horses and one cat. Thirteen paired samples were submitted and thus there were 138 animals for which individual samples were submitted for testing.
There were ten samples consistent with current exposure to leptospirosis, all based on the results of a single titer. One case was a horse, the remaining nine were dogs. There was variety of age and breed among the dogs. History of illness and vaccination status were unknown in the animals.
The titers for which dogs in Washington State had the highest titer included. L bratislava, L. canicola, L grippotyphosa, L. icterohaemorrhagica, and L. pomona. The three dogs in Montana had highest titers to L. bratislava and L. grippotyphosa (2). The horse had equally high titers to L. bratislava and L. pomona.
Results consistent with current exposure came from the months of January, March, May, September, October, and November. The horse and one dog tested positive in May. Four dogs tested positive in November; one of these from a clinic in Puyallup, the other three from a clinic in Billings, Montana. The clinics of record for the dogs with titers consistent with current exposure were also located in Spokane, Bainbridge Island, Lynnwood, Olympia, Shelton and Wenatchee. The horse was seen at a clinic in Buckley.
For comparison, 161 to 189 animals/year were tested for leptospirosis from 2012 through 2017. The number of animals having MAT titers consistent with current exposure was 17 in both 2012 and 2013, 29 in 2014, 20 in 2015, 19 in 2016 and 6 in 2017.
Eighteen patients had samples submitted for Leptospira PCR testing. Eight samples were whole blood, seven were done on urine and three on both. All Leptospira PCR testing was negative. Serology done on three of these patients also did not support concurrent exposure to leptospirosis. If leptospirosis is suspected in a patient, both serology and PCR testing should be done. There are false negatives with both tests. Seventeen patients were tested with the Leptospira Rapid Screen test performed at Phoenix Lab. All results were negative and no other tests for leptospirosis were done on these patients.
Leptospirosis is a reportable disease to the Washington State Department of Health. Diagnostic laboratories and attending veterinarians are required to report results consistent with current exposure.