CORVALLIS, Ore. – The Veterinary Diagnostic Laboratory at Oregon State University is working with the Oregon Marine Mammal Stranding Network to test California sea lions for leptospirosis, a bacterial disease that can infect numerous animals, including humans.
An increasing number of sea lions have been reported dead on Oregon beaches during the past year, but officials aren’t sure if animal deaths are increasing or the reporting of those deaths has improved, says Jim Rice, an OSU research assistant who coordinates the statewide stranding network. Leptospirosis is considered a likely candidate for their cause of death.
“A lot of the deaths are in the southern part of the state, where we previously had very little coverage,” explained Rice, who works for the OSU Marine Mammal Institute, headquartered at the university’s Hatfield Marine Science Center in Newport. “We now have more eyes on the beaches looking for dead or stranded animals.
“But the fact remains that there are a number of sea lions on the beaches that are dead or extremely emaciated and leptospirosis is a strong possibility,” Rice added. “Some of the emaciated sea lions disappear after a day or two on the beach, so it’s possible they may have recovered, or it’s possible they relocated and died elsewhere.”
Leptospirosis can be found in a variety of animal species. The bacteria usually target the kidneys, but other organs can be affected and damage can be considerable. In late 2006, outbreaks were reported among racehorses in Kentucky, dogs in Maryland, and even a group of hunters in Montana who had drank water from a contaminated spring.
Humans get leptospirosis through contact with fresh water, damp soil or vegetation that has been contaminated by the urine of infected animals. Persons who swim, wade, raft or canoe in infected waters can get the disease, which also is a problem for agricultural workers in flooded areas, residents of tropical areas and soldiers.
The disease enters the body through broken skin and mucous membranes. Symptoms include fever, headache, chills, nausea and vomiting, eye inflammation and sore muscles. More severe cases, often resulting in hospitalization, can involve internal bleeding, kidney failure and liver damage.
In Oregon, the Veterinary Diagnostic Laboratory at OSU’s College of Veterinary Medicine already has performed necropsies on more than a dozen sea lions and a number have tested positive for leptospirosis. But standard tests for the disease can result in “false negatives,” so technicians and graduate students in the lab are developing a PCR (polymerase chain reaction) test for this disease that will be more sensitive and specific.
PCR is a molecular-based system that is used for the diagnosis of many different diseases. A PCR test for leptospirosis is already in use in other parts of the country, and once in place at OSU’s Veterinary Diagnostic Lab, it will help identify the disease in seal lions as well as other infected species including sheep, horses and dogs, according to Jerry Heidel, director of the lab.
“If leptospirosis is causing the deaths in sea lions, we’d like to know if it is a unique bug, or the same strain that infects sheep and other animals,” Heidel said. “Conceivably there could be a unique salt water version of the bacteria and the PCR will help us determine that.”
Emilio DeBess, Oregon’s Public Health Veterinarian, has recognized the importance of the work, Heidel said, and “is providing essential support for the research.”
Dan Rockey, head of the OSU Veterinary Diagnostic Lab’s bacterial section, is working on the PCR assays with Dan Lewer, a third-year doctor of veterinary medicine student, and Kelsi Sandoz, a doctoral student in molecular and cell biology. Lewer spent three years working with OSU’s Marine Mammal Institute and the multi-agency Oregon Marine Mammal Stranding Network, where he saw a number of sea lions that were sick.
“It seemed like a lot more of the juveniles ended up dying from the infection, whereas the affected adults showed clinical signs of compromised immune systems that otherwise weakened them,” Lewer said. “Some of the sick adults die, but most recover unless they are sick for another reason, compounding the issue. The animals that I saw had bad kidney infections that appeared quite painful and they would often seek and drink fresh water, which was kind of unusual.”
Many of the sea lions had pneumonia, which may have been a result of compromised immune systems. Laboratory testing also found abnormalities in the kidneys, typical of leptospirosis.
OSU bacteriologist Rockey says leptospirosis can be severe when it crosses species into humans and he urged caution when people – or their pets – encounter stranded marine mammals on beaches.
Leptospirosis can be fairly virulent, Rockey pointed out. There are about 30 to 100 cases reported in humans each year with a majority of the cases being trappers, soldiers, agricultural employees and slaughterhouse workers. However, the disease is under-diagnosed, he added, and the numbers are likely much higher.
“It is the cross-species nature of this serious disease that has led to this collaborative research effort,” Heidel pointed out.
The Oregon Marine Mammal Stranding Network is a collaborative volunteer effort to respond to reports of sick or dead marine mammals – including whales, seals and sea lions – and report data about the strandings to the National Marine Fisheries Service. It is headquartered at OSU’s Hatfield Marine Science Center and coordinated by Rice.
Partners in the Oregon Marine Mammal Stranding Network include OSU, Portland State University, the University of Oregon’s Institute for Marine Biology, the Oregon Department of Fish and Wildlife, the Oregon State Police, the Oregon Department of Parks and Recreation and others.
Persons seeing dead or sick marine mammals on Oregon beaches are encouraged to call the network at 1-800-452-7888.